MAIN from MCQs Flashcards

Question

What are the different parts of a sarcomere?

Answer 1

Z-discs: ends of a sarcomere I band: only actin (thin) filament A band: overlap of actin and myosin filaments H zone: myosin filament only M disc: anchoring point of thick filaments

Answer 2

Calcium stimulates the release of more calcium from the sarcoplasmic reticulum Inhibited by dantrolene

Answer 3

Ryanodine Receptor (CICR) Inositol Triphosphate Receptor (calcium channel) Phospholamban (inhibits sarcoplasmic reticulum calcium ATPase)

Answer 4

Desmosome Junctional Complex: provide structural integrity and tensile strength Gap Junctions: hexameric proteins (connexons) that span the sarcolemma and allow small molecules to pass

Answer 5

Dimers in a staggered helical fashion with globular heads forming six rows Central portion of adjacent filaments joints at M-disc by creatine kinase, M protein and myomesin Tail is made up of light meromyosin (LMM) and heavy meromyosin (HMM) arranged in an alpha helix with a flexible hinge region

Answer 6

Two actin filaments are arranged in a helix Tetramer of alpha-tropomyosin is wound around it (blocking the binding of myosin heads to actin) Inhibitory (TnI), calcium-binding (TnC) and tropomyosin-binding (TnT) troponins are found on tropomyosin

Answer 7

At rest, tropomyosin blocks myosin binding sites on actin Calcium binds to TnC triggering the unbinding of tropomyosin, making the binding sites available for engagement Myosin head binds and fully displaced tropomyosin allowing more heads to bind Once calcium is sequestered, tropomyosin will bing to actin again

Answer 8

The fibres are arranged into a single overlapping and looping band extending from the pulmonary artery to the aorta This explains the ascending, descending and rotational forces during systole

Answer 9

Atrial systole Isovolumetric contraction Rapid ejection Reduced ejection Isovolumetric relaxation Rapid filling Reduced filling

Answer 10

A wave: atrial contraction C wave: isovolumetric contraction causes AV valves to bulge into atria X descent: atrial relaxation + pulling downwards of AV ring during early rapid ejection V wave: ventricular systole Y descent: AV valves open and blood rapidly leaves the atria into the ventricle during diastole

Answer 11

Incisura: sharp downward deflection occurring immediately after the aortic valve closes as blood being ejected from the LV suddenly stops Dicrotic Notch: smaller notch caused by brief backflow of blood as the aortic valve closes and the aorta recoils in on itself

Answer 12

3rd Heart Sound Occurs during early rapid ventricular filling due to tensing of connective tissues that support the valve cusps Occurs in conditions associated with ventricular dilation 4th Heart Sound Occurs during atrial systole Represents vibration of the ventricular wall during atrial contraction Occurs in conditions associated with stiff ventricles

Answer 13

Area within the loop (pressure x volume)

Answer 14

The gradient of the end-systolic pressure volume relationship (ESPVR) and end-diastolic pressure volume relationship (EDPVR) is the reciprocal of the ventricle's compliance Shallower gradient means greater change in volume for a small change in pressure (i.e. more compliant ventricle)

Answer 15

Ejection from the RV begins earlier in systole before peak RV pressure is reached Pulmonary circulation is high capacitance and low pressure, so RV ejection continues whilst RV pressure is falling (up to 60% of stroke volume ejected after peak systolic pressures)

Answer 16

Nernst: predicts transmembrane potential based on one ion at a time Goldman Constant Field: considers all major ions

Answer 17

0: depolarisation, Na channels open allowing Na influx 1: Na channels close and K channels open, allowing K efflux 2: Ca channels open allowing Ca influx to balance K efflux 3: Ca channels close, K efflux continues causing repolarisation 4: Na/K ATPase re-established resting membrane potential and concentration gradients

Answer 18

I and aVF as they are at right angles to each other Should be -30 to +90 degrees

Answer 19

Phase 4: initially at -60 mV, funny sodium channels open allowing sodium influx, at -50 mV T-type Ca channels open, then at -40 mV L-type Ca channels open, reaching threshold potential Phase 0: ongoing flow through L-type Ca channels leads to depolarisation Phase 3: Ca channels close and opening of K channels returns to membrane potential

Answer 20

P wave: < 0.12 seconds PR Interval: 0.12-0.20 seconds QRS Complex: < 0.12 seconds QT Interval Men: < 440 ms Women: < 460 ms

Answer 21

Increases Na and Ca permeability resulting in faster upward drift of pacemaker potential and increased heart rate In myocardial cells, increased calcium influx leads to stronger contraction

Answer 22

Vagus nerve releases acetylcholine to stimulate M2 receptors Leads to opening of K channels that hyperpolarises the cells, thereby slowing the rate at which the threshold potential in pacemaker cells

Answer 23

Atmosphere: 21.2 kPa Alveolus: 14 kPa Arterial: 13.3 kPa Mixed Venous: 5.3 kPa

Answer 24

Conducting Zone - No alveoli - Generations 1-16 (trachea to terminal bronchioles) - Volume: 150 mL - Bulk flow during inspiration and expiration - Warming and humidifying inspired air Respiratory Zone - Has alveoli - Generations 17-23 (bronchioles to alveoli) - Volume: 3000 mL - NO bulk flow, gases move by diffusion  - Function: gas exchange 

Answer 25

Alveolar Minute Ventilation = (Tidal Volume – Dead Space) x Respiratory Rate 

Answer 26

Anatomical: upper airways and conducting zone Alveolar: proportion of minute ventilation that does NOT take part in gas exchange due to entering unperfused or underperfused alveoli

Answer 27

Surface area of the lungs  Diffusion constant for oxygen  Thickness of the alveolar and capillary membrane Difference between the partial pressure of oxygen in the alveoli and the blood

Answer 28

Flow of Gas is directly proportional to: (A/T) x D(P1 - P2) A: surface area T: thickness of interface D: diffusion constant for oxygen P1: partial pressure in alveolus P2: partial pressure in capillary

Answer 29

250 mL/min

Answer 30

0.25 seconds NOTE: red cell transit time through the capillaries is 0.75 seconds

Answer 31

The total proportion of the circulation entering the LEFT side of the heart which has bypassed the oxygenation process of the lungs 

Answer 32

Bronchial circulation and Thebesian drainage (venous drainage from heart muscle into the left ventricle) 

Answer 33

The weight of the lungs compresses the bases meaning that the intrapleural pressure at the bases is less negative This means that the bases have a lower resting volume and require less pressure to bring about a change in volume (i.e. are more compliant)

Answer 34

Zone 1: alveolar pressure greater than arterial pressure so there is no flow (does NOT exist under normal circumstances) Zone 2: arterial > alveolar > venous - flow is dependent on arterial-alveolar pressure gradient Zone 3: arterial > venous > alveolar - flow determined by arterio-venous gradient

Answer 35

Shunt fraction is higher towards the bases Dead space is greater towards the apices

Answer 36

The PO2 at the apex is about 40 mm Hg higher than at the base  due to differences in V/Q The difference in ventilation between the apex and the base is much less than the change in perfusion  Most blood comes from the bases of the lungs which has a lower pO2 and higher pCO2 – this will lower the pO2 and increase the pCO2 of arterial blood when compared to alveolar gas  NOTE: normal alveolar-arterial oxygen difference is 4 mm Hg

Answer 37

High or Low V/Q Ratios Low V/Q Ratio: ventilation is significantly reduced relative to perfusion, leads to fall in PAO2 and even greater fall in PaO2, this can be partially corrected by increasing FiO2 High V/Q Ratio: PAO2 remains stable but PaO2 falls due to reduced perfusion

Answer 38

Qt x CaO2 = (Qs x CvO2) + ((Qt - Qs) x CcO2) Qs/Qt = (CcO2 - CaO2)/(CcO2 - CvO2) Qs = shunt blood flow Qt = total blood flow (cardiac output monitoring) CcO2 = End capillary oxygen content (estimated using alveolar gas equation) CaO2 = arterial oxygen content (from arterial blood gas) CvO2 = mixed venous oxygen content (from pulmonary artery floatation catheter sample)

Answer 39

CaO2 = (Hb x 1.39 x SaO2) + (0.003 x PaO2) NOTE: 1.39 mL of oxygen is carried per gram of fully saturated haemoglobin Hb in grams per 100 mL PaO2 in mm Hg

Answer 40

Alkalosis Hypothermia Decreased 2,3-DPG

Answer 41

Lungs - CO2 is eliminated and pH rises, thereby shifting the curve to the left - This enhances the binding of oxygen to haemoglobin Tissues - Cellular metabolism leads to CO2 and H+ production, thereby shifting the curve to the right - This means that the haem releases oxygen more readily 

Answer 42

Produced as side reaction from glycolysis Binds to beta-globin and reduces haemoglobin's affinity for oxygen Improves oxygen offloading in anaemia and low oxygen states

Answer 43

Protoporphyrin ring (four pyrole rings) and iron in its ferrous (Fe2+) state NOTE: protoporphyrin is synthesised in the mitochondria from glycine and succinyl CoA and combined with ferrous iron

Answer 44

Haemoglobin A: 2 alpha and 2 beta Haemoglobin A2: 2 alpha and 2 delta Haemoglobin F: 2 alpha and 2 gamma

Answer 45

By the reticuloendothelial system Globin chains are broken down into amino acids which are recycled Iron is reused by the bone marrow to make more haemoglobin Protoporphyrin is opened to form biliverdin, which is metabolised to bilirubin

Answer 46

The amount of oxygen (in mL) carried by each gram of haemoglobin  Values in vitro are 1.39 mL/g whereas in vivo its 1.34 ml/G - this is thought to be due to the presence of minor haemoglobin variants like HbA2 and HbF

Answer 47

Refers to the reduced affinity of oxygen for haemoglobin when pH is lower  (and carbon dioxide is higher) This is adaptive – for example, the pH in exercising muscles is low and this helps offload oxygen 

Answer 48

Uptake of foetal CO2 by maternal blood shifts the maternal oxy-haemoglobin curve to the right, and the foetal curve to the left 

Answer 49

Stored blood quickly loses 2,3-DPG and its ability to deliver oxygen 

Answer 50

There are four alpha globin genes on chromosome 14 - Alpha thalassemia results from mutations to 1 to 4 of these genes  There are two beta globin genes on chromosome 11  - Mutations in these genes causes beta thalassemia  - It usually manifests at 6 months of age when HbA takes over from HbF 

Answer 51

Glutamic acid is substituted for valine at position 6 of the beta globin chain

Answer 52

Binding changes the confirmation of haemoglobin making it less likely to release oxygen (I.e. shifting the curve to the left) and it reduces the availability of binding sites for oxygen

Answer 53

20 mL/100 mL

Answer 54

VO2 = CO x (Arterial O2 Content – Mixed Venous O2 Content) = CO(CaO2 – CvO2) 

Answer 55

Normal mixed venous PO2 is around 5.3 kPa - at this pO2, haemoglobin is 75% saturated  Remember, 100% saturated blood contains 20 mL/100 mL of oxygen (meaning that 75% saturation will give 15 mL/100 mL of oxygen) Therefore: VO2 = 5000 x (20-15)/100 = 250 mL/min

Answer 56

Oxygen delivery is insufficient and the oxygen extraction ratio has been increased to compensate NOTE: normal is around 75%

Answer 57

Glucose --> 2 Pyruvate via glycolysis in the cytoplasm 2 Pyruvate --> 2 Acetyl CoA due to oxidative decarboxylation in the mitochondria Free Fatty Acids --> Acetyl CoA via beta oxidation Amino Acids --> Pyruvate + Acetyl CoA + Krebs Cycle Intermediates via oxidation

Answer 58

2 ATP 2 CO2  6 NADH+ 2 FADH

Answer 59

In the mitochondria, reduced enzymes (NADH and FADH) are reoxidised releasing electrons and energy used to convert ADP to ATP 1 NADH2 = 3 ATP 1 FADH2 = 2 ATP Oxygen is the final electron acceptor which combines with hydrogen ions to produce water 

Answer 60

Hypoxia Hypoxia Anaemic Hypoxia Ischaemia/Stagnant Hypoxia Histotoxic Hypoxia

Answer 61

2 mins anoxia = irreversible cell damage  4 mins anoxia = cell death 

Answer 62

LOCAL: acid accumulation from anaerobic respiration leads to right shift of ODC, 2,3-DPG also rises, vasodilation due to low pO2, high pCO2 and low pH VENTILATORY: minute ventilation increases when pO2 < 7 kPa CARDIOVASCULAR: Stimulation of the chemoreceptors results in vasoconstriction and tachycardia resulting in improved tissue perfusion by increasing blood pressure and heart rate

Answer 63

50-150 mm Hg

Answer 64

6.7 kPa NOTE: brain is responsible for 20% of total body oxygen consumption

Answer 65

75% Compared to 25% in other tissues. This can increase to 90% when demand increases (e.g. exercise)

Answer 66

Inhibition of nitric oxide production Local production of vasoconstrictors (e.g. endothelin) Direct effect of hypoxia on vascular smooth muscle 

Answer 67

Due to the mixSting with expired gas from unperfused alveoli

Answer 68

(CO2 x 100)/Alveolar Ventilation = ~5%

Answer 69

Increased inspired pCO2 (rebreathing) Primary respiratory depression (e.g. CNS depression) Increased CO2 production (e.g. sepsis, MH) Compensatory (to metabolic alkalosis)

Answer 70

Increased cerebral blood flow Increased ICP (due to vasodilation) Narcosis (at pCO2 > 12 kPa) Autonomic effects (due to increased circulating catecholamines)

Answer 71

CO2 rapidly crosses the BBB and, in the CSF, dissolves to release H+ (which cannot go back across the BBB leading to a drop in CSF pH) BBB is more permeable to CO2 than it is to H+

Answer 72

Linear increase in minute ventilation Pulmonary vasoconstriction (if PaCO2 > 7) ODC shifts to the right

Answer 73

Impaired heart rate and contractility (due to acidosis) Systemic vasodilation and pulmonary vasoconstriction Arrhythmia Increased catecholamine release (opposes the direct myocardial impairment mentioned above)

Answer 74

Bicarbonate: 18 mmol H+ per L Plasma Proteins: 1.7 mmol H+ per L Haemoglobin: 8 mmol H+ per L Phosphate: 0.3 mmol H+ per L TOTAL: 28 mmol H+ per L

Answer 75

Zinc Zinc hydrolyses water to a reactive Zn-OH species  Nearby histidine removed H+ from Zn and transfers to any buffer molecules near the enzyme Carbon dioxide combined with Zn-OH forming HCO3- The HCO3- dissociates from the zinc atom 

Answer 76

Amino groups of haemoglobin can combine with CO2 to form carbamic acid Deoxyhaemoglobin is about 3.5 times more effective at carbamino carriage than oxyhaemoglobin NOTE: this is a major component of the Haldane effect. Oxygenation reduces its affinity for CO2.

Answer 77

Physiological phenomenon where the binding of oxygen to hemoglobin in the lungs promotes the release of carbon dioxide, and conversely, the release of oxygen from hemoglobin in the tissues facilitates the uptake of carbon dioxide.

Answer 78

Imidazole group of histidine Each Hb tetramer has 38 histidine molecules

Answer 79

Buffering capacity is a measure of a solution's ability to resist changes in pH when acid or base is added  A buffer works best when pKa is close to physiological pH because it means that, at physiological pH, the buffer has significant amounts of both its acid and its conjugate base to be able to neutralise any acid or base that is added to the solution, thereby minimising changes in pH 

Answer 80

In deoxyhaemoglobin, the imidazole group of histidine is more basic As oxygen dissociates, it becomes more basic and binds more H+ Removal of H+ shifts the carbonic acid equilibrium towards H+ and HCO3- generation, thereby 'consuming' CO2 This leads to increased movement of CO2 into the red cells Deoxyhaemoglobin also has increased carbamino carriage

Answer 81

Haldane effect is what happens to pH and CO2 binding because of oxygen, and Bohr effect is what happens to oxygen binding because of CO2 and lower pH.

Answer 82

Haemoglobin buffering (H+ soaked up by histidine residues) Hamburger Shift (HCO3- exchanged for Cl- by Band 3 protein) NOTE: hereditary spherocytosis is caused by inherited defect in Band 3

Answer 83

Paramagnetic gases are attracted by a magnetic field (and can be analysed by a paramagnetic analyser) due to the presence of unpaired outer orbital electrons. Examples: oxygen, nitric oxide

Answer 84

A substance above its critical temperature cannot be liquified irrespective of the pressure applied to it.

Answer 85

-118 degrees

Answer 86

Dynamic compliance is affected by both airway resistance and elastic resistance, while static compliance is affected by elastic resistance alone.

Answer 87

The sieving coefficient provides a measure of how different molecules move across a semi-permeable membrane. In renal replacement therapy, it is the ratio of the concentration of a molecule in the ultrafiltrate compared to the concentration in the blood. NOTE: smaller molecules equilibrate across the membrane more readily and have a coefficient around 1

Answer 88

Transpulmonary pressure = pressure in the right side of the heart – pressure in the left side of the heart. NOTE: Pulmonary capillary wedge pressure is often used as a surrogate for left atrial pressure

Answer 89

Blocks post synaptic β1 receptors (part of the autonomic nervous system).

Answer 90

In pulse oximetry, red (660nm) and infrared (940nm) LEDs blink on and off 30 times per second. The degree of absorbance of these wavelengths by a photodetector is measured, and is correlated with known data to provide an estimate of oxygen saturations. Oxygenated haemoglobin absorbs infrared (940nm) light to a greater degree than deoxygenated haemoglobin. The reverse is true of red light. The off:off signal allows for the photodetector to establish the degree of ambient light which is then subtracted from the received signal.

Answer 91

Anterior rami of L2-L4

Answer 92

Closing capacity (the sum of residual volume and closing volume), is the lung volume at which small airways begin to close during expiration. With advancing age, it is increased to the extent that it may exceed FRC. This leads to closure of the small airways during normal tidal breathing.

Answer 93

Convert AC to DC current (knowing as rectification) May also be referred to as a rectifier

Answer 94

Lipid solubility: More lipid soluble, more transfer Ionisation: More ionised, less transfer Protein binding: More protein binding, less transfer pH: Determines degree of ionisation, which in turn affects transfer Molecular weight: Large, bulky molecules, pass less readily.

Answer 95

CO2 is more soluble in water as the temperature decreases such that maintenance of the same PCO2 in the blood when hypothermia requires more total CO2  Decreasing temperature reduces the ionisation of water so pH increases by around 0.016 per degree fall in temperature Therefore, if CO2 production and excretion remain constant, hypothermia would lead to alkalosis

Answer 96

Animals try to maintain blood pH in hypothermia by hypoventilating (this is seen in hibernating animals)

Answer 97

The ionisation state of histidine and, hence, its buffering ability changes with temperature to a similar degree to the ionisation of water  So, as temperature decreases and blood/tissue pH rises, the ionisation of histidine can buffer this change in pH 

Answer 98

Increased inspired CO2: rebreathing Increased production of CO2: hyperthermia, hyperthyroidism, laparoscopic surgery Decreased excretion: increased dead space, failure of respiratory muscle function

Answer 99

The partial pressure of oxygen within the alveolus once the partial pressure of oxygen delivered and the amount consumed to meet the metabolic demands of the body have been considered.

Answer 100

PAO2 = FiO2(Patm - Ph2o) - (PCO2/RQ)

Answer 101

Air becomes 100% saturated with water as it passes through the airways The SVP of water at body temperature is 6.3 kPa As per Dalton's law, as the vapour takes up space within the airways, it must be subtracted from the partial pressure of atmospheric air

Answer 102

It doesn't - the FiO2 remains the same, however, the total atmospheric pressure decreases meaning that the pO2 will decrease

Answer 103

Caused by excessive pulmonary vasoconstriction 

Answer 104

1 atmosphere for every 10 m of depth

Answer 105

Barotrauma in air-filled spaces (e.g. lungs, ear) Arterial air embolus Bubbles forming in vessel poor tissues (e.g. cartilage) with avascular necrosis  Potentially permanent neurological damage

Answer 106

Anaerobic infections CO poisoning Decompression sickness

Answer 107

If hypoxia at sea level, more vulnerable to desaturation and requiring more oxygen at altitude  Pressurisation and depressurisation in planes occurs suddenly which can cause air filled spaces (e.g. pneumothorax, bulla) to expand rapidly Boiling pressure of volatiles falls

Answer 108

Two atoms share one or more outer shell electrons The negatively charged electrons are attracted to both nuclei simultaneously and this overcomes the repulsion which would otherwise exist between two nuclei, thereby forming a strong bond Occurs between non-metals

Answer 109

An outer electron is transferred from one atom to another The electron-accepting atom becomes negatively charged (anion) whilst the other becomes positive (cation) resulting in an electrostatic attraction between them Occurs between metals and non-metals

Answer 110

Energy required to change one unit of mass from liquid to gas (e.g. water boiling)

Answer 111

Energy required to transform matter from one state to another

Answer 112

Energy required to change one unit of mass from solid to liquid (e.g. when ice melts)

Answer 113

Determines the energy needed to raised 1 kg of the substance by a temperature of 1 degree

Answer 114

Q = cmΔT Q: energy required c: specific heat capacity m: mass ΔT: temperature change

Answer 115

4.18 J/g/C

Answer 116

When the water starts becoming a vapour (changing phase), it is absorbing energy (latent heat of vaporisation) and the temperature does not rise

Answer 117

Pressure and temperature where all three states can coexist

Answer 118

Minimum pressure required to liquefy the gas at the critical temperature

Answer 119

Any substance in the gas phase at a temperature lower than its critical temperature This means that vapours can be condensed into a liquid or to a solid by increasing the pressure without reducing the temperature

Answer 120

Solid: A state of matter with a fixed shape and volume, where particles are tightly packed and vibrate in place. Liquid: A state of matter with a fixed volume but no fixed shape, allowing it to flow while particles move more freely than in a solid. Gas: A state of matter with no fixed shape or volume, where particles move rapidly and spread out to fill any container.

Answer 121

CONSTANT VELOCITY: objects move in a straight line at constant speed or remain stationary unless a force acts upon the object

Answer 122

Acceleration of a body is proportional to the force applied and inversely proportional to the mass of the object F = m x a

Answer 123

Force applied to an object per unit area P = F/A

Answer 124

There is a linear relationship between the force applied and the extension of a spring within the elastic limits for that spring F = -kx F: force k: spring constant x: extension

Answer 125

The degree of stiffness or springiness The higher the spring constant the more difficult it is for the spring to extend The amount of displacement from equilibrium can be positive (extension) or negative (compression) - the negative sign, therefore, indicates that the spring exerts a force in the opposite direction to the displacement

Answer 126

Temperature at which the saturated vapour pressure is equal to atmospheric pressure NOTE: At boiling point, further heat does NOT increase the temperature but provides the latent heat of vaporisation which makes gas molecules evaporate from the liquid phase

Answer 127

Atmospheric pressure pushes down on the liquid, preventing vaporisation. When the liquid's saturated vapour pressure matches the atmospheric pressure, the gas molecules inside the liquid can form stable bubbles without being crushed by external pressure. These bubbles rise and escape, leading to boiling. NOTE: this is why the boiling point is lower at higher altitudes

Answer 128

Pressure exerted by the vapour phase of a substance when in equilibrium with the liquid phase (i.e. molecules entering liquid phase are equal to molecules leaving it)

Answer 129

It will shift the equilibrium favouring the movement of molecules out of the liquid phase which increases the initial rate of vaporisation but indirectly leads to a lowering of the temperature, a fall in the saturated vapour pressure and, ultimately, a lower vaporisation rate

Answer 130

A higher SVP means that the agent will more readily vaporise NOTE: a standard temperature must be set when comparing SVP

Answer 131

Boiling Point: 23 SVP at 20 degrees: 89 kPa

Answer 132

Boiling Point: 59 SVP at 20 degrees: 21 kPa

Answer 133

Boiling Point: 49 SVP at 20 degrees: 32 kPa

Answer 134

Boiling Point: 50 SVP at 20 degrees: 33 kPa

Answer 135

Boiling Point: 57 SVP at 20 degrees: 23.3 kPa

Answer 136

Boiling Point: -88 SVP at 20 degrees: 5200

Answer 137

At room temperature, it mainly exists in the vapour phase Tec 6 heats desflurane to 39 degrees and injects it directly into the fresh gas flow Given desflurane's tendency to vaporise, using a standard vaporiser would require a very high fresh gas flow and its high latent heat of vaporisation would lead to cooling and inconsistent vaporisation

Answer 138

High alveolar ventilation = faster onset because more rapid increase in alveolar partial pressure High FRC = slower onset because of dilution of agent S High cardiac output = slower onset because of more rapid removal from the alveoli (alveolar partial pressure cannot build fast)

Answer 139

Halothane: 2.3 Isoflurane: 1.4 Sevoflurane: 0.65 Nitrous Oxide: 0.47 Desflurane: 0.45 NOTE: water solubility decreases as molecular weight decreases

Answer 140

The lower the blood: gas partition coefficient the faster the onset of action because the gas is better able to achieve high alveolar partial pressures as it does not transfer into the blood as readily

Answer 141

The minimum alveolar concentration of an anaesthetic agent that prevents movement in response to a standard skin incision in standard conditions in 50% of subjects when breathing 100% oxygen in the absence of other analgesic or anaesthetic agents NOTE: inversely related to potency (smaller MAC means more potent)

Answer 142

Nitrous Oxide: 104 Desflurane: 6.6 Sevoflurane: 2 Isoflurane: 1.1 Halothane: 0.75

Answer 143

Potentiate GABA-A and glycine receptor, and may inhibit NMDA receptors

Answer 144

MAC increases with oil: gas partition coefficient

Answer 145

Young age Chronic alcohol consumption Hyperthermia Hyperthyroidism Cocaine and amphetamine use

Answer 146

Neonates and elderly Acute alcohol intoxication Hypothermia Hypothyroidism Other sedatives Pregnancy

Answer 147

Liquid at room temperature Stable at room temperature and in light Non-flammable Inert in contact with metal, rubber and soda lime Inexpensive Environmentally safe Low latent heat of vaporisation High saturated vapour pressure

Answer 148

Pleasant smell No respiratory irritation Low blood: gas partition coefficient (fast onset/offset) Potent (high oil: gas partition coefficient so low MAC) Minimal metabolism Excretion via the lungs Cardiovascular stability Analgesic properties Non-epileptogenic No increase in intracranial pressure

Answer 149

Cerebral vasodilation (resulting in raised ICP) Excitatory phenomena (agitation/delirium - most common with sevoflurane)

Answer 150

Reduced alveolar ventilation (due to reduced tidal volume and only slight increase in respiratory rate) Bronchodilation (sevoflurane and isoflurane)

Answer 151

Decreased MAP (usually by decreasing SVR though halothane reduces cardiac output) Sevoflurane can prolong QTc NOTE: desflurane and sevoflurane cause an increase in HR

Answer 152

CYP450 pathways produce a toxic metabolite called trifluoroacetic acid which led to some patients going into acute fulminant hepatitis NOTE: most other volatile agents are excreted unchanged by the lungs

Answer 153

Rare autosomal dominant (chromosome 19) condition that can be triggered by volatile agents and suxamethonium Incidence of 1 in 10,000

Answer 154

Muscle rigidity Tachycardia Rising ETCO2 Rising oxygen requirement Hyperpyrexia Metabolic and respiratory acidosis

Answer 155

Triggering agents (volatiles or suxamethonium) causes uncontrolled release of free calcium from the sarcoplasmic reticulum due to a mutation in the ryanodine receptor of the sarcoplasmic reticulum

Answer 156

Consider using regional anaesthesia Avoid suxamethonium and volatiles Use TIVA Use a clean machine (no volatiles used by machine beforehand) Have dantrolene to hand Monitor temperature and ETCO2 closely

Answer 157

A measure of a fluid's resistance to flow.

Answer 158

Constant viscosity regardless of flow rate NOTE: non-Newtonian fluids can become more or less viscous with increasing flow rate

Answer 159

Hydrogen bonds between water molecules on the surface of a liquid are stronger than those in the middle as there are fewer surrounding molecules This pulls neighbouring molecules as close to each other as possible (causing the bubble shape)

Answer 160

The larger the radius of the vessel, the greater the wall tension required to withstand a given internal fluid pressure

Answer 161

Sphere: ΔP = 2T/R Cylinder: ΔP = T/R NOTE: wall tension and surface tension are measured in force per unit length (N/m)

Answer 162

Initially, it looks like a cylinder and the increase in radius leads to increasing wall tension in a vicious cycle If it bulges towards a more cylindrical shape, the tension will decrease because the wall tension of a sphere is half that of a cylinder for the same difference in pressure and radius.

Answer 163

ΔP = 2T/R Smaller alveoli have a higher pressure for a given surface tension. This means that smaller alveoli are harder to inflate and would empty into larger alveoli. Surfactant reduces surface tension and is present in greater concentrations in smaller alveoli.

Answer 164

Product of the force applied and the distance the object is moved Work = Force x Distance

Answer 165

Capacity for doing work

Answer 166

Rate at which energy is being done (or the rate of energy transfer) Power = Work Done/Time Taken

Answer 167

The amount of energy required to exert a force of one newton through a distance of one metre A calorie is another unit for energy and is approximately 4.2 J

Answer 168

Watt 1 watt = 1 joule per second

Answer 169

Work Done = Force x Distance Force = Pressure x Area Work Done = Pressure x Area x Distance Volume = Area x Distance Work Done = Pressure x Volume

Answer 170

Energy is lost due to airway resistance At end inspiration and end expiration, the pressure between the lungs and ventilator will temporarily equilibrate because there is no air flow meaning that there can be no resistance

Answer 171

Elastic hysteresis - different volumes for identical pressures during inspiration and expiration This occurs because lung tissue resists stretching during inspiration and recoils more readily during expiration Surfactant dilutes during inspiration leading to increasing surface tension

Answer 172

Change of volume with respect to pressure (a measure of ease of expansion) C = ΔV/ΔP Measured in metres per Newton

Answer 173

Elastance is the reciprocal of compliance

Answer 174

Age Emphysema

Answer 175

Your lungs need to be compliant enough to expand relatively easily during inspiration They also need to be elastic enough to deflate during expiration without requiring too much work from the expiratory muscles

Answer 176

The work of one inspiration is around 0.36 J NOTE: for 15 breaths/min Power = 0.36 x 15/60 = 0.09 J/s = 90 mW As the respiratory muscles are only 90% efficient, the power required for resting breathing is around 900 mW The total metabolic rate of a subject at rest is 80-90 W so respiratory power is about 1% of energy consumed by the body

Answer 177

Rapid breathing causes higher flow rates resulting in more turbulence Turbulent flow (as per the relationship described above) requires more power than laminar flow for a given flow rate resulting in higher energy consumption by the respiratory muscles The oxygen demands of the hyperactive respiratory muscles can exceed the supply of oxygen resulting in hypoxia

Answer 178

At rest, the mechanical output power of the heart is 1.3 W Efficiency of the Heart 10% of energy supplied to the heart is converted into mechanical energy 90% is converted to heat This means the heart requires 13 W of power to function at rest

Answer 179

A supraglottic airway device used for ventilation during general anesthesia, designed to seal the upper airway and facilitate breathing The COBRA airway has a ramp which helps to guide tracheal tubes towards the larynx.

Answer 180

Unidirectional valves are between the patient and the reservoir bag on both inspiratory and expiratory limb. Fresh gas flow introduced between soda lime and the inspiratory valve. APL valve between expiratory valve and soda lime. The ventilator is typically located between the unidirectional valve in the expiratory limb and the soda lime

Answer 181

Gastric Acid: Parietal Cells Gastrin: G-Cells Pepsinogen: Chief Cells Somatostatin: D-Cells

Answer 182

Rate of change in the plasma concentration per unit time.

Answer 183

Time taken for the plasma concentration to reach zero, had it continued at its initial rate. This is also the time for the plasma concentration to reach 1/e of its original value, which is roughly 37%.

Answer 184

t1/2 = 0.693 x Vd/Cl t1/2 = 0.693/k t1/2 = 0.693 x time constant

Answer 185

20-30 cm H2O

Answer 186

Thiopentone is buffered at a pH of 10.5 at which point the water-soluble enol form is favoured At physiological pH, it becomes a more lipid soluble keto form which can cross the blood-brain barrier

Answer 187

A long inlet port into the vaporising chamber ensures that the bypass channel is not contaminated by retrograde flow (creates increased resistance to backflow) Downstream flow restrictors maintain vaporiser at a pressure greater than at the gas outlet. Downstream pressure relief valves act to prevent back pressure being transmitted to the ventilator. Anti-spill valves prevent contamination of the breathing circuit. Wicks and baffles are used to ensure gas leaving the vaporisation chamber is fully saturated with vapour.

Answer 188

A supramaximal stimulus of 50mA is used in peripheral nerve stimulators. This is 25-50% higher than that needed to produce a maximal response which ensures all motor fibres depolarise simultaneously and eliminates variation due to impedance and position of electrodes.

Answer 189

Sweat glands NOTE: the rest uses noradrenaline

Answer 190

Advantages: no sampling tube, reduced chance of obstruction, no lag time, no pollution, no effect due to changes in water vapour pressure. Disadvantages: sensor windows clog with secretions, bulky, increased risk of patient cross-contamination.

Answer 191

Advantages: easy to connect, no problem with sterilisation, can be used in awake patients, easy to use in unusual patient position e.g. prone, light weight, robust. Disadvantages: lag time, possible sampling tube obstruction, water vapour pressure can change ETCO2 concentrations, sampled gas vented to atmosphere or returned to circle system, moisture trap required to dry gas, pressure drop along sampling tube affects ETCO2 concentrations.

Answer 192

A mainstream analyser would add minimal dead space and be able to rapidly display changes in carbon dioxide with a high respiratory rate and small tidal volume. A rapid response time is desired, and this is less possible with side stream capnography.

Answer 193

It makes it impossible to deliver an oxygen concentration below 25% E.g. when nitrous oxide is turned up to 9 L/min, the oxygen flow rate will increase to 3 L/min to achieve a concentration of 25%

Answer 194

Digoxin Spironolactone Isoniazid Cimetidine

Answer 195

Coherent bundle (to transmit image) Non-coherent/illumination bundle (to transmit light) NOTE: a working channel surrounded by a flexible steel braid, angulation wires and a protective sheath

Answer 196

The coherent sheath can consist of as many as 10’000 fibres of diameter 5-20 μm.

Answer 197

2,6-diisopropylphenol

Answer 198

Dermatome: anterior aspect of thigh Myotome: hip flexion

Answer 199

Low penetration rate Effective bidirectionally Small internal volume (minimise dead space) Minimal resistance to gas flow Effective when wet or dry Disposable Cheap Transparent and lightweight

Answer 200

1/Rtot = 1/R1 + 1/R2 + 1/R3 + … 1/Rn, where n is the number of parallel branches.

Answer 201

Loading dose (mg) = concentration (mg/ml) x volume of distribution (ml)

Answer 202

90-95% calcium hydroxide. 2-5% sodium hydroxide. Silica and zeolite – varying amounts. Indicator dye NOTE: pH is 13.5 with a moisture content of 14-19%. Calcium carbonate is formed during the series of reactions between carbon dioxide and the constituents of soda lime.

Answer 203

Pressure and temperature are directly proportional

Answer 204

Volume and temperature are directly proportional

Answer 205

Product of pressure and volume is constant (k=PV). Therefore, P1V1 = P2V2 in a closed system.

Answer 206

At a given temperature, the amount of gas dissolved in a liquid is directly proportional to the partial pressure of gas in equilibrium with the liquid. Increasing the temperature will decrease solubility of gas dissolved in the fluid causing bubbles to form.

Answer 207

Describes how the rate of a diffusion of a substance is inversely proportional to its molecular weight.

Answer 208

ECG SpO2 NIBP a Capnography (if airway device in place)

Answer 209

Protein Binding 98%

Answer 210

Protein Binding 80%

Answer 211

Protein Binding 25%

Answer 212

Protein Binding 75%

Answer 213

Non-competitive NMDA antagonist

Answer 214

150 mL NOTE: total volume of CSF produced per day is 450 mL

Answer 215

5 second tetanic stimulus (50 Hz) followed by a 3 second pause and then 20 stimuli at a rate of 1 Hz. During the period of stimulation, pre-synaptic receptors are activated which leads to the synthesis and mobilisation of additional acetylcholine. This explains why twitches appear following tetanic stimulation, yet did not appear with the conventional train of four. NOTE: used for deep neuromuscular block

Answer 216

Decrease in the amplitude of an oscillation as a result of energy loss in a system due to frictional or resistive forces. The damping coefficient gives a measure of how quickly an oscillating system will come to rest at a new value.

Answer 217

250 ml/min to meet basal oxygen consumption

Answer 218

Highly lipid soluble (600 x morphine) meaning that it enters and accumulates in tissues This gives it a high context-sensitive half-time meaning that a timely wake up is impractical.

Answer 219

Inhibits nitric oxide induced cGMP activity resulting in vasoconstriction

Answer 220

The amount of charge that passes a given point, per second, when 1 ampere of current is flowing.

Answer 221

Children: C2/C3 Adults: C5/C6

Answer 222

Ensures that only one vaporiser % control dial may be turned on at any time through the use of interlocking extension rods

Answer 223

Hepatic artery Portal vein Branch of biliary tree

Answer 224

Hepatic portal vein 60% flow 40% oxygen NOTE: common hepatic artery is a branch of the coeliac trunk

Answer 225

Reduced protein concentration in CSF limits buffering capacity allowing changes in pH to occur This affects central chemoreceptors which controls ventilation

Answer 226

Levetiracetam (30-60 mg/kg over 5 minutes, maximum 3g) Phenytoin (20 mg/kg by slow IV infusion over 20 minutes with ECG monitoring) Phenobarbital (20 mg/kg IV over 5 minutes)

Answer 227

680 L Pressure of 137 bar

Answer 228

Dibucaine number Patient's plasma is added to a mixture of benzylcholine Emitted light is measured Dibucaine (inhibits plasma cholinesterase if cholinesterase is normal) is then added Dibucaine reduces the emission of light if pseudocholinesterase is normal Normal reduction in light emission with dibucaine is 80% NOTE: with other subtypes of pseudocholinesterase, the dibucaine number is lower because there is less inhibition of pseudocholinesterase by dibucaine

Answer 229

Cricothyroid muscle Innervated by the external laryngeal nerve (which is a branch of the superior laryngeal nerve, which is a branch of the vagus nerve)

Answer 230

Resistance describes the opposition to flow of direct current Reactance is used when the current is alternating Impedance (Z) is the sum of resistive and reactive components NOTE: all are measured in ohms

Answer 231

If two thermodynamic systems are in equilibrium with a third then they are also in equilibrium with each other

Answer 232

Energy can neither be created or destroyed only converted from one form to another

Answer 233

Entropy (i.e. a measure of unavailable energy) tends to increase with time.

Answer 234

As a system approaches absolute zero (-273.15ºc) all processes cease and entropy approaches a minimum

Answer 235

Partial pressure at which aerobic metabolism is no longer possible. This is normally around 0.3 kPa

Answer 236

Cells are unable to utilise oxygen despite an adequate supply This leads to reduced cellular consumption and venous oxygen saturations may be elevated

Answer 237

Allows compensation for wide variations in thoracic impedance by electronically adjusting waveform magnitude and duration Lower peak current delivered Less energy required for defibrillation Improved safety profile NOTE: biphasic means that current flows in one direction before reversing

Answer 238

1: sodium deoxycholate haemolyses erythrocytes releasing Hb 2: sodium nitrite converts Hb to MetHb which then reacts with sodium azide to give azidemethaemoglobin 3: absorbance is measured at two wavelengths (570 nm and 880 nm). Degree of absorbance is relative to Hb concentration so estimate is generated 4: after each reading, photometer zeros itself and checks the intensity of the light source and photocell

Answer 239

Small, compact device used to measure tidal volume and minute volume of expiratory flow.

Answer 240

25 L of CO2

Answer 241

Class 1: a mains powered device enclosed within an earthed metal casing to ground any leakage current Class 2: double insulated electrical device, this mitigates the need for an earth wire Class 3: SELV (safety extra low voltage) of typically 24-50V. These devices may be battery powered or connected to mains via a transformer.

Answer 242

Type B: touches skin but does not penetrate (e.g. ECG) Type BF: part that touches the patient is electrically isolated from the rest of the device (e.g. thermometer) Type CF: for equipment that touches the heart or is inserted into the body (e.g. pacing wires)

Answer 243

This is a compensatory mechanism where the hepatic artery vasodilates in response to reduced portal venous flow Adenosine is secreted at a constant rate into the space of Mall (periportal space) via oxygen-independent mechanisms. Reduced portal blood flow leads to reduced clearance of adenosine and the accumulating adenosine has a direct vasodilatory effect on the hepatic artery.

Answer 244

Glycopeptide antibiotic Inhibit cell wall synthesis by binding to and interfering with the ongoing synthesis of peptidoglycan cell wall.

Answer 245

Muscle spindles are stretch transducers that maintain a constant muscle length despite a change in load. Golgi tendon organs are found in muscle tendons and function to limit tension generated within the muscle.

Answer 246

Where a resistor and capacitor are placed in series as a circuit. It acts as a low pass filter i.e. allows frequencies below a certain value to pass

Answer 247

(age/2) + 12

Answer 248

Tyrosine kinase linked receptor

Answer 249

Equal volumes of an ideal gas at standard temperature and pressure will contain an equal number of molecules, and that one mole of an ideal gas at standard temperature and pressure occupies 22.4 litres.

Answer 250

Prostaglandin analogue used in management of PPH It can precipitate bronchospasm

Answer 251

Potassium channel activator Activation of ATP-sensitive potassium channels within the walls of arterioles causes hyperpolarisation, which reduces intracellular calcium. In turn, this leads to arteriolar vasodilation and subsequent reduced blood pressure.

Answer 252

Previous cardiac arrest due to VF or unstable VT VT with structural heart disease Non-ischaemic dilated cardiomyopathy Severely impaired ejection fraction (< 35%) despite 3 months of optimal medical management

Answer 253

Skin Subcutaneous tissue Supraspinous ligament Interspinous ligament Ligamentum flavum Epidural space

Answer 254

L-tyrosine --> L-Dopa by tyrosine hydroxylase L-Dopa --> dopamine by dopa decarboxylase Dopamine --> noradrenaline by dopamine hydroxylase Noradrenaline --> adrenaline by PNMT (phenylethanolamine N-methyltransferase)

Answer 255

Anticholinergic effects – dry mouth, dry nose, blurred vision, constipation, urinary retention, sweating, increased body temperature. CNS effects – drowsiness, confusion, myoclonus, seizure, coma. Cardiovascular effects: tachycardia, arrhythmias, hypotension, transient hypertension, VT, VF and prolonged QT interval.

Answer 256

273.16 K, and sub-atmospheric pressure (611 Pa) NOTE: this is the point at which it exists in solid, liquid and gas phases at equilibrium

Answer 257

pKa: 7.7 Protein Binding: 55% Solubility: 50 times the solubility of procaine

Answer 258

Phrenic nerve palsy The phrenic nerve runs on the anterior aspect of the anterior scalene

Answer 259

Aminoglycosides (the higher the concentration, the greater the bactericidal action) NOTE: beta-lactams are time-dependent

Answer 260

1) Inflation in diastole – higher early diastolic blood pressure (via reduction of apparent internal volume of aorta) leading to improved end organ perfusion, particularly the heart. 2) Deflation as late as possible – results in reduced end diastolic pressure in the aorta, reducing afterload and myocardial O2 demand.

Answer 261

Intercostal space > caudal > epidural > brachial plexus > femoral > subcutaneous

Answer 262

Area under velocity time graph x aortic cross-section x heart rate NOTE: area under the velocity-time graph is referred to as stroke distance

Answer 263

Anode: Silver Cathode: Platinum

Answer 264

Radiofrequency (RF) energy is applied perpendicularly to the applied magnetic field at the Larmor frequency which rotates the net magnetisation of hydrogen ions in tissue. When the RF energy is switched off, net magnetisation returns to equilibrium and energy is lost to surrounding tissue. This is relaxation.

Answer 265

Frequency of the current (at 50-60 Hz the sensitivity of biological tissues to unwanted electrical stimulus is maximal)

Answer 266

900-1200 dynes.sec.cm-5

Answer 267

1-4 hours NOTE: clearance of 6-10 mL/kg/min

Answer 268

Alpha intercalated cells in the collecting duct

Answer 269

Momentum of the vanes can cause an overestimation

Answer 270

Prevent protein synthesis by binding to the 30S ribosomal subunit

Answer 271

Minimise dead space and prevent rebreathing. NOTE: tidal volume should be at least 5 times the internal filter volume

Answer 272

Cori cycle

Answer 273

Aspirin – continue. Clopidogrel and prasugrel – 7 days. Ticagrelor – 5 days. Tirofiban – 8 hours. Abciximab – 2 days.

Answer 274

More potent Leads to less histamine release Similar duration of action

Answer 275

Clindamycin, gentamicin and tetracycline inhibit protein synthesis. Clindamycin and erythromycin inhibit the 50S ribosomal subunit. Gentamicin and tetracycline inhibit the 30S ribosomal subunit.

Answer 276

Mapleson A (Magill) FGF is near the reservoir bag and APL valve is near the patient

Answer 277

Mapleson D FGF near the patient APL valve near the bag

Answer 278

Carbon dioxide maximally absorbs IR radiation at 4.3 μm and nitrous oxide at 4.5 μm, however these spectra can overlap leading to an overestimation of end-tidal CO2 measured by IR spectroscopy.

Answer 279

Nausea/vomiting, a coarse tremor, oligouria, ataxia, hyper-reflexia, nystagmus, and convulsions/coma.

Answer 280

Ratio of dead space volume (Vd) to tidal volume (Vt) is equal to: (PaCO2 - PeCO2)/PaCO2 Pa = arterial Pe = expired

Answer 281

M1: brain and secretory glands M2: heart, affects pacemaker M3: smooth muscle of bronchioles and arterioles, also found in the bladder M4: CNS M5: regulate dopamine release in the CNS

Answer 282

Radiation (loss via infrared radiation): 40% Convection (loss to air currents): 30% Evaporation (loss of heat energy due to vaporisation): 20% Respiratory losses: 5-10% Conduction (loss to direct transfer to surfaces): 5%

Answer 283

Ethyl violet – white to purple. Phenolphthalein – pink/red to white. Clayton yellow – pink/red to yellow/cream. Ethyl orange – orange to yellow. Mimosa Z – red to white.

Answer 284

Sensory: medial 1.5 digits Motor: majority of small muscles in the hand except LOAF (median nerve)

Answer 285

Patients admitted for elective surgery should have a BP below 160/100 mm Hg in primary care On the day of surgery, you can proceed if blood pressure is below 180/110 mm Hg

Answer 286

Ketamine: phencyclidine Propofol: phenol Thiopentone: barbituric acid Etomidate: imidazole

Answer 287

pKa 8.7 Relative lipid solubility: 30 x morphine Relative potency: 0.1 x morphine Vd: 4 L/kg Protein binding: 60%

Answer 288

Aminosteroids: rocuronium and vecuronium

Answer 289

Desflurane has a low boiling point, and therefore fluctuations in temperature lead to significant fluctuations in saturated vapour pressure (SVP), which unless accounted for, would lead to substantial variation in the concentration of desflurane to the patient. To avoid this, the Tec 6 vapouriser is heated to 39 degrees and therefore the delivery of desflurane is predictable.

Answer 290

Air is passed through a constriction leading to an increase in velocity and decrease in pressure (conservation of energy) as described by the Bernoulli effect. This reduction of pressure leads to entrainment of water via the Venturi effect.

Answer 291

Pentameric ligand gated ion channel 2 alpha, 1 beta, 1 delta, 1 epsilon NOTE: gamma instead of epsilon in foetus

Answer 292

Due to the increased parasympathetic tone in children compared to adults, they are prone to significant bradycardia under vagal stimulation

Answer 293

Usually 16G Huber tip with blunt leading edge and angled tip to allow catheter to be passed Lee's lines to allow measurement of depth Macintosh wings to stabilise the needle Stylet introducer to prevent coring of tissue A loss of resistance syringe is used when performing an epidural, but is not a feature of the Tuohy needle.

Answer 294

At steady state - input = output Infusion Rate = Elimination Rate Elimination Rate = Clearance (L/min) x Steady State Conc Infusion Rate/Clearance = Steady State Conc

Answer 295

Prolonged R Time: anticoagulant or clotting factor deficiency Low Max Amplitude + Long K Time: weak clot suggestive ineffective platelet or fibrinogen action Short Lysis Time + High CL30: overactivity of fibrinolytic system

Answer 296

0.22 micron mesh to prevent the passage of bacteria, viruses and foreign bodies into the epidural space.

Answer 297

Absolute: mass of water vapour in a given volume of gas at a given temperature and pressure (g/m3) Relative: ratio of actual mass of water vapour compared to maximum amount of water vapour the gas could contain at the same temp and pressure

Answer 298

NF is proportional to √(r²/clρ), where r = radius of the tubing, c = compliance, l = length and ρ = density of the fluid

Answer 299

Has a natural frequency 10x higher than the fundamental frequency (sine wave 1-2 Hz, corresponds to heart rate 60-120 bpm), Frequency range of 0.5 to 40 Hz to include the first 10 harmonics of the heart rate

Answer 300

A resonant sine wave will be superimposed on the pressure wave. This will raise the systolic blood pressure, reduce the diastolic blood pressure, but should have no effect on the mean arterial pressure.

Answer 301

As temperature increases, resistance through a thin piece of metal increases linearly Slow response time and fragile Needs Wheatstone bridge to increase sensitivity

Answer 302

Consists of a semiconductor for which there is a non-linear relationship between resistance and temperature Cheap and small so can be used for invasive monitors (e.g. pulmonary artery flotation catheter) Respond quickly to changes but can have calibration error

Answer 303

A material whose electrical conductivity is is between an conductor and an insulator Conductivity can be controlled by adding impurities (doping), applying electrical fields or increasing the temperature

Answer 304

In a semiconductor, electrons exist in two energy bands: - Valence Band: electrons are bound tightly to atoms and can't move freely - Conduction Band: electrons are free to move enabling conduction At room temperature, most electrons are in the valence band, however, applying energy (e.g. heat) enables the electrons to jump across the band gap to the conduction band so it can conduct electricity

Answer 305

Thermocouples rely on the Seebeck (thermoelectric) effect. At the junction of two dissimilar metals, a voltage will be produced in proportion to the temperature difference between two such junctions. Typically copper and constantan are the metals used. The response is nearly linear and passes through the origin as a temperature difference of zero produces zero output voltage. Multiple thermocouples in series produce a thermopile which will increase sensitivity.

Answer 306

Oculomotor Nerve Trochlear Nerve Ophthalmic Nerve (Nasociliary, Lacrimal, Frontal) Abducens Nerve Superior Ophthalmic Vein Branch of inferior ophthalmic vein

Answer 307

PHASE 1 Oxidation Reduction Hydrolysis Dealkylation Deamination

Answer 308

All twitches present < 70% occupancy 1 twitch lost = 70% 2 twitches lost = 80% 3 twitches lost = 90% All twitches lost = 95-100%

Answer 309

Q = (πr4ΔP)/8nl where r = radius, ΔP = pressure gradient, n = viscosity, l = length, Q = flow rate.

Answer 310

Q = (πr4ΔP)/8nl This is analogous to Ohm’s law (V = IR –> I = V/R), where voltage is represented by the pressure gradient, current is represented by the flow rate, and resistance is given by 8nl/πr4.

Answer 311

At the bottom (low-flow), the space between the bobbin and wall is narrow. Gas flow is laminar and dependent on viscosity. At the top (high flows) the space between the bobbin and wall is wider. Gas flow is more turbulent and dependent on density. The pressure difference across the bobbin is constant at all points in the rotameter.

Answer 312

At the bottom of a rotameter, the gap between the bobbin and tube is narrow, so flow is laminar and mainly affected by viscosity — the internal friction of the gas. At the top, the gap is wider, flow becomes turbulent, and is mainly influenced by density, which affects the inertia and turbulence of the gas.

Answer 313

They bind more readily to inactivated or open sodium channels and so affect nerves with a rapid firing rate (e.g. sensory nerves) compared to motor nerves

Answer 314

Enflurane and Isoflurane

Answer 315

Dihydrocodeine

Answer 316

1: Bolus Dose at 1.5 ml/kg over 1 min 2: Infusion at 15 mL/kg/hour 3: Second Bolus + Increase Infusion to 30 mL/kg/hour (if cardiovascular instability not sorted)

Answer 317

History of ischaemic heart disease Active GI bleeding Active GI ulceration Cerebrovascular disease CABG IBD Heart failure Peripheral vascular disease

Answer 318

Low PaO2 High PaCO2 Low pH High [H+]

Answer 319

NOT Absorbed: magnesium and aluminium Absorbed: sodium bicarbonate and sodium citrate NOTE: aluminium causes constipation whereas magnesium causes diarrhoea

Answer 320

30 mL in circuit draw-over variable bypass vaporiser NOT temperature compensated Small, cheap, lightweight Variable output

Answer 321

Variable bypass draw-over vaporiser NOT actively temperature compensated but incorporates an ethylene glycol heat sink Any anaesthetic agent can be used by changing a removable scale on the dial

Answer 322

State Entropy: calculated from low frequency range waves Response Entropy: calculated from high frequency waves including EMG activity from frontalis muscle As a patient wakes, the difference between SE and RE increases due to diminishing effect of drugs affecting the central nervous system and the increased contribution of EMG values from the frontalis muscle. RE increases more quickly than SE.

Answer 323

12 ml/kg i.e. 840 ml for a 70kg adult.

Answer 324

Derived from medial cord of brachial plexus which is comprised of nerve roots C8-T1

Answer 325

Lumbricals 1+2 Opponens Pollicis Abductor Pollicis Brevis Flexor Pollicis Brevis

Answer 326

Requires a blood sample to be taken and spectrophotometric techniques are then performed that are able to provide information regarding oxyhaemoglobin, deoxyhaemoglobin, methaemoglobin and carboxyhaemoglobin

Answer 327

Increase the boiling point by 0.51ºc (ebullioscopic constant) Decrease the freezing point by 1.86ºc (cryoscopic constant) Increase the osmotic pressure.

Answer 328

Boiling occurs when vapour pressure = atmospheric pressure Solute particles get in the way of water molecules escaping into the gas phase, thereby lowering the vapour pressure for a given temperature This means you have to heat the solution to a higher temperature to boil

Answer 329

Freezing happens when water molecules arrange into a solid crystal structure Solute particles disrupt this orderly arrangement, making it harder for water to freeze. Therefore, you must lower the temperature further to freeze the solution → freezing point goes down.

Answer 330

Median, ulnar, radial and musculocutaneous nerves at the level of the axillary artery The musculocutaneous nerve lies separately between corocobrachialis and biceps brachii, and needs significant redirection of the needle to anaesthetise it.

Answer 331

Class Ia – blocks fast Na+ channels in cardiac myocytes and prolong refractory period e.g. procainamide, quinidine, disopyramide. Class Ib – blocks fast Na+ channels in cardiac myocytes and shortens refractory period e.g. lidocaine, phenytoin, mexiletine. Class Ic – blocks fast Na+ channels in cardiac myocytes and no effect on refractory period e.g. fleicanide, propafenone. Class II – β adrenoreceptor blockade e.g. atenolol, propranolol, esmolol. Class III – K+ channel blockade e.g. amiodarone, sotalol. Class IV – Ca++ channel blockade e.g. verapamil, diltiazem.

Answer 332

Pressure generator, time-cycled, minute volume divider. Two knobs are able to change from controlled to manual and to adjust the inspiratory time. The inflation pressure is adjusted by sliding a weight to a different position on top of the main bellows. Fresh gas flow drives the ventilator. In inspiration a small bellows receives FGF and the main bellows deliver their content to the patient. During expiration the small bellows delivers their content to the main bellows until a predetermined tidal volume is reached.

Answer 333

Sevoflurane (200 g/mol)

Answer 334

Centrally acting ganglion blocking drug Functions centrally to reduce blood pressure by competitive antagonist of nicotinic acetylcholine receptors in the parasympathetic and sympathetic ganglia

Answer 335

Physical properties that are dependent on number of dissolved particles rather than the identity of the solute. Includes elevation of boiling point, reduction of freezing point, reduction in vapour pressure and change in osmotic pressure. NOTE: this is how an osmometer works

Answer 336

Clear Fluid: 20 drops Blood: 15 Drops

Answer 337

Method of continuous, non-invasive blood pressure measurement. A small cuff placed around the finger is inflated or deflated by a controller system to keep the blood volume in the finger constant (as measured by plethysmography). The applied pressure to keep blood volume constant is comparative to arterial blood pressure.

Answer 338

If it was added earlier to the mixture, a crack in an adjacent flowmeter will mean that the oxygen follows the path of least resistance and escapes via the cracked flowmeter rather than to the patient - thereby delivering a hypoxic mixture

Answer 339

15% of cardiac output at rest Which is around 750ml/min

Answer 340

Supraventricular only: digoxin, verapamil, adenosine. Ventricular only: lidocaine, phenytoin. Both: amiodarone, beta-blockers, disopyramide, procainamide, fleicanide.

Answer 341

Avoid the risk of inducing ventricular fibrillation Risk is highest around 50-60Hz, which is the frequency of mains electricity

Answer 342

Chloride - 115-125 mmol/L

Answer 343

VENOUS: 10% dissolved, 60% bicarbonate, 30% carbamino ARTERIAL: 5% dissolved, 90% bicarbonate, 5% carbamino

Answer 344

Potency: lipid solubility (more lipid soluble, more potent) Duration of Action: protein binding (higher protein binding, longer duration) Speed of Onset: pKa (lower pKa, faster speed of onset)

Answer 345

36.5 degrees

Answer 346

95% protein boud Vd of 2-70 L/kg Half-life of 20-100 days

Answer 347

The pump used to generate vacuum should be able to generate a negative pressure of -400 mmHg or 53 kPa. The minimum requirement of suction is to generate a vacuum of 500 mmHg in 10 seconds with a displacement of air of 25 L/min as such it is considered a high pressure, low flow system.

Answer 348

PCT: carbonic anhydrase inhibitors Ascending limb loop of Henle: osmotic and loop diuretics Early DCT: thiazide diuretics DCT: potassium sparing diuretics Late DCT and Collecting Duct: aldosterone antagonists

Answer 349

Flow is proportional to the radius squared Flow is proportional to the square root of the pressure gradient Flow is inversely proportional to the length and density of the fluid

Answer 350

Carotid artery Internal jugular vein Vagus nerve

Answer 351

184.5 NOTE: it is a structural isomer of isoflurane

Answer 352

Initially a high output of 1-3 mA is chosen and the needle advanced slowly towards the nerve until contraction is noted. The output is then reduced until maximal stimulation is achieved with minimum output from the nerve stimulator. Typically 0.3-0.5 mA suggests the needle tip is touching or very close to the nerve. If contraction occurs at ≤ 0.2mA it suggests that the needle tip is intraneural and should be withdrawn.

Answer 353

Heat energy lost When a ferromagnetic material is placed in a magnetic field, it will become magnetised (O to A) When the field is removed, it remains weakly magnetised (A to B) Area within the loop is heat loss

Answer 354

PV = nRT P = pressure (Pa) V = volume of gas (m³) n = number of moles (mole) R = ideal gas constant (8.31 J/K/mol) T = temperature (Kelvin)

Answer 355

Rate of Diffusion is proportional to: Area x Concentration Gradient/Thickness

Answer 356

EMF describes the driving voltage of a battery Voltage is known as potential difference and represents the difference in electric potential between two points in a circuit

Answer 357

Process of rendering an object free from all pathogenic organisms excluding bacterial spores

Answer 358

Method of disinfection that uses temperatures of 70 °c for 30 minutes

Answer 359

At least hourly

Answer 360

CPP = DBP – LVEDP

Answer 361

Low dose (< 5 µg/kg/min): increased renal blood flow through agonism of D1 and D2 Moderate dose (5-10): beta adrenoceptor agonist with positive inotropy High dose (> 15): alpha agonist causing vasoconstriction

Answer 362

Prilocaine

Answer 363

Increased sodium and calcium permeability, which favours a more rapid depolarisation towards threshold potential during phase 4

Answer 364

Mapleson D

Answer 365

Absorption of energy by an oscillating or precessing system. Precession refers to the movement of nuclei around a magnetic field.

Answer 366

All block fast Na channels in cardiac myocytes Class Ia – PROLONGS the refractory period e.g. procainamide, quinidine, disopyramide. Class Ib – SHORTENS the refractory period e.g. lidocaine, phenytoin, mexiletine. Class Ic – NO EFFECT on the refractory period e.g. fleicanide, propafenone.

Answer 367

Oesophageal barrier pressure = lower oesophageal sphincter pressure – intragastric pressure

Answer 368

Needle contacts the anterior tubercle of C6 (Chassaignac's tubercle) NOTE: the stellate ganglion lies at C7 formed by the fusion of the inferior cervical and T1 ganglia

Answer 369

Between the second and third tracheal cartilage rings

Answer 370

Measurement of total magnetic field passing through a given area NOTE: when divided by the size of the area, it is called magnetic flux density

Answer 371

Magnetic Flux: Weber (Wb) Magnetic Flux Density: 1 Tesla = 10,000 Gauss NOTE: 1 Tesla = 1 Wb/m²

Answer 372

The point at which inspired air reaches 37ºc and a relative humidity of 100%. This is normally achieved a few centimeters distal to the carina.

Answer 373

Stewart-Hamilton equation

Answer 374

Normal saline is pressurised to 300 mmHg and runs at a rate of 2-4 ml/hr via a flushing device. This prevents clot formation, keeping the arterial line patent and reducing damping.

Answer 375

Removes a specific frequency from a signal

Answer 376

Ergometrine can cause coronary vasospasm and hypertension and therefore is contraindicated in pre-eclampsia.

Answer 377

It neutralises upstream circuit noise (i.e. rejects signals common to both inputs)

Answer 378

Obstruction of the common gas outlet can cause rising pressure within the circuit that can transmit gases back into the anaesthetic machine causing damage and contamination This valve opens at 35-40 kPa of pressure

Answer 379

Atlantoaxial instability Atlas = C1 Axis = C2

Answer 380

The absorption spectra of carboxyhaemoglobin and oxyhaemoglobin are similar at 660 nm. This leads to an overestimation via spectrophotometric methods of SpO2.

Answer 381

The fluid requirement in the first 24 hours is equal to 4ml x weight (kg) x %burns Half of this is given in the first 8 hours, and the remainder in the remaining 16 hours.

Answer 382

Air: 4-5 hours 100% Oxygen: 1 hour

Answer 383

4-10 mg/kg

Answer 384

Autosomal recessive mutation on chromosome 3

Answer 385

Originates as a continuation of the sigmoid sinus Exits the jugular foramen Runs through the neck to subclavian vein

Answer 386

Probenecid is a renal tubular blocking agent. Penicillins are normally excreted via tubular secretion in the nephron. Blocking this secretion increases plasma levels approximately 2-4 times.

Answer 387

Z = d/fa Where Z = impedance, d = distance between the plates, f = frequency of current and a = area of plates.

Answer 388

Flow of 35-75 L/min Pressure of 4 bar Bypassing the flowmeters and vaporiser

Answer 389

Yellow – breathing filters for viruses, bacteria and particulate matter. Blue – heat and moisture exchange. Green – heat and moisture exchange and filter.

Answer 390

Calculates the electrical potential for an INDIVIDUAL ion, and thus allows for the estimation of how each ion affects the membrane potential.

Answer 391

Membrane potential = RT/ZF x ln (extracellular concentration/intracellular concentration) where R = universal gas constant T = temperature (kelvin) Z = Valency F = Faraday’s constant ln = natural logarithm

Answer 392

Phenoxybenzamine Non-selective irreversible alpha antagonist (new receptors must be synthesised to overcome the effect)

Answer 393

Mu-1 = analgesic + physical dependance Mu-2 = respiratory depression, reduced peristalsis, euphoria and meiosis

Answer 394

Brain Leads to analgesia, antidepressant effect and physical dependence

Answer 395

Brain and spinal cord Leads to spinal analgesia, sedation and miosis

Answer 396

Brain and spinal cord Leads to anxiety, depression, appetite modulation, and is thought to be involved in tolerance

Answer 397

Apixaban, rivaroxaban and edoxaban

Answer 398

The theory that mechanical work may be transferred to heat energy and heat energy to work, the magnitude of one being proportional to the other. This is the principle used in the generation of electricity in coal power stations.

Answer 399

PVR = 80 x (Mean pulmonary artery pressure – Left atrial pressure)/Cardiac output. NOTE: multiplying by 80 is the factor required to change from mmHg·min/L to dyne.s-1.cm-5

Answer 400

1 – neonates up to 5 kg, cuff volume 4 ml. 1.5 – infants 5-10 kg, cuff volume 7 ml. 2 – children 10-20 kg, cuff volume 10 ml. 2.5 – children 20-30 kg, cuff volume 14 ml. 3 – adults 30-50 kg, cuff volume 20 ml. 4 – adults 50-70 kg, cuff volume 30 ml. 5 – adults 70-100 kg, cuff volume 40 ml. 6 – adults over 100 kg, cuff volume 50 ml.

Answer 401

Uncoupling of opioid receptors from their G-protein, which underpins the decreased receptor sensitivity that is observed

Answer 402

pCO2 in blood Consists of a measuring electrode (silver/silver chloride) and reference electrode (mercury/mercury chloride) surrounded by film of NaHCO3 and permeable teflon membrane allowing CO2 to diffuse from sample to solution In solution, CO2 is converted to H+ via CA H+ interact with buffer around reference electrode leading to potential difference between two electrodes which leads to voltage that correlates with pCO2

Answer 403

Carotid bodies have high flow so get all of their oxygen from dissolved O2 - therefore mainly responds to changes in pO2 (ventilatory) Aortic bodies have lower flow and respond to changes in both oxygen tension and oxygen content

Answer 404

13700 kPa (137 bar) + 101 kPa (≈1 bar) = 13800 kPa NOTE: once filled, if taking up Mount Everest, the absolute pressure does not change because it is sealed

Answer 405

Stimulation causes increased adenylate cyclase activity Increased cAMP Activation of PKA Activation of myosin light chain phosphatase Smooth muscle relaxation

Answer 406

The process of rendering an object free from all pathogenic organisms except bacterial spores.

Answer 407

The process of rendering an object free from all pathogenic organisms including bacterial spores.

Answer 408

The process of removing contaminants such that they are unable to reach a site in sufficient quantities to initiate an infection. Consists of cleaning, disinfection and sterilisation.

Answer 409

The ideal blood pressure cuff bladder length is ≥ 80% of the patient’s arm circumference and the width is ≥ 40% of the patient’s arm circumference.

Answer 410

Isolated forearm technique The forearm is isolated with a tourniquet prior to injection of muscle relaxant. This means if the patient is aware but ‘paralysed’ they would still be able to indicate using this hand.

Answer 411

The primary bile acids in humans are cholic acid and chenodeoxycholic acid. Secondary bile acids are formed within the colon from primary bile salts via the action of bacterial flora. Examples include lithocholic acid and deoxycholic acid.

Answer 412

Bound to Gq subunit Activation leads to cleavage of PIP2 to IP3 and DAG This leads to increased calcium entry

Answer 413

Genetic polymorphisms 50% of Caucasians are slow acetylators

Answer 414

Inotropic component, represents myocardial contractility. A slow rise suggests inotropes are needed.

Answer 415

Represents systemic vascular resistance. Low SVR has a steep downstroke and low dicrotic notch. High SVR has a shallow downstroke and high dicrotic notch.

Answer 416

Stroke volume

Answer 417

4x 50 mA stimuli being delivered at a rate of 2 Hz

Answer 418

Silver and Mercury

Answer 419

Retrieval (via a low pressure suction) Filter (150 microns) Centrifuge Disposal of waste Wash and resuspension Reinfusion (solution with haematocrit 60%)

Answer 420

Pneumatically powered oxygen failure alarm based on a single stage regulator When oxygen pressure falls, the force pushing up on the diaphragm reduces to less than the opposing force of the spring. This opens the poppet valve allowing oxygen to flow through the whistle. Must have auditory sound of at least 60 dB lasting 7 seconds

Answer 421

When oxygen pressure falls below 200 kPa

Answer 422

Ambient air is filtered and pressurised to 137 kPa It enters one of the parallel towers on either side of the mix tank Air is forced through a molecular sieve made from zeolite (aluminium and silica crystals) which attracts nitrogen but allows oxygen to pass A changeover switch is operated to pressurise the alternate tower and nitrogen is removed from the first tower by using a vacuum allowing the zeolite to regenerate

Answer 423

In the CSF: Calcium: Lower Sodium: Similar H+: Higher Magnesium: Higher Chloride: Higher

Answer 424

Mimics the effect of motilin by acting as an agonist at motilin receptors at the gastric antrum and proximal duodenum.

Answer 425

Nitrofurantoin Amiodarone Azathioprine Bleomycin Bisulfan Chlorambucil Cyclophosphamide Methotrexat Mitomycin Sulfasalzine

Answer 426

c = f λ where c = speed of light (m/s) f = frequency (Hz), and λ = wavelength (m)

Answer 427

E = h f where h is Planck’s constant

Answer 428

Immediate – failure, haemorrhage, tube misplacement, occlusion of tube by herniated cuff, occlusion of tube by tracheal wall. Delayed – blockage with clot or secretions, overinflation of cuff leading to mucosal ulceration. Late – granuloma formation, persistent sinus, scar formation, tracheal dilatation.

Answer 429

Monitoring: 0.5 to 40 Hz Diagnostic: 0.05 to 100 Hz

Answer 430

Weight = (age+4) x2

Answer 431

300 mcg intramuscularly In the theatre setting, 0.1ml/kg intravenously of 1:100,000 (1ml of 1:10,000 diluted into 10ml) may be used instead.

Answer 432

1 gram of adrenaline in 1000 mL (e.g. 1 mg/mL) 1 in 10,000 = 100 mcg/mL 1 in 100,000 = 10 mcg/mL

Answer 433

t1/2 = 0.693 x Vd/Cl t1/2 = 0.693/k t1/2 = 0.693 x time constant

Answer 434

Stimulation of the ophthalmic nerve (CN Va) by traction on the extraocular muscles leads to a significant increase in vagal outflow, which can cause asystole.

Answer 435

Don't need laryngoscopy Improved cardiovascular stability (whereas you get hypertension with laryngoscopy) Less rise in intra-ocular pressure Decreased coughing on emergency

Answer 436

Non-cardioselective beta-blocker. It blocks both α1 and β receptors. The ratio of α to β blockade is dependent upon the route of administration. When given orally the ratio is 1:3 (α to β) and 1:7 when given intravenously.

Answer 437

Synthetic beta-2 and dopamine receptor agonist

Answer 438

Selective phosphodiesterase III inhibitors

Answer 439

Selective phosphodiesterase V inhibitors

Answer 440

Zygoma and the greater wing of sphenoid

Answer 441

It is converted to pyruvate by lactate dehydrogenase in the cytoplasm of cells Pyruvate can then enter the mitochondria and enter the Krebs cycle or may be converted to glucose in the liver or kidneys In skeletal muscle, 75% of lactate produces is oxidised and used as a fuel source Gluconeogenesis is an aerobic process. It is more efficient when muscle activity stops.

Answer 442

Steam (gold-standard) via an autoclave Ethylene oxide Hydrogen peroxide gas plasma Ozone Ionising radiation Dry hot air

Answer 443

Performed in an autoclave and is highly effective, non-toxic and inexpensive. There are 4 variable parameters: steam, pressure, temperature and time. Sterilisation is achieved using temperatures of 121 ºc for 30 minutes or 132 ºc for 4 minutes at a pressure of 2.25 bar. Heat-labile materials such as plastics often may not be sterilised via steam.

Answer 444

Vanillylmandelic acid (VMA) by COMT and MAO

Answer 445

Quartz crystals exhibit a natural resonant frequency when stimulated. Two crystals are used, one of which is coated in a lipid layer. The lipid layer is able to absorb volatile anaesthetic agents which will change the resonant frequency. The change of frequency is directly proportional to the partial pressure of volatile.

Answer 446

Floor of the fourth ventricle

Answer 447

The absorbance of light is equal to log(I0/I1) = αlc Where α = extinction coefficient, l = path length and c = sample concentration.

Answer 448

Umbilical vein: 80-90% Aorta: 65-70% Umbilical artery: 40%

Answer 449

Osmolarity is a measure of the number of osmoles (osmotically active particles) per litre of solution. Osmolality is the number of osmoles per kg of solvent. Osmolality is preferred as the volume of solvent changes slightly with temperature, however its weight does not.

Answer 450

Direct renin inhibitor Prevents conversion of angiotensinogen to angiotensin I

Answer 451

Upper airway – 40 μm. Bronchi/bronchioles – 8-15 μm. Peripheral conducting airway – 3-5 μm. Alveoli – 0.8-3 μm.

Answer 452

Nitrous Oxide: 1800 L Oxygen: 680 L NOTE: as nitrous oxide is a liquid, it can store more

Answer 453

52 bar This is the saturated vapour pressure of nitrous oxide at 20 ºc, and is therefore the cylinder pressure of a full nitrous oxide cylinder. At 15 degrees the answer would be 44 bar.

Answer 454

Cathode reaction (platinum): O2 + 2H2O + 4e– -> 4OH– Electrolyte reaction: 4NaCl + 4OH– -> 4NaOH + 4Cl– Anode reaction (silver): 4Ag + 4Cl– -> AgCl + 4e–

Answer 455

May cause oligohydramnios and poor renal development

Answer 456

Elimination (mg/min) = concentration (mg/ml) x clearance (ml/min)

Answer 457

TWO mechanisms - Blockage of the α2δ subunit of L type voltage gated calcium channels - Modulating GAD (glutamic acid decarboxylase) - leading to increased levels of GABA

Answer 458

In the intercalated cells of the collecting duct, you find H+/K+ exchangers. In acidosis, more hydrogen ions are excreted into the urine which leads to the retention of potassium

Answer 459

Left facing bevel allows an optimal view of the glottis and the tip of the endotracheal tube together. As the tube is inserted from the right side of the mouth, a left facing bevel means the tip of the tube can be more easily visualised as it is sited between the vocal cords.

Answer 460

Primary means of elimination of ammonia (mitochondria and cytosol of hepatocytes) Ammonia is converted to carbamoyl phosphate by carbamoyl phosphate synthetase (rate-limiting) Carbamoyl phosphate reacts with ornithine to form citrulline Citrulline is converted to urea

Answer 461

Adenine is able to increase red cell ATP levels, thereby increasing red cell survival to 35 days

Answer 462

Allows a greater volume of plasma to be removed from the blood in order to use FFP as a source of coagulation factors

Answer 463

PC BRAS Phenytoin Carbamazepine Barbiturates Rifampicin Alcohol (chronic) Sulfonylureas

Answer 464

O DEVICES Omeprazole Disulfiram Ethanol (acute) Valproate Isoniazid Cimetidine Erythromycin Sulfonamides

Answer 465

The current travelling between the two electrodes minimises the risk of the current travelling through the pacemaker

Answer 466

Date of test Test pressure Chemical formula for gas Tare weight

Answer 467

Consists of a silver tube filled with ether with a thermometer. Air is bubbled through the ether causing a drop in temperature (latent heat of vaporisation). Condensation forms on the silver tube at the dew point. The temperature at which this occurs may be used to calculate the relative humidity using look up tables.

Answer 468

Directs IVC (placental, high‑O₂) flow across the foramen ovale → left atrium → left ventricle → carotids. Keeps SVC (brain‑desaturated) blood in the right heart → pulmonary artery → ductus arteriosus → placenta. Net effect: the fetus sends its most oxygen‑rich blood to the brain while shunting lower‑O₂ blood back for re‑oxygenation.

Answer 469

F=ρghA where ρ = density of the fluid g = acceleration due to gravity h = height (depth) of the fluid column A = cross‑sectional area

Answer 470

CUFFED: (age/4) + 3.5 UNCUFFED: (age/4) + 4

Answer 471

Nitric oxide activates guanylate cyclase which converts GTP to cGMP Increased cGMP leads to decreased calcium entry to cells which therefore causes vasodilation

Answer 472

Single‑use, balloon‑type infusion pump for continuous drug delivery on the move. Consists of: Balloon (100–600 mL) is filled and stretched; recoil pushes drug out. Flow restrictor fixes rate (~5–10 mL/h). Optional squeeze chamber after restrictor lets patient give extra bolus (PCA); refilling time = lock‑out.

Answer 473

SMMACKK Seconds (s) – time Mole (mol) – amount/quantity of substance Metre (m) – length Ampere (A) – electrical current Candela (cd) – intensity of illumination Kelvin (K) – thermodynamic temperature Kilogram (kg) – mass

Answer 474

It can precipitate out of solution

Answer 475

660 nm: oxy absorbs LESS than deoxy 805 nm: isobestic point 940 nm: oxy absorbs MORE than deoxy

Answer 476

Interception: > 1 µm Intertial Impaction: >0.5-1 µm Gravitational settling: >5 µm Brownian diffusion: < 0.5 µm Electrostatic interaction – charged particles are attracted to oppositely charged fibres on the filtration medium

Answer 477

Lateral ventricles Via foramen of Monro into the third ventricle Via aqueduct of Sylvius to fourth ventricle From fourth ventricle into the subarachnoid space via: - Foramen of Magendie medially - Foramen of Luskha laterally Reabsorption into dural venous sinuses

Answer 478

Inhibit DNA synthesis by inhibiting DNA gyrase and topoisomerase.

Answer 479

Inhibit protein synthesis by binding to the 50S ribosomal subunit

Answer 480

Zone 1 (peri‑portal) – high O₂ and nutrients → energy‑intensive tasks: glycogenolysis, gluconeogenesis, β‑oxidation, cholesterol synthesis. Zone 3 (centrilobular) – low O₂, rich in CYP‑450 → drug and toxin biotransformation.

Answer 481

Aka thermoelectric effect The generation of a voltage at the junction of two dissimilar metals which varies according to temperature

Answer 482

High volume (e.g. Bier's block, FIB, epidural) Increased vascularity (e.g. paravertebral)

Answer 483

Left-facing bevel: better view of tip Murphy's eye: allows ventilation if tip obstructed Magill curve: follows anatomy of upper airway Low pressure, high volume cuff Vocal cord guide

Answer 484

14G (orange) 270 ml/min. 16G (grey) 180 ml/min. 18G (green) 80 ml/min. 20G (pink) 54 ml/min. 22G (blue) 31 ml/min.

Answer 485

Transformer NOTE: it is used in a defibrillator circuit to step up the voltage

Answer 486

50% This leads to an increase in GFR meaning that a low creatinine is to be expected in pregnancy

Answer 487

LATERAL: medial border of sartorius MEDIAL: lateral border of adductor longus Contains femoral nerve, artery and vein, and the femoral canal (which contains lymphatics and loos connective tissue)

Answer 488

I: chamber(s) paced – V (ventricle), A (atrium), D (ventricle and atrium), O (none). II: chamber(s) sensed – V (ventricle), A (atrium), D (ventricle and atrium), O (none). III: mode of response – T (triggered), I (inhibited), D (triggered or inhibited), O (none). IV: programmable functions – R (rate modulated), O (none). V: multi-site pacing – O (none), A (atria), V (ventricles), D (dual).

Answer 489

Two or more substances mixed together where the heavier substance will eventually settle out under gravity.

Answer 490

A type of mixture where a substance is evenly dispersed through another which will not settle out under gravity. It may be made of solids, liquids and gases and consists of an internal phase (small particles) and an external phase through which internal phase is dispersed.

Answer 491

It is a ‘liquid in liquid’ colloid or a colloidal mixture of two or more immiscible liquids. Energy input is required from shaking or stirring and emulsifiers may be used to provide stabilisation.

Answer 492

Dye dilution is susceptible to a recirculation hump where the dye returns to the heart and is pumped around again

Answer 493

Describes the separation of ions by a balancing act of electrostatic forces and concentration gradients. This is the underlying principle of the resting membrane potential. The Na/K ATPase pumps 3 Na out and 2 K in. The cell is more permeable to K, which then exit the cell down their concentration gradients. However, negative charged molecules, such as proteins, are unable to follow. Therefore, the extracellular environment is positively charged relative to the intracellular environment. This is the resting membrane potential.

Answer 494

Flow time is the duration of forward blood flow (corrected means adjusted to heart rate by dividing by √cycle time) Low FTC = impeded filling or emptying (e.g. hypovolaemia, mitral stenosis, PE) High FTC = vasodilated circulation (e.g. sepsis) A normal FTC is 330-360ms.

Answer 495

A process that allows the basic removal of plasma water (ultrafiltrate) from the blood together with very small molecules via solvent drag. It is primarily used to correct volume overload and does not require replacement of body fluid. Typical pore size is approximately 20 kDa.

Answer 496

Prevent transmission of accidental movements of the breathing system to the endotracheal tube

Answer 497

600 mL per day 90% absorbed in the terminal ileum

Answer 498

Antistatic flooring (mean resistance of 20-50 kiloohms) Theatre crocs are antistatic Rotameters on machine are antistatic Relative humidity kept above 50%

Answer 499

1 in 20,000

Answer 500

Severe aortic regurgitation Aortic dissection Sepsis Severe peripheral vascular disease

Answer 501

Limb ischaemia (thromboembolism or mechanical obstruction) Bleeding Infection Balloon rupture

Answer 502

P-Amino Benzoic Acid (PABA)

Answer 503

One single mark at the tip so that it may be identified on removal They have 5 single markings at 1 cm intervals from 5-9 cm, a double marking at 10cm, 1cm intervals from 10-14cm, a triple marking at 15cm and then quadruple markings at 20cm.

Answer 504

Pethidine Tramadol

Answer 505

Inductor One Henry is the inductance when one ampere flowing in a coil generates a magnetic field strength of one weber i.e. H = Wb/A.

Answer 506

An electrical component that stores energy in a magnetic field when current flows through it It opposes any change in the current flowing through it which is useful for smoothing our surges

Answer 507

Exit between the anterior and middle scalenes, before running in close proximity with the subclavian artery.

Answer 508

A Wheatstone bridge measures an unknown resistance (Rx) by balancing two resistor ratios: R3/R1 = Rx/R2. When balanced, the voltage between branches is zero. This high sensitivity allows precise detection of small changes, like in arterial line transducers where it filters out common noise.

Answer 509

1: idiopathic 2: secondary to left sided heart disease 3: secondary to chronic hypoxia or lung disease 4: secondary to chronic thromboembolism 5: rarer causes.

Answer 510

Thiopentone Sevoflurane Ketamine Oxycodone Ephedrine

Answer 511

Sodium channel blockers Calcium current inhibitors GABA enhancers Glutamate blockers Carbonic anhydrase inhibitors Calcium channel blockers Other

Answer 512

Phenytoin Carbamazepine Lamotrigine

Answer 513

Ethosuximide

Answer 514

GABA enhancer: levetiracetam GABA-A agonists: benzodiazepines, barbiturates GABA reuptake inhibitor: tiagabine GABA transaminase inhibitor: vigabatrin GAD modulators: gabapentin, valproate

Answer 515

NMDA blocker: felbamate AMPA/kainate blocker: topiramate

Answer 516

They do NOT act on GABA receptors They bind to α2δ subunit of voltage gated calcium channels and reduce calcium influx into presynaptic neurons. This inhibits the release of excitatory neurotransmitters such as glutamate, norepinephrine, and substance P. The result is decreased neuronal excitability, which helps control seizures and reduce neuropathic pain.

Answer 517

Modulates synaptic neurotransmitter release through binding to synaptic vesicle protein (SV2A) in the brain

Answer 518

Spontaneous: efficient - FGF must equal the minute volume Controlled: inefficient - high pressure forces fresh gas out of the APL, FGF of 2-3 x minute volume needed to prevent rebreathing

Answer 519

70-110 mL/kg/min

Answer 520

60% ester hydrolysis by non-specific esterases 40% Hofmann degradation (slows in acidosis and cold)

Answer 521

COCP Sulfonamides Salicylates Penicillins Iodides Tetracyclines

Answer 522

pH < 4 (in vial) midazolam is ionised and exists in an open ring structure which is water soluble pH > 4 (in blood) midazolam forms a lipophilic, closed ring structure

Answer 523

The nucleus contains an uneven number of protons and neutrons The direction of spin is perpendicular to the axis of rotation

Answer 524

Water vapour content of expired gas Inspiratory and expiratory flow rates (slower means more time that gas is in contact with HMEF material) Volume of HMEF material (larger = more efficient) Thermal conductivity (low conductivity maintains greater temperature difference between either side of the HMEF and enables more heat and moisture to be transferred)

Answer 525

Inhibit formation of ergosterol from lanosterol via inhibition of lanosterol 14 α-demethylase e.g. fluconazole, voriconazole, itraconazole.

Answer 526

Amphotericin bind to ergosterol and create pores in the fungal cell membrane resulting in a disrupted electrochemical gradient and cell death. NOTE: they are nephrotoxic e.g. amphotericin B, nystatin.

Answer 527

Inhibit β1-3 glucan synthase. They are used to treat invasive candidiasis e.g. caspofungin, anidulafungin, micafungin.

Answer 528

Azoles (e.g. fluconazole) Polyenes (e.g. amphotericin) Echinocandins (e.g. anidulafungin)

Answer 529

Vomiting Alopecia Liver toxicity Pancreatitis/pancytopenia Retention of fat Oedema Appetite increase Tremor Enzyme inhibition

Answer 530

Mean right atrial pressure: 0-5 mmHg. Right ventricular pressure: 20-30/0-5 mmHg. Pulmonary artery pressure 20-30/10-20 mmHg. Pulmonary capillary wedge pressure: 6-12 mmHg.

Answer 531

4 produced, 2 consumed – 2 ATP gain. 2x NADH yield 6 ATP in oxidative phosphorylation.

Answer 532

2x NADH yield 6 ATP

Answer 533

Direct production of two ATP. 6x NADH yield 18 ATP and 2x FADH2 yield 4 ATP

Answer 534

Deuterium oxide Inulin – Extracellular fluid Plasma – Radiolabelled albumin, Evan’s blue Red cell volume – Radiolabelled red cell

Answer 535

Radiolabelled albumin Evan's blue

Answer 536

Ulnar nerve Innervates adductor pollicis and is easily accessible during surgery Correlates closely with return of function to the muscles that are most sensitive to neuromuscular blockade

Answer 537

Class III antiarrhythmic (blocks K+ channels thereby slowing depolarisation and increasing action potential duration) IT also shows class I, II and III properties

Answer 538

IV Loading dose is 300mg diluted in 5% dextrose over 1 hour followed by 900mg over 24 hour ORAL 200 mg TDS for 1 week, then 200 mg twice daily for a further week, followed by maintenance dose, usually 200 mg daily or the minimum dose required to control arrhythmia

Answer 539

Prolonged QT Pneumonitis Peripheral neuropathy Corneal microdeposits (not anterior uveitis) Cirrhosis Photosensitive slate-grey skin Hypo or hyperthyroidism

Answer 540

Excess heparin (acidic) Old blood (continued anaerobic metabolism leads to lower pH)

Answer 541

Weak bases

Answer 542

Immune mediated process that takes around 5 days to develop after starting heparin therapy Caused by production of IgG antibodies to heparin once it has bound to platelet factor 4 (PF4). The antibodies attach themselves to the heparin-PF4 complex and activate other platelets leading to thrombosis and a fall in platelet count.

Answer 543

4Ts score Magnitude of platelet fall Timing of platelet fall Thrombosis or other sequelae Other potential causes of thrombocytopaenia

Answer 544

Increased K+ (from cell death) Fall in pH (from cell death) Fall in 2,3-DPG leads to left shift in oxyhaemoglobin curve

Answer 545

Immediate reversal after RSI: 16 mg/kg Deep block (1-2 twitches on post-tetanic count): 4 mg/kg Moderate block (2 twtiches on ToF): 2 mg/kg NOTE: no dose alteration in renal impairment

Answer 546

EXTRAVASATION: alkaline so causes significant localised tissue damage INTRA-ARTERIAL: crystallises and occludes distal vasculature NOTE: intra-arterial injection can be managed with an intra-arterial injection of papaverine or a sympathetic block of the affected limb

Answer 547

Voriconazole NOTE: fluconazole is usually the antifungal of choice for most other candida infections

Answer 548

Pulse oximetry: 20 seconds Capnography: 3.8 seconds

Answer 549

INCREASED AFFINITY Increased pH Decreased Temp Decreased 2,3-DPG Decreased pCO2 Methaemoglobinaemia Carbon monoxide

Answer 550

DECREASED AFFINITY Reduced pH Increased temp Increased 2,3-DPG Increased pCO2 Anaemia Pregnancy Altitude

Answer 551

Reversible ADP receptor (P2Y12) inhibitor Administered IV with rapid onset Plasma half-life of 3-5 mins Does NOT require activation by the liver

Answer 552

Excess lactate from the muscles is transported to the liver where it undergoes gluconeogenesis (spends 6 ATP) Pyruate is generated which can be used in the Kreb's cycle Can only occur under aerobic conditions New glucose is transported to the muscle where it is used for glycolysis or converted to glycogen and stored

Answer 553

Location in the breathing circuit Gas composition Gas temperature Humidity Dead space

Answer 554

Supersaturation A temporary state where water vapour exceeds saturation because condensation hasn't yet occurred Ultrasonic humidifiers can create this by releasing ultra-fine droplets that elevate moisture levels in a very efficient way

Answer 555

Amplifier: amplifies small biological signals Filters: isolate the relevant frequency range (i.e. excluding artefact) Analogue-to-digital converters Microprocessors: interpret and display data

Answer 556

0.3 µm NOTE: efficiency size refers to the particle size that is hardest for the filter to capture because it's too small for interception, inertial impaction and gravitational settling, and too large for Brownian motion

Answer 557

It is a prodrug Once converted to its active form, it inhibits thyroid peroxidase Interferes with the synthesis of T3 and T4

Answer 558

Yohimbine Trazodone

Answer 559

Phentolamine Labetalol Phenoxybenzamine NOTE: α1 >> α2

Answer 560

Magnetic hysteresis loop. The axis represent: H – magnetic field applied in Weber, B – magnetic flux density in Tesla. OA – initial magnetisation. AB – magnetic field removed, flux density does not return to 0 therefore object remains weakly magnetised. BA – magnetisation if magnetic field reapplied. BC – magnetising force of reversed polarity required to fully demagnetise material. CD – larger reversed polarity magnetic field required to saturate in opposite direction. DA – further reversal of polarity of magnetic field.

Answer 561

A CR circuit consists of a capacitor and resistor in series. It acts as a high-pass filter, allowing high-frequency signals to pass while blocking low-frequency signals (like DC). It's commonly used in signal processing to remove unwanted low-frequency noise.

Answer 562

Argon (400-600 nm): visible blue/green lasers. Used in ophthalmic surgery. Nd:YAG (1060 nm): near infrared and used for endoscopic surgery CO2 (10,600 nm): far infrared, poor tissue penetration, used for superficial airway surgery

Answer 563

Dual-circuit, gas-vapour injection vaporiser designed for desflurane Has a sealed, heated vaporising chamber (39 degrees at 2 atmospheres) to keep desflurane in vapour form It injects precise amounts of desflurane into the FGF downstream A differential pressure transducer sense FGF pressure and two pressure regulating resistors adjust internal desflurane vapour pressure to match FGF pressure (enables reliable injection of desflurane) The second resistor sets the output concentration

Answer 564

Glass absorbs infrared radiation and would decrease the amount of infrared reaching the detector

Answer 565

Peptide hormone produced in the liver that inhibits iron absorption and transport by binding to ferroportin channels in the basolateral membrane of enterocytes This prevents iron from leaving the enterocytes

Answer 566

< 1 hour after a long infusion

Answer 567

Weak bases

Answer 568

There is a perceived lack of glucose because the glucose cannot enter cells

Answer 569

Based on metabolism Class 1: captopril – an active drug with active metabolites. Class 2: enalapril and ramipril are prodrugs which become active after hepatic metabolism. Class 3: lisinopril – an active drug which is excreted unchanged.

Answer 570

Local anaesthetics bind more readily to inactivated or open sodium channels and as such will preferentially affect nerves with a rapid firing rate (i.e. sensory nerves) in comparison to those with a lower firing rate (i.e. motor nerves).

Answer 571

In MRI, relaxation refers to the process by which net magnetisation returns to equilibrium after the radiofrequency (RF) pulse is turned off. This occurs through two mechanisms: T1 relaxation (spin-lattice): the time taken for magnetisation to realign with the main magnetic field by releasing energy to surrounding tissue. T2 relaxation (spin-spin): the time taken for protons to lose phase coherence with each other in the transverse plane. T1 reflects recovery of alignment; T2 reflects loss of synchrony. Both are negative exponential processes and vary by tissue type.

Answer 572

Mapleson F (Jackson-Rees modification of Ayre’s T-piece) cannot be attached to scavenging, and therefore exhaled gas will exit through the end of the reservoir bag directly into the environment.

Answer 573

Between the internal surface of the internal oblique and the external surface of transversus abdominus This is where local anaesthetic is injected for a TAP block

Answer 574

Primarily by blocking serotonin and noradrenaline transporters on the pre-synaptic membrane Other effects - Cardiac sodium and calcium channel blockers - 5HT antagonist - Alpha-1 antagonist - NMDA antagonist - H1 and H2 antagonist - Muscarinic antagonist

Answer 575

When the blood-brain-barrier is intact mannitol is unable to cross. If this membrane is disrupted by trauma then mannitol may cross making cerebral oedema much worse. For this reason it should only be given under the advice of a neurosurgeon.

Answer 576

Thiopentone Derived from barbituric acid which is comprised of two nitrogen and four carbon molecules, with their respective side groups. Alteration of the side groups around this ring is what forms other barbiturates, including phenobarbitone.

Answer 577

The method of cycling determines when a ventilator changes from its inspiratory phase to expiratory phase. Most commonly time cycled ventilators are used, i.e. the expiratory phase begins after a pre-set inspiratory time is reached. Flow cycling is less common in newer machines.

Answer 578

Both nitrous oxide and carbon dioxide have the same molar mass (44 g/mol) and so will have the same mass/charge ratio leading to overlap in detection and a falsely high reading.

Answer 579

Product of the gyromagnetic ratio of the isotope and the magnetic field strength Determines the rate of precession of an object about an external magnetic field

Answer 580

Detachable handle for insertion along the hard palate Gastric tube lumen Integrated bite block Pilot balloon Cuff inflation line Inflatable cuff Dorsal cuff to improve seal pressure to 35 cm H2O

Answer 581

Describes how the uptake or release of a substance by an organ/system is equal to flow multiplied by the difference between arterial and venous concentrations Mathematically: M = Q x (A-V) where M = uptake, Q = flow, A = arterial concentration, V = venous concentration

Answer 582

Size = age/4 + 4

Answer 583

1.01 bar 14.69 psi 101.3 kPa 1033 cm H2O 760 mm Hg

Answer 584

Rapid onset and offset NOTE: it has the highest global warming potential of any volatile agent

Answer 585

Volume of plasma from which a drug is completely cleared per unit time (ml/min). It is equal to the volume of distribution multiplied by the rate constant (the reciprocal of the time constant).

Answer 586

Procaine Amethocaine Cocaine NOTE: broken down by pseudocholinesterase

Answer 587

Ropivacaine Prilocaine Lidocaine Bupivacaine NOTE: broken down by hepatic amidases

Answer 588

Unchanged dose the day before Reduce by 20% on morning of surgery

Answer 589

Miss more than one meal Type 1 diabetes who have no had their basal insulin Poorly controlled diabetes (HbA1c > 69 mmol/mol) Emergency surgery

Answer 590

Foetal circulation has a lower pH than the maternal circulation Bupivacaine is a weak base with a pKa of 8.1 It is more ionised in the lower pH environment of the foetal circulation leading to accumulation

Answer 591

Decreased slope of phase 0 of cardiac action potential Increased effective refractory period Increased action potential duration Example: procainamide, quinidine, disopyramide

Answer 592

Decreased slope of phase 0 of cardiac action potential Decreased effective refractory period Decreased action potential duration Example: lidocaine, phenytoin, mexiletine

Answer 593

Decreased slope of phase 0 of cardiac action potential Normal effective refractory period Normal action potential duration Example: flecainide, propafenone

Answer 594

Decreases slope of phase 4 of PACEMAKER potential Decreases slope of phase 0 of pacemaker potential

Answer 595

Prolongs repolarisation Prolonged effective refractory period Prolonged action potential duration Examples: amiodarone, sotalol

Answer 596

Slows depolarisation of pacemaker cells Increased PR interval Increased effective refractory period

Answer 597

Oxygen knob is always furthest to the left Colour coded (white) as per pipeline oxygen Slightly larger Ridged texture Hypoxic guard (linking oxygen and nitrous oxide valves so that minimum deliverable oxygen concentration when nitrous is used is 25%)

Answer 598

0.1 mg/kg NOTE: this is the most potent neuromuscular blocker

Answer 599

By inhibiting cyclo-oxygenases, NSAIDs inhibit the production of prostacyclin, which is a potent dilator of the afferent renal arteriole. This reduces glomerular blood flow, which in turn can reduce the glomerular filtration rate, which manifests as kidney injury.

Answer 600

Protein: 0.2-0.4 g/L White Cells: 0-5 per µL Glucose: 60-70% of blood glucose

Answer 601

Phase 1 – Onset of manoeuvre. Increased intrathoracic pressure temporarily increases venous return. Blood pressure rises. Phase 2 – Sustained intrathoracic pressure leads to reduced venous return, so BP falls until a compensatory tachycardia restores BP towards normal. Phase 3 – Pressure is released, causing blood to pool in the venous reservoir that was generated. BP falls. HR remains elevated. Phase 4 – Raised heart rate causes a transiently elevated BP as venous return returns to normal. As BP is now elevated, a reflex bradycardia follows.

Answer 602

Refers to which main bronchus the endobronchial tube enters. Has two openings. A proximal opening to the trachea above the carina, and a distal opening which is located in the left main bronchus. These openings correspond to the proximal lumens: clear for trachea, blue for bronchial. If the tracheal cuff is inflated and the clear lumen connected to the breathing circuit then both lungs can be ventilated. When the blue cuff (endobronchial cuff) is also inflated and the breathing circuit connected to the clear lumen, then only the right lung will be ventilated. If the breathing circuit were connected to the blue lumen (with both cuffs inflated) only the left lung would be ventilated.

Answer 603

GTN absorbs into PVC bags and giving sets (so glass bottles or polyethylene syringes and infusion lines should be used) Sodium nitroprusside must avoid direct exposure to sunlight as it can liberate cyanide ions (giving set should be opaque or wrapped in foil) Oxygen should be given to reduce shunt caused by impaired hypoxic pulmonary vasoconstriction

Answer 604

Superior: A line connecting the medial and lateral epicondyles Lateral: Medial border of brachioradialis Medial: Lateral border of pronator teres Floor: Proximally by brachialis, distally by supinator Roof: A combination of skin and fascia including the bicipital aponeurosis

Answer 605

Non-parametric statistical hypothesis test that compares the frequency of observed results against the expected frequency if there were no difference between groups. It is primarily used when examining categorical variables, and whether the difference between observed and expected frequencies are due to chance.

Answer 606

Standard deviation of a group of sample means taken from the same population (i.e. a measure of how far the sample mean of the data is from the true population mean) SEM = σ/√(n-1) or sometimes quoted as σ/√n where σ is the standard deviation of the population and n is the number of samples. If a sample size is doubled then the SEM will be reduced by a factor of √2.

Answer 607

R time (reaction time) is the time taken between beginning an assay and point when the amplitude is 2 mm. This represents the time for fibrin formation to begin.

Answer 608

Time from the R time to when the amplitude is 20mm wide. This is used as a measure of clot strengthening.

Answer 609

Angle to the horizontal made by straight line between the R time and K time. This represents how quickly a clot forms.

Answer 610

The maximum amplitude of the graph and represents the maximum strength of clot.

Answer 611

Width of the graph 30 minutes after maximum amplitude. It represents fibrinolysis.

Answer 612

Allow movement of air via the nasal and oral route enabling speaking and coughing Improved weaning from ventilator

Answer 613

Nitrous oxide – Xenon – Desflurane – Sevoflurane – Enflurane – Isoflurane – Halothane

Answer 614

It is a parametric test which may be used on continuous, quantitative data.

Answer 615

Multiplication becomes addition: log(xy) = log(x) + log(y). Division becomes subtraction: log(x/y) = log(x) – log(y). The reciprocal becomes negative: log(1/x) = -log(x). Power becomes multiplication: log(xn) = n.log(x). Any log of its own base is one: log10(10) = 1. Any log of one is zero: log10(1) = 0. NOTE: a logarithm is defined as the power (x) to which a base must be raised in order to produce a given number

Answer 616

Hypoventilation Rebreathing Sepsis Malignant hyperthermia Hyperthermia Hypermetabolism

Answer 617

Poor perfusion Pulmonary embolism Myocardial infarction Hypovolaemia Hypotension Hyperventilation.

Answer 618

At room temperature for 3-5 days

Answer 619

2 groups, paired: Student’s paired t-test. 2 groups, unpaired: Student’s unpaired t-test. > 2 groups, paired: Paired ANOVA (analysis of variance). > 2 groups, unpaired: Unpaired ANOVA.

Answer 620

2 groups, paired: McNemar’s test. 2 groups, unpaired: χ² with Yates’ correction (Chi-squared). > 2 groups, unpaired: χ²

Answer 621

2 groups, paired: Wilcoxon signed rank. 2 groups, unpaired: Mann-Whitney U test. > 2 groups, paired: Friedman. > 2 groups, unpaired: Kruskal-Wallis.

Answer 622

Level 1a: systematic review or meta-analysis of one or more randomised controlled trials (RCTs). Level 1b: At least one RCT. Level 2a: At least one well-designed, controlled, non-randomised study. Level 2b: Cohort studies. Level 3: Case control studies or case series. Level 4: expert opinion.

Answer 623

CRITICAL ITEMS: enter normally sterile field, or vascular system through which blood flows. There is a high risk of infection, and these items should be sterilised e.g. catheters. SEMI-CRITICAL ITEMS: touch mucus membranes or broken skin barriers. There is an intermediate risk of infection and these items require high level disinfection e.g. laryngoscopes. NON-CRITICAL ITEMS: only contact intact skin. There is a low risk of infection, and these items require low level disinfection e.g. blood pressure cuff, tympanic thermometer.

Answer 624

Class I – soft palate, uvula, fauces and pillars visible. Class II – soft palate and fauces visible, tip of uvula obscured. Class III – soft palate and base of uvula only visible. Class IV – hard palate only.

Answer 625

Patient breathes air through their mouth prior to taking a maximal breath of 100% oxygen. In expiration, the concentration of nitrogen in expired gas is measured and plotted. Phase 1: no nitrogen detected as 100% oxygen is expired from conducting airways Phase 2: alveolar gas begins to appear and therefore the concentration of nitrogen begins to increase Phase 3: plateau is observed, as alveolar gas continues to be expired from alveoli. Phase 4: late upstroke in the nitrogen concentration because apical alveoli, which are on a flatter part of the compliance curve than basal alveoli, have received less of the 100% oxygen breath and so contain more nitrogen. As the small airways begin to close, these apical alveoli continue to empty, leading to an increase in expired nitrogen.

Answer 626

Provides a method of comparing two methods of measurement and establishing their degree of agreement.

Answer 627

Provides a visual representation of effect size for individual studies within a meta-analysis

Answer 628

Used to visually inspect for evidence of reporting bias

Answer 629

Propionic acids – ibuprofen Acetic acid derivative – diclofenac, ketorolac Arboacetic acids – indomethacin Enolic acids – piroxicam Acetylsalicylic acid – aspirin.

Answer 630

CEPHALIC (30%): anticipation of food leads to vagal stimulation, increased motility, secretion of gastric juices and release of gastrin and histamine GASTRIC (60%): gastric distension stimulates mechanoreceptors and initiates vagal reflex. Antral distension in presense of peptides stimulates further gastrin release. INTESTINAL (10%): duodenal distension and presence of peptides and amino acids leads to further gastrin secretion. Increasing acidity leads to release of secretin by duodenal S cells which inhibits further gastrin release.

Answer 631

Metabolised to trifluroacetyl metabolites, which bind to liver proteins. This leads to an autoantibody response, which induces significant, life-threatening, centrolobular necrosis.

Answer 632

Carbohydrates: 1 Protein: 0.8-0.9 Fat: 0.7

Answer 633

Radial nerve Biceps tendon Brachial artery Median nerve

Answer 634

When energy is supplied to an atom it results in electrons being raised to a higher energy level. When these spontaneously fall back to ground state a photon of energy is released which is fluorescence.

Answer 635

Carbon monoxide

Answer 636

Neutralisation It is positively charged, and therefore binds and neutralises heparin into an inactive complex that is subsequently excreted.

Answer 637

Water: 30-40 ml/kg/day. Energy: medical patients 30 kCal/kg/day, post operative 30-45 kCal/kg/day, hypercatabolic 45-60 kCal/kg/day. Protein: medical patients 1 g/kg/day, post operative 2 g/kg/day, hypercatabolic 3 g/kg/day.

Answer 638

Phase 4 of Fowler’s curve reflects the continued emptying of apical alveoli after basal ones have closed. These apical alveoli had more nitrogen to begin with (because they received less of the 100% O₂ breath — due to lower ventilation and flatter compliance). This shift in gas source causes the rise in nitrogen concentration seen in Phase 4.

Answer 639

1: 68.2% 2: 95.4% 3: 99.7%

Answer 640

Mode < Median < Mean

Answer 641

ARR = incidence in control group – incidence in treatment group The number needed to treat is 1/ARR

Answer 642

Middle meningeal artery

Answer 643

Saphenous nerve

Answer 644

Red – halothane Purple – isoflurane Yellow – sevoflurane Blue – desflurane Orange – enflurane

Answer 645

GTPase The alpha subunit of the G-protein is linked to an intrinsic GTPase, which catalyses the breakdown of GTP into GDP and Pi. This deactivates the receptor, leading to the return of the G-protein to its resting state

Answer 646

Grade I – full view of the glottis. Grade IIa – partial view of the glottis. Grade IIb – arytenoids or posterior part of vocal cords just visible. Grade III – epiglottis only visible. Grade IV – neither epiglottis nor glottis visible.

Answer 647

Masterpass: 53 Peck & Hill: 80

Answer 648

Variance is the average of the squared deviations from the mean Standard Deviation (s) = the square root of the variance

Answer 649

Delta 0-4 Hz, deep sleep. Theta 4-8 Hz, deep relaxation. Alpha 8-13 Hz, relaxation. Beta 13-30 Hz, conscious thought.

Answer 650

Frequency below which 95% of brain wave activity occurs

Answer 651

A sensing/occluding cuff is inflated over systolic blood pressure and slowly deflated Oscillations in the cuff are measured Oscillations start = systolic Maximal oscillations = MAP Oscillations stop = diastolic

Answer 652

y = a(1-e-kt)

Answer 653

Phase 1: 20-50 healthy volunteers. This phase examines pharmacokinetic and pharmacodynamic effects. Phase 2: 50-300 volunteers. Further pharmacokinetic and pharmacodynamic effects. Examination of different drug doses and frequencies. Phase 3: 250-1000+ volunteers. Randomised controlled trials comparing the drug with current treatments and assessment of frequent side effects. Phase 4: Post marketing surveillance of rare side effects.

Answer 654

Pleated hydrophobic filter with heat and moisture exchanger NOTE: pleated hydrophobic filters are more efficient than electrostatic filters

Answer 655

A Cardiff aldasorber is a passive scavenging device that removes volatile anaesthetic agents from waste gases via charcoal absorption. It connects directly to scavenging tubing but does not absorb carbon dioxide or nitrous oxide. It must be replaced every 12 hours, and exhaustion is indicated only by increased cannister weight. Heating the aldasorber can release the absorbed volatile agents.

Answer 656

Unfractionated heparin (IV) – 4 hours (check APTT). LMWH (prophylactic dose) – 12 hours LMWH (treatment dose) – 24 hours Warfarin – INR < 1.5

Answer 657

Oxygen delivery (DO2) = cardiac output x oxygen content Cardiac output (ml/min) = heart rate (beats/min) x stroke volume (ml/beat) Oxygen content = (bound oxygen) + (dissolved oxygen) = (Hb (g/dL) x 1.34 x SpO2) + (0.0225 x PaO2)

Answer 658

If having surgery in the morning and expected to miss only one meal Basal insulin should remain unchanged Morning and lunchtime short-acting insulin should be omitted No dose change the day before surgery

Answer 659

System is unable to prevent oscillations in response to a step change. The new value is reached quickly but the system oscillates before eventually settling at the new value. Typical damping coefficient is 0-0.3

Answer 660

Has a blunted response to a step change. A long time is taken to reach the new value but there is no overshoot. The damping coefficient is >1.

Answer 661

Has a damping coefficient of 1. This provides quickest attainment of the new input value with no overshoot. This is still slower than optimal damping.

Answer 662

Has a damping coefficient of 0.64. This is the best combination of rapid response to a stepped change in input and minimal overshoot. There are no more than 2 oscillations prior to attaining the new value.

Answer 663

Spontaneous = Inefficient (FGF = 2 x MV) Controlled = Efficient (FGF = MV)

Answer 664

Accuracy is the ability of a measuring device to record the actual value being measured, i.e. how close to the bullseye is an arrow. Precision is the reproducibility of repeated measurements and how spread out they are, i.e. how tightly packed are a group of fired arrows (regardless of where they hit the target).

Answer 665

24% – 1:25 28% – 1:10 35% – 1:4.6 40% – 1:3.1 60% – 1:1

Answer 666

Protein binding is increased in alkaline blood, and therefore in those with a significant overdose, a plasma pH of 7.5-7.55 is the goal in order to reduce the mass of unbound, active drug NOTE: they cause cardiotoxicity due to their effect on sodium channels

Answer 667

In aortic stenosis, up to 40% of preload is supplied by the atrial contraction Loss of the atrial kick can lead to significantly reduced cardiac output

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