From MCQs Flashcards
What are the three main problems that can arise when giving three drugs through one TIVA line?
Common Dead Space: an alteration in the administration rate of one drug will affect the others
Reflux: obstruction can cause drugs to go up gravity-fed lines (they need anti-reflux valves)
Siphoning: if a syringe driver is placed above the patient and the syringe plunger is not held firmly in place, the difference in hydrostatic pressure can make the drug flow freely. They have anti-siphon valves.
Which airway devices are commonly used in ENT surgery?
Armoured ETT (kink resistant)
Ring-Adair-Elwyn tube (north- or south-facing)
Laser tubes (for laser surgery)
Flexible LMAs
Which factors affect whether a drug would cross the placenta or not?
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.
How does cardiac output change in pregnancy?
Increases
Due to a 30% increase in stroke volume
Also 25% increase in heart rate
List the structures in the bronchial tree from largest to smallest.
Trachea
Main bronchus
Lobar bronchus
Segmental bronchus
Terminal bronchiole
Respiratory bronchiole
Alveolus
What is the peak absorbance of infrared radiation for anaesthetic gases, nitrous oxide and carbon dioxide?
Anaesthetic Gases: 8-9 µm
Nitrous Oxide: 4.6 µm
Carbon Dioxide: 4.3 µm
What is the interaction between omeprazole and clopidogrel?
Omeprazole inhibits CYP2C19 which is responsible for converting clopidogrel into its active form
What is the maximum dose of levobupivacaine that can be used?
2 mg/kg
What are the parasympathetic ganglia in the head and neck?
Ciliary
Pterygopalatine
Submandibular
Otic
What measure is most important in reducing the risk of delivering a hypoxic mixture via a cylinder of entonox?
A dip tube to the bottom of the entonox cylinder will mean the lowest % of oxygen delivered will be 20%.
List the appropriate sizes of blood pressure cuff for different groups of people.
3cm – infant.
6cm – child.
9cm – small adult.
12cm – adult.
15cm – large adult.
What is the partial pressure of oxygen and oxygen saturation of blood in the umbilical vein?
Umbilical vein goes from the mother to the baby
pO2 4.7
SpO2 80-90%
What type of reaction occurs between neostigmine and the active site of acetylcholinesterase?
Carbamylation
Hydrolysing this bond takes longer than hydrolysing the bond between acetylcholine and acetylcholinesterase
What is the mechanism of action of dipyridamole?
Phosphodiesterase inhibitor
Inhibits the breakdown of cAMP
In the platelet, cAMP reduces aggregation
Which receptors are found in the chemoreceptor trigger zone?
Histmine (H1)
Muscarinic
Dopaminergic (D2)
Serotonergic (5-HT3)
Opioid
Adrenoceptors (alpha 1 and alpha 2)
In a galvanic fuel cell, which type of reaction takes place at each electrode?
Lead Anode: electrons are lost in an oxidation reaction
Gold Cathode: electrons are gains in a reduction reaction
Outline the NAPSE coding of cardiac pacemakers.
Position I: chamber(s) paced – V (ventricle), A (atrium), D (ventricle and atrium), O (none).
Position II: chamber(s) sensed – V (ventricle), A (atrium), D (ventricle and atrium), O (none).
Position III: mode of response – T (triggered), I (inhibited), D (triggered or inhibited), O (none).
Position IV: programmable functions – R (rate modulated), O (none).
Position V: multi-site pacing – O (none), A (atria), V (ventricles), D (dual).
Describe the mechanism of action of opioids on opioid receptors.
Via GPCRs (Gi)
Ligand binding leads to closure of VGCCs on the presynaptic membrane and CAMP levels fall
Potassium efflux leads to hyperpolarisation
Leads to decreased neurotransmitter released and pain transmission
Outline the mechanisms of heat loss from the body in theatre and their relative contributions.
Radiation (40%)
Convection (30%)
Evaporation (15%)
Conduction (5%)
Respiratory losses (10%)
What are the 8 methods of classifying a ventilator?
Method of cycling: volume, time, pressure.
Inspiratory phase gas control: volume, pressure.
Source of power: electric, pneumatic.
Suitability of use: operating theatre, ICU.
Paediatric use: yes, no.
Method of operation: pressure generator, flow generator.
Sophistication: SIMV, PS, CPAP etc.
Function: minute volume divider, bag squeezer, intermittent blower.
How does a Haemocue work?
STEP 1: sodium deoxycholate haemolyses erythrocytes releasing haemoglobin
STEP 2: sodium nitrite converts haemoglobin to methaemoglobin. Methaemoglobin reacts with sodium azide to give azidemethaemoglobin.
STEP 3: absorbance is measured at two wavelengths: 570nm and 880nm to compensate for turbidity in the sample.
STEP 4: after each reading the photometer zeros self and checks the intensity of the light source and photocell.
A Hemocue has an accuracy of +/- 0.5g/dL of lab measured values and the result takes 45-60 seconds.
What are the components of the Apfel score?
1) Female sex.
2) Non-smoker.
3) History of PONV or motion sickness.
4) Planned use of post-operative opioids.
What is the Bainbridge reflex?
Increase in heart rate in response to atrial stretch
Aims to clear the central circulation of this extra volume and returning atrial and ventricular pressures back to normal
What is the hydrogen ion concentration at physiological pH?
40 nmol/L