Clinical sciences Flashcards
(209 cards)
1
Q
Give two respiratory complications of hyperoxia
A
- Absorption atelectasis
- Acute lung injury/ARDS
- Abolishment of hypoxic pulmonary vasoconstriction and V/Q mismatch
2
Q
Give two vascular complications of hyperoxia
A
- Systemic vasoconstriction
- Prothrombotic state
3
Q
Give two neurological manifestations of hyperbaric hyperoxia
A
- Headache
- Seizures
- Coma
4
Q
List three conditions for which hyperoxia for non-hypoxaemic patients may be beneficial
A
- Carbon monoxide poisoning
- Cyanide poisoning
- Cluster headache
5
Q
Give three cellular mechanisms of damage in hyperoxia
A
- Damage to DNA and impairment of DNA repair causing cell abnormality or death
- Damage of RNA and impairment of transcription and protein synthesis
- Lipid peroxidation causing damage to cell membranes
- Oxidation of amino acids affecting protein function
- Oxidation of enzymes causing loss of enzymatically mediated reactions
6
Q
State two dangers of hyperoxia during neonatal resuscitation
A
Retinopathy
Bronchopulmonary dysplasia
7
Q
Give two anaesthetic considerations in manageng a paitient with previous bleomycin chemotherapy
A
- Consider neuraxial or regional techniques to avoid administration of oxygen
- Tolerate O2 sats > 85% if known bleomycin injury and 88-92% if possible bleomycin lung injury
- If GA required, aim for lung protective ventilation
Risk of pulmonary fibrosis on exposure to oxygen
8
Q
State the BTS guidelines for target oxygen saturations in patients admitted to ICU
A
- Initiate resus with reservoir mask at 15L/min
- Once stabilised, titrate oxygen therapy to target O2 sats 94-98%
- If risk of hypercapnic respiratory failure, target 88-92%
9
Q
List two approaches to avoid unintentional hyperoxia
A
- Oxygen to be specifically prescribed
- Target oxygen saturations should be documented
- 15L/min oxygen restricted to medical emergencies and resuscitation
- ABG analysis for titration of O2 therapy where feasible
10
Q
State four mechanisms by which heat is lost during anaesthesia and surgery
A
- Radiation
- Convection
- Evaporation
- Conduction
11
Q
Describe two physiological methods of temperature conservation in response to heat loss
A
- Piloerection
- Peripheral vasoconstriction
- Shivering
- Non-shivering thermogenesis
12
Q
List three patient factors in adults that increase the risk of development of inadvertent perioperative hypothermia or its consequences
A
- Low BMI
- Older age
- Cardiovascular co-morbidities
- High ASA
Unmanaged preoperative hypothermia - ?not really a patient factor
13
Q
Why does regional anaesthesia increase the rik of perioperative hypothermia
2
A
- Sympathetic blockage cases vasodilation
- Motor blockade reduces shivering
- Sensory blockade affects detection of cold
14
Q
Why are neonates at higher risk of developing inadvertent perioperative hypothermia
2
A
- Greater body surface area to mass ratio
- Less subcutaenous adipose tissue, poorer insulation
- Immature hypothalamus so thermoregulation responses are inefficient
- Inability to communicate need for warmer environment
15
Q
List two haematological consequences of hypothermia
A
- Impaired platelet function
- Impaired clotting factor function
- Hyperfibrinolysis
16
Q
Why does hypothermia increase the risk of post-operative wound infection
A
- Impaired immune system function
- Vasoconstriction to skin impairs delivery of oxygen and nutrients
17
Q
How does hypothermia affect duration of neuromuscular blockade
A
- Reduced hepatic blood flow causes prolonged action of aminosteroids
- Reduced rate of Hoffman degradation causes prolomged action of atracurium and cisatracurium
18
Q
List two medications that can be used to treat post-operative shivering
A
- Pethidine
- Clonidine
- Doxapram
19
Q
List four consequences of immunosuppressant drugs tacrolimus and mycophenolate
A
Tacrolimus
* Increased risk of malignancy long term
* Electrolyte disruption
* Reduced seizure threshold
* Arrythmias
* Diabetes
Mycophenolate
* Increased risk of malignancy long term
* Increased risk of infection
* Bone marrow failure
20
Q
List four alterations in cardiac physiology following heart transplant
A
- Loss of vagal tone but maintained effect of circulating catecholamines, resting heart rate 90-100bpm and loss of vagal reflex archs e.g. occulocardiac, peritoneal stretch, carotid massage
- Blunted heart rate response to intraoperative triggers such as larungoscopy, surgical stimulation or light anaesthesia
- Slower heart rate response to postural changes, exaggerated postural hypotension
- Loss of baroreceptor reflex, no compensatory tachycardia to hypotension
21
Q
List four comorbidities that a patient is at increased risk of following heart transplant
A
- Cardiac allograft vasculopathy
- Hypertension and diabetes
- Symptomatic arrythmias and conduction disorders
- Rejection causing reduction in graft function
- Epilepsy
- Gallstones and pancreatitis
22
Q
List four investigations that may be required to assist in the evaluation of cardiac function preoperatively
A
- ECG
- Chest X-ray
- ECHO
- Pacemaker interrogation
- Functional assessment of heart function
- Coronary CT or angiogram
23
Q
State how the following drugs would affect cardiovascular physiology in a patient with a heart transplant:
* Adenosine
* Adrenaline
* Atropine
* GTN
A
- Adenosine: exaggerated reduction in heart rate, risk of asystole
- Adrenaline: exaggerated increase in heart rate and contractility
- Atropine: no effect on heart rate or blood pressure
- GTN: causes vasodilation to reduce blood pressure without reflex tachycardia
Transplanted heart shows supersensitivity to directly acting agents
24
Q
List the three underlying factors that cause venous thromboembolism
A
- Blood stasis
- Hypercoagulability
- Endothelial injury
25
List five patient risk factors for the development of VTE
* Malignancy
* Previous VTE
* Prolonged immobility
* Trauma
* Infection
* Smoking
* Pregnancy
26
List three contraindications to the application of anti-embolic stockings
* Peripheral vascular disease
* Severe peripheral neuropathy
* Open leg wounds
27
How do intermittent pneumatic compression devices prevent VTE
* Prevents venous stasis by mimicking effect of calf muscule pump
* Promotes fibrinolysis
28
List the acceptable values of INR, APTT and platelet count for safe performance of spinal anaesthesia
* INR < 1.4 (< 1.5 if for hip fracture)
* APTT 20-35s
* Platelets > 75 x 10^9/L
28
After what time interval can treatment dose low molecular weight heparin be given following removal of an epidural catheter
4 hours
29
Give patient risk factors for the development of vertebral canal haematoma from anicoagulation
* Female
* Increased age
* Spinal pathology
30
Give 2 indications for IVC placement
* Proximal DVT in a patient whom anticoagulation is contraindicated
* Proximal DVT whilst on anticoagulation, after addressing reasons for treatment failure
31
Give the WHO classification of obesity by BMI
* > 25 kg/m2 overweight
* > 30 kg/m2 obese class 1
* > 35 kg/m2 obese class 2
* > 40kg/m2 obese class 3
32
What is meant by the term lean body mass?
The difference between measured body mass and the mass deemed to be due to fat content
33
What dose of rocuronium would you use in an obese patient for rapid sequence induction, how do you calculate it and why
1.2mg/kg calculated according to lean body mass because rocuronium is a very polar molecule with a small volume of distribution limited to blood circulation
34
Describe four effects of obesity on respiratory physiology, giving an implication for the provision of anaesthesia for each
* Increased basal oxygen requirements so elevated minute ventilation, risk of desaturation during airway management
* Reduced functional residual capacity due to intra-abdominal fat and diaphragmatic splinting, tendency to desaturate at onset of apnoea
* Adiposity within chest and abdomen causes closure of small airways, difficulty with intraoperative ventilation with risk of high airway pressures and atelectasis
* Adiposity within chest reduces compliance and reduces efficiency of respiratory mechanics, increased risk of post-operative respiratory failure
35
Give five approaches to maximise efficiency of ventilation of obese patients perioperatively
* HFNO to maintain saturations during apnoeic intubation period
* Lung protective ventilation with higher PEEP to counteract effects of reduced lung compliance
* Use of recruitment maneruvres if derecruitment suspected
* Adequate intraoperative muscle relaxation to aid chest wall compliance
* Intraoperative head up tilt to decrease effect of diaphragmatic splinting
* Establishment on NIV pre-operatively if OSA suspected
36
Define the term frailty
Increased vulnerability due to poor resolution of homeostasis after stressor
37
List four cardiovascular changes that occur in elderly patients and anaesthetic implications of each
* Atherosclerosis and hypertension: need to maintain blood pressure at usual levels to ensure cerebral perfusion
* Calcification of cardiac valves: fixed cardiac output states and inability to cope with larger fluid boluses
* Beta adrenergic receptors are downregulated: impaired response to catecholamines, hypotension more difficult to treat
* Loss of cells in AV-node and conduction pathways: susceptible to arrhythmias
38
List four respiratory changes that occur in elderly patients and anaesthetic implications of each
* Increased closing capacity, reduced FRC: tendency for alveoli to collapse causing atelectasis
* Loss of upper airway muscle: increased risk of obstructive sleep apnoea
* Reduced chemoreceptor function: less response to hypoxia and hypercarbia
* Gas exchange impaired across alveolar membrane: reduced ability to compensate for post-operative pulmonary complications e.g. pneumonia
39
Give three further changes that occur in elderly patients involving the renal and MSK system
* Reduced activity of renine-angiotensin-aldosterone-system: less able to compensate for hyper/hypovolaemia
* Reduction in number of nephrons: reduced ability to excrete anaethetic drugs
* Sarcopenia: impaired thermogenesis, positioning difficulties
* Osteoporosis: potential chronic pain
40
State three reasons why the elderly may be more susceptible to hypotension associated with neuraxial anaesthesia
* Reduced carotid baroreceptor response to decreased BP
* Downregulation of cardiac beta adrenergic receptors limits cardiac response to low BP
* Ventricular wall thickening means reduced ability to increase stroke volume
* Aortic valve calcification may cause fixed cardiac output states, leading to myocardial ischaemia from hypotension and heart failure
41
Give three pharmacokinetic changes in the elderly that may impact response to intravenous anaesthetic agents
* Reduced protein production, reduced protein binding and higher active drug concentration
* Contracted blood volume may lead to increased drug concentration after bolus administration
* Reduced cardiac output and so prolonged arm-brain circulation time may delay apparent onset of action
* Reduced total body water, increased concentration of water soluble drugs
* Decreased hepatic blood flow, reduced hepatic clearance
* Decreased glomerular filtration rate, slower excretion and prolonged duration of certain medications
42
Define the term post-operative cognitive dysfunction
Decline in cognition compared to baseline following surgery
43
Give four risk factors for the development of post-operative cognitive dysfunction
* Increasing age
* Lower level of education
* Pre-existing congitive impairment
* Post-operative infection
44
Define pulmonary hypertension
Mean pulmonary artery pressure ≥ 25 mmHg at rest or ≥ 30 mmHg when exercising
45
List five categories of pulmonary hypertension
1. Pulmonary arterial hypertension e.g. idiopathic, connective tisue disease, drug and toxins
2. Left heart disease
3. Chronic lung disease
4. Other multisystemic disorders e.g. sarcoidosis
46
Give the cardiovascular consequences of chronic pulmonary hypertension
* Hypertrophy of right ventricle
* Remodelling of right ventricle leads to tricuspid regurgitation
* In right ventricular hypertrophy, right ventricle coronary perfusion in systole decreases and stops
* Increased oxygen demand of the right ventricle with reduced perfusion leads to ischaemia, fibrosis and diastolic then systolic dysfunction
* Reduced right ventricular output and deviation of intraventricular septum leads to left ventricular failure
47
Give four specific goals of anaesthesia management for a patient with pulmonary hypertension
* Minimise increases in pulmonary vascular resistance by avoiding hypoxia, hypercarbia, hypothermia, pain/sympathetic, acidosis, high airway pressures, nitrous oxide
* Avoid reduction in systemic vascular resistance
* Invasive BP monitoring
* Cardiostable induction
* Vasoconstrictor to mitigate vasodilatory effects of GA/neuraxial
* Maintain right ventricular preload with appropriate fluid loading, treat blood loss, consider cardiac output monitoring to guide fluids
* Maintain sinus rhythm, normal rate
* Avoid tachycardia which impairs diastolic filling time, avoid pain and light anaesthesia
* Avoid bradycardia which impairs forward flow (prompt management of vagal bradycardia)
* Maintain contractility of right ventricle using inotropes if required
48
List four classes of medication used in the management of chronic pulmonary hypertension
* Calcium channel blockers e.g. amlodipine
* Endothelin receptor antagonists e.g. bosentan
* Phosphodiesterase-5 inhibitors e.g. sildenafil
* Prostaglandins e.g. inhaled iloprost
* Soluble guanylate cyclase stimulators e.g. riociguat
49
Give the management of acute pulmonary hypertension
* Correct any precipitants—hypoxia, hypercapnia, acidosis, high airway pressures, arrhythmias and pain.
* Pulmonary vasodilator therapy—prostacyclin analogues nebulised iloprost or epoprostenol, i.v. epoprostenol, nitr**ic** oxide
* Support the right ventricle—dobutamine, milrinone.
* Maintain RV perfusion—noradrenaline, vasopressin.
* Reduce RV overload—diuretics
## Footnote
Question previously: give two pharmacological management options for acute pulmonary hypertension
50
Describe the pathophysiology of pulmonary hypertension
* Sustained pulmonary vasocontriction
* Cellular proliferation of intima, media and adventitia of endothelium
* Localised thrombi formation
* Remodelling depletes nitric oxide and prostaglandin
51
Explain how pulmonary hypertension affects maternal physiology of pregnancy
* Increasing levels of progesterone normally cause pulmonary vasodilation and recruitment of non-perfused pulmonary arterioles to compensate for increased oxygen demand. In PH, this does not happen due to sustained vasocontriction and thickened vessel walls.
* Increased cardiac output leads to further right ventricular strain and right ventricular ischaemia. Systolic dysfunction then leads to intraventriclar bowing and reduced right sided output, causing left ventricular failure.
52
List the symptoms and signs of pulmonary hypertension
Symptoms:
* Dry cough
* Fatigue
* Peripheral oedema
* Chest pain
* Syncope
Signs:
* Raised JVP
* Tachycardia
* Hepatomegaly
* Hypoxia
* Systolic murmur - tricuspid regurgitation
* ECG changes: p-pulmonale, RV strain, RBBB,
53
List three investigations which are requested for an obstetric patient with pulmonary hypertension
* Functional status assessment e.g. WHO-FC/6 minute walk test
* ECG
* ECHO
* NT-proBNP
54
Risks of GA in pulmonary hypertension
* Depressed cardiac contractility
* Sympathetic response to laryngoscopy
* Reduced preload due to vasodilatory properties of GA medications
* Increased PVR from positive pressure ventilation
55
Risks of neuraxial in pulmonary hypertension
* (Would always be epidural or CSE in labour to prevent sudden changes in blood pressure)
* Risk of failure and emergency GA conversion
* Hypotension and systemic vasodilation reduces preload
56
List four effects of cigarette smoking on the cardiovascular system with the underlying mechanism of each
* Hypertension due to accelerated atherosclerosis formation and raised catecholamine levels
* Tachycardia due to raised stimulation of nicotinic receptors and release of catecholamines
* Ischaemic heart disease due to atherosclerosis and prothrombotic state (carbon monoxide, nicotine, polcythaemia)
* Heart failure secondary to myocardial infarction (IHD) and increased ventricular afterload (hypertension)
57
Describe three pathophysiological mechanisms by which cigarette smoking can impair systemic oxygen delivery
* Hypoxic hypoxia: airway and respiratory conditions relating to smoking result in reduced oxygen availability within the alveolus
* Anaemic hypoxia: 1) haemoglobin has increased affinity for carbonmonoxide, reducing available Hb for oxygen carriage 2) CO shifts of oxygen dissociation curve to left reducing ability of haemoglobin to release oxygen
* Histotoxic hypoxia: inhibition of cytochrome oxidase by carbon monodise reduces oxygen-dependent synthesis of ATP in mitochondria
58
List five effects of cigarette smoking on the respiratory system that are relevant to the conduct of general anaesthesia
* Increased upper airway irritability, increased risk of laryngospasm
* Increased lower airway reactivity, increased risk of bronchospasm and mucus secretion
* Impaired mucociliary transport and secretion clearance, increased risk of pneumonia and shunt
* Increased closing capacity, increased risk of atelectasis
* Accelerated rate of FEV1 reduction with age, significantly reduced level is predictive of post-operative respiratory complications
* Increased risk of PE due to hypercoagulability
59
List three other perioperative complications that cigarette smokers are at increased risk of
* Surgical site infections
* Anastomotic breakdown
* Longer post-operative stay
* Increased risk ICU admission
60
List three physiological benefits of smoking cessation 24 hours prior to surgery
* Reduced circulating nicotine levels, reduced catecholamine levels, reduced myocardial oxygen demand
* Reduced circulating carbon monodixe, improved oxygen delivery to tissues incl. myocardium and reduced risk of perioperative ischaemic event
* Blood coagulability begins to normalise reducing risk of perioperative thromboembolic events
61
Give two drug classes used to aid smoking cessation
* Nicotine receptor agonists e.g. nicotine gum
* Nicotinic receptor antagonist e.g. bupropion
* Nicotinic receptor partial agonist e.g. varenicline
62
Outline the production and circulation of cerebrospinal fluid
* Choroid plexus secretes sodium into lateral and fourth bentricles creating osmotic pressure and drawing water to create CSF
* Production is 500ml/day, volume present is 150mls
* Lateral ventricles drain into third ventricle via foramen of Munro
* Third ventricle drains into fourth ventricle via aqueduct of Sylvius
* Fourth ventricle drains into subarachnoid space via foramina of Magendie and Luschka
* CSF is absorbed by arachnoid granulations through the dura
63
How does intracranial pressure affect production and absorption of CSF
* Production is opposed if intracranial pressure rises as CSF hydrostatic pressure opposes the osmotic pressure generated by the sodium gradient
* Absorption via arachnoid granulations is dependent on CSF pressure being higher than venous pressure, higher CSF pressure creates a steeper gradient and faster absorption
* Small increases in ICP can be "buffered" by movement of CSF into spinal cord
64
List four differences between biochemistry of CSF and plasma
* CSF sodium levels higher than plasma
* Chloride levels higher
* pH lower (acidic) partly due to higher pCO2
* Glucose ≥ 2/3 of level in plasma
* Low protein level
* Osmolarity is equal in CSF and serum
65
List three diagnostic indications for lumbar puncture
* CNS infection sampling for culture
* Diagnosis of subarachnoid haemorrhage
* Diagnosis of MS/GBS
66
List three therapeutic indications for lumbar puncture
* Intrathecal chemotherapy
* Treatment of benign intracranial hypertension
* Neuraxial anaesthesia
67
Give procedural factors that predispose to development of post-dural puncture headache after lumbar puncture
* Multiple punctures
* Larger gauge needle
* Use of traumatic, cutting needle rather than pencil point
68
List three patient factors that predispose to the development of PDPH
* Younger adults (not children)
* Female
* Pregnancy
* Low BMI
69
List two causes of primary hyperparathyroidism
* Parathyroid adenoma
* Parathyroid gland hyperplasia
70
Give three biochemical abnormalities seen in primary hyperparathyroidism
* Elevated parathyroid hormone
* Elevated calcium
* Reduced phosphate
* Elevated ALP
71
Name five systemic effects of hyperparathyroidism
* Renal stones
* Bone fractures
* Peptic ulceration
* Non specific abdominal pain
* Weakness
* Memory impairment
* Conduction defects
| Hypercalcaemia: stones, bones, abdominal gorans, psychic moans
72
State two specific preoperative concerns when providing anaesthesia for parathyroidectomy
* Underlying cause of hyperparathyroidism e.g. as part of CKD
* Propensity to fractures: careful manual handling, consider bisphosphonate treatment
* Impact of hypercalcaemia e.g. cardiac rhythm
73
List five specific intraoperative anaesthetic conditions when providing anaesthesia for parathyroidectomy
* Surgical field is near airway: reinforced tube or LMA
* Positioning is supine with sandbag under shoulders: care - risk of pathological fractures
* Potentially prolonged surgery: need for warming, pressure area care
* Methylene blue to identify glands, risk of anaphlaxis
* Recurrent laryngeal nerve monitoring may be required: short acting NMBD
* Minimise coughing to ensure haemostasis: smooth emergence e.g. with remifentanil
74
Give three specific post-operative complications following parathyroidectomy
* Hypocalcaemia
* Recurrent laryngeal nerve palsy
* Haematoma (rare: causes airway obstruction)
* Incompelte resection
75
Define functional residual capacity
* Volume of air in the lungs after normal expiration
76
List four factors that reduce FRC
* Supine posture
* Anaesthesia
* Raised intra-abdominal pressure e.g. obesity, pregnany, ascites
* Younger age
77
Apart from FRC, give three factors that determine how long oxygen saturation can be maintained in an apnoeic patient
* Fraction of inspired oxygen preceeding apnoea
* Presence of shunt (reduces effectiveness of preoxygenation)
* Alveolar pressure of carbon dioxide (or approximation by arterial pressure of carbon dioxide) - results in reduced PAO2
* Rate of oxygen consumption
* Patency of airway
78
State five practical aspects of performing successful preoxygenation
* Explanation to patient to improve compliance
* Tight fitting mask
* Tidal breathing
* Use of 100% oxygen
* Ramped position to increase size of FRC
* Consider other measures to improve FRC e.g. NG drainage of stomach contents if obstruction
* Gas flow to exceed patient's minute ventilation
79
How can the adequacy of preoxygenation be assessed
Monitor fraction of expired oxygen to target greater than 0.9
80
Give two clinical advantages of preoxygenating a fit adult prior to anaesthesia
* Provides a margin of safety in unpredicted difficult airway
* Provides margin of safety in adverse incidents at induction e.g. anaphylaxis, laryngospasm
81
Give three clinical disadvantages of preoxygenating a fit adult prior to anaesthesia
* Prolongs induction
* Intolerance of tight fitting mask, sense of claustrophobia
* Increases alveolar collapse at induction, increased risk of atelectasis and post-operative hypoxia
82
Define the terms systematic review and meta-analysis
* Meta-analysis: quantitative review of data from primary studies that are similar in nature to reach a statistical conclusion to a specific question
* Systematic review: qualitative review of the data in all availavle similar studies in response to a specific research question
83
List four factors that help to ensure a high quality conclusion from meta-analysis
* Clearly defined question
* Clear and reproducible methodology
* Comprehensive search of all available databases
* Clear and valid criteria for inclusion and exclusion of studies
* Consideration of publication bias
84
Explain what is meant by sensitivity and specificity
* Sensitivity refers to a test's ability to correctly identify patients with the issue in question (= true positives/true positives + false negatives)
* Specificity refers to a test's ability to correctly identify the patients without the issue in question (= true negatives/true negatives + false positives)
85
State how positive predictive value and negative predictive value can be calculated
* PPV = true positives/ true positives + false positives
* NPB = true negatives / true negatives + false negatives
86
When interpreting a forest plot, what is represented by the
1. Central vertical line
2. Diamond at the bottom of the plot
3. Size of each rectangular block
1. Central vertical line: line of equality, any study with 95% CI that crosses the line did not show a significant difference
2. Diamond at the bottom of the plot: pooled analysis of all the studies, gives a representation of overall effect
3. Size of each rectangular block: represents the weight of that study on overall meta-analysis (largely determined by sample size)
87
Rank the five levels of scientific proof used to grade medical evidence
1. Meta analysis or large RCT
2. At least one well designed RCT
3. Non randomised trials e.g. cohort studies, mateched case-control
4. Non-experimental studies from more than one research group
5. Case report or expert opinion
88
List four non invasive methods of cardiac output monitoring
* Transthoracic echocardiogram
* Finapres (finger arterial pressure)
* Partial gas rebreathing
* Externally placed doppler measurement
* Bioimpedance monitoring
89
What is the gold standard cardiac output monitoring device
* Pulmonary artery catheter
90
What is the doppler effect and equation
V= ∆F x c/ 2F(e) x cosƟ
Velocity = shift in frequency x speed of sound in blood/ 2 x emitted frequency x cosin(angle of between emitter probe and object)
Doppler effect is the change in perceived frequency of a sound wave when the source is moving in relation to the observer. Frequence increases as distance between observer and source reduces.
91
Describe how an oesophageal doppler probe measures cardiac output
* Oesophageal probe is placed so that tip faces decending aorta at T5/6, waves are emitted from probe, reflected from red cells and detected by probe
* The doppler equation allows calculation of the velocity of red blood cells in the descending aorta as they move away from the probe
* Cardiac output is the product of the stroke distance x cross sectional area x heart rate
* The velocity-time integral gives the stroke distance and is determined by AUC
* The cross sectional area of the descending aorta is assumed from normograms taking age, weight and height into account
* Correction factor is applied because 70% of cardiac output is expected to enter descending aorta
92
Give four limitations of use when using an oesophageal doppler probe to measure cardiac output
* Probe placement normally requires a sedated or anaesthetised patient
* Small changes in probe placement lead to significantly different readings
* Arrythmias give beat to beat variability in measurements e.g. in AF
* Measurement is based on the following assumptions
* Laminar flow in aorta ( more turbulent if atherosclerosis)
* 70% cardiac output entering descending aorta (changes in redistributed circulation e.g. shock)
* Diameter of aorta assumed constant (decreases in hypotension, may have aneurysmal segments)
* Cross sectional area of aorta assumed through normogram (in reality varies in individuals)
* Negligible blood flow in diastole (reverse flow in aortic regurgitation)
* Probe is placed to assume parallel positioning of descending aorta to oesophagus
93
# Oesophageal doppler
List physiological parameters that are reflected by peak velocity, corrected flow time and stroke distance
* Peak velocity: myocardial contractility
* Corrected flow time: systemic vascular resistance
* Stroke distance: stroke volume
94
# Oesophageal doppler
State what happens to corrected flow time in a patient with sepsis
Corrected flow time becomes longer
95
# Oesophageal doppler
State what happens to corrected flow time in a hypovolaemic patient
Becomes shorter
96
Give four potential technical problems with TIVA and how they might be prevented
* Electrical failure leading to pump failure: alarm if threat of power loss, regular maintenance and checks
* Failed drug delivery due to disconnection: luer lock connectors
* Tissued cannula: large bore cannula visible, use of depth of anaesthesia monitoring, high pressure alarm on pump
* Drug remaining in cannula at end of case: flush cannula at end of case, systems e.g. witnessed flushing of cannulas at recovery handover
* Wrong drug in pump: labelling and two-person check when preparing medication
97
Give potential patient complications with TIVA
* Accidental awareness
* Hyperalgesia following remifentanil infusion
* Excessive dosing with haemodynamic consequences in elderly
98
List three types of infusion control devices used in clinical settings
* Gravity driven e.g. with roller clamp on standard fluid administration set
* Volumetric pump
* Syringe driver
99
List three general and three specific characteristics of pumps used for target controlled infusion of anaesthesia
General
* Clear user interface, control buttons and screen
* High pressure detection with alarm
* Powered by mains and rechargable battery with alarm if threat of power loss
Specific:
* Formula based rate of infusion by patient characteristics
* Screen shows drug and algorithm
* Ability to input patient characteristics
100
List three specific indications for TIVA
* Severe PONV with volatile anaesthesia
* Malignant hyperthermia
* Anticipated difficult airway
* Tubeless field surgery
101
List four features of a TIVA giving-set that helps ensure drug delivery
* Luer lock connections
* Anti-reflux valve at fluid line connector
* Drug and fluid lines join together as close as possible to patient to minimise dead space
* Giving set or connections may be colour coded
102
List four precautions that should be undertaken to help guarantee drug delivery when administering TIVA
* Pumps undergo regular maintenance
* Anaesthetist should be trained in TIVA
* Pumps plugged into charge when not in use
* Correct entry of patient data
* Lines primed
* Appropriate volume alarms and response to alarms
* Intermittent check that the expected volume of drug has been infused
103
Outline the basic physical principles involved in the formation of an ultrasound image
* Transducer contains piezoelectric crystals which emit ultrasonic waves when a current is applied
* Ultrasound waves are reflected at interfaces between structures of different densities
* The piezoelectric crystals receive the reflected ultrasonic wave resulting in a change in voltage
* Electric signals are filtered and processed to produce a two-dimensional image
* Sound waves reflecting off more distant tissues take longer to return, allowing the microprocessor to assess depth of the imaged structure
104
Give three patient factors that may influence ultrasound image quality
* Obesity
* Positioning
* Compliance to remain still
105
Give four acoustic artefacts that may influence the ultrasound image quality
* Contact artefact: probe not in good contact with skin
* Acoustic shadowing: tissues deep to dense structures will not be seen as most of the waves have been reflected back
* Post-cystic enhancement: ultrasound passes readily through fluid filled structures resulting in enhancement of structures deep to them
* Reverberation artefact: multiple reflections between structure and probe result in multiple representations of the structure on screen
* Insufficient resolution: use of wavelength that is greater than size of structures imaged leads to failure to detect structure
* Anisotropy: image is dependent on angle to ultrasound at which they are viewed - when the angle between probe and skin is more acute, the image quality becomes poorer
106
Which two needling techniques are commonly used in ultrasound guided nerve blocks. Give an advantage and disadvantage of each
* In plane: needle visualised along full length so good visualisation of needle tip near nerve, but difficult to keep needle in view
* Out of plane: shortest skin-nerve distance so less painful, needle only seen as bright dot so cannot tell whether visualising tip of needle or shaft
107
How is dopler effect used in clinical practice
* Echocardiography to determine valve pathology and flow function of heart
* Umbilical artery dopplers for fetal wellbeing
* Oesophageal doppler for invasive cardiac monitoring
* Transcranial doppler for assessment of cerebral pefusion
* Limb dopplers to assess for peripheral arterial disease
* Venous dopplers to assess for DVT
108
State the frequency of ultrasound probe most commonly used for vascular access in adults
* 5-15MHz
109
List five pieces of information that TTE can provide in a haemodynamically unstable patient
* Evidence of left ventricular failure
* Evidence of right ventricular failure
* Evidence of volume status e.g. hypovolaemia
* Evidence of tamponade
* Evidence of regional wall motion abnormality
110
Give four echo assessments that are facilitated by the doppler effect
* Assessment of valve function by assessment of flow
* Cardiac output by velocity time integral through left ventricular outflow tract
* Degree and direction of shunt in congenital heart disease
* Dynamic obstructions
111
State the reason why carbon dioxide absorbs infrared radiation
Molecules containing dissimilar atoms absorb infrared light
112
Give one other expired gas that can be measured by infrared absorption
* Nitrous oxide
* Volatiles
113
Why are the measuring chamber windows of the capnograph made of crystal
To allow only a specific wavelength of light through the chamber
This is the wavelength that is maximally absorbed by the gas being measured
114
State the physical laws that underpin the ability of a capnograph to measure carbon dioxide
* Beer's law: absorption of infrared is proportional to concentration of sample
* Lambert's law: absorption of infrared is proportional to path length
115
List three diagnoses that can be made when continuous capnography is used in an anaesthetised patient. For each, state how the value of etCO2 and waveform would change
* Acute reduction in cardiac output: rapidly reducing etCO2 value, normal morphology waveform with reducing height
* Soda lime exhuastion: elevated etCO2, baseline waveform does not return to zero
* Disconnection of breathing system: no etCO2 and loss of waveform
* Inadequate paralysis: potential rise in etCO2, Curare clefts in plateau of waveform
116
Name four clinical situations and locations where continuous capnography should be available for use
* Emergency department resus
* Interventional radiology
* Theatre complex
* Recovery
* Cardiac arrest environments
* GA environments
* Sedation environments
117
List three advantages of low-flow anaesthesia
* Economy
* Pollution reduction
* Conservation of heat and moisture (although HME surpasses this)
118
List four disadvantages of low flow anaesthesia
* Difficult to predict inhaled concentrations of gases at very low flows
* Requires a leak free system, not suitable for poorly fitting LMA
* Slow response to changed settings on vaporiser
* Accumulation of unwanted gases e.g. carbon monoxide
119
What is the theoretical minimal fresh gas flow that may be used in a circle system for a 70kg adult patient
* 250ml/min
120
List two components of soda lime
* Calcium hydroxide
* Sodium hydroxide
* Potassium hydroxide
* Water
121
List two advantages of using soda lime in a breathing system other than CO2 absorption
* Heat generation
* Moisture generation
122
Describe the stages in performing a two-bag test when checking an adult circle breathing system
* Visually inspect tubing for damage, breaks or kinking
* Attach test lung on patient end
* Set fresh gas flow to 5L/min and manually ventilate, checking whole breathing system is patent and unidirectional valves are moving appropriately
* Check function of APL by squeezing both bags together
* Turn off ventilator and fresh gas glow. Turn on and off each vaporised. There should be no loss of volume.
123
List the components of the anaesthetic equipment that must be checked before the start of each case
* Breathing system
* Ventilator
* Airway equipment
* Suction
124
List three diagnostic indications for arterial cannulation other than blood pressure monitoring
* Frequent blood sampling
* Cardiac output monitoring
* Diagnostic angiography
125
List three therapeutic indications for arterial cannulation
* Thrombolysis
* ECMO
* Cardiopulmonary bypass
126
Explain what is meant by gauge pressure
Pressure relative to atmospheric pressure
127
How may an invasive arterial pressure measuring system be calibrated
* Zero: stopcock closed to patient, cap opened to air. Press zero on module and check the trace is flat at 0mmHg, then replace cap and open stopcock
* Level: place transfucer at level of heart
* Calibrate clinically: compaire invasive blood pressure with non-invasive monitoring (systolic usually 5-10mmHg higher and diastolic 5-10mmHg lower in NIBP)
128
Define damping with reference to clinical measurement
* Dampling is a decrease in amplitude of oscillation and increase in response time as a result of energy losses
129
State two causes of damping withint an invasive arterial blood pressure measurement system
* Excessive tubing length
* Air bubbles in column of fluid between patient and transducer
130
State how an under-damped invasive arterial blood pressure measuring system would affect measured blood pressure
* Over-read the systolic
* Under-read diastolic
* No change in MAP
131
State three other sources of error when measuring invasive arterial pressure
* Failure to zero
* Failure to keep transducer level
* Transducer drift (distortion of transducer material over time)
* Resonance
132
List three indications for insertion of an implantable cardiac defibrillator
* Secondary prevention in patients with history of VT/VF who have survived cardiac arrest or have LVEF < 35% but NYHA no worse than III
* Secondary prevention in patients who have survived cardiac arrest due to coronary artery spasm
* VF or haemodynamically unstable VT > 48 hrs after MI in absence of ongoing ischaemia
* Familial arrythmogenic conditions e.g. long QT
133
STate three ways in which surgical diathermy may affect the ICD
* Damage to device causing malfunction
* Inappropriate firing due to sensing of diathermy
* Energy induction in cardiac leads causing burning and scar development (less conductive)
134
State the meaning of three letters in ICD nomenclature
First letter: chambers that can be shocked in event of arrythmia
Second letter: chambers that can be paced in event of tachycardia
Third letter: method of detecting tachycardia
Fourth letter: chambers that can be paced in event of bradycardia
135
State the meaning of the three letters in pacemaker nomenclature
1: Pacing
2: Sensing
3: Response
136
State four specific preoperative preparations that may be required for a patient with an ICD listed for elective surgery
* History assessing for device failure e.g. episodes of syncope, excessive shocking
* Review device registration card
* Ensure satisfactory ICD check within past six months
* Discussion with surgeon regarding need of diathermy
* If interference likely, may require reprogramming/deactivation and device check postoperatively
137
State four specific intraoperative preparations that may be required for a patient with an ICD having elective surgery.
* External defibrillator pads to be applied A-P to to minimise current passage through device
* Ensure availability of cardiac physiologist
* Avoid diathermy use if possible or use bioplar keeping cables away from ICD
* Avoid precipitants of arrhythmia e.g. electrolyte abnormalities
* Consider cardiac output monitoring
138
List two postoperative considerations for a patient with an ICD following surgery.
* Patient to remain fully monitored in a high-observation area with ECG monitoring and immediate access to defibrillation until ICD reactivated
* ICD to be reactivated and checked for functionality
139
How do you manage an ICD if a patient requires emergency surgery
* If out-of-hours or time not permitting usual methods, secure clinical magnet over implant to deactivate shock mode
* Apply external defibrillator
140
List four factors that may influence the choice of target plasma concentration value when using TCI propofol
* Cardiovascular stability
* Age
* Preoperative patient anxiety
* Co-administration of CNS depressants e.g. opioids
* Regional anaesthesia
* pEEG outputs
141
List three methods of monitoring depth of anaesthesia when using TIVA
* Clinical signs e.g. sweating, lacrimation, movement
* Clinical observations e.g. heart rate, blood pressure, respiratory rate if not paralysed
* pEEG monitoring, waveform and number
142
Two hours after the start of uneventful surgery with TIVA the patient moves during a point of high surgical stimulation. Describe four aspects of immediate management
* Ask surgeon to stop
* Verbal reassurance to patient
* Increase reminfentanil TCI
* Check patency of lines and pump function
* Document events
143
List three causes of accidental awareness under anaesthesia specifically when using TIVA
* Human error resulting in incorrect concentration of drug selected, incorrect pump programming
* Lack of training with TIVA e.g. guided by pEEG number, unaware of delay
* Anaesthetic not delivered e.g. cannula tissued, TIVA line disconnected
144
List three differences between the March and Schnider models for TCI propofol
* March requires patient body mass inputted, Schnider calculates lean body weight using sex, weight and height
* March assumes compartment sizes proportional to body mass, Schnider assumes fixed V1 and V3, V2 influenced by age
* March - rate constants for slow and fast redistribution are fixed, Schnider - rate constants for fast influenced by age, rate constants for slow redistribution are fixed
* March has a larger V1 so larger initial bolus, Schnider has a smaller fixed size V1
* March has constant elimination rate, Schnider has elimination rate adjusted to lean body weight
145
What is the volume of distribution, pKa and clearance of propofol
* Vd 4L/kg
* pKa 11
* Clearance 25-60ml/kg/min
146
In the compartment model, what is represented by V1, V2, V3
V1: central compartment into which drug is injected and cleared, represents plasma
V2: well perfused tissue e.g. muscle
V3: less well perfused tissue e.g. adipose
147
Describe how TCI devices ensure a steady state blood concentration
* Bolus: a bolus is delivered proportional to the desired concentration for the estimated volume of V1 compartment
* Transfer: the drug moves into compartments V2 and V3, the rate of which is estimated by the algorithm, which delivers further infusion of the drug to account for this. Once the estimated volume of V2 and V3 have been delivered, this rate of infusion ceases.
* Elimination: the drug is eliminated from the central V1 compartment, the rate of which is supplemented by the infusion pump once the drug has reached steady-state
| Bolus, transfer, elimination
148
Give two pharmacological properties of a drug that will affect equilibration with effect site
* pKa
* Lipid solubility
* Plasma protein binding
149
Describe the pharmacokinetic principles that allow effect-site targeting when using TCI propofol
* Assumed that effect site volume is neglibible
* Assumes that there is a rate constant that determines movement of drug to effect site but not a reciprocal one
* Has been derived indirectly by finding the point at which peak effect concentration is in equilibrium with plasma concentration and peak anaesthetic agent effect clinically
150
Define context sensitive half time
Time taken for a concentration of drug to reduce by half once an infusion at steady state has stopped
151
Give two pharmacokinetic properties of propofol that account for its fast offset time when given by infusion
* Rapid hepatic metabolism that exceeds redistribution from V2+3 back to V1
* Propofol has no active metabolites
152
List four advantages of using a TCI device for infusion of propofol compared to a manual propofol infusion regimen
* Bolus dose and infusion rate determined by computer models based on patient and drug characteristics, more likely to be accurate
* Able to reach steady state more rapidly
* More rapid wake-up at end of surgery by reducing excessive dosing
* Less labour intensive
153
Name four indications for antiplatelet drugs in clinical practice
* Primary prevention of ischaemic heart disease
* Secondary prevention of ischaemic heart disease after MI
* Secondary prevention of cerebrovascular disease after stroke
* Peripheral vascular disease
154
List five antiplatelet agents in clinical use and their underlying mechanism of action
* Aspirin: Irreversible COX (COX-1 preference at low doses), which inhibits thromboxane production
* Clopidogrel: P2Y12ADP receptor antagonist prevents platelet aggregation
* Abciximab: Glycoprotein IIb/IIIa receptor inhibitor, prevents platelet cross-linking via fibrinogen or anchoring to endothelial wall via von Willibrand's factor
* Dipyridamole: phosphodiesterase inhibitor reduces breakdown of cAMP, maintaining platelets in inactivated state
* Prostacyclin: binds to platelet G-protein coupled receptor, increased cAMP production and maintains platelets in inactivated state
155
List three possible causes of thrombocytosis
* Essential thrombocythaemia
* Polycythaemia vera
* Myelofibrosis
* Inflammation
156
List three causes of thrombocytopenia
* B12 or folate deficiency
* Idiopathic thrombocytopenic purpura
* Radiation
157
Outline two mechanisms of spontaneous recovery from neuromuscular blockade following administration of rocuronium
* Rocuronium is redistributed down concentration gradient into plasma
* Reduction in plasma concentration driven by biliary and renal excretion as well as a small proportion of hepatic metabolism
158
Which class of drug does neostigmine belong to
Reversible acetylcholinesterase inhibitor
159
Describe the mechanism of action of neostimine in reversing neuromuscular blockade
* Non competitive antagonist of acetylcholinesterase in synaptic cleft
* Less breakdown of acetylcholine means greater concentration to outcompete neuromuscular blocker
160
Give two advantages and three disadvantages of using neostigmine for reversal of neuromuscular blockade
Pros:
* Inexpensive
* Familiar
Cons:
* Unwanted muscarinic receptor action requires co-administration of glycopyrrolate to avoid bradycardia, confers wide range of possible side effects of which confusion is pertinent
* Ineffective in CICO situations where muscle relaxant has just been given
* Slow onset of action with peak effect after 8 miniutes
* Ceiling of effect - increasing dose does not necessarily increase efficacy
161
Which class of drug does sugammadex belong to
Gamma cyclodextrin
162
Describe the MOA of sugammadex in reversing neuromuscular blockade
* Ring like structure with lipophilic inner surface and hydrophilic outer surface, encapsulates aminosteroid
* Rocuronium-sugammadex complex is renally cleared
163
Give three advantages and two disadvantages of using sugammadex for reversal of neuromuscular blockade
Pros:
* Can be used to fully reverse in CICO situations
* No significant cardiovascular effects
* No risk of recurarisation because encapsulation is irreversible
Cons:
* Flucloxacillin may displace muscle relaxant, potentiating block
* Sugammadex encapsulates progresterone, reducing efficacy of oral contraceptives
* Only effective with aminosteroid muscle relaxants e.g. rocuronium, not benylisoquinoliums e.g. atracurium
164
List two post-operative pulmonary complications associated with inadequate reversal of neuromuscular blockade
* Alveolar hypoventilation, hypoxia and hypercapnia
* Pulmonary aspiration
165
List four clinical features that may indicate autonomic involvement in a patient with diabetes
* Orthostatic hypotension
* Resting tachycardia
* Gastroparesis
* Loss of bladder control
* Sweating/reduced ability to sweat
166
List three microvascular complications of diabetes
* Retinopathy
* Neuropathy
* Nephropathy
167
List three macrovascular complications of diabetes mellitus
* Coronary artery disease
* Cerebrovascular disease
* Peripheral vascular disease
168
What is the recommended upper limit of HbA1c for elective surgery
69mmol/mol
169
State the Association of Anaesthetists of Great Britain & Ireland (AABGI) guidance for perioperative blood glucose monitoring in diabetic patients.
* Target CBG 6-10mmol/L
* Check CBG pre-induction and at least hourly thereafter
* Reduce time interval between checks if results are outside acceptable range
170
List three classes of oral hypoglycaemic agents that are available and describe the mechanism of action and a side effect for each
* Biguanides e.g. metformin: improves peripheral insulin sensitivity - nausea and loss of apetite
* Sulphonylureas e.g. gliclazide: stimulates pancreatic insulin secretion - weight gain
* SGLT-2 inhibitors e.g. canaglifozin: inhibits reuptake of glucose from the kidney - increased risk UTIs, polyurea
* Thiazolidinediones e.g. pioglitazone: improves peripheral insulin sensitivity - increased risk of cardiovascular death
* Alpha-glucosidase inhibitors e.g. acrabose: inhibits breakdown of disaccharides in the gut, inhibits carbohydrate absorption - bloating
* Meglitinides e.g. repaglinide: stimulates pancreastic insulin secretion - weight gain
* DPP4 inhibitors e.g. sitagliptin: inhibits DPP4 from breaking down GLP1 to enhance insulin secretion and reduce glucagon release - pancreatitis
* GLP1 analogues: mimic endogenous GLP to enhance insulin secretion and reduce glucagon release - reduced gastric emptying
171
Give the diagnostic criteria of DKA
* pH < 7.3 or bicarb > 15mmol/l
* BGC > 11mmol/L or known diabetic
* Ketones > 3 mmol/l or 2+ ketonuria
172
State the treatment of hypoglycaemia in a diabetic patient under GA
* 50ml 20% glucose if CBG 4-6
* 100mls 20% glucose if CBG < 4
173
Give two indications for the perioperative use of VRIII for patients with T2DM
* Patients taking insulin who will miss more than one meal
* HbA1c > 69 mmol/mol
* Patients requiring emergency surgery with CBG > 10 mmol/l
* Patients with recurrent hyperglycaemias
174
List patient related and anaesthetic related risk factors for PONV
Patient related:
* Female
* Non smoker
* Migraines/motion sickness
* History PONV
* Younger age
Anaesthetic:
* Use of post-operative opioids
* Use of volatiles
* Nitrous oxide use
* Neostigmine use
* Stomach distension due to BVM ventilation
Surgical
* Middle ear
* Strabismus
* Gynaecology
* Laproscopic
* Neurosurgery
175
Give two complications of PONV in adults
* Reduced patient satisfaction
* Delayed discharge from recovery/hospital
* Delayed return to oral intake
* Suture/wound dehiscence
* Aspiration
* Dehydration
* Electrolyte imbalance
* Oesophageal rupture
* Raised intracranial/intraoccular pressure
176
State the location of the vomiting centre
Medulla
177
List three inputs to the vomiting centre
* Cerebral cortex
* Vestibular centre
* Chemoreceptive trigger zone
* Gastrointestinal
* Baroreceptors
178
For the following drugs, state the reeptor they target and the location of action of each
* Cyclizine
* Hyoscine
* Ondansetron
* Prochloperazine
* Cyclizine: H1, vestibular and vomiting centre
* Hyoscine: muscarinic acetylcholine, vestibular and vomiting centres, chemoreceptive trigger zone
* Ondansetron: 5HT3, GI tract, chemoreceptive trigger zone, vomiting centre
* Prochloperazine: D2, GI tract, chemoreceptive trigger zone, vomiting cenre (give domperidone in Parkinson's as it does not cross BBB)
179
Give two non-pharmacological interventions that have been shown to be effective in reducing PONV in adults
* Acupressure
* Aromatherapy
* Avoid dehydration
* Gum chewing
180
Give three constituents of daily fluid maintenance for an otherwise well adult who is having a short period wihtout oral intake
* 25-30ml/kg/day water
* 1mmol/kg/day of sodium, potassium and chloride
* 50-100g/day glucose (100ml 5% contains 5g)
181
List three ways you would assess the hydration status of a patient
* History: presence of third, risk factors for dehydration e.g. fever, reduced intake, diarrhoea
* Clinical examination: skin turgour, mucous membranes, central and peripheral capillary refill gradient, urine output, pulse volume, peripheral or pulmonary oedema
* Blood results: lactate, sodium
* Review fluid balance chart including intake and outputs, urine outpput
182
List three causes of perioperative hypovolaemia
* Excessive starvation
* Bowel prep for GI surgery
* Pyrexia
* Blood loss
* Insensible losses via open body cavities
* Third spacing due to inflammatory response
183
Give the osmolality, sodium, chloride and potassium concentrations in 1L Harmann's, sodium chloride 0.9% and sodium chloride 0.18% with 4% glucose
* Hartmann's: 278 mOsm/kg, Na 131 mmol/L, Cl 111 mmol/l, K 5 mmol/l
* 0.9% NaCl: 308 mOsm/kg, Na 154 mmol/L, Cl 154 mmol/L
* 0.18% NaCl with 4% glucose: 284 mOsm/kg, Na 31mmol/L, Cl 31 mmol/L
184
State the metabolic disturbance associated with infusion of large quantities of 0.9% sodium chloride
Hyperchloraemic metabolic acidosis
185
What is meant by "balanced" intravenous fluids
Reduced chloride content compared to 0.9% NaCl with alternative anions used
186
Give three aspects of a patient's history that suggest malnutrition
* Low BMI
* Long term GI disease
* Inflammatory conditions
* Alcohol excess
187
List three perioperative benefits of nutritional support in a malnourished patient
* Improved wound healing
* Improved immune function
* Improved rehabilitation due to maintenance of muscle strength
188
List four components of a standard nutritional regimen with the standard daily requirement for each.
* 25-30ml/kg/day water
* 1mmol/kg/day of sodium, potassium and chloride
* 0.1mmol/kg/day calcium and magnesium
189
Give three advantages of enteral nutrition
* Cheaper than TPN, avoids line infections
* Reduced risk of stress ulceration
* Maintenance of gut integrity
190
Give three disadvantages of enteral nutrition
* May not be absorbed so ineffective nutrition
* Risk of aspiration
* Necrosis and bleeding of nose or small bowel due to erosion by feeding tube
191
Give the daily energy requirement of a health 70kg adult
1750-2100 kcal/day
192
Give the recommended daily proportions of carbohydrate, fat, and protein in a healthy adult.
* 50% carbohydrate
* 25% fat
* 25% protein
193
Define refeeding syndrome
Potentially fatal shifts in electrolytes and fluids that may occur upon feeding after a period of malnourishment.
194
Explain the underlying pathophysiology of refeeding syndrome.
1. Chronic malnutrition causes depletion of electrolytes through reduced intake
2. Serum concentrations are maintained better than intracellular concentrations as much ionic movement across cell membranes is energy dependent, and the intracellular compartment becomes contracted
3. Upon refeeding, the sudden availability of glucose causes insulin-driven movement of potassium into cells and provides an energy source for other active electrolyte transort mechanisms
4. Depleted intravascular reserve results in dysfunctional cellular activity, alters electrochemical membrane potentials and results in arrythmias and seizures
195
List the three major electrolyte abnormalities seen in respiratory syndrome
* Hypophosphataemia
* Hypokalaemia
* Hypomagnesaemia.
196
What is the most common nutritional deficiency in refeeding syndrome
B1
197
List five risk factors for refeeding syndrome
* Low BMI
* Unintentional weight loss
* Poor or absent nutritional intake for 5-10 days
* Low serum potassium
* Alcohol misuse
* Administration of chemotherapy, insulin, antacids and diuretics
198
Type I and Type II error
Type I: false positive, incorrect rejection of null hypothesis
Type II: false negative, failure to reject false null hypothesis
199
Pros and cons of retrospective trials
- can be done inexpensively, in less time and to answer questions which would not be ethical to study prospectively
- often incomplete data, recall bias and cannot randomise
200
Phases of a clinical trial
Phase 1: screen for safety in small group of healthy individuals
Phase 2: establish efficacy against placebo
Phase 3: confirmation of safety and efficacy in larger group
Phase 4: ongoing evaluation and safety
201
Explain the principle of MRI
* Hydrogen atoms are abundant in the body
* Hydrogen atoms posess a property called spin
* When surrounded by a strong magnet, spin aligns with the magnetic field
* As pulses of magnetic field are applied, the atoms align and relax, emitting energy
* The frequency of energy corresponds with the type of hydrogen bond
* Energy is detected by receiving coils and translated onto pixels on a screen
202
Three nuclei of vagus nerve
Dorsal nucleus of the vagus
Nucleus ambiguus
Nucleus tractus solitarius
203
Immediate relations of right vagus nerve at C6
Anterior: right thyroid lobe
Posterior: anterior scalene
Medial: common carotid
Lateral: internal jugular
204
Immediate relations of right vagus nerve at T4
Anterior: SVC
Posterior: right lung/oesophagus
Medial: trachea
Lateral: azygous vein, brachiocephalic vein
205
Branches of vagus nerve
APE SCRAP
Auricular
Pharyngeal
Esophageal
Superior laryngeal
Cardiac
Recurrent laryngeal
Anterior trunk
Posterior trunk
206
At what level does the vagus nerve pass through the diaphragm
T10
207
Indications for vagal nerve stimulator
Treatment resistant epilepsy and depression
208
Perioperative considerations for vagal nerve stimulator
Avoid monopolar diathermy
Place defibrillator pads as far away from device as possible
