SBA 300 Paper 5

Question 1

1. An asthmatic 40-year-old woman with myasthenia gravis (MG) presents for a
   multi-level lumbar decompression. She was diagnosed with MG 8 years ago,
   has difficulty with swallowing solids, and her current medication includes
   pyridostigmine 720mg/day and her forced vital capacity (FVC) is 2.9 litres.
   Which of the following is most likely to predict her requirement for a period of
   postoperative ventilation?
   A Bulbar symptoms
   B Pyridostigmine use of 720mg/day
   C FVC of 2.9 litres
   D Duration of disease >6years
   E Concurrent history of asthma

Answer 1

1. D Duration of disease >6 years
   Myasthenia gravis (MG) is an autoimmune disease with a prevalence between 1
   in 10,000–100,000. Women are more likely to be affected with a female:male ratio
   of 3:2. The disease is caused by IgG antibodies to the post-synaptic acetylcholine
   (ACh) receptors at the neuromuscular junction of skeletal muscle. These receptors
   are occupied by the antibodies and ultimately destroyed through complement-
   mediated immune processes. MG is therefore associated with fatiguing muscle
   weakness, as only a limited response to ACh released at the neuromuscular junction
   is possible and any subsequent stimulation results in fewer and fewer receptors
   available for activation.
   The extent of muscle involvement and severity of disease was classified by Osserman
   as seen in Table 5.2.15% of patients fall into Class I, the remaining 85% suffer from generalised MG.
   Cardiac and smooth muscle is entirely unaffected.
   An anaesthetic and surgery can impact on a patient withMG in a number of ways.
   The physiological stress in itself can exacerbate symptoms and, for a patient who
   may be unable to achieve adequate tidal volumes or cough ordinarily, lack of pre-
   operative planning could prove fatal.
   There are four recognised risk factors that are associated with an increased likelihood
   of requiring a period of postoperative ventilation.
2. MG duration of >6 years – this has the greatest predictive value
3. Concurrent history of chronic respiratory disease
4. Pyridostigmine requirements of >750mg/day in the preceding 48 hours
5. Forced vital capacity <2.9 litres
   Other considerations for trying to predict the need for respiratory support include
   surgery – type, length and need for intubation; anaesthetic – general +/– local, need
   for muscle relaxation and perhaps reversal; medication – opiate use in a patient
   with affected respiratory reserve, drugs such as aminoglycosides or beta-blockers
   that can cause an exacerbation of MG and administration of the patient’s normal medication immediately post operatively, i.e. conversion of oral pyridostigmine to
   intravenous equivalent doses (30mg orally = 1mg intravenously).
   The factor most likely to predict this patient’s requirement for postoperative
   ventilation is her duration ofMG of >6 years.

Question 2

2. You are anaesthetising a 68-year-old patient for bowel resection for sub-acute
   obstruction. He had been vomiting intermittently for 3 days. After induction of
   anaesthesia he became hypotensive so you commenced a noradrenaline infusion
   which is currently running at 0.2µg/kg/min. A thoracic epidural has been sited but
   only a test dose has been given so far. Blood pressure is 110/70 and capillary refill
   time is 4 seconds. An oesophageal Doppler is in situ. Based on the waveform and data shown in Figure 5.1, what is the appropriate first
   course of action?
   A Increase the noradrenaline infusion
   B Commence a dobutamine infusion
   C Commence the epidural infusion and leave the noradrenaline
   D Commence a GTN infusion and leave the noradrenaline
   E Administer 250mL of Hartmann’s solution and decrease the noradrenaline

Answer 2

E Administer 250mL of Hartmann’s solution and decrease
the noradrenaline
The oesophageal Doppler is a minimally invasive cardiac output monitor. The
physical principle underlying the technology is the Doppler Effect, where the
changing frequency of ultrasound waves reflected from red blood cells as they pass
along the descending aorta is used to calculate the blood velocity. The Doppler
equation uses this frequency shift to estimate the velocity of red blood cells as they
pass the probe. By integrating this with time, and taking the area under the curve
(velocity vs time) the velocity time integral can be calculated (VTI). This is a measure
of stroke distance (Figure 5.2, distance=velocity x time). When multiplied by the
aortic cross sectional area the stroke distance gives the volume of blood passing the
probe in a given period of time. The aortic cross sectional area is usually estimated from a normogram based on the
patient’s age, weight and height (which are input by the operator at start up) but can
also be measured with transoesophageal echocardiography. It should be apparent
that not all of the blood ejected via the aortic valve travels in the descending aorta
so a correction factor is used to account for coronary, brachiocephalic, carotid
and subclavian flow to give a figure for stroke volume (SV). Cardiac output is then
calculated by multiplying SV by heart rate.
Correct positioning of the probe gives the characteristic waveform seen above.
Elements of the waveform can be used to indicate left ventricular contractility,stroke volume, preload and afterload. When interpreting data from the oesophageal
Doppler it is important to appreciate the interdependency of the variables.
Peak velocity
The speed at which blood is ejected from the left ventricle is proportional to
inotropy. It declines with age, with normal values for a 20-year-old being around
100 cm/s compared with around 30–60cm/s at the age of 90. The peak velocity
measurement in the patient in question is 22cm/s; almost certainly lower than
expected. As well as reflecting contractility, peak velocity (PV) is inversely related to
afterload for a given level of inotropy.
Stroke distance/stroke volume
Although stroke volume involves the use of an estimated aortic cross sectional area,
the values are almost certainly more familiar to most than those of stroke distance.
The patient in the question has a low stroke volume which should then prompt the
user to think about the causes of this - low preload, pump failure, dysrhythmia, high
afterload, and then to use the other information (both from the Doppler and clinical
sources) to guide treatment. The stroke volume calculated in this example is lower
than would be expected.
FTc = flow time corrected = systolic ejection time corrected for heart rate
This has been used as a measure of preload because the fuller the left ventricle is, the
longer it will contract. However, this assumes a given level of inotropy and afterload
and therefore is susceptible to changes in these variables, not just preload. Normal
FTc is 330-360 ms (based on the assumption that systole occupies around a third of
the cardiac cycle (corrected for a heart rate of 60, so a total cycle time of 1000ms = 1
s). In the patient described above, the FTc is 250 ms so is lower than expected.
Afterload
Changes in afterload will alter the width and peak of the waveform according to the
work undertaken by the left ventricle. An increase in afterload will result in shorter
FTc and lower PV whilst lowering afterload with reduce left ventricular work and
result in higher PV and longer FTc.
Any change in left ventricular dynamics will therefore lead to a change in the shape
of the waveform created (assuming other factors including aortic cross section and
regional blood flow are constant).
To summarise the data from the patient above, he has a good chance of
preoperative hypovolaemia, compounded by surgery and general anaesthesia and
has Doppler data suggestive of: low cardiac output, low stroke volume, low peak
velocity and low FTc.
The most likely clinical explanation for this is that the patient is being over-treated
with a vasoconstrictor (in this case noradrenaline) which is in turn masking
significant hypovolaemia; A is therefore not the correct option. The appropriate first step is therefore option E; to give a fluid bolus and assess response; an appropriate
Doppler response would be widening of the waveform and an increase in the area
under the curve (and so stroke volume). This may allow a reduction in the dose of
catecholamine which in turn will reduce afterload and improve myocardial oxygen
balance and contractility.
Although commencement of the epidural infusion is part of optimal perioperative
management, doing so before correction of hypovolaemia may lead to hypotension
and escalating noradrenaline requirements (a similar scenario may occur with GTN).
It should be noted that epidurals, and indeed anaesthetic agents, will alter the shape
of the Doppler waveform by lowering systemic vascular resistance and therefore
raising FTc, making the waveform appear wider.
Although cardiac index is low, in primary pump failure left ventricular end-diastolic
volume would be expected to increase leading to normal FTc. In addition, the
patient already has a tachycardia, which dobutamine may well exacerbate, and so
option B is not currently advisable.

Question 3

3. A patient in the cardiac intensive care unit suffers a cardiac arrest following three
   vessel coronary artery bypass grafting. He has epicardial pacing wires with the box
   set to DDD. The monitor shows pulseless electrical activity with pacing spikes.
   Cardiopulmonary resuscitation (CPR) is commenced.
   What is the most appropriate next step?
   A 1mg adrenaline IV
   B 300mg bolus of amiodarone
   C Institution of external pacing
   D Exclusion of a tension pneumothorax
   E Turn off the pacemaker

Answer 3

E Turn off the pacemaker
Although the incidence of cardiac arrest post cardiac surgery is low (0.7–2.9%),
survival following an arrest is high, primarily due to a reversible cause often being
present. In up to 50% of cases ventricular fibrillation (VF) is the cause. A protocol
has been developed and published by the European Association for Cardiothoracic
Surgery. In the situation described above, the patient is being paced, so underlying
VF would not be immediately obvious.
Accordingly, the appropriate first step would be to cease pacing, check the
underlying rhythm and defibrillate as indicated. If 3 DC shocks are unsuccessful,
300mg amiodarone can be given whilst preparing for sternotomy.
If no dysrhythmia is present, attention should then turn to other reversible causes
such as tamponade, tension pneumothorax and haemorrhage. Asystole or severe
bradycardia would be treated with pacing (in this instance via the epicardial wires)
or atropine pending immediate sternotomy.
Concurrent management would include verification of endotracheal tube
placement, ventilation with 100% oxygen, CPR and further DC shocks every 2
minutes in the case of an ongoing shockable rhythm.
Immediate use of adrenaline, and especially doses of 1mg, followed by correction
of a reversible cause and restoration of cardiac output may lead to severe rebound
hypertension and consequent bleeding. Answer A would not be an appropriate first
step in this instance.

Question 4

4. A 70-year-old smoker with limited mouth opening having previously undergone
   a neck dissection with adjuvant radiotherapy is scheduled for surgery to treat his
   right middle lobe tumour. A difficult airway is anticipated and it is likely that post-
   operative ventilatory support will be required.
   Which of the following is the most appropriate airway management strategy?
   A Fibreoptic intubation with a single-lumen tube and a right sided bronchial
   blocker
   B Fibreoptic intubation with a single lumen tube and a left sided bronchial
   blocker
   C Videolaryngoscopy and insertion of a left sided double-lumen tube
   D Fibreoptic left sided endobronchial intubation with a single-lumen tube
   E Awake tracheostomy and insertion of right sided double-lumen endobronchial
   tracheostomy tube

Answer 4

A Fibreoptic intubation with a single-lumen tube and a
right sided bronchial blocker
Anaesthetists are often asked to isolate and selectively ventilate a single lung to
improve the surgical field. Lung isolation is achieved by collapsing the lung in the
operative hemithorax and can be achieved by the use of double lumen tubes,
bronchial blockers and endobronchial tubes. Familiarity with the advantages
and disadvantages of these different techniques is important, particularly when
presented with patients who are likely to have a difficult intubation and need post-
operative ventilation.
In the case above, the safest way to establish an appropriate airway is by performing
an awake oral or nasal fibreoptic intubation with a single lumen tube followed
by insertion of a right sided bronchial blocker to collapse the operative lung. A
bronchial blocker is a balloon tipped device which can be inserted down a single
lumen endotracheal tube and be placed under fibrescopic guidance into main
bronchi or lobar segments to cause distal lung deflation. Bronchial blockers can
be useful in patients with difficult airways when there is a plan to ventilate post-
operatively, since a potentially hazardous tube exchange at the end of the operation
is avoided. Compared to double lumen tubes however, bronchial blockers achieve
less reliable and slower lung deflation with an increased likelihood of intra-operative
dislodgement. The inflated balloon also prevents access to the deflated lung for
suctioning or oxygen delivery.
Double lumen tubes consist of a tracheal and an endobronchial tube attached to
one another in parallel thereby allowing isolation of either lung when correctly sited.
They are divided into right and left-sided tubes according to the orientation of the
endobronchial tube within the tracheobronchial tree. Since the right upper lobe
bronchus arises in closer proximity to the carina when compared to the left, there
is a higher risk of inadvertent upper lobe collapse when right sided tubes are used.
Advantages of double lumen tubes over bronchial blockers include the ability to
deflate and re-expand both lungs easily intra-operatively (Table 5.3). There is also
unimpeded access to either lung for bronchoscopy, suctioning and oxygen delivery.
Since double lumen tubes are large diameter and pre-shaped, they may be difficult
to site in patients with a limited mouth opening (case above) or with distorted lower
airway anatomyAn uncut single lumen tracheal tube can be advanced into a bronchus to isolate the
lungs in emergency situations such as an acute contralateral tension pneumothorax or
airway haemorrhage. For elective operations however, the use of double lumen tubes
or bronchial blockers are better choices for controlled lung isolation (Figure 5.3Rarely, patients may require lung isolation via a tracheostomy and double lumen
endobronchial tracheostomy tubes are available for this purpose. In the above
scenario where there has been previous surgery and radiotherapy to the neck, the
formation of a tracheostomy may be technically challenging.

Question 5

5. A 75-year-old man is to have a cystoscopy and bladder biopsy as a day surgery
   case. He has a 40 pack year history of smoking. Recent spirometry has shown his
   FEV1/FVC is 0.6, and echocardiography has shown an ejection fraction of 40%. He
   has been consented for a spinal anaesthetic.
   What is the most appropriate solution for the spinal injection?
   A Hyperbaric bupivacaine 0.5% 2mL
   B Hyperbaric bupivacaine 0.5% 2mL with 300µg diamorphine
   C Plain bupivacaine 0.5% 2mL with 10µg fentanyl
   D Hyperbaric prilocaine 2% 2mL with 10µg fentanyl
   E Hyperbaric lignocaine 2% 2mL with 10µg fentanyl

Answer 5

5. D Hyperbaric prilocaine 2% 2mL with 10µg fentanyl
   A spinal anaesthetic in this patient with significant respiratory disease avoids the
   need for airway manipulation and ventilation, with the risks of increased airway
   reactivity, pneumothorax and postoperative respiratory compromise. Selective
   spinal anaesthesia is a technique favoured in day surgery that describes a block
   concentrated on the operative site and aims for a predominately sensory rather than
   complete motor block. In higher risk day surgery patients it allows earlier recovery
   and mobilisation and avoids the cardiovascular instability associated with more
   extensive spreadThe ideal agent for such a block would:
   t have a rapid onset
   t provide a dense predictable sensory block
   t have a short duration of action to allow early recovery and ambulation
   t have a favourable side-effect and safety profile
   Hyperbaric prilocaine 2% has been licensed for spinal use in the UK since 2010 and
   is now widely accepted as the agent of choice for day surgery. It has both a rapid
   onset and resolution of block and confers a higher degree of cardiovascular stability
   compared to bupivacaine.
   Low doses of hyperbaric bupivacaine can achieve selective blockade but doses
   higher than 7mg are associated with urinary retention especially in those having
   urology procedures and those older than 70 years. Plain solutions are slightly
   hypobaric at 37oC and less predictable as they produce greater variability in spread,
   so are less likely to result in a selective block.
   Lignocaine has an early onset time and a short duration of action, but has been
   associated with TNS (transient neurological symptoms – self-limiting pain and
   dysaesthesia in the buttocks) especially after day surgery in the lithotomy position.
   Fentanyl acts synergistically with the local anaesthetic allowing reduced dose and
   prolonged analgesia. Using small doses (10–25µg) avoids respiratory depression and
   is less likely to cause pruritus.
   Before attempting to mobilise after a spinal anaesthetic, patients should have
   return of perianal sensation, plantar flexion of the foot to pre-operative strength
   and proprioception of the big toe, and discharged after voiding and other standard
   criteria have been met.

Question 6

6. You are asked to review a confused 72-year-old man in recovery. He has had a
   transurethral resection of his prostate for benign prostatic hyperplasia (BPH). A
   brief assessment reveals him to be disorientated in time and place, and restless.
   Whilst you review his anaesthetic chart he has a short seizure, which resolves
   spontaneously.
   After assessing his airway breathing and circulation, which of the following would
   be the best immediate management:
   A Administration 2mg of intravenous midazolam
   B Starting an infusion of magnesium sulphate
   C Sending an urgent U&Es, FBC and osmolality, and prepare intravenous
   lorazepam in case of further seizure
   D Administering 20–40mg of intravenous frusemide
   E Infusing 1–2mL/kg 3% NaCl

Answer 6

6. C Sending an urgent U&Es, FBC and osmolality, and
   prepare intravenous lorazepam in case of further seizure
   Transurethral resection of the prostate (TURP) is a common procedure, and the best
   available treatment for benign prostatic hyperplasia (BPH) with obstructive lower urinary
   tract symptoms. TURP syndrome is caused by the absorption of hypotonic irrigation
   fluid. The quantity of absorbed fluid is important and the probability of developing TURP
   syndrome increases with the following factors which all increase absorption:
   t Length of resection, especially >1 hour
   t Significant bleeding, implying large quantities of open vessels
   t Bladder or prostatic capsular perforation, (fluid is rapidly absorbed from the
   peritoneum)
   t Height of the irrigation fluid bag. This corresponds to the hydrostatic pressure
   within the bladder. Heights >70 cm are unusual
   The syndrome is caused by changes in:Volume
   This is biphasic in nature. Initially, the circulation absorbs large volumes and there
   can be hypertension with a reflex bradycardia. This may also cause signs and
   symptoms of volume overload with left sided heart failure and pulmonary oedema.
   Later as the irrigation fluid shifts to the extracellular space (due to its hypotonic
   composition), there may be a relative hypovolaemia and hypotension. It’s worth
   bearing in mind that the first stage of hypertension is often masked by the low
   systemic vascular resistance (SVR) state of a spinal sympathetic block.
   Treatment of hypervolaemia resulting in left ventricular failure (LVF) involves
   frusemide, but hypervolaemia without LVF is better treated with mannitol as this
   lowers serum sodium less than frusemide. Hypotension and reduced heart rates are
   addressed with vasoconstrictors, calcium and atropine.
   Plasma sodium and osmolality
   The hyponatraemia of TURP syndrome is mainly dilutional, and produces headaches,
   nausea and vomiting, seizures and coma. However, of the two values, osmolality
   is by far the more important. This is because rapid falls in osmolality cannot be
   countered by pumps in neuronal cell walls, and the cells thus get flooded with water
   down its osmotic gradient, leading to cerebral oedema and increased intracranial
   pressure. If osmolality is relatively normal, low sodium does not need treatment in an
   asymptomatic patient. Sodium should only be corrected slowly to prevent pontine
   demyelination, and only correct until symptoms resolve, not to normal values.
   Treatment of hyponatraemia should be titrated to symptoms, slowly, not >1mmol/L/
   hour. Remember to measure the osmolality also. If the sodium is <120mmol/L, give
   3% NaCl (weight in kg x 0.6 x 2 = number of mL 3% NaCl needed to elevate sodium
   by 1mmol/L).
   Glycine
   Although glycine is an inhibitory neurotransmitter, it does have effects increasing
   NMDA receptor activity. This can produce the phenomenon of dis-inhibition,
   such that the first neurological symptoms may be of irritability and seizures. As
   concentrations increase, coma may follow. Due to its physiological antagonist
   action at NMDA receptors magnesium is a useful second line treatment for seizures
   associated with TURP syndrome.
   Treatment of seizures is supportive and if needed involves benzodiazepines such as
   lorazepam and if required magnesium.
   The first stems A and B suggest treatments primarily focussed on seizure control.
   While the possibility of a further seizure should be at the forefront of one’s mind,
   a self-terminating isolated seizure may not require treatment. Instead the focus
   should be on identifying the severity of the condition and thus determining whether
   specific treatment is required, as in stem C. Empirical treatment without knowing the
   sodium or osmolarity first may be dangerous (E), and treatment with frusemide (D) is
   reserved for heart failure secondary to fluid overload

Question 7

7. An obese 45-year-old woman with progressive conductive hearing loss secondary
   to chronic suppurative otitis media is due to undergo tympanoplasty. During the
   preoperative safety check list, the team is informed by the surgeon that intubation
   and facial nerve monitoring is required.
   Which of the following would be the most appropriate to use as part of your
   anaesthetic technique?
   A Remifentanil infusion
   B Ketamine bolus
   C Nitrous oxide
   D Clonidine infusion
   E Magnesium sulphate infusion

Answer 7

A Remifentanil infusion
The middle ear is a delicate air filled cavity containing three ossicles which transmit
sound vibrations from the eardrum to the cochlea. Due to its small size, location
and fragile content, the provision of anaesthesia for surgery to this unique site is
especially challenging.
Maintaining the surgical field is difficult since small amounts of bleeding or
movements can significantly degrade the view during microsurgery. Furthermore,
the use of neuromuscular blocking drugs to provide akinesia is frequently restricted
due to the need for intraoperative facial nerve monitoring. A smooth, cough-free
wake up is desirable to avoid compromising the surgical result, and patients are at
an increased risk of developing post-operative nausea and vomiting.
Remifentanil is the most appropriate drug to use in this scenario since it addresses a
number of problems associated with middle ear surgery anaesthesia in addition to
providing adequate intraoperative analgesia. To minimise blood loss, remifentanil
can be used to rapidly control the blood pressure to deliver safe hypotensive
anaesthesia and a stable pulse in suitable patients. Remifentanil also allows
mechanical ventilation without neuromuscular blocking agents which enables
uninterrupted facial nerve monitoring. Remifentanil also attenuates coughing on
emergence, and if used in conjunction with propofol as part of a total intravenous
anaesthetic, reduces the incidence of post-operative nausea and vomiting.
Ketamine produces intense analgesia and dissociative anaesthesia via NMDA
receptor antagonism at both spinal cord and central sites. It can however cause
hypertension due to an increased sympathetic outflow which can result in bleeding
into the surgical field. Another drawback is the risk of emergence delirium and
coughing due to hypersalivation after extubation. For these reasons, it is not the
most appropriate option.
Nitrous oxide produces analgesia by inducing endogenous opioid release centrally.
Unfortunately, since the relative solubility of nitrous oxide in blood is far greater than
that of nitrogen, it will diffuse into the middle ear cavity at a more rapid rate than
nitrogen can leave. Subsequent raised middle ear pressures can cause displacement
of tympanoplasty grafts and promote nausea and vomiting, making this option
inappropriate.
Clonidine is a central acting presynaptic α2 adrenoceptor agonist with numerous
effects which lend themselves favourably to anaesthesia for middle ear surgery.
Not only does clonidine provide intraoperative analgesia, but also a reduction in
sympathetic outflow and therefore hypotension to minimise blood loss. Its sedative
effects may also contribute to a smooth wake up. In contrast to remifentanil
however, clonidine does not obviate the need to administer neuromuscular blocking
drugs which will interfere with facial nerve monitoring.
Magnesium is a versatile drug also with many favourable pharmacodynamic
properties. As a result of its NMDA receptor antagonism, magnesium provides
analgesia. It also inhibits smooth muscle contraction and has a direct vasodilator
effect which causes hypotension. Magnesium does impede neuromuscular
transmission by inhibiting acetylcholine release at the pre-synaptic nerve terminal, but this is not enough on its own to cause paralysis and allow safe, controlled
ventilation.

Question 8

8. A 63-year-old man with a confirmed inherited pseudocholinesterase deficiency
   (EuEa) is attending for his first course of electroconvulsive therapy.
   Which of the following drug combinations is most appropriate for his induction of
   anaesthesia?
   A Propofol and mivacurium
   B Propofol and rocuronium
   C Propofol and alfentanil
   D Thiopentone and rocuronium
   E Thiopentone and alfentanil

Answer 8

B Propofol and rocuronium
The choice of anaesthetic agents for ECT depends on the ability to:
t provide rapid onset and recovery from unconsciousness
t provide adequate muscle relaxation to avoid injury from an uncontrolled tonic-
clonic seizure
t have minimal effect on the seizure duration or quality
The original gold standard was methohexital as it has minimal anticonvulsant
properties, rapid induction and recovery, and a wide therapeutic range. However, it
has now been replaced by newer hypnotic agents, and the widespread availability
of propofol, its good cardiovascular stability profile and quick emergence properties,
mean that it is the most commonly used agent. Low doses such as <1mg/kg are
used to avoid reducing duration of seizures. Etomidate may reduce seizure threshold
allowing lower currents to be used, but has a pronounced hyperdynamic response
and long emergence times. Thiopentone reduces the duration of seizures and
there is an increased arrhythmia risk. Inhalational induction with sevoflurane has
a reduced seizure duration compared to methohexital and is time consuming for
the anaesthetist. It is important that whichever agent is chosen, the same one is
used throughout the course of treatment to avoid influencing changes in seizure
threshold. Combining with opioids may reduce seizure duration but overall has an
induction agent sparing effect.
Muscle relaxants are essential in preventing uncontrolled convulsions and
musculoskeletal injury. Succinylcholine is still the most commonly used, typically a
dose of 0.5mg/kg.
Mivacurium is short acting and doses 0.15mg/kg should be used to control
muscle movements. Individuals with variations in the genes coding for the
pseudocholinesterase enzyme exhibit prolonged neuromuscular blockade. 4
alleles are described depending on the degree of enzyme inhibition; normal (Eu),
atypical or dibucaine resistance (Ea), fluoride resistant (Es) and silent (Es). 96% of
the population is homozygotes for the normal gene. Homozygotes for the atypical
or silent gene exhibit prolonged paralysis for up to 4 hours and homozygotes for
the fluoride resistant up to 2 hours. Heterozygotes exhibit mild prolonged paralysis
up to 10 minutes. Both suxamethonium and mivacurium are contraindicated in
cases of pseudocholinesterase deficiency, even in heterozygotes with intermediate
dibucaine numbers. Rocuronium or vecuronium are the most appropriate
alternatives, in view of the increasing availability of sugammadex.

Question 9

9. A 70-year old man is scheduled for foot surgery under general anaesthesia and a
   sciatic nerve block. There are no ultrasound machines available and you decide on
   a landmark technique to perform the block.
   Which one of the following described techniques results in the most proximal
   approach to performing a sciatic nerve block?
   A Mansour’s approach
   B Raj’s approach
   C Labat’s approach
   D Beck’s approach
   E Guardini’s approach

Answer 9

A Mansour’s approach

○ The merger of the anterior rami of spinal nerves L4, L5, S1, S2, S3 and S4 forms the sacral
plexus.
○ This plexus provides sensory and motor innervation to the posterior thigh, most
of the lower leg and the foot.
○ The two most important branches for the lower limb
surgery are the sciatic nerve and the posterior femoral cutaneous nerve of the thigh.

○ The sciatic nerve is derived from the ventral rami of L4–S3 and is the longest and widest nerve in the body. It supplies the posterior thigh and almost the entire lower
limb below the knee. It exits the pelvis through the greater sciatic notch below the
piriformis muscle to enter the lower limb between the ischial tuberosity and the
greater trochanter. The sciatic nerve then descends in the posterior thigh toward the popliteal fossa where it runs posterolateral to the popliteal vessels in the upper part of the fossa.
○ The sciatic nerve is actually a mixture of two nerves from its origin (tibial and common peroneal nerves). In the pelvis, the two nerves are packed together by
connective tissues to form the sciatic nerve. At the proximal pole of the popliteal
fossa, the sciatic nerve divides into its component nerves. Sometimes, the two
components separate early at the upper thigh or even in the pelvis.
○ The posterior femoral cutaneous nerve (PFCN) is found in the pelvis from the anterior rami of S1, S2 and S3. This is purely a sensory nerve and it descends with
the sciatic nerve in the upper part of the thigh. It gives off the inferior cluneal nerve (sensation to the lower buttock), perineal branches (sensation to the external genitalia), and femoral and sural branches (sensation to the back of the thigh and calf). It ends in the popliteal fossa where it anastomoses with the sural nerve.
The most common indications for sciatic nerve block are anaesthesia and
postoperative analgesia for foot and ankle surgery. It is also useful for operations above the knee, and for management of chronic pain conditions in the lower limbs such as sciatic neuropathy.
Various approaches have been described to block the sciatic nerve because of its
deep location and the difficulties associated with positioning.
● Mansour’s parasacral block:
Mansour describes this block in 1993.
• It is the most proximal approach to sciatic nerve and mainly used to provide analgesia following major ankle and foot surgeries. It is more than an isolated sciatic nerve block
because it may block the entire sacral plexus, and this is advantageous for knee and above the knee operations when compared with distal sciatic nerve approaches. It
reliably blocks the two components of sciatic nerve and the PFCN.
The patient is positioned in the lateral decubitus position and a line is drawn connecting the posterior superior iliac spine (PSIS) and the ischial tuberosity. The
point of insertion is 6 cm caudal from PSIS along this line. A 100mm insulated block needle is used because the nerve is deep in this area. The motor response is
inversion and planter flexion (tibial) or dorsiflexion and eversion (peroneal) that can be elicited at a depth of 7–9 cm.
● Labat’s transgluteal approach:
This is a posterior approach to the sciatic nerve (Figure 5.4). The patient is positioned in Sims’ position (lateral decubitus with a slight
forward tilt) with the operative side up and hip flexed. Three lines are drawn. Line 1 is
connecting the PSIS and the greater trochanter (GT), line 2 is extended from the GT
to the sacral hiatus and line 3 is dropped perpendicularly from the midpoint of line 1
to intersect line 2. The needle entry point is where line 3 and line 2 meet. A 100mm
22G block needle is used and inserted perpendicular to all planes. The sciatic motor
response is usually observed at around 5–8 cm depth.
● Raj approach (lithotomy subgloteal): This has the advantages of supine approach to the sciatic nerve and easy landmarks. The patient is posited in a
supine position with both hip and knee flexed. A line is drawn extending from
the greater trochanter and the ischial tuberosity. The sciatic nerve twitches are
elicited by inserting a 100 mm 22G block needle perpendicularly at the line midpoint. (Figure 5.5)
● Beck’s anterior approach:
This approach to a sciatic nerve block has the advantage
of maintaining the patient in the supine position and the lower limb in the neutral
position. A longer needle (150 mm) is needed because the nerve is deep to the
adductors. Three lines are drawn: line 1 connects the anterior superior iliac spine and
the pubic tubercle, line 2 is parallel to line 1 but drawn from the greater trochanter, and line 3 is dropped perpendicularly from the junction of the medial and the
middle thirds of line 1 to intersect line 2. The needle insertion point is where line 3
intersects line 2. This block is technically challenging and requires a deep insertion of
the needle, hence can be a painful block to perform awake (Figure 5.5).
● Guardini’s subtrochanteric approach:
This block uses a lateral approach to the
sciatic nerve with a supine position and neutral lower limb. The point of entry is 4 cm
distal and 2 cm inferior to the greater trochanter. A 100mm 22G needle is used to
perform this block. It is not a common approach because it is technically difficult to
perform and may be painful (Figure 5.6).
● Popliteal approach: this is the most common approach to sciatic nerve because the
nerve is superficial and easy to find either by a peripheral nerve stimulator (PNS) or
ultrasound (US) technique (Figure 5.6).
There are two approaches to PNS guided popliteal block: posterior and lateral. Posterior approach: with the patient prone, a triangle is drawn in the popliteal fossa.
The popliteal crease forms the base, the biceps femoris tendon forms the lateral
border and semimembranosus tendon forms the medial border. A line is drawn
connecting the apex to the midpoint of the base. The needle entry point is 1cm
lateral to this midline and around 7–9cm above the skin crease (base). A 50mm 22G
block needle is used for this block and 25–40mL of local anaesthetic may be used.
In most people, the sciatic nerve divides into tibial and common peroneal nerves
near the apex of the popliteal fossa (8–10cm above the crease). However, in some
patients, as previously mentioned, the nerve separates more proximally. Therefore,
multi-stimulation or US-guided technique is advocated for a successful block.
Lateral approach: with the patient supine and the hip flexed to 30 degrees and the
groove between the vastus lateralis and biceps femoris is palpated. A 100mm 22G
block needle is inserted perpendicularly about 7–9cm above the popliteal fossa
crease. The common peroneal nerve is stimulated in this approach.
Ultrasound guided popliteal nerve block: a linear high frequency US probe is
placed parallel to the popliteal fossa crease. Then the probe is moved proximally
until the popliteal artery pulsation is seen. The sciatic nerve (or its two components)
is generally located lateral and superficial to the popliteal artery. The best place to
inject local anaesthetic is just before the division of the sciatic nerve. This can be
obtained by tracing the two components upwards until a single nerve is seen.

Question 10

10. A 68-year old man with emphysema is listed for elbow surgery under regional
    anaesthesia.
    Which of the following would be the most appropriate nerve block for this patient?
    A Interscalene brachial plexus block
    B Supraclavicular brachial plexus block
    C Medial infraclavicular brachial plexus block
    D Axillary brachial plexus block
    E Mid-arm peripheral nerve block

Answer 10

10. D Axillary brachial plexus block
    Patients undergoing upper limb surgery have several options of anaesthesia,
    including local, regional and general anaesthesia. Brachial plexus block represents
    the most common use of nerve blocks in current regional anaesthetic practice.
    There are different approaches to block the brachial plexus. According to the site of
    the surgery they are divided into two groups: blocks above the clavicle (interscalene
    and supraclavicular) and blocks below the clavicle (infraclavicular and axillary).
    Interscalene blocks are mainly indicated for shoulder and upper arm surgery. This
    approach targets the upper roots (C5-C7) and, because of the vertical arrangement
    of the brachial plexus roots in the interscalene groove, C8 and T1 nerve roots are
    missed, hence the ulnar nerve may not be blocked. Therefore, this approach is
    unreliable for hand and forearm surgery. Because the phrenic nerve runs anterior
    to the anterior scalene muscle, local anaesthetic injection at this level will almost
    always lead to a phrenic nerve blockade and may present a significant problem in
    patients with respiratory compromise, while the rare but important side effect of
    pneumothorax is also a possibility. The interscalene approach to a brachial plexus
    block is therefore is unsuitable in this clinical scenario.
    Supraclavicular blocks are performed at the level where the brachial plexus trunks
    are in close proximity to each other so the entire upper limb is blocked reliably.
    The usual indications of this block are arm and hand surgery, but it can also be
    used for shoulder surgery if a suprascapular block is performed separately. Ulnar
    sparing might be a problem with the supraclavicular approach because of the
    medial location of the inferior trunk in this area; however the use of ultrasound
    might overcome this problem. The incidence of pneumothorax in supraclavicular
    blocks is high due to the proximity of the brachial plexus to the dome of the pleura
    at this level. However, the risk of pneumothorax can be reduced with a modified
    approach and the use of ultrasound. This block may present a danger for patients
    with respiratory problems such as emphysema, hence should be avoided unless
    performed by anaesthetists with extensive skill in this technique.
    Infraclavicular blocks are performed at the level of the cords of the brachial plexus
    (See Figure 4.1). It blocks each of the three cords of the brachial plexus and therefore
    it anesthetises the entire arm successfully. It is a simple block to perform without
    the aid of ultrasound; however, the infraclavicular approach to brachial plexus block
    is not popular because of the fairly high failure rate and the risk of pneumothorax.
    The use of ultrasound significantly improves the success rate of this block but is
    remains a difficult procedure to perform. This block is not suitable for patients with
    respiratory compromise, again due to the high pneumothorax risk, particularly with
    a medial infraclavicular approach.
    The safest and the most commonly used and studied brachial plexus approach is
    the axillary block. It has few side-effects and usually covers the entire upper limb with the exception of the lateral part of the arm and the forearm, which requires
    additional musculocutaneous nerve block. This approach blocks the brachial
    plexus terminal branches and depends on the relationship of nerves to the axillary
    vessels. It is usually performed for elbow, arm and hand surgery. With no risk of
    pneumothorax and phrenic nerve block, the axillary block is the most suitable
    brachial plexus approach for patients with respiratory problems and lung diseases,
    and is therefore the most appropriate choice of block in this scenario.
    Radial, ulnar and median nerves can all be easily blocked in the arm as well.
    However, the duration of the regional anaesthesia tends to be shorter than with
    brachial plexus blocks. It is also limited by the requirement to block several nerves
    and the application tourniquet for most surgery. Therefore, this mid-arm peripheral
    nerve block is not the optimal option to consider in this clinical scenario.

Question 11

11. You have been called to assist in the care of a 17-year-old girl who has become
    increasingly agitated in the emergency department. She has a history of mental
    illness and has recently been behaving strangely. Now her actions are violent and
    compromising her safety and that of those around her. You are unable to assess her
    formally, and she has not had any blood tests, intravenous access or observations.
    Security officers are present, and the emergency department registrar tells you
    he would like to perform bloods, a CT head and a lumbar puncture. The plan has
    been approved by the girl’s mother and the paediatric consultant.
    How will you proceed?
    A Use security staff to hold the patient, insert intravenous access, and give 2mg
    midazolam and 2µg/kg fentanyl in the room
    B Use security staff to hold the patient, and give intramuscular 4mg/kg
    ketamine, then transfer to the resuscitation bay
    C Do nothing, and refuse to get involved with this case
    D Encourage her to take 20mg oral temazepam and review
    E Using security staff to hold the patient, transfer to theatre, and perform an
    inhalational induction with sevoflurane

Answer 11

11. B Use security staff to hold the patient, and give 4mg/kg
    ketamine intramuscularly, then transfer to rhesus
    The usual tenets of sedation applicable in the elective situation are not necessarily
    appropriate in the emergency setting. The important issues here are consent,
    holding/restraint as well as the provision of safe sedation.
    Consent
    At the age of 17 the patient is legally still a child. If she were able to demonstrate
    maturity and understanding and be judged to be Gillick competent, she would be
    able to give her consent. When it comes to refusing treatment the child may not do
    this in the same way, even if competent. A parent may still be able to consent for the
    child in this case. In the case of a parent refusing treatment on behalf of their child,
    (which the medical team believe is indicated), an interim care order may be granted
    by the Courts allowing treatment.
    In this scenario, the child lacks capacity. In England a doctor may act to provide
    treatment in the best interests of a child, even without parental consent. In this
    case parental assent/consent was available. All clinical information should be
    nevertheless clearly documented, alongside the reasons for the treatment plan, and
    a consent Form 4 could also be used for procedures, e.g. the CT/lumbar puncture.
    Holding and restraint
    In general, the principle is to use restraint only as a technique of last resort. Minimal force
    required for safety (of staff and patient) should be employed, by appropriate numbers of
    experienced and trained staff. The plan should be discussed with the parent beforehand,
    and opportunity for a discussion with parent and child should exist afterwards.
    Answering notes
    In this instance, oral medication is impractical (in option D), and as outlined above
    the legal case to intervene is clear, ruling out the attractive option of C. This leaves the use of intramuscular, intravenous or inhalational methods alongside minimal
    restraint. Most emergency departments would lack the facility of an anaesthetic
    machine, thus the degree and duration of restraint needed to transfer this girl to
    theatre and perform an inhalational induction makes option E impractical and
    dangerous. Holding to achieve intravenous access may be reasonable, but the
    choice of agents is not, as the CT scan and bloods should be relatively painless
    therefore the fentanyl in option A may not be required, as such the increased
    number of agents only serves to increase risks. In addition, a single dose of
    midazolam is unlikely to be successful for the duration of the investigations required.
    Thus, the option which minimises holding, involves only one agent, and provides an
    appropriate duration would be intramuscular ketamine. Thought does have to be
    given to inserting intravenous access and establishing safe monitoring for transfer,
    which is probably best achieved in a resuscitation area

Question 12

12. A 34-year-old man sustained a traumatic brain injury 3days ago and is currently
    intubated and ventilated on the intensive care unit. The nurse informs you during
    your daily review that the plasma sodium concentration is 121mmol/L.
    What other piece information would be most useful in establishing the cause?
    A Urine output volume measurement
    B Central venous pressure measurement
    C Degree of peripheral oedema
    D Urinary osmolarity measurement
    E Plasma osmolarity measurement

Answer 12

A Urine output volume measurement
This question is testing your knowledge and reasoning in an attempt to differentiate
between two common causes of hyponatraemia in a patient with a head injury. The
differential diagnosis is between syndrome of inappropriate anti-diuretic hormone
(SIADH) and cerebral salt wasting (CSW).
Hyponatraemia is serious: in-hospital mortality is increased by 2–4 times and a
difference in survival outcome is still present at 1-year follow-up. Correcting the serum
sodium concentration is also hazardous and if done too rapidly may precipitate severe
neurologic complications, such as central pontine myelinosis, which can produce
spastic quadriparesis, swallowing dysfunction and pseudobulbar palsy.
The classic way to differentiate between causes of hyponatraemia is to assess fluid
balance (see Table 5.4).
CSW is a condition that is poorly understood. Proposed mechanisms include
increased sympathetic activity causing a higher glomerular filtration rate and excess
atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) release resulting
in reduced renal water re-absorption.
It occurs most commonly in traumatic brain injury and presents in the first week
after injury and is normally self-limiting. The key clinical feature is hypovolaemia
with a high urine output production. The serum osmolarity may be normal or high
and urinary sodium is usually raised. The management involves replacing sodium
and water with 0.9% sodium chloride and if symptoms develop (anorexia, confusion,
unconsciousness and seizures) hypertonic saline may be indicated.
SIADH occurs as a result of traumatic brain injury, sub-arachnoid haemorrhage, brain
tumors and meningitis. Excess ADH results in increased water absorption from the
collecting duct of the nephron. The key clinical feature is hypervolaemia and low
urinary volume. The plasma has a low serum osmolarity due to the dilutional effect
of excess water and the urine osmolarity is usually high. The management involves
restricting water intake.In the intensive care unit great care is paid to getting the ‘numbers’ right. The fluid
balance is often adjusted according to a planned daily target. Central venous
pressure is of dubious benefit and a discrete value as is offered here is unhelpful.
Peripheral oedema may be multi-factorial and may be apparent even in the presence
of intravascular volume depletion. Osmolarity measurements are important in
making the diagnosis but in both differential diagnoses it may be normal and a
urinary sodium concentration is the more discerning test.
Considering the available options in the question above, urine output is the most
important piece of information: a high urine volume being produced in CSW and a
low urine volume being produced in SIADH.

Question 13

13. A 13-year-old boy presented to the emergency department with acute severe asthma
    1 hour ago. His usual peak expiratory flow (PEF) is 68%, and takes long acting E2
    agonist and high dose corticosteroid inhalers with montelukast tablets. You arecalled for advice as despite 4 x 2.5mg nebulised salbutamol, 500µg nebulised
    ipratropium and 40mg of soluble prednisolone the patient’s PEF remains 35%
    predicted, respiratory rate 32 per minute, speaking words, Spo2 93% on 10L/min of
    warm humidified supplemental oxygen and transcutaneous carbon dioxide level of
    5.1kPa.
    Which of the following should be the next intervention?
    A Rapid sequence induction using thiopentone and suxamethonium following
    by positive pressure ventilation on an anaesthetic machine using isoflurane to
    maintain anaesthesia and ease bronchoconstriction
    B Commence an intravenous salbutamol infusion at 10µg/minute
    C Give 20mmol of intravenous magnesium sulphate over 10–20 minutes
    D Give a further 5mg nebulised salbutamol
    E Give a loading dose of 5mg/kg aminophylline followed by an infusion at
    500µg/kg/hour

Answer 13

13. C Give 20mmol of intravenous magnesium sulphate over
    10–20 minutes
    This child has acute severe asthma and has failed to respond adequately despite
    optimal first line therapy. Though at risk of further deterioration, the severity of his
    current condition does not warrant intubation and positive pressure ventilation
    – both of which may be hazardous. There is no evidence to support an additional
    dose of nebulised salbutamol, or the use of intravenous bronchodilators. The next intervention likely to reverse his current pathophysiology is intravenous
    (as opposed to nebulised) magnesium sulphate although the optimal regime
    remains controversial.

Question 14

14. During the high dependency unit ward round you are called to the bedside of a 64-year-old gentleman with a background of hypertension who is awaiting primary angioplasty planned for the following day after being admitted with a non-ST
    segment elevation myocardial infarction. He is feeling anxious and has central chest pain. The heart rate has recently increased to 150 beats per minute and the blood pressure is 90/60mmHg. The ECG shows atrial fibrillation and widespread ST segment depression.
    What is your immediate course of action?
    A Ring the anaesthetist on call and arrange for direct current (DC) cardioversion in theatre
    B Ring the anaesthetist on call and arrange for direct current (DC) cardioversion on the HDU
    C Administer amiodarone 300mg intravenously over 30 minutes
    D Administer 2 g intravenous magnesium and optimise the serum potassium concentration
    E Ring the cardiologist on call and organise an urgent angiography

Answer 14

14. D Administer 2 g intravenous magnesium and optimise
    the serum potassium concentration
    ○ Atrial fibrillation (AF) is a common problem in the critical care environment with up to 15% of medical critical care patients developing AF at some point during their stay.
    The risk factors for developing AF are:
    Patient factors:
    t
    • Age >65 years old
    • Disease severity
    • Hypertension
    • Previous AF
    • Congestive heart failure
    • Chronic obstructive pulmonary disease
    • Previous use of calcium-channel blockers, beta-blocker or angiotensin-converting enzyme-inhibitor and withdrawal of catecholamine infusions
    Acute illness:
    • Hypoxia
    • Cardiac ischaemia
    • Sepsis or systemic inflammatory response syndrome
    • Fluid shifts (hypervolaemia and hypovolaemia)
    • Low serum magnesium and potassium Iatrogenic
    • Intra-cardiac catheter: central line or pulmonary artery catheter
    ○ AF probably occurs as a result of a final atrial insult (the last straw) on the
    background of chronic disease most commonly hypertensive or ischaemic
    myopathy. A sudden change in atrial dimensions as a result of filling pressures (either too high with fluid or too low with dehydration and sepsis), a change in electrochemical gradients across the myocyte (potassium and magnesium flux) or an ischaemic event are the common precipitating factors.
    ○ In health the atria contribute around 10% of cardiac output, increasing to 30% during exercise. This is well tolerated in patients with normal left ventricular function but in patients who depend on the higher filling pressures, loss of the ‘atrial kick’ results in low cardiac output. In addition the tachycardia results in poorer coronary blood flow and increased myocardial oxygen demand, which can result in even poorer ventricular performance. Patients in AF stay longer in ICUs and have an increased mortality in a general population but a causative relationship is hard to prove in medical or cardiac ICUs.
    Management of acute compromised AF (as in this scenario) is not that easy from an exam point of view: most intensivists practice on their experience and there are no randomised controlled trials to base your decisions on. Advanced Life Support guidelines suggest direct current (DC) cardioversion in the peri-arrest scenario and all critical care recommendations are based on a mixed group of studies, which compare effective treatments. So what do you do?
    In summary, the available evidence suggests:
    • Magnesium is more effective than amiodarone in restoring sinus rhythm, equally effective as amiodarone at achieving rate control and is safe
    • Amiodarone infusion converts AF into sinus rhythm in 70% of cases in the first 12 hours in medical critical care patients and 75% within 48 hours in general ICU population
    • In a mixed population with left ventricular impairment amiodarone did not cause significant haemodynamic compromise but transient hypotension may occur in systemic illness
    • The success rate of DC cardioversion in post-surgical and medical critical care patients is low and the recurrence rate is high
    • Digoxin is not effective in this population
    ○ Given the information above, and that the single best answer questions test judgment and reasoning (not just recall of life-support algorithms) the question can be re-visited. DC cardioversion requires sedation, which takes time to organise no matter where you do it. It also has a low chance of success in this patient group and a high chance of recurrence as the presumed ischaemic focus has not been dealt with. Expediting the angiography may be prudent but you must stabilise the patient first. The choice between amiodarone and magnesium is less obvious, but given that
    magnesium causes less hypotension and is at least as effective as amiodarone at rate and rhythm control, this is the most appropriate first step.

Question 15

15. A 72-year-old man on the intensive care unit has an APACHE II score of 48.
    Which of the following variables is the most heavily weighted in intensive care
    severity of illness scoring systems?
    A Age
    B Glasgow coma scale
    C Systolic blood pressure / dose of vasopressor
    D Pao2:Fio2 (PF ratio)
    E Arterial lactate concentration

Answer 15

15. B Glasgow coma scale
    Most scoring systems use the Glasgow coma scale (GCS) or include data from the
    GCS to assess the degree of neurological system failure. Furthermore, the GCS
    frequently makes up a large component of the acute physiology score or equivalent.
    For example, GCS constitutes 25% of the physiological score in Acute Physiology
    and Chronic Health Evaluation (APACHE) II, 20% in APACHE III and 22% in Simplified Acute Physiology Score (SAPS) II. The explanation for this is that in multivariant
    analysis of admission physiological variables, GCS is often the most highly predictive
    of hospital mortality

Question 16

16. A 34-year-old woman with end-stage liver disease due to auto-immune hepatitis
    presents with a 2-day history of productive cough and breathlessness and
    has been commenced on antibiotics for a chest infection. She has stigmataof decompensated liver disease with peripheral oedema and ascites. Her
    blood pressure is 70/40mmHg, her heart rate is 130 beats per minute and her
    temperature 38.9oC. An arterial blood gas analysis returned a lactate concentration
    0f 6.8mmol/L.
    Which of the following treatment options do you administer first?
    A 20mL/kg Hartmann’s solution
    B 20mL/kg 0.9% sodium chloride
    C 10mL/kg gelofusine
    D 10mL/kg human albumin solution (HAS) 20%
    E Commence vasopressor support as soon as possible

Answer 16

16. B 20mL/kg 0.9% sodium chloride
    Don’t panic – this question isn’t actually testing your knowledge of the big fluid trials that have been published in the last couple of years (although they are interesting).
    This is a question of judgement and emergency management.
    Even though the history seems complicated, here is a case of classic sepsis or septic shock (depending on how much fluid has been given so far). The more complicated aspects include liver failure which produces a multitude of problems when trying to assess fluid balance:
    • Sodium and water retention due to failure to metabolise steroid hormones
    (including aldosterone) result in oedema
    • Ascites and peripheral oedema may develop due to portal hypertension
    • Cardiac failure may occur secondary to chronic volume overload, due to the causative disease process itself (e.g. alcoholic cardiomyopathy) or a pericardial effusion
    These patients are often intra vascularly volume depleted associated with total body water overload, which is harder to recognise and manage.
    The lactate in Hartmann’s solution is usually metabolised very quickly in the liver into bicarbonate which then acts as a buffer within the plasma. In this case administering lactate-containing solutions to a septic patient who hyperlactaemic and is unable to metabolise it is counter-intuitive. In some analysis colloid administration is associated with an increased incidence of renal impairment, length of stay in ICU and mortality (which extends beyond the use of starch containing solutions). Also in terms of cardiovascular parameters there is no difference between crystalloid and colloid administration. See Table 5.5 for a quick summary of the fluid trials.
    Considering the options in the question, the choice remains between 0.9% sodium chloride administration and vasopressor administration. As you have not been told how much intravenous fluid has been administered (as is often the case), with the knowledge that resuscitation on medical wards tends to be on the conservative side and with a patient that needs immediate intervention the choice in this case is 0.9% sodium chloride (although this is contentious in a patient with liver cirrhosis).
    A timely and appropriately aggressive intervention is probably the most important factor in this case

Question 17

17. A 29-year-old woman, with a history of rheumatic fever is undergoing a category 1 Caesarean section under general anaesthesia for cord prolapse. After delivery of the baby and placenta, the estimated blood loss is 1100mL. The patient receives a total of 10 IU of syntocinon intravenously plus 10 IU/hour intravenous syntocinon infusion, intravenous ergometrine 500µg, 250µg intramuscular carboprost, misoprostol 1mg rectally, four units of packed red blood cells and two units of fresh frozen plasma. As the obstetricians are closing, the patient begins to produce frothy pink sputum up the endotracheal tube.
    Which of the following is the least likely cause of the pink frothy sputum?
    A Syntocinon
    B Ergometrine
    C Carboprost
    D Blood products
    E Misoprostol

Answer 17

17. E Misoprostol
    This woman has a history of rheumatic fever and may well have valvular heart disease. Stenotic valvular lesions can lead to fixed cardiac output states, with atrial contraction being more essential for adequate ventricular filling. Tachycardia or tachyarrhythmias will compromise this and lead to reductions in cardiac output, hence the need to maintain sinus rhythm. The systemic vascular resistance must also
    be maintained, as well as the preload.
    Uterotonics are necessary in this situation to control the ongoing haemorrhage, however, they can precipitate pulmonary oedema in patients with cardiac disease.
    Syntocinon can cause vasodilatation, tachycardia and pulmonary oedema, hence potentially compromising the cardiac output in fixed output states. It has been stated that the bolus dose of syntocinon should be avoided in severe cardiac disease, and an infusion used instead. Ergometrine can cause hypertension and increase the risk of myocardial infarction and pulmonary oedema. Carboprost also has the potential to cause pulmonary overload.
    Transfusion-related acute lung injury (TRALI) can occur following transfusion of blood products, and leads to pulmonary oedema, hypotension and hypoxia.
    Misoprostol is a prostaglandin E1 analogue and although there are rare reports of pulmonary oedema in the literature, it is unlikely to have caused this fast an onset of pulmonary oedema via rectal administration. It is therefore the least likely cause of this patient’s apparent pulmonary oedema.

Question 18

18. You have been fast bleeped to one of the delivery rooms on labour ward where a 38-year-old multiparous woman who is in the first stage of labour has suddenly become short of breath. Initial observations show oxygen saturations of 87%, a respiratory rate of 35, heart rate of 110 beats per minute and a blood pressure of 85/40mmHg.
    What is the least likely cause of her presentation?
    A Amniotic fluid embolism
    B Pulmonary embolism
    C Antepartum haemorrhage
    D Anaphylaxis
    E Tension pneumothorax

Answer 18

18. C Antepartum haemorrhage
    The differential diagnosis of this presentation includes all of the above answers.
    It is clinically difficult to distinguish between amniotic fluid embolism (AFE) and pulmonary embolism, as they can both present with cardiovascular and respiratory compromise. Certain aspects of this case pointing more towards AFE include the advanced maternal age, multiparity and onset during labour. AFE is one of the six direct causes of death as identified in the most recent Centre for Maternal and Child Enquiries (CMACE) report (2006–2008). The other five are:
    • Sepsis (commonest cause)
    • Pre-eclampsia and eclampsia
    • Thrombosis and thromboembolism
    • Early pregnancy deaths
    • Haemorrhage
    Management of AFE is supportive, which may include intubation and ventilation and delivery of the baby.
    Anaphylaxis and tension pneumothorax can also cause the above symptoms and auscultation of the chest would reveal wheezing or absent breath sounds respectively.
    Although haemorrhage causes hypotension, tachycardia and tachypnoea, it does not usually present with a sudden onset of breathlessness and hypoxia.

Question 19

19. A 6-week-old boy presents with a 3-day history of progressive non-bilious vomiting and poor feeding. An ultrasound scan confirms the diagnosis of pyloric stenosis.
    The capillary blood gas is shown in Table 5.1.The paediatric surgical team wants to perform an urgent pyloromyotomy. The infant last fed 12 hours previously.
    The immediate anaesthetic management of this infant should be:
    A Perform a rapid sequence induction because of delayed gastric emptying
    B Insert a nasogastric tube to aspirate any residual gastric content before
    induction of anaesthesia
    C Postpone anaesthesia and surgery until the infant is adequately fluid
    resuscitated and the acid-base balance corrected
    D Perform a caudal block after induction of anaesthesia to minimise analgesic
    opioid requirement
    E Arrange for postoperative intensive care monitoring because of increased risk
    of apnoea

Answer 19

19. C Postpone anaesthesia and surgery until the infant is
    adequately fluid resuscitated and the acid-base balance
    corrected Pyloric stenosis is not a surgical emergency, but is a medical emergency. Gastric outlet obstruction and vomiting of gastric acid cause dehydration, hypovolaemia and a hypokalaemic, hyponatraemic, hypochloraemic metabolic alkalosis. Pre-operative rehydration and correction of acid-base and electrolyte abnormalities should be the immediate treatment goal.
    There is little or no gastric emptying with pyloric stenosis. Aspirating the gastric content with a nasogastric tube and performing a rapid sequence induction are sensible precautions, but are not be the immediate anaesthetic management.
    There is increased risk of postoperative apnoea with pyloric stenosis. Using local or regional anaesthesia to minimise postoperative analgesic opioid requirement and arranging close post operative monitoring are sensible, but are not the immediate anaesthetic management.

Question 20

20. A healthy 15 kg 3-year-old boy is scheduled for an elective right orchidopexy for cryptorchidism. Intravenous induction was performed with fentanyl, propofol and rocuronium, and facemask ventilation was satisfactory. Direct laryngoscopy showed a grade 3 view. You had two unsuccessful attempts at intubation with direct laryngoscopy.
    The surgeon wants to proceed with surgery because this patient was previously cancelled for an upper respiratory tract infection.
    The best course of action now is:
    A Insert a supraglottic airway device to ensure airway patency and adequate
    ventilation. Proceed with surgery with positive pressure ventilation through
    the supraglottic airway device
    B Reverse rocuronium with sugammadex, monitor neuromuscular blockade
    with a peripheral nerve stimulator. Wake the patient up and postpone surgery
    C Insert a supraglottic airway device to ensure airway patency and adequate
    ventilation. Perform a fibreoptic intubation through the supraglottic airway
    device and proceed with surgery
    D Ensure airway patency and adequate ventilation using facemask. Perform a fibreoptic intubation and proceed with surgery
    E Have two further attempts at laryngoscopy. Check head and neck position,
    laryngoscopy technique, external laryngeal manipulation and adequate
    paralysis. Consider using a different laryngoscope, a smaller tube, a stylet or a bougie

Answer 20

20. E Have two further attempts at laryngoscopy. Check
    head and neck position, laryngoscopy technique,
    external laryngeal manipulation and adequate paralysis.
    Consider using a different laryngoscope, a smaller tube, a
    stylet or a bougie.
    The Association of Paediatric Anaesthetists of Great Britain and Ireland (APAGBI)
    and the Difficult Airway Society (DAS) published several joint guidelines on airway
    management in children in 2012 (Figure 5.7). In an unanticipated difficult tracheal
    intubation during routine induction of anaesthesia, when mask ventilation is
    satisfactory, no more than four attempts should be made at direct laryngoscopy and
    intubation. After four attempts, the secondary tracheal intubation plan should be
    initiated, which may include proceeding with surgery with a supraglottic airway device
    if appropriate, fibreoptic intubation if indicated, or postponing surgery otherwise.
    In this clinical scenario, it would therefore be most appropriate to optimise patient
    position, laryngoscopic technique and consider the use of alternative equipment.

Question 21

21. A 30-year-old man with Crohn’s disease has had a right hemicolectomy. You are asked to see him in recovery for uncontrolled abdominal pain. He declined an epidural preoperatively. Intraoperatively he had paracetamol and 20mg morphine.
    So far in recovery he has had a total of 25mg morphine with little effect. He is alert but very distressed with a normal respiratory rate. He does not normally take any strong opiates and has no allergies.
    What would be the most appropriate next step in the management of his acute pain?
    A Further titrate morphine up to a maximum of 20mg provided there are no
    overt signs of overdose
    B Give 2mg midazolam
    C Give 10mg ketamine intravenously
    D Give 100mg tramadol intravenously
    E Give 50µg clonidine intravenously

Answer 21

21. C Give 10mg ketamine intravenously
    Poorly controlled pain at the time of surgery is now thought to predispose to chronic post surgical pain. This patient has already received a large dose of morphine without much effect so further loading is also likely to be ineffectual. Midazolam should not be used as a treatment for pain. Tramadol is a general opioid receptor agonist but has particular affinity for the μ receptor. It also prevents the re-uptake of noradrenaline and serotonin so may confer some benefit.
    Ketamine is an NMDA antagonist that non-competitively blocks the NMDA receptors resulting in an ‘anti-hyperalgesic’ and ‘anti-tolerance’ effect. Ketamine has been shown to reduce pain intensity by up to 25% and reduce analgesic requirements by up to 50% in the first 48-hours postoperatively.
    Doses of greater than 30mg in a 24-hour period do not result in improved pain scores. In this setting major side-effects are uncommon.
    Clonidine is thought to confer some analgesic benefit but is less effective than Ketamine and non-steroidal anti-inflammatory drugs. It also results in unwanted hypotension and bradycardia.

Question 22

22. A 23-year-old woman had an above knee amputation for a localised osteosarcoma.
    She has developed unusual sensations at the amputated limb, pain at the stump,
    and a feeling that the limb is still there.
    Which of the following features are most likely to suggest true phantom limb pain
    in this patient?
    A Painful sensations at the stump
    B Good response to opioid analgesia
    C Intermittent pain
    D Inadequately working preoperative epidural analgesia
    E Sensations that the amputated limb is still present

Answer 22

22. C Intermittent pain
    There are three different sensations patients may experience in amputated limbs:
    • Stump pain: This is pain localised at the surgical site
    • Phantom sensations: This occurs when the patient feels that the limb is present but is not always painful
    • Phantom pain: This is pain that arises in the imagined, amputated limb
    Phantom pain, occurring in 30–85% of post-amputation patients, is very difficult to treat and tends to respond poorly to opioids. Various pharmacological therapies have been trialled, with some success with calcitonin, amitriptyline and gabapentin, although non-pharmacological therapies have an important role. Pre-emptive epidural analgesia has not been shown to reduce the incidence of development of phantom limb pain. The pain is most commonly intermittent and only rarely does the pain become constant. In this patient therefore, true phantom pain is most likely suggested by pain that is intermittent in nature.

Question 23

23. A 62-year-old woman presents for a left lobectomy. She is generally fit and well,
    and not on any regular medications.
    Which of the following is the best option for analgesic management:
    A Lumbar epidural
    B Intrathecal diamorphine
    C PCA morphine
    D Interpleural block
    E Thoracic epidural

Answer 23

23. E Thoracic epidural
    Thoracotomy ranks amongst the most painful of surgical procedures. Apart
    from patient discomfort, the consequences of post-thoracotomy pain lead to
    several other complications. Reduced tidal volumes from shallow breathing
    and the inability to cough may result in hypoxia and hypercarbia, placing the
    patient at increased risk of developing respiratory failure and postoperative
    pneumonia. This is further complicated by increased myocardial oxygen
    demand from the sympathetic response to pain, which may precipitate an
    adverse cardiac event.
    There are several possible options for achieving analgesia. What method is chosen
    depends on patient, anaesthetic and surgical preference (Table 5.6).
    In the above clinical scenario therefore, the most appropriate analgesic option
    would be a thoracic epidural.

Question 24

24. A 48-year-old man is referred to the pain clinic with poorly controlled upper
    abdominal pain. He is known to have pancreatic cancer, which is now palliative.
    As a result of his medication he is now feeling increasingly tired and is having
    difficulty concentrating.
    He is on the following medication:
    r Paracetamol 1g four times daily
    r Gabapentin 900mg three times daily
    r Modified release oxycodone 30mg twice daily
    r Immediate release oxycodone 10mg for breakthrough pain
    What would be the most appropriate treatment option?
    A Increase modified release oxycodone to 40mg twice daily and immediate
    release oxycodone to 15mg for breakthrough pain
    B Add amitriptyline
    C Perform a coeliac plexus block
    D Perform a lumbar sympathetic block
    E Perform a thoracic paravertebral block T10–T12

Answer 24

24. C Perform a coeliac plexus block
    A coeliac plexus block can be used to relieve autonomically mediated pain from
    non-pelvic abdominal organs. It is most commonly used in intractable malignant
    pain. Firstly it would be performed with local anaesthetic to assess efficacy and then
    can be repeated as a neurolytic block with 6% aqueous phenol.
    The coeliac plexus consists of coeliac ganglia that lie on either side of the L1
    vertebral body. It provides the autonomic supply to the non-pelvic abdominal
    organs and the first two-thirds of the large intestine.
    It consists of:
    t Greater splanchnic nerve: T5–T6 to T9–T10
    t Lesser splanchnic nerve: T10–T11
    t Least splanchnic nerve: T11–T12The left and right vagal trunks supply the parasympathetic supply to the upper
    abdominal organs.
    This block is certainly not without its risks and should only be used once other
    avenues have been exhausted.
    The potential complications include profound hypotension, bleeding from aortic or
    inferior vena caval injury and sexual dysfunction. Should the phenol be injected into
    the arterial supply of the spinal cord this can even result in paraplegia.
    A lumbar sympathetic block would have no benefit in pancreatic pain. Similarly a
    paravertebral block from T8–T10 would be necessary to block the innervation to the
    pancreas.

Question 25

25. A 4.2 kg, 26-day-old neonate is admitted for repair of an inguinal hernia. He was born at term by normal vaginal delivery. There are no other known medical problems and no allergies. What would be the most appropriate analgesic plan for post operative pain relief? A Single shot caudal combined with 15mg/kg paracetamol intravenously 6-hourly and codeine phosphate 1mg/kg orally 6-hourly as required B Single shot caudal combined with 10mg/kg paracetamol orally 6-hourly and ibuprofen 5mg/kg orally 8-hourly as required C Single shot caudal combined with 10mg/kg paracetamol orally 6-hourly and codeine phosphate 1mg/kg orally 6-hourly as required D Local anaesthetic infiltration by surgeon combined with paracetamol 7.5mg/ kg intravenously 6-hourly and codeine phosphate 1mg/kg orally 6-hourly as required E Local anaesthetic infiltration by surgeon combined with paracetamol 15mg/kg orally 6-hourly and morphine sulphate 100µg/kg orally 4–6-hourly as required

Answer 25

25. C Single shot caudal combined with 10mg/kg paracetamol orally 6-hourly and codeine phosphate 1mg/kg orally 6-hourly as required Despite having immature nociceptive pathways, it is now well accepted that neonates experience pain and as such, post operative pain needs to be well managed. As with adults, a multimodal approach should be used to minimise side- effects. Paracetamol is the most commonly used analgesic both in the adult and paediatric populations and should be used as a base in most analgesic regimes. However as per the British National Formulary (BNF) the paracetamol dose varies: Orally: t Preterm neonate 28–32 weeks post-conceptual age 20mg/kg loading dose followed by 10–15mg/kg 8–12-hourly. Maximum dose 30mg/kg daily t Neonate over 32 weeks post-conceptual age 20mg/kg loading dose followed by 10–15mg 6–8-hourly. Maximum dose 60mg/kg daily Intravenously: t Preterm neonate over 32 weeks post-conceptual age 7.5mg/kg 8-hourly. Maximum dose 25mg/kg daily t Neonate 10mg/kg 4–6 hourly. Maximum dose 30mg/kg daily Non steroidal anti-inflammatory drugs (NSAIDs) should also be used in children wherever possible. However, ibuprofen is not recommended for neonates or infants under 5 kg and diclofenac is not recommended for infants under 6 months. Opiates should also be used with care in this setting. Codeine is a pro-drug that is metabolised to morphine via the p450 cytochrome. The particular enzyme responsible, CYP2D6, has low activity at birth and becomes more effective with age. In addition to its immaturity, it also exhibits genetic polymorphism leading to significant differences in efficacy between patients. This explains its good safety profile in the young but is perhaps not the best analgesic agent. However, the combination of paracetamol and codeine has been shown to reduce postoperative pain in infants. Morphine is also commonly used and can be administered via a number of different routes. Reduced doses should be used in neonates due to their increased potency. This is due to a combination of an immature blood-brain barrier and reduced protein binding. Morphine will also have a longer duration of action due to slower metabolism (immature enzymes) and reduced excretion (reduced glomerular filtration rate). Local anaesthetic, whether in the form of surgical wound infiltration, nerve block or regional technique, should be used wherever possible. Caudals remain the most popular central neuroaxial technique used in neonates. Opioids are not commonly added to the local anaesthetic due to concerns over postoperative respiratory depression. In the neonates, caudals result in adequate analgesia below T10.

Question 26

26. A 26-year-old woman was pulled unconscious from a campervan fire and was intubated at the scene. She has 40% burns with moderate inhalational injury, and has been fluid resuscitated according to the Parkland formula. Her heart rate is 96 beats per minute, blood pressure 110/77 mmHg, capillary refill time <2 seconds, temperature 38°C, and urine output is 70ml/hour. Arterial blood gas analysis on a Fio2 of 50% shows: pH 7.12, Pao2 40 kPa, Paco2 3.3 kPa, HCO3 – 16 mmol/L, base excess –4.0, lactate 12.3 mmol/L. What is most likely to account for the lactic acidosis: A Sepsis B Volume depletion C Acute kidney injury from rhabdomyolysis D Cynaide poisoning E Ethanol poisoning

Answer 26

26. D Cyanide poisoning In the Western world, the most common cause of cyanide poisoning is house fires and subsequent smoke inhalation. When exposed to high temperatures, products containing carbon and nitrogen may liberate cyanide during combustion. These materials include wool, silk and synthetic polymers. Cyanide toxicity is dangerous as it prevents aerobic cell metabolism, causing intracellular hypoxia by reversibly binding to cytochrome oxidase a3 within the mitochondria, which is essential for oxidative phosphorylation. Oxidative phosphorylation is crucial to the synthesis of adenosine triphosphate (ATP) and the continuation of cellular respiration. As supplies of ATP become depleted, mitochondria cannot extract or use the oxygen they are exposed to. As a result, metabolism shifts to glycolysis through anaerobic metabolism which produces lactate. Production of lactate results in a high anion-gap metabolic acidosis. The cells are no longer able to use oxygen for aerobic metabolism which results in high venous oxygen saturations. Signs and symptoms of cyanide poisoning occur soon after exposure. Early manifestations include anxiety, headache and mydriasis. As hypoxia progresses, GCS drops and seizures can occur. Cyanide poisoning should be suspected in burns patients with an unexplained and persistent lactic acidosis despite adequate fluid resuscitation. Currently there is no test available for rapid diagnosis of cyanide poisoning, so treatment should be based on clinical suspicion. The treatment of choice for cyanide poisoning in burns patients is hydroxocobalamin. Hydroxocobalamin binds to cyanide to form the non-toxic cyanocobalamin (vitamin B12) which is then excreted by the kidneys. Cyanide has a greater affinity for hydroxocobalamin than for cytochrome oxidase a3 within the mitochondria. This then allows the mitochondria to perform aerobic metabolism. As it binds with cyanide without forming methaemoglobin, it is particularly helpful in burns patients who may have part of their haemoglobin in the form of carboxyhaemoglobin thus already reducing their oxygen carrying capacity. Cyanide (CN–) is metabolised in any of the three following pathways: t Converted by rhodanase in liver to thiocyanate (SCN–) which is then excreted in urine. This is the major pathway, accounting for 80% of CN– metabolism t Combines with vitamin B12 to form cyanocobalamine (non-toxic) which is also excreted in the urine t Combines with methemoglobin to form cyanomethemoglobin (non-toxic) Sepsis can be a major problem in the burns patient but not at this early stage and prophylactic antibiotics are not advocated. Volume depletion is also a likely contender but not in the context of a good urine output and normal capillary refill time. Acute kidney injury (AKI) in burns patients can also be problematic but again too early to show such gross acid base anomalies. AKI may be due to either volume depletion or rhabdomyolysis, the latter of which is a particular problem in electrical burns. Substance abuse must always be considered in this group of patients and alcohol intoxication also leads to a lactic acidosis but not of this severity

Question 27

27. You are anaesthetising a 72-year-old man for an elective open abdominal aneurysm. He is a known hypertensive and type II diabetic and his medication includes amlodipine 5mg, ramipril 10mg and metformin 1 gm b.d. What is the single most important intervention that would limit potential postoperative renal impairment? A Start dopamine at 2.5µg/kg/min B Administer mannitol 20% 0.5 g/kg C Optimise his circulatory blood volume D Keep his circulating haemoglobin >90 g/L E Administer furosemide 40mg

Answer 27

27. C Optimise his circulatory blood volume Renal impairment is a significant postoperative complication following elective aortic aneurysm repairs. It is associated with prolonged hospital stay, risk of progression to renal replacement therapy and increased mortality. The pathophysiology of renal impairment during an aortic aneurysm repair is multifactorial. It involves decreased blood flow across the renal arteries during aortic cross-clamping, cholesterol emboli as a result of clamping a heavily calcified aorta, the use of nephrotoxic medication in the preoperative phase and ischaemia-reperfusion syndrome. Over the last decade several drugs listed as options in the question have been researched in an attempt to find one to prevent the development of acute kidney injury. Low dose dopamine and dopexamine were used in an attempt to stimulate diuresis postoperatively. Free radical scavengers such as mannitol given before or soon after aortic cross-clamping also failed to show a decrease in postoperative renal impairment. Except fornachieving an optimum intravascular volume by replacing losses and correcting any coagulation abnormalities, all the other strategies have failed to produce a positive result.

Question 28

28. A 6-year-old boy is admitted with fulminant hepatic failure, bleeding oesophageal varices, ascites and marked splenomegaly. His liver function tests show an elevated bilirubin, alanine transaminases and aspartate transaminases. He has low albumin, prolonged prothrombin time and examination of his cornea on slit lamp examination demonstrate a brown, dark ring encircling his iris. Which of the following is the most likely diagnosis for this clinical picture? A Alpha-1 antitrypsin deficiency B Wilson’s disease C Primary biliary cirrhosis D Haemochromatosis E Sclerosing cholangitis

Answer 28

28. B Wilson’s disease ○ Kayser-Fleischer rings (brown or dark rings encircling the iris) are pathognomonic of Wilson’s disease which is an autosomal recessive inherited disorder characterised by toxic accumulation of copper in the liver and brain. The ATP7B enzyme prevents excessive accumulation of copper by either combining it with caeruloplasmin and releasing it into the bloodstream, or secreting it in the bile. The functions of this enzyme are affected in Wilson’s disease, causing the toxic accumulation of copper in the blood. Children usually present with hepatic complications such as hepatitis, cirrhosis or fulminant hepatic failure. Adults tend to present with neurophsychiatric signs including dysarthria, tremors, seizures, migraine, ataxia, cognitive decline and behavioral disturbances. Kayser-Fleischer rings are caused by deposition of copper in the Descemet’s (basement) membrane and can be visualised by slit lamp examination. Treatment for Wilson’s disease consists of administering chelating agents like penicillamine or in extreme cases hepatic transplantation. ○ Alpha-1 antitrypsin is a protease inhibitor and its deficiency leads to cholestasis and pulmonary symptoms including emphysema. ○ Primary biliary cirrhosis is caused by damage of interlobular bile ducts, leading to cholestasis coupled with portal hypertension and cirrhosis. ○ Haemochromatosis is caused by increased iron absorption and deposition in the liver, heart or pancreas. ○ Primary sclerosing cholangitis is inflammation of intra- and extra-hepatic ducts, which leads to liver failure and death.

Question 29

29. A 92-year-old man is brought to emergency department with a fractured neck of femur following a fall. To be categorised using the fraility phenotype, which of the following characteristics would not be assessed? A Self-reported exhaustion B Mental state C Weight loss D Grip strength E Low activity

Answer 29

29. B Mental state The elderly proportion of society is expected to increase significantly over the coming years, leading to a higher rate of surgery in this age group. The postoperative morbidity associated with surgery in the geriatric population is high due to multiple comorbidities and the influence of geriatric syndromes. These syndromes can be collectively termed as a phenotype as they cannot be termed into a disease process or an organ specific pathology. Frailty is thus termed as ‘a condition associated with a decreased physiological reserve across various organ systems that can lead to an increased vulnerability to physiological stressors'. Having a tool to measure frailty helps to stratify this population according to their risks. Fried et al. originally described the frailty phenotype based upon features observed across more than 500 patients over 65 years. t Weight loss (unintentional): >10 pounds from baseline in prior year t Sarcopenia (loss of muscle mass): grip strength - lowest 20th population centile (by gender and body mass index) t Weakness: self-reported exhaustion t Poor endurance: Walking time per 15 feet, slowest 20th population centile (by gender and height) t Slowness: kcal per week, lowest 20th population centile t Low activity: males <383 kcal/week, females <270 kcal per week Mental state is not incorporated in frailty assessment. Positive frailty phenotype: >3 criteria present Intermediate or pre-frail : 1 or 2 criteria present The frailty phenotype is predictive of progressive decline, repeated falls, hospital visits and eventually death.

Question 30

30. A new antiemetic drug is being evaluated. The percentage of patients who suffered postoperative nausea and vomiting (PONV) after administration of either the drug or placebo is reported: r percentage of patients with PONV after drug A = 20% r percentage of patients with PONV after placebo = 25% Which of the following is the number needed to treat (NNT)? A 20 B 25 C 5 D 75 E 1

Answer 30

30. A 20 The number needed to treat (NNT) is the number of patients to whom a clinician would need to administer a particular treatment for one patient to receive benefit from it. The NNT is calculated either as: t 100/absolute risk reduction (ARR) expressed as a percentage, or t 1/ARR expressed as a proportion The absolute risk reduction is defined as: Control event rate – experimental event rate; which in the example given above equates to: 25–20% = 5% The NNT is therefore: 100/5 or 1/0.05 depending on whether the ARR is expressed as a percentage or number. The NNT is therefore 20. NNTs have a number of important limitations. The true value of a NNT can be higher or lower than the value given; It is therefore useful to know the 95% confidence intervals of the NNT. If there is a large confidence interval there can be less certainty in the reported NNT and so clinical decisions based on this must be made with caution. An additional important point is that the NNT depends on the baseline frequency of a given event. So, in the case of PONV, advances in perioperative care and surgical techniques may mean that the baseline frequency of PONV changes over time; A NNT of 8 observed for agent A based on a study from 1970 may not necessarily be comparable to a NNT of 10 for agent B based on a similar study conducted in 2010.