El-Boghdadly - 5 Flashcards
- 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 720 mg/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 720 mg/day
C FVC of 2.9 litres
D Duration of disease > 6 years
E Concurrent history of asthma
A
- 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 complementmediated
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.
Table 5.2 Osserman Classification for the severity of MG
CLASS I Limited to eye muscle involvement
CLASS IIa Mild and generalised, responding to treatment
CLASS IIb Moderate and generalised, response to treatment not satisfactory
CLASS III Severe and generalised, including respiratory dysfunction
CLASS IV Requiring ventilation
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 with MG 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 preoperative
planning could prove fatal.
There are four recognised risk factors that are associated with an increased likelihood
of requiring a period of postoperative ventilation.
1. MG duration of > 6 years – this has the greatest predictive value
2. Concurrent history of chronic respiratory disease
3. Pyridostigmine requirements of > 750 mg/day in the preceding 48 hours
4. 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
- 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 0.2 μg/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 250 mL of Hartmann’s solution and decrease the noradrenaline
E
- E Administer 250 mL 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.
- 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 1 mg adrenaline IV
B 300 mg bolus of amiodarone
C Institution of external pacing
D Exclusion of a tension pneumothorax
E Turn off the pacemaker
A
- 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,
300 mg 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.
- 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 postoperative 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
D
- 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 postoperative
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 postoperatively,
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 anatomy.
Table 5.3 Advantages of double lumen tube and bronchial blockers
Double lumen tubes Bronchial blockers
Rapid lung deflation Slower lung deflation
Allows rapid isolation of either lung Time consuming to change isolated lung
Allows suctioning, oxygen delivery to either lung No access distal to the inflated balloon
Difficult to site in smaller airways Easier to site in smaller airways
Requires tube exchange in intubated patients Easy to use in intubated patients
- 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% 2 mL
B Hyperbaric bupivacaine 0.5% 2 mL with 300 μg diamorphine
C Plain bupivacaine 0.5% 2 mL with 10 μg fentanyl
D Hyperbaric prilocaine 2% 2 mL with 10 μg fentanyl
E Hyperbaric lignocaine 2% 2 mL with 10 μg fentanyl
C
- D Hyperbaric prilocaine 2% 2 mL with 10 μg 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 spread
The ideal agent for such a block would:
• have a rapid onset
• provide a dense predictable sensory block
• have a short duration of action to allow early recovery and ambulation
• 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
- 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 2 mg 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 20–40 mg of intravenous frusemide
E Infusing 1–2 mL/kg 3% NaCl
C
- 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:
• Length of resection, especially > 1 hour
• Significant bleeding, implying large quantities of open vessels
• Bladder or prostatic capsular perforation, (fluid is rapidly absorbed from the
peritoneum)
• 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:
- 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
A
- 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.
- 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
B
- B Propofol and rocuronium
The choice of anaesthetic agents for ECT depends on the ability to:
• provide rapid onset and recovery from unconsciousness
• provide adequate muscle relaxation to avoid injury from an uncontrolled tonicclonic
seizure
• 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 <1 mg/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 0.5 mg/kg.
Mivacurium is short acting and doses 0.15 mg/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.
- 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
C
- 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 100 mm 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.
- 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
C
- D Axillary brachial plexus block
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
- 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 2 mg midazolam and 2 μg/kg fentanyl in the room
B Use security staff to hold the patient, and give intramuscular 4 mg/kg ketamine, then transfer to the resuscitation bay
C Do nothing, and refuse to get involved with this case
D Encourage her to take 20 mg oral temazepam and review
E Using security staff to hold the patient, transfer to theatre, and perform an inhalational induction with sevoflurane
B
- B Use security staff to hold the patient, and give 4 mg/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.
- A 34-year-old man sustained a traumatic brain injury 3 days 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 121 mmol/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
E
- 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.
- 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 β 2 agonist and high dose corticosteroid inhalers with montelukast tablets. You are called for advice as despite 4 x 2.5 mg nebulised salbutamol, 500 μg nebulised
ipratropium and 40 mg 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 5.1 kPa.
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 10 μg/minute
C Give 20 mmol of intravenous magnesium sulphate over 10–20 minutes
D Give a further 5 mg nebulised salbutamol
E Give a loading dose of 5 mg/kg aminophylline followed by an infusion at 500 μg/kg/hour
C
- C Give 20 mmol 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.
- 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 90/60 mmHg. 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 300 mg 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
E
- 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:
• 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
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.
- 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
A
- 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.
