Download Question 1 : FT

Case 26: Anaesthetics and ICU SAQs (SET 1)
Authors and Affiliations
Hannah Pham
MBBS VI
School of Medicine
University of Adelaide
Dr Mark Plummer, MBBS
Research Fellow
Discipline of Acute Care Medicine
University of Adelaide
Case Overview
SAQ.
Learning Objectives
SAQ.
Question 1 : FT
Question Information:
A 50-year-old woman is diagnosed with necrotising fasciitis in the forearm. She undergoes an elbow
amputation conducted under general anaesthesia. She is seen day 2 post-operatively and now
complains of pain where her †œarm used to be†•.
Question:
What is the diagnosis? (1 mark) Justify your answer. (1 mark) In your justification, suggest an option for
management. (1 mark)
Choice 1: null Score : 0
Choice Feedback:
Answer
Phantom pain (1)
Justification
†¢ Phantom pain is any type of noxious sensory phenomenon in a missing limb or organ. (1)
†¢ The appropriate management is to provide analgesia, but given the nature of the pain, it is unlikely
to respond to simple analgesics alone. Intravenous (IV) calcitonin has been shown to be effective in
managing acute phantom limb pain. Other agents such as ketamine can provide short term relief.
Appropriate management: analgesia (1)
†¢ IV calcitonin infusion, subcutaneous or intranasal
†¢ Ketamine
Other agents:
†¢ Morphine controlled-release or infusions
†¢ Gabapentin
†¢ Lignocaine
†¢ Amitriptyline and tramadol
†¢ Local anaesthetic injections
References
†¢ Mcintyre, Pamela E; Scott, David A; Schug, Stephan A; Visser, Eric J; Walker, Suellen M. Acute
Pain Management: Scientific Evidence, Third Edition, 2010. Australian and New Zealand College of
Anaesthetists and Faculty of Pain Medicine.
Question 2 : FT
Question Information:
A 60-year-old man is seen in pre-admission clinic. He is expected to undergo a right hemi-colectomy in
four weeks†™time for colorectal cancer. His medications are reviewed and he is noted to be taking
aspirin/clopidogrel following the insertion of a drug-eluting stent 12 months ago.
Question:
What is the most appropriate recommendation regarding his antiplatelet therapy? (1 mark) Justify your
answer. (2 marks)
Choice 1: null Score : 0
Choice Feedback:
Answer
Cease clopidogrel 5 days prior to surgery (0.5), continue aspirin (0.5)
Justification
†¢ This patient is planned for an elective non-cardiac surgery. He is on dual anti-platelet therapy for a
drug-eluting stent. Twelve months have passed, which is an acceptable time frame in which to cease
his medication to enable surgery. (1)
†¢ The risk of bleeding in a hemi-colectomy is high but perhaps equal to his risk of stent thrombosis at
six months. (1)
Notes
†¢ He should have his clopidogrel ceased and aspirin continued with the view of re-commencing
aspirin/clopidogrel as soon as possible in the post-operative period.
References
†¢ UpToDate article †œAntiplatelet therapy after coronary artery stenting†•
Question 3 : FT
Question Information:
A medical student has just intubated a patient (under supervision) in an elective theatre list.
Question:
What is the gold standard for confirming correct placement of the endotracheal tube? (1 mark)
Choice 1: null Score : 0
Choice Feedback:
AnswerExpired concentrations of carbon dioxide or Capnography (1)
Notes
†¢ The measurement of carbon dioxide in expired gas (capnography) is the gold standard for
confirming correct placement of an endotracheal tube.
†¢ One should also directly visualise the endotracheal tube passing between the vocal cords, but this
is not always possible. Other less reliable means of confirming correct placement include fogging in the
tube on expiration, chest auscultation for equal air entry, and inspecting the chest wall for equal rise and
fall.
Question 4 : FT
Question Information:
A 73-year-old man is attending his general practice for routine follow-up. Two days earlier, he was
discharged from hospital for management of a fractured left distal radius sustained during a mechanical
fall. He is currently taking regular paracetamol and oxycodone for analgesia.
His previous admission notes are reviewed, and his blood tests, electrocardiogram, and imaging
including CT head and spine were unremarkable. At present, he is eating and drinking normally.
He has a past history of hypertension on hydrochlorothiazide, and hypercholesterolaemia on
atorvastatin. He has a 20 pack year smoking history.
On examination, his pulse rate is 80/min, blood pressure 130/80mmHg, and respiratory rate 14/min. He
is alert and oriented to time, place, and person. His left forearm is in a cast. The capillary refill time is
less than two seconds, he is well-perfused peripherally, and his skin turgor is normal. His mucous
membranes are moist. His chest is clear on auscultation. His heart sounds are dual and there are no
murmurs. His abdomen is soft and non-tender.
His blood is taken today, which shows a sodium of 125mmol/L [135-135].
He is referred to the Emergency Department where further investigations are undertaken and show:
†¢ Serum osmolality 230mosm/kg [275-295]
†¢ Urine osmolality 292mosm/kg [50-100]
†¢ Urinary sodium 60mEq/L [20-40]
Question:
What definitive treatment does this man require? (1 mark) Justify your answer. (2 marks)
Choice 1: null Score : 0
Choice Feedback:
Answer
Fluid restriction (1)
Justification
†¢ The most likely cause of this man's presentation is hyponatraemia secondary to opioid and thiazide
diuretic-induced syndrome of inappropriate anti-diuretic hormone secretion (SIADH) (1)
†¢ The definitive treatment for SIADH, in which there is an increase in total body water relative to
normal sodium, is fluid restriction (ideally less than1 .5 litres a day) (1)
Notes
†¢ The serum osmolality is low which suggests hypotonic (true) hyponatraemia as opposed to
pseudohyponatraemia secondary to hyperlipidaemia, hyperproteinaemia, or hypertonic hyponatraemia
associated with hyperglycaemia or mannitol use.
†¢ Urine osmolality and urinary sodium are inappropriately high. These findings support a diagnosis of
SIADH, where excessive ADH secretion results in increased water reabsorption, †œconcentrated†•
urine and a dilutional hyponatraemia.
†¢ The goal of treatment is to correct hyponatraemia at a rate that does not cause neurologic
complications. Serum sodium levels should be raised by no more than 9mmol/L in the first 24 hours as
there is a risk of cerebral pontine myelinosis (CPM) when the rate of correction is excessive.
References
†¢ http://emedicine.medscape.com/article/242166-workup
†¢ UpToDate article "Treatment of hyponatremia: Syndrome of inappropriate antidiuretic hormone
secretion"
Question 5 : FT
Question Information:
You are called to assess a 65-year-old woman in recovery after an elective right total knee replacement
(performed under general anaesthesia) for hypertension. Her current blood pressure is 180/100mmHg,
which has been confirmed on a manual reading three times.
Her usual blood pressure is around 155/90mmHg. Her regular medications include perindopril and
hydrochlorothiazide, which were continued peri-operatively.
She denies headache, visual disturbance, chest pain, dizziness, palpitations, and dyspnoea. She
reports throbbing pain in her right knee at present with a pain score of 7 out of 10.
On examination, her pulse rate is 80/min, respiratory rate 14/min, oxygen saturation 100% on room air,
and temperature 36.9C. She is tender to palpate over the right knee incision. Her peripheral pulses are
strong. The capillary refill is less than two seconds.
An indwelling catheter is in situ and is draining clear urine.
A bedside electrocardiogram shows sinus rhythm with no acute changes. Her pre-operative blood tests
were within the normal range.
Question:
What is the appropriate medical management of this patient? (1 mark) Justify your answer. (1 mark)
Choice 1: null Score : 0
Choice Feedback:
Answer
Analgesia (1)
Justification
†¢ The patient†™s post-operative hypertension is likely due to pain in her knee. (1)
Notes
†¢ Other causes to consider include agitation, hypercarbia, hypoxia, hypervolaemia, and bladder
distension.
†¢ Therapy for sustained hypertension (systolic blood pressure greater than 180mmHg or diastolic
blood pressure greater than 110mmHg) should only be considered once remedial causes (as above)
have been excluded and treated.
References
†¢ UpToDate article †œPerioperative management of hypertension†•
Question 6 : FT
Question Information:
You are the intern attending a medical emergency team call for hypotension. A 60-year-old man is day
one post open nephrectomy for a renal mass. The procedure was uncomplicated and he is currently on
an epidural infusion of fentanyl and bupivacaine for analgesia. He has no other background history. He
had a pre-operative echocardiogram which was unremarkable.
On examination, his pulse rate is 150/min, blood pressure 80/50mmHg, respiratory rate 18/min, and
temperature 35.9C. His oxygen saturation is 100% on 4 litres of oxygen. His peripheries are cool to
touch. Two 14 gauge cannulas are inserted in his cubital fossa and intravenous fluids are given.
Despite this, his blood pressure remains low at 87/50mmHg.
A bedside electrocardiogram shows an irregularly irregular rhythm with absent P waves. His blood is
collected for urgent analysis. The complete blood examination and arterial blood gas are unremarkable.
The biochemistry and troponin level are pending.
Question:
What is the definitive treatment of this man†™s condition? (1 mark) Justify your answer. (2 marks)
Choice 1: null Score : 0
Choice Feedback:
Answer
Cardioversion (1)
Justification
†¢ The patient is currently in rapid atrial fibrillation (pulse rate 150/min). (1)
†¢ The definitive treatment is cardioversion given the recent onset, haemodynamic compromise (cool
peripheries, hypotension, tachycardia), and duration of this episode (less than 48 hours). The preoperative echocardiogram is reassuring as we can be confident that the patient does not have an atrial
thrombus. (1)
Notes
†¢ Care should be taken to correct the precipitant of atrial fibrillation as recurrence of his AF may
occur. Blood should be collected for complete blood examination, electrolytes, urea, creatinine,
biochemistry, coagulation studies, and thyroid function tests. Electrolyte abnormalities (especially in
magnesium and potassium) should be corrected immediately.
†¢ Old electrocardiograms would be required to compare to in order to determine if this is a first
episode of AF. If so, cardioversion using DC shock (electrical) would be preferred, but the decision of
medical or electrical cardioversion is clinician-dependent. Anti-arrhythmic drugs may be administered
prior to cardioversion to increase the chance of successful reversion and to prevent recurrence.
†¢ The timing of cardioversion is determined by the duration of the episode. Given this episode has
been ongoing for less than 48 hours, there is a low risk of thromboembolism. Anticoagulation may be
bypassed in this time frame if the patient has a low stroke risk profile. This decision is cliniciandependent.
†¢ If the duration of this episode was greater than 48 hours, cardioversion should be postponed until
after three weeks of anticoagulation or a transesophageal echocardiogram has been performed to
exclude left atrial thrombus. Anticoagulation should then also be continued for four weeks post
cardioversion.
†¢ Amiodarone would be drug of choice if medical cardioversion was used.
†¢ The best chance to restore and maintain sinus rhythm in a patient with new AF is when it is first
diagnosed.
References
†¢ Electronic Therapeutic Guidelines on Atrial Fibrillation
†¢ UpToDate article †œManagement of new onset atrial fibrillation†•
Question 7 : FT
Question Information:
You are the intern attending a code blue. A 60-year-old man has fallen out of bed and has hit his head.
He was admitted with a pulmonary embolus and is on a therapeutic heparin infusion.
He is currently unconscious and not responding. His breathing is shallow. His left pupil is dilated (6mm)
and non-reactive to light. His right pupil is 3mm. An urgent CT head shows an extradural haematoma
and he is planned for emergency surgery.
Question:
How should his heparin be managed? (1 mark) Justify your answer. (1 mark)
Choice 1: null Score : 0
Choice Feedback:
Answer
Reversal of heparin with protamine sulphate (1)
Justification
†¢ The patient has suffered a head trauma with intracranial haemorrhage (ICH). The heparin infusion
has predisposed him to bleeding and will likely exacerbate any traumatic bleed already present (1).
Notes
†¢ Haematoma expansion is associated with worse outcomes and can be demonstrated on serial CT
scans. It occurs in 15-38% of patients over the first 24 hours.
†¢ Protamine sulphate is recommended for urgent treatment of patients with heparin-associated ICH.
It can be administered via slow intravenous infusion.
References
†¢ UpToDate article †œThe use of antithrombotic therapy in patients with an acute or prior
intracerebral haemorrhage†• (section †œAcute intracerebral haemorrhage†•)
Question 8 : FT
Question Information:
A 55-year-old woman is brought in by ambulance following an intentional drug overdose. She is drowsy.
Two hours ago, she took forty 10mg tablets of oxycodone with a bottle of wine.
On examination, her Glasgow coma score is 9, pulse rate 60/min, blood pressure 110/50mmHg,
respiratory rate 8/min, oxygen saturation 90% on room air, and temperature 35.9C. Her pupils are
pinpoint bilaterally. Her airway is supported with jaw thrust and oxygen via mask is applied.
Question:
What definitive treatment does she require? (1 mark) Justify your answer. (2 marks)
Choice 1: null Score : 0
Choice Feedback:
Answer
Naloxone (1)
Justification
†¢ The most imminent threat is depressed respiratory drive resulting from opioid overdose. (1)
Naloxone is a short-acting opioid antagonist which should be administered immediately as intravenous
boluses (eg, 0.05mg) titrating upward until respiratory rate is 12/min or greater, rather than titrating to
conscious level. (1)
Notes
†¢ A naloxone infusion may be required following restoration of ventilation depending on the opioid
taken. This is performed by determining total initial dose required to reinstate breathing and giving two
thirds of that dose every hour.
†¢ Excessive naloxone may produce withdrawal, which should be managed expectantly. Opioids
should not be administered in managing withdrawal.
†¢ This patient should be ventilated using bag-valve-mask immediately given the threat to her airway.
If the patient becomes apnoeic, a higher initial dose of naloxone (0.2-1.0mg) would be considered.
†¢ Activated charcoal and gastrointestinal decontamination are almost never indicated in opioid
poisoning.
References
†¢ UpToDate article †œAcute opioid intoxication in adults†•
Question 9 : FT
Question Information:
A 25-year-old woman is brought into the emergency department unconscious and unresponsive. She
was found alone in her room one hour ago surrounded by empty pill bottles and an empty bottle of
wine. Her breathing is shallow with a respiratory rate of 9/min. She has pinpoint pupils bilaterally. There
is the smell of alcohol on her breath.
She is given naloxone immediately. A catheter is inserted to monitor her fluid balance and to collect
urine for dipstick analysis and further testing.
Question:
Which is the most important blood drug level(s) to determine? (1 mark) Justify your answer. (2 marks)
Choice 1: null Score : 0
Choice Feedback:
Answer
Serum paracetamol level (0.5) and blood alcohol level (0.5)
Justification
†¢ A paracetamol level should always be considered in patients who have taken an overdose,
especially as it is unclear from this history what drugs have been taken. (0.5) This is to guide potential
treatment with N-acetyl cysteine. (0.5)
†¢ A blood alcohol level should also be taken given the confounding presentation of alcohol and drug
overdose. (1)
Notes
†¢ The shallow breathing and pinpoint pupils suggest opioid overdose, which justifies the use of
naloxone. A suitable regimen is an initial bolus dose with increasing doses every 2-3 minutes if there is
no response.
†¢ Immunoassay screens for drugs of abuse can detect opioids, benzodiazepines, cocaine
metabolites, barbiturates, tricyclic antidepressants, tetrahydrocannabinol, and phencyclidine in urine.
Positive and negative screens neither confirm nor refute a poisoning diagnosis, despite results being
available within one hour. Therefore, comprehensive toxicology should be reserved for those with
severe or unexplained toxicity.
References
†¢ http://www.patient.co.uk/doctor/opiate-poisoning
†¢ UpToDate article †œGeneral approach to drug poisoning in adults†•
Question 10 : FT
Question Information:
A 52-year-old woman underwent an elective total hysterectomy under general anaesthesia. The
procedure was longer than expected due to bleeding at the surgical site. The surgeon closed up 20
minutes ago. The patient received propofol, rocuronium, sevoflurane, fentanyl, and droperidol intraoperatively. She has been extubated but has not yet roused. A peripheral neuro-stimulatory test is
performed, which indicates continued paralysis.
Question:
What treatment(s) should be given to reverse her paralysis? (1 mark) Justify your answer. (1 mark)
Include in your justification the mechanism of action for the treatment(s) used. (1 mark)
Choice 1: null Score : 0
Choice Feedback:
Answer
Acetylcholinesterase inhibitor (eg, neostigmine) (0.5) and an anti-muscarinic (eg, atropine,
glycopyrrolate) (0.5)
Justification
†¢ She has received rocuronium, a non-depolarising neuromuscular blocking agent (0.5) which works
by competitively binding to acetylcholine (ACh) receptors on the post-synaptic membrane. This does
not cause depolarisation but rather prevents ACh from binding at the neuromuscular junction.
Rocuronium has the most rapid onset of any non-depolarising neuromuscular blocking agent.
†¢ Neostigmine is an acetylcholinesterase inhibitor which interferes with the breakdown of ACh both
in the neuromuscular junction and systemically. This increases the amount of ACh within the
neuromuscular junction overcoming the inhibition by rocuronium. (1 †“ should provide mechanism of
action of acetylcholinesterase inhibitors)
†¢ Atropine or glycopyrrolate are anti-muscarinic agents which should be administered concurrently
with neostigmine (0.5) to prevent the unwanted side effects of increasing systemic ACh concentration
eg, bradycardia, salivation, and increased bowel peristalsis.
Notes
†¢ Sugammadex is a chelating agent that reverses the effects of neuromuscular blocking drugs. It
works by binding with molecules of rocuronium or vecuronium thus inhibiting these agents from binding
to the post-synaptic ACh receptor. Its onset of action is faster than neostigmine.
†¢ Succinylcholine (suxamethonium) is a depolarising neuromuscular blocking agent that works by
binding to post-synaptic nicotinic receptors and acting like ACh by inducing depolarisation. It is an
analogue of ACh. This is manifest by skeletal muscle fasciculations. Paralysis follows due to
†œdesensitisation†• of receptors.
References
†¢ UpToDate article †œInduction of general anaesthesia†•
†¢ UpToDate article †œNeuromuscular blocking agents (NMDA) for rapid sequence induction
intubation in adults†•
Question 11 : FT
Question Information:
A 55-year-old woman has an arterial blood gas performed.
The arterial blood gas shows:
pH
7.15 [7.35-7.45]
PaO2
80 [80-100]
PaCO2
HCO3
28 [35-45]
19 [22-26]
Venous blood results show:
K
4.5 [3.5-4.9]
Na
Cl
138 [137-145]
105 [100-109]
HCO3
25 [22-32]
Question:
What is the abnormality demonstrated on this arterial blood gas? (1 mark) List two causes of this
picture. (2 marks)
Choice 1: null Score : 0
Choice Feedback:
Answer
Normal anion gap metabolic acidosis (0.5) with respiratory compensation (0.5)
1 mark for 2 causes
1. Renal tubular acidosis
2. Diarrhoea
3. Secretory adenomas
4. Ammonia chloride poisoning
5. Interstitial nephritis
6. Acetazolamide administration
Synopsis
Recommended learning outcomes from this set of Anaesthetics and ICU SAQs include:1.Phantom limb
pain2.Peri-operative antiplatelet management3.Intubation4.Hyponatraemia5.Post-operative
hypertension6.Atrial fibrillation management7.Management of heparin8.Opioid overdose9.Paracetamol
overdose10.Reversal of paralysis11.Arterial blood gas interpretation