Paper I — 2015 September (Supplementary) (2010 Scheme) — Q2
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Paper I
2015 September (Supplementary) (2010 Scheme) · 40 marks · 120 min
Question
Read the clinical problem and answer the following questions: 30 years old man was admitted
in emergency ward with acute abdominal pain. After diagnosed with acute appendicitis, he was
taken for surgery. On the operation table, after administration of a skeletal muscle relaxant,
patient developed difficulty in breathing and went in for apnoea.
(a) Which skeletal muscle relaxant is responsible for this reaction. 1 mark(s)
(b) What is the reason for the apnoea. 3 mark(s)
(c) How will you manage the patient. 2 mark(s)
Q26 marksEssays
Answer
(a) Skeletal muscle relaxant responsible
Suxamethonium (Succinylcholine) — the depolarizing neuromuscular blocker classically implicated in prolonged apnoea
(b) Reason for the apnoea
This is “scoline apnoea” — suxamethonium is normally rapidly hydrolysed by plasma pseudocholinesterase (butyrylcholinesterase), giving it a very short duration of action
Some individuals have a genetically determined atypical/deficient form of plasma pseudocholinesterase (autosomal recessive trait), which hydrolyses suxamethonium very slowly or not at all
In such patients, suxamethonium’s neuromuscular blocking action is grossly prolonged, causing sustained paralysis of the respiratory muscles and prolonged apnoea after a standard dose
(c) Management
Continue mechanical ventilation/assisted respiration and maintain anaesthesia/sedation until neuromuscular function recovers spontaneously (may take hours)
Do NOT give further muscle relaxants or anticholinesterase reversal agents (ineffective against depolarizing block and can worsen it)
Confirm the diagnosis with a dibucaine number test (measures pseudocholinesterase activity/genotype) and counsel the patient and family regarding the genetic trait for future anaesthetic exposures
Fresh frozen plasma (source of normal pseudocholinesterase) may be considered in severe/prolonged cases
