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The severe generalised weakness including loss of all eye movements suggested a peripheral neuromuscular weakness. Since this followed a general anaesthetic with neuromuscular blockade, the most likely explanation was a delayed recovery from this agent. The main differential diagnosis is a pontine ischaemic event (the classical cause of locked-in syndrome) where upgaze and blink are preserved, although the normal imaging is against this.

We gave sugammadex 400 mg (4 mg/kg), a neuromuscular blockade reversal agent of rocuronium, and within minutes his motor function improved. On re-examination, he was orientated to self and place, and moved all limbs. He stated that he had been awake since leaving the operating theatre and recalled everything, including the CT scan, but had been paralysed and unable to respond. Figure 2 outlines the timeline.

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Figure 2

Timeline of events.

Non-depolarising neuromuscular blockers are competitive acetylcholine antagonists that bind to the alpha subunits of nicotinic receptors on the postsynaptic membrane. This prevents depolarisation at the neuromuscular endplate and causes muscular paralysis. Examples may include rocuronium and vecuronium, which are often used to facilitate endotracheal intubations and adjuvant sedation.1 Delayed paralysis is possible and can be difficult to diagnose despite the patient being conscious.2 The incidence of residual paralysis after emergence from anaesthesia is unclear, as the reported frequencies vary widely.3 When a patient does not respond to stimuli after surgery, neurologists are often called urgently to assess the patient.

However, the effect of neuromuscular blocking agents such as vecuronium and rocuronium rarely lasts for hours unless there is significant liver and/or kidney dysfunction. The mean clinical duration of rocuronium is usually less than 60 min; it is primarily eliminated via the liver and has no metabolite.4 One report described vecuronium’s effect lasting for 8 hours, despite no identified precipitating risk factors.5 An important differential diagnosis of coma is the locked-in syndrome, caused by a midbrain stroke, with retained vertical eye movements and blinking.6

In this patient, the effect of rocuronium lasted for at least 8 hours, and he did not recover until receiving a reversal agent. Risk factors for prolonged effect can include certain medications, autoimmune disorders, neuromuscular conditions and electrolyte abnormalities.1 7 This patient was not cooled during surgery, had no acidosis and no history of neuromuscular or autoimmune disease; we, therefore, found no explanation for this prolonged recovery. This unusual case illustrates the importance of considering the diagnosis of iatrogenic neuromuscular blockade in postoperative weakness.