Prolonged apnoea after suxamethonium for ECT48-year-old woman, 62 kg, severe depression, for her first ECT session

The patient

The examiner asks

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1. Consider

   She is still not breathing twenty minutes after the treatment. What is going on?

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   • A 48-year-old on sertraline, still apnoeic twenty minutes after suxamethonium at her first ECT. Patient
   • Suxamethonium 1 mg/kg should wear off in 5 to 10 minutes, so this block is prolonged. Disease
   • Likeliest cause: low or abnormal plasma cholinesterase, which cannot clear her suxamethonium.
   • Her first exposure to suxamethonium, so an inherited enzyme variant leads my list.
   • Esmolol today inhibits the enzyme too, but adds only a minor prolongation. Stem trigger
   • First suxamethonium exposure means a nerve stimulator check; it separates paralysis from failure to wake. Crisis

2. Crisis

   Train-of-four shows no twitches. How do you manage her now?

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   • She is paralysed and may be awake, so she gets hypnotic before anything else. Crisis
   • Propofol, an ECT induction dose, then an anaesthetic infusion at 100–200 mcg/kg/min.
   • Supraglottic airway or tube, then ventilate her to a normal end-tidal CO2. Airway
   • No neostigmine: it blocks the enzyme that clears suxamethonium and can deepen her block. Crisis
   • No plasma either; transfusion risks outweigh a few hours of ventilation.
   • Quantitative TOF monitoring; extubate only once her TOF ratio is 0.9 or more.

3. Crisis

   Forty minutes in, before the infusion is running, HR rises to 118 and BP to 172/98; tears are running from her eyes. What do you do?

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   • She is aware and paralysed until proven otherwise: a new surge with no stimulus. Crisis
   • ECT's own sympathetic surge settles quickly, so this late rise is not the seizure. Disease
   • Propofol bolus now, infusion at 100–200 mcg/kg/min, ventilation unchanged. Crisis
   • Check her end-tidal CO2 and saturation; hypercarbia or hypoxia also raise heart rate and pressure.
   • Talk to her: she is safe, the weakness will pass, and we are breathing for her.
   • She stays sedated and ventilated in recovery or ICU until her block has gone. After surgery

4. Plan

   She recovers after three hours. What happens next?

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   • Cholinesterase activity and dibucaine number, sent the day after, since suxamethonium interferes with the assays. (After surgery)
   • Dibucaine number about 80 is normal, 40 to 60 heterozygous, under 30 homozygous.
   • If it is inherited, her first-degree relatives are offered testing and she carries an alert card.
   • Future ECT: rocuronium 0.6 mg/kg with sugammadex reversal, instead of suxamethonium.
   • I ask her about recall, explain what happened, and document it for her psychiatrist.