Comment on Residual neuromuscular blockade following electroconvulsive therapy

We read with interest the study by Maghami and Currigan ¹ investigating post-procedural residual neuromuscular paralysis with electroconvulsive therapy (ECT). Using a metric (‘T1’) derived from train-of-four data, they reported ‘potentially clinically significant residual neuromuscular blockade’ in 61% (14/23) of patients. We wish to comment on several aspects of these data.

Importantly, Maghami and Currigan did not measure outcomes of their patients once they left the ECT suite, so it is unknown if their measurement of residual paralysis has any clinical significance. Specifically, there was no measurement of airway complications in the recovery area.

ECT is one of the few procedures under anaesthesia that routinely uses succinylcholine and is short enough that one can observe the length of time that the paralysis lasts. In most other settings, patients who receive succinylcholine are subsequently intubated or the procedure lasts long enough for the paralysis to wear off. Furthermore, ECT does not require a complete muscle block, nor paralysis deep enough to facilitate intubation, so a lower dose is routinely used.

Typically, ECT patients are managed by the anaesthesiologist until they meet the criteria for transfer to the post-anaesthesia care unit (PACU), which includes closely monitoring haemodynamics and oxygen saturation. At that point, the patient is breathing on their own, able to maintain a stable saturation, swallowing any secretions. It is not possible to measure the degree of residual neuromuscular blockade in this setting (other than immediately after the end of the ECT seizure) without subjecting patients to painful stimuli, as the anaesthesia wears off quickly.

Maghami and Currigan state that ‘the ideal dose of NMBD [neuromuscular blocking drug] to give prior to ECT is unknown’. ECT has been performed in tens of millions of patients since its introduction in 1938; ² general anaesthesia with muscle relaxation using succinylcholine has been the standard of care since the early 1950s. The appropriate range of succinylcholine for ECT is well established, and is typically 0.5–1.0 mg/kg, with a small percentage of outliers requiring more, or less. ³ Standard practice at the first ECT is to give a bolus dose based on the patient’s lean body mass, then adjust, as indicated at subsequent treatments. Both of us (CHK and EOB), have each participated in more than 20,000 ECT procedures and can attest that the clinical monitoring practice described above is satisfactory to prevent serious sequelae from residual neuromuscular blockade in virtually all cases.

A small number of ECT patients, for whom succinylcholine is relatively or absolutely contraindicated, will require rocuronium or another non-depolarising NMBD. For such patients, the availability of sugammadex is very helpful. However, the time frame of reversal with ECT requires higher doses (up to 16 mg/kg), compared with those required (~2–4 mg/kg) at the end of most other procedures. ⁴ Furthermore, many ECT patients are initially treated three times per week, making the expense of sugammadex prohibitive.

ECT is a remarkably safe, effective and widely adopted procedure. We strongly agree that careful monitoring for residual neuromuscular blockade is vital to good practice, but that it can be achieved by standard clinical anaesthesia patient monitoring, without the added complication of measuring train-of-four ratios and single-twitch heights.