The effects of etomidate on seizure duration and electrical stimulus dose in seizure-resistant patients during electroconvulsive therapy

Objective: Methohexital used to be the preferred anesthetic used in electroconvulsive therapy (ECT). Since 1999, there have been supply problems for this drug, and there has been no clear guidance regarding which anesthetic should be used preferably in ECT. Most clinics use thiopental or propofol, although these drugs may increase the seizure threshold. We investigated if etomidate improves seizure duration compared with thiopental in cases where eliciting seizures becomes problematic. Methods: During our routine delivery of ECT at a general psychiatric hospital in Cardiff, UK, we observed 5 patients who had ECT courses with thiopental and did not achieve adequate seizure duration despite very high electric stimulation. They later relapsed and received second courses of ECT under etomidate. We compared the seizure duration and the electric charge needed to produce the seizures for a total of 46 pairs of ECT sessions given under the 2 anesthetics on the same patients. Results: The average electric stimulation dose required to induce seizures was reduced from 638 to 497 millicoulombs (95% confidence interval, 60-221; P = 0.001). Despite the lower dose, the length of observed seizure duration increased by 10.3 seconds (65%) and that of the electroencephalograph-recorded duration increased by 8.7 seconds (41%) (P < 0.001). Conclusions: Etomidate has a distinct advantage over thiopental in producing seizures of adequate duration during ECT and should be used as the first-line measure in augmenting seizures in patients who have very high seizure thresholds.