The Anaesthetic-ECT Time Interval in Electroconvulsive Therapy Practice - Is It Time to Time?

•Novel study exploring the effect of the time interval between anaesthetic injection and ECT stimulus on seizure quality.•ECT-anaesthetic time interval measured in a standardised way.•Analysis accounted for inter and intra individual variability in seizure quality.•Possible implications for ECT clinical practice.

BackgroundBecause most common intravenous anaesthetics used in ECT have anticonvulsant properties, their plasma-brain concentration at the time of seizure induction might affect seizure expression. The quality of ECT seizure expression has been repeatedly associated with efficacy outcomes. The time interval between the anaesthetic bolus injection and the ECT stimulus (anaesthetic-ECT time interval) will determine the anaesthetic plasma-brain concentration when the ECT stimulus is administered.ObjectiveThe aim of this study was to examine the effect of the anaesthetic-ECT time interval on ECT seizure quality and duration.MethodsThe anaesthetic-ECT time interval was recorded in 771 ECT sessions (84 patients). Right unilateral brief pulse ECT was applied. Anaesthesia given was propofol (1-2 mg/kg) and succinylcholine (0.5-1.0 mg/kg). Seizure quality indices (slow wave onset, amplitude, regularity, stereotypy and post-ictal suppression) and duration were rated through a structured rating scale by a single blinded trained rater. Linear Mixed Effects Models analysed the effect of the anaesthetic-ECT time interval on seizure quality indices, controlling for propofol dose (mg), ECT charge (mC), ECT session number, days between ECT, age (years), initial seizure threshold (mC) and concurrent medication.ResultsLonger anaesthetic-ECT time intervals lead to significantly higher quality seizures (p < 0.001 for amplitude, regularity, stereotypy and post-ictal suppression).ConclusionsThese results suggest that the anaesthetic-ECT time interval is an important factor to consider in ECT practice. This time interval should be extended to as long as practically possible to facilitate the production of better quality seizures. Close collaboration between the anaesthetist and the psychiatrist is essential.