Postictal generalized electroencephalographic suppression following electroconvulsive therapy: Temporal characteristics and impact of anesthetic regimen

Objective: Postictal generalized electroencephalographic suppression (PGES) has been defined as electroencephalographic (EEG) activity of less than 10 microvolts following a generalized seizure. PGES is associated with an increased risk of sudden unexplained death in epilepsy, as well as treatment efficacy of electroconvulsive therapy (ECT). We investigated the impact of anesthetic on PGES expression and temporal characteristics. Methods: We recorded postictal EEG in 50 ECT sessions in 11 patients with treatment resistant depression (ClinicalTrials.gov NCT02761330). For each participant, repeated sessions included either ketamine or etomidate general anesthesia during ECT. An automated algorithm was employed to detect PGES within 5 minutes after seizure termination. Results: PGES was detected in 31/50 recordings, with intermittent epochs recurring up to five minutes after seizure termination. PGES total duration was greater following ketamine than etomidate anesthesia (p = 0.04). PGES expression declined loglinearly as a function of time (r = -0.89, p < 10^-4). EEG amplitude during PGES did not vary linearly with time. Conclusions: PGES can occur intermittently for several minutes following seizure termination. Anesthetic effects should be considered when correlating PGES duration to clinical outcomes. Significance: Prolonged EEG monitoring several minutes following seizure termination may be necessary to fully evaluate the presence and total duration of PGES.