To Örebro University

BACKGROUND: Seizure duration during electroconvulsive therapy (ECT) correlates with treatment efficacy and may be influenced by depth of anaesthesia. The Patient State Index (PSi), derived from processed EEG, offers a potential method to monitor depth of anaesthesia during ECT. This study examined the correlation between pre-ictal PSi and EEG-seizure duration.

METHODS: In this prospective observational study, adult patients undergoing routine ECT at a Swedish university hospital were monitored using the SedLine pEEG system. Anaesthetic care followed standard protocols and the clinical team was blinded to PSi values. Pre-ictal PSi was defined as the final value prior to the ECT stimulus. EEG-seizure duration and relevant clinical variables were extracted from health records. The primary outcome was the association between pre-ictal PSi and EEG-seizure duration, analysed using a linear mixed-effects model adjusting for age and use of benzodiazepines or anticonvulsants. Secondary analyses explored sex and age effects on PSi over time and differences between baseline and pre-ictal PSi.

RESULTS: Eighty-seven ECT sessions in 37 patients were analysed. Median baseline PSi was 94 (IQR 4) and pre-ictal PSi was 38 (IQR 31; p < 0.001). No correlation was found between pre-ictal PSi and EEG-seizure duration. There were no significant effects of age or sex on pre-ictal PSi while there was a significant difference between sexes on baseline PSi. Artefact and EMG activity in the EEG signal were minimal.

CONCLUSION: Pre-ictal PSi was not associated with EEG-seizure duration.

EDITORIAL COMMENT: This study found no evidence to support a correlation between pre-ictal Patient State index and seizure duration, thereby challenging any clinical utility for guiding ECT administration.