Relationship Between Anesthesia Depth and Quality of Seizures in Patients Undergoing Electroconvulsive Therapy

Objectives Electroconvulsive therapy under general anesthesia is an established treatment for mood disorders, such as therapy-resistant depression. As most anesthetic drugs used for induction of anesthesia increase the seizure threshold, adequate depth of anesthesia without diminishing the therapeutic efficacy of interventions is crucial. The aim of this study was to investigate whether anesthesia depth as assessed by Narcotrend (NCT) monitoring correlates with maximum seizure quality. Methods An observational study was performed in psychiatric patients undergoing multiple interventions of electroconvulsive therapy. Seizure quality of each attendance was assessed evaluating electroencephalogram end point, electromyogram end point, postictal suppression index, the midictal amplitude, and a 3-step overall graduation. Narcotrend was used to assess anesthesia depth according to index-based electroencephalogram findings. Measurements were obtained before induction of anesthesia, before stimulation, and after arousal. Data were analyzed by means of linear mixed models and generalized estimating equations models. Results A total of 105 interventions in 12 patients were analyzed. Anesthesia depth before stimulation was significantly associated with seizure quality (standardized β = 0.244, P = 0.010), maximum sustained coherence (β = 0.207, P = 0.022), and electroencephalogram duration (β = 0.215, P = 0.012). A cutoff value of 41 or greater versus 40 or less for the NCT index was found appropriate to differentiate between good and less satisfactory overall seizure quality. Conclusions Anesthesia depth index assessed by NCT monitoring was positively associated with seizure quality. Narcotrend monitoring may be useful in assessment of optimal anesthesia depth before stimulation.