Electroconvulsive therapy (ECT) is an effective psychiatric treatment and relies on an iatrogenically induced, generalized seizure. Seizure quality scores have been developed to predict treatment outcomes of ECT. Its intensity can be governed by various parameters like electrode placement, anesthesia, and the systemic levels of CO₂.
The aim of this retrospective study was to investigate whether reducing end-tidal CO₂ (etCO₂) through hyperventilation prior to ECT seizure would improve seizure quality score considering electrode placement and anesthetic agent. Case notes from 2023 were reviewed and seizure quality scores, pre-seizure etCO₂, electrode placement, and anesthetic agent were obtained. The resulting 732 ECTs from 68 patients were analyzed.
Lower etCO₂ and its interaction with main anesthetic agent and different bilateral electrode placement were not significantly associated with improved seizure quality overall. Higher age was associated with a decrease in seizure quality (β = -0.03, SE = 0.01, z = − 5.58, p < .001). Post-hoc power analysis indicated sample sizes of at least 400 patients to detect isolated etCO2 effects.
Seizure quality should be understood as a complex interplay of technical, neurophysiological, and patient-related factors. Large and standardized multicenter studies are needed to explore the influence of treatment protocols on seizure quality. Electroconvulsive therapy (ECT) is an established and effective treatment for severe mental illness, including major depressive disorder, schizophrenia, and other severe psychiatric conditions1,2,3,4.
It is conducted as an interdisciplinary effort between psychiatry and anesthesiology5,6,7: Modern ECT is accompanied by an anesthetic agent and muscle relaxant in combination with additional medication like remifentanil8. Moreover, vital parameters such as heart rate, blood pressure, and oxygenation are monitored including electroencephalogram (EEG) for patient safety and seizure evaluation. Although ECT is highly effective, variability in treatment response and relapse remains substantial: In a meta-analysis from 2018, ECT achieved a pooled response rate of 74.2% for major depressive disorder and 77.1% for depressive episodes in bipolar disorder9.
In a Swedish cohort study with 285 patients suffering from schizophrenia, the response rate for ECT was 73%10. A meta-analysis on relapses following successful ECT in depression reports a relapse rate of 51.1% by 12 months following successful initial treatment11. Another meta-analysis on ECT treatment in schizophrenia reported a relapse rate of 41.4% after 12 months12.
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