The effects of hyperventilation on seizure length and cerebral oxygenation during electroconvulsive therapy

Previous studies have reported that hyperventilation prolongs seizure length. However, there is no clear consensus in clinical guidelines on how to perform hyperventilation during Electroconvulsive Therapy (ECT). The present study aims to investigate the effects of hyperventilation on seizure length and cerebral oxygenation.

Forty patients aged 18-65 and classified as ASA I-II, who would have their first ECT course were included in the study. Ethics committee approval was obtained and all patients' consent was taken. The consecutive patients were randomized into two groups as follows: group H (20 patients; target etCO₂: 25-30 mmHg) and group N (20 patients; target etCO₂ 35-40 mmHg). All patients were ventilated with a facial mask for two minutes and later were ventilated by a laryngeal mask (LMA) for one minute. Vital signs, peripheric oxygen saturation (SpO₂), and regional oxygen saturation (rSO₂) were measured before general anesthesia induction, on the 3^rd minute of ventilation with an LMA (LMA₃), on the 1^st minute postictal (PI₁), on the 5^th (PI₅), and 10^th (PI₁₀) minutes. The motor seizure duration, Richmond sedation-agitation scale, and the time needed to reach Aldrete Score 9 were also recorded.

There was a significant difference between the groups when they were compared concerning seizure length and recovery time. However, when we compared the rSO₂ values that were measured at different times in group H, the difference between the measurements was statistically significant. When rSO₂ values in group H were compared in doubles, there were significant differences between measurements between the basal and LMA₃, basal and PI₁, and the basal and PI₅. When Richmond agitation scores in both groups are compared, there were no significant differences between the groups.

This study found that seizure length was longer, and the recovery time was shorter in group H. There was a contribution of hyperventilation on cerebral oxygenation that was measured on the same person at different times, but cerebral oxygenation was not statistically different from patients that were normoventilated. More studies are required to form a consensus regarding how hyperventilation applies to ECT.