Electroconvulsive therapy (ECT) is a highly efficacious therapy for psychiatric disorders, especially major depressive disorder, bipolar disorder and catatonia resistant to psychopharmacology or drug-psychotherapy combination therapy. At therapy induction, usually a series of 10-12 ECT sessions is planned with two to three days in between sessions. Thereafter, maintenance therapy can be continued with longer session intervals thereafter to avoid relapses and to support further drug and psychotherapy treatment. Without maintenance therapy, relapses can happen in up to 80% of all patients within one year.

Nowadays conducted under general anaesthesia (etomidate in the investigator's centre) and muscle relaxation (suxamethonium) to prevent adverse events, ECT can be challenging for the anaesthesiologist, as it usually leads to rapid cardiovascular changes such as sudden bradycardia due to vagal discharge, followed by sympathetic counter regulation associated with tachycardia and hypertension. For the patient, known immediate side effects are headache in about 30% and postictal confusion and delirium in up to 65%. This confusional state can lead to involuntary movements and agitation and therefore be harmful for patients and attending staff. It usually resolves within 45 minutes but nevertheless seems to be linked with adverse side effects like persistent retrograde amnesia. Identified risk factors are long seizure time and pre-existing catatonic features. Postictal delirium has been classified by Kikuchi et. al. into four categories from no delirium, mild, moderate or severe delirium. Moderate to severe delirium needing restraints or sedative medication like benzodiazepines or Propofol was present 36% of patients, which is in line with older data. The more severe forms of delirium are easily recognised in clinical practice because of the need for intervention. When including mild forms, delirium was present in 52% of all patients in the study of Kikuchi et al. In newer studies using a more sensitive tool (CAM-ICU, Confusion Assessment Method - Intensive Care Unit) to assess the presence of delirium, the rates are up to 65% at 10 minutes after ECT stimulation respectively 10 minutes after arrival in the post-anaesthesia care unit. CAM-ICU is a brief but sensitive test, which has been extensively validated in the intensive care setting. Therefore, it seems that postictal delirium is frequently underdiagnosed in clinical practice. As we know from the intensive care literature, even hypoactive forms of delirium are associated with higher complication rates and higher mortality and therefore cannot be neglected.

In previous small studies, premedication with promethazine, midazolam and dexmedetomidine successfully reduced incidence of postictal delirium. Dexmedetomidine, a highly selective, relatively short acting alpha2-agonist, has been more extensively studied in the setting of ECT and has recently been able to show his potency to reduce postictal delirium by a third when given as a bolus pre-induction in a randomised controlled trial.

In this prospective, randomised, placebo-controlled, triple-blind, single-centre, two-arm parallel groups superiority trial, the investigators aim to lower incidence and severity of postictal delirium and agitation using a pre-induction dose of 2 mcg/kg clonidine intravenously compared to placebo (sodium chloride). The investigators also hypothesise, that a pre-induction dose of clonidine will reduce incidence of postictal agitation, the need for sedative rescue medication and the need for short-acting antihypertensive medication. It therefore might increase patient safety and cost effectiveness without prolonging post-anaesthesia care unit stay or negatively affecting treatment efficacy.