Prolonged and severe post-electroconvulsive therapy delirium with concurrent clozapine therapy

To the Editor

Case

A 42-year-old single man diagnosed with clozapine-resistant schizophrenia with stable pituitary micro-adenoma was admitted for electroconvulsive therapy (ECT) augmentation. At admission, he was on clozapine 750 mg/d, aripiprazole 10 mg/d, sodium valproate 1000 mg/d and clonazepam 1 mg/d. During the admission, clonazepam was changed over to lorazepam because the latter was easier to cease prior to ECT. Also, aripiprazole was discontinued. His blood reports were unremarkable except for high serum clozapine at 1634 µg/L (norclozapine 541 µg/L). There were periods of high serum clozapine (1075–1359 µg/L) in the last 3 years, despite being on a stable dose of clozapine. Neurosurgical second opinion considered him suitable for ECT.

For ECT, the patient received propofol 100 mg for induction and suxamethonium 50 mg for muscle relaxation. Right unilateral ultra-brief (RUL UB) ECT was started at 19.2 mC because of concomitant sodium valproate, and this resulted in a 25-second seizures. The patient achieved Aldrete discharge score of 10 by 16 minutes and was transferred to the ward. Two hours later, he developed disorientation, disorganisation, sexual disinhibition and increased auditory hallucinations. He received olanzapine 10 mg and two doses of intramuscular haloperidol 5 mg stat as he refused oral medications, and he was nursed in seclusion for safety reasons. His clinical presentation remained unstable for the next 2 days when he had a fall with suspected seizures and was transferred to emergency department (ED). He had a seizure in ED and was admitted to a medical ward for 5 days for investigations and treatment before returning to the psychiatric ward.

Discussion

Prolonged post-ECT delirium following the first RUL UB ECT has not been reported before. Both ECT (Grover et al., 2015) and clozapine (Das et al., 2020) can precipitate delirium. There are no specific ECT parameters associated with post-ECT delirium, but available reports involve bilateral ECT (Grover et al., 2015, 2020). The anticholinergic properties of clozapine pose a risk factor for post-ECT delirium (Das et al., 2020). In our patient, it is possible that the high serum clozapine level before starting ECT could have increased the risk of delirium, thereby causing protracted and severe delirium. In this context, we recommend that it is important to achieve a safe serum clozapine level before starting ECT.

We confirm that verbal informed consent was sought from the patient presented in this case prior to submission.