Electroconvulsive therapy and intraocular pressure

Psychiatric patients receiving phenothiazine, tricyclic antidepressant and antiparkinsonian drugs for prolonged periods, occasionally develop mydriasis and angle closure glaucoma. Suxamethonium, usually given to modify the convulsion of electroconvulsive therapy (ECT) increases intraocular pressure (IOP) by about 7-8 mmHg, the increase being maximal and having returned to baseline 2 min and 6 mins after injection, respectively. We studied the effects on IOP of an electrically induced convulsion following induction of anesthesia using methohexitone 1 mg.kg(-1) and suxamethonium 0.5 mg.kg(-1) in 21 consecutive cooperative psychiatric patients, all receiving antipsychotropic drugs. IOP was recorded sequentially from before induction of anesthesia to after resumption of spontaneous respiration. Their mean IOP was 15.3 (SD 3.7) mmHg prior to induction of anesthesia, 13.5 (SD 3.5) mmHg after loss of eyelash reflex following injection of methohexitone, 16.1 (SD 2.4) mmHg after cessation of muscle fasciculations induced by suxamethonium, 19.2 (SD 5.6) mmHg after cessation of convulsion and 15.5 (SD 4.4) mmHg following resumption of regular spontaneous respiration. The successive stepwise changes in the mean IOP were all statistically significant (p < 0.001 each change compared with the preceding pressure; paired 't' tests). These data reveal that the reduction in IOP produced by methohexitone is reversed by the increase in IOP produced by suxamethonium. Collated with the time course of the effects of barbiturates and suxamethomium on IOP, the increase in IOP observed following the induced convulsion was not greater than that expected after suxamethonium alone, suggesting that the induced convulsion during ECT does not pose an ocular hazard to psychiatric patients receiving medications which have iatrogenic glaucomatous potential.