Enflurane Diltiazem

Halothane and enflurane have direct cardiac inhibitory effects similar to verapamil and diltiazem and these effects may summate. Interaction may also cause an additive effect on conduction with, e.g. isoflurane or halothane. 

Impaired myocardial conduction has been seen in two patients taking diltiazem after they were anaesthetised with enflurane, and prolonged anaesthesia has been seen with verapamil and eto-midate, but it has been suggested that chronic administration of oral calcium-channel blockers up to the day of surgery is usually beneficial. Intravenous dihydropyridines have been used to control peri-operative hypertension, but the use of intravenous verapamil is not recommended in patients anaesthetised with either halothane or enflurane. 

The authors of a review concluded that intravenous verapamil or diltiazem are not recommended in patients anaesthetised with either halothane or enflurane, especially if the patients have eardiac failure or eonduction disturbanees. ... 

Hantler CB, Wilton N, Learned DM, Hill AEG, Knight PR. Impaired myocardial conduction in patients receiving diltiazem therapy during enflurane anesthesia. Aneshesiology (1987) 67, 94-6. 

---