A comparison of alfentanil and fentanyl in short operations with special reference to their duration of action and postoperative respiratory depression.

Ninety women undergoing short gynaecological operations were included in a double-blind comparison of fentanyl and alfentanil, a structurally related and very short-acting narcotic analgesic. Anaesthesia was induced by methohexitone followed by a double-blind injection of either alfentanil (0.5 mg/ml) or fentanyl (0.05 mg/ml). Depending on the expected duration of the procedure 3 or 5 ml of the analgesic was given. For the same duration of anaesthesia, respiratory depression had to be reversed in 11% of the alfentanil and 51% of the fentanyl group and the time of awakening was significantly shorter in the alfentanil group. Cardiovascular parameters remained stable with both analgesics. There were no troublesome side-effects.