Effect of alfentanil and fentanyl on recovery from brief anaesthesia.

One hundred female patients were allocated randomly to receive either no analgesic supplementation to methohexitone, nitrous oxide in oxygen anaesthesia, or supplements of fentanyl 1.5 micrograms kg-1 or alfentanil 8, 12 or 16 micrograms kg-1. No differences were seen in the time to recover consciousness, regain orientation or manipulate shapes into a box. Analgesic supplementation resulted in a decrease in the requirement for methohexitone, and improved operating conditions. Some patients in each group who received fentanyl or alfentanil became apnoeic for more than 30 s duration. The duration of apnoea increased with larger doses of alfentanil.