Alfentanil-mediated analgesia during propofol injection: no evidence for a peripheral action

We have investigated if alfentanil acts via peripheral opioid receptors torelieve the pain which occurs on injection of propofol. Thirty secondsbefore induction of anaesthesia and immediately after a tourniquet at 50 mmHg greater than systolic pressure was inflated on the upper arm, patientswere given either placebo (n = 22), alfentanil 1 mg (n = 22) or lignocaine40 mg (n = 22) via an i.v. cannula in the dorsum of the hand. Pain duringinjection of propofol was assessed using a three-point verbal rating scale,recorded at 8-s intervals. We found a significant reduction in pain afterlignocaine compared with the two other groups (P < 0.001), but there wasno difference between the placebo and alfentanil groups. We conclude thatalfentanil does not relieve pain on injection with propofol via an actionon peripheral opioid receptors when alfentanil is limited to the forearmfor 30 s before induction of anaesthesia.