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

We have investigated if alfentanil acts via peripheral opioid receptors to relieve the pain which occurs on injection of propofol. Thirty seconds before induction of anaesthesia and immediately after a tourniquet at 50 mm Hg greater than systolic pressure was inflated on the upper arm, patients were given either placebo (n = 22), alfentanil 1 mg (n = 22) or lignocaine 40 mg (n = 22) via an i.v. cannula in the dorsum of the hand. Pain during injection of propofol was assessed using a three-point verbal rating scale, recorded at 8-s intervals. We found a significant reduction in pain after lignocaine compared with the two other groups (P < 0.001), but there was no difference between the placebo and alfentanil groups. We conclude that alfentanil does not relieve pain on injection with propofol via an action on peripheral opioid receptors when alfentanil is limited to the forearm for 30 s before induction of anaesthesia.