Pre-emptive analgesia from intravenous administration of opioids. No effect with alfentanil.

Forty patients undergoing total abdominal hysterectomy were randomly allocated to receive either 40 micrograms.kg-1 of alfentanil on induction of anaesthesia or 40 micrograms.kg-1 of alfentanil after the skin incision. Postoperative pain relief was provided with morphine from a patient-controlled analgesia system. The amount of morphine consumed in the operating theatre, while in recovery and for the first 24 h postoperatively was recorded. Pain scores were assessed at 24 h using a visual analogue scale. There were no differences found between the two groups for morphine consumption but the 'pre-emptive' group had significantly higher pain scores at rest. We conclude that there is no clinically useful pre-emptive analgesic effect with this dose of alfentanil and that therefore systemic opioid premedication is unlikely to decrease postoperative analgesic requirements through the mechanism of pre-emptive analgesia.