Target-controlled infusion of alfentanil for postoperative analgesia: a feasibility study and pharmacodynamic evaluation in the early postoperative period

We have examined the feasibility of target-controlled infusion ofalfentanil (TCIA) and the pharmacodynamics of alfentanil in the earlypostoperative period. Patients were allocated randomly to one of the threegroups to receive balanced anaesthesia with bolus injections of fentanyl(group F), sufentanil (group S) or alfentanil (group A). In the recoveryroom all patients received the same analgesic regimen, comprising TCIA. Toevaluate the efficacy of postoperative analgesia, pain scores were measuredon a visual analogue scale (VAS) and patients indicated a need foradditional analgesia. EC50, the concentration at which, with a 50%probability, patients reported adequate analgesia, was estimated usinglogistic regression. Six patients did not complain of pain. The time fromthe last intraoperative bolus injection of opioid until patients complainedof postoperative pain was shorter (P < 0.05) in group A (mean 68 min)than in group F (101 min) and group S (136 min). The time to onset ofsatisfactory analgesia was comparable in the three groups (median 18 min ingroup F, 15 min in group S and 14 min in group A). EC50 of alfentanil wasdetermined in 28 patients; mean values were 26 ng ml-1 (group F), 39 ngml-1 (group S) and 52 ng ml-1 (group A). We conclude that TCIA, under theconditions studied, resulted in a fast onset of adequate analgesia,irrespective of the opioid administered during operation. Also, there wasno effect of opioids administered during operation on postoperativepharmacodynamics of alfentanil.