Remifentanil versus alfentanil in a balanced anesthetic technique for total abdominal hysterectomy.

STUDY OBJECTIVES

To compare the intraoperative effects and recovery characteristics of remifentanil hydrochloride and alfentanil when administered as part of balanced anesthesia, and to assess the effects of an additional remifentanil infusion administered as analgesic pretreatment before removal of the uterus.

DESIGN

Multicenter, double-blind, randomized, parallel-group study.

SETTING

Two university hospitals.

PATIENTS

35 ASA physical status I, II, and III women scheduled for elective total abdominal hysterectomy with general endotracheal anesthesia.

INTERVENTIONS

Patients were premedicated with midazolam 0.05 mg/kg intravenously (i.v.). Anesthesia was induced with thiopental 2 mg/kg, vecuronium 0.15 mg/kg, and a single dose of opioid over 60 seconds (Pump 1): remifentanil 2 micrograms/kg (Remi/Placebo and Remi/Remi groups) or alfentanil 50 micrograms/kg (Alf/Placebo group). Anesthesia was maintained with a nitrous oxide/oxygen mixture (66:34 ratio) and a continuous opioid infusion: remifentanil 0.25 microgram/kg/min (Remi/Placebo and Remi/Remi) or alfentanil 0.5 microgram/kg/min (Alf/Placebo). At skin incision, a second blinded drug infusion was also initiated (Pump 2): remifentanil 0.25 microgram/kg/min (Remi/Remi) or saline placebo (Remi/Placebo and Alf/Placebo). Intraoperative responses were controlled with single doses of opioid and/or rate titrations via Pump 1. Pump 2 was terminated on removal of the uterus. Pump 1 was terminated at skin closure.

MEASUREMENTS AND MAIN RESULTS

The mean (+/- SD) opioid infusion rates administered for the duration of Pump 2 to suppress responses to removal of the uterus were 0.49 +/- 0.27 microgram/kg/min, 1.99 +/- 1.34 micrograms/kg/min, and 0.49 +/- 0.07 microgram/kg/min for the Remi/Placebo, Alf/Placebo, and Remi/Remi groups, respectively. At these rates, similar proportions of patients in the Remi/Placebo (67%) and the Alf/Placebo (60%) groups had responses. Fewer patients had responses in the Remi/Remi group (8%) compared with the Remi/Placebo and Alf/Placebo groups (p < 0.05). The mean total opioid doses used during maintenance were 84.6 micrograms/kg (Remi/Placebo), 393 micrograms/kg (Alf/Placebo), and 68.7 micrograms/kg (Remi/Remi). Awakening times were significantly shorter (p < 0.05) in the remifentanil population compared with the alfentanil population, but discharge times were similar. More patients received naloxone to reverse opioid effects in the alfentanil population (60%) than in the remifentanil population (20%) (p < 0.05).

CONCLUSIONS

A mean remifentanil infusion of 0.49 microgram/kg/min is as effective as a mean alfentanil infusion of 1.99 micrograms/kg/min in suppressing intraoperative responses. Doubling of the remifentanil infusion to 0.5 microgram/kg/min before the major stress event improves suppression of responses and lowers intraoperative use of remifentanil without prolonging recovery times. Remifentanil allows faster awakening times than alfentanil, but preemptive administration of postoperative analgesics is recommended to facilitate discharge.