Comparison of fentanyl and butorphanol for outpatient anaesthesia

Equianalgesic doses of butorphanol (40 micrograms X kg-1) and fentanyl (2.0 micrograms X kg-1) were compared as supplements to balanced general anaesthesia for outpatient laparoscopic procedures. Thirty-six adult female patients (ASA physical status I or II) participated in the study. The study drugs (butorphanol or fentanyl) were given just prior to induction of anaesthesia in a double-blind fashion. Following induction with a standard dose of thiopentone and tracheal intubation using succinylcholine, nitrous oxide in oxygen and a succinylcholine infusion were used for maintenance of anaesthesia. Seventeen of the 18 patients in the butorphanol group and 14 of the 18 patients in the fentanyl group showed signs of light anaesthesia and required supplementation with isoflurane. Induction, maintenance and recovery characteristics were not different in the two groups except that the post-intubation arterial pressure and heart rate in the fentanyl group were significantly higher than the base line values and the patients receiving butorphanol were more drowsy and also more pain-free in the postoperative period. The incidence of nausea and vomiting was high in both groups. Overall, butorphanol (40 micrograms X kg-1) used as part of a standard balanced general anaesthetic for a standard outpatient procedure was not superior to fentanyl (2 micrograms X kg-1) used in the same fashion.