Effect of addition of various doses of fentanyl intrathecally to 0.5% hyperbaric bupivacaine on perioperative analgesia and subarachnoid-block characteristics in lower abdominal surgery: a dose-response study.

Abstract

The purpose of this randomized, double-blind, placebo-controlled trial is to study the effect of adding various doses of fentanyl to 2.2 mL of bupivacaine (0.5% hyperbaric), for spinal anesthetic in non-obstetric population undergoing superficial lower abdominal surgery (hernia repair). A population of 60 patients belonging to ASA classes I and II, scheduled for elective inguinal hernia repair, were randomized to receive a spinal anesthetic with 2.2 mL of bupivacaine (0.5% hyperbaric) and saline (control group), or fentanyl 10, 20, 30, or 40 microg. The volume of injected drug was kept constant at 3 mL by adding preservative-free saline for blinding purposes. Subarachnoid block characteristics, drug-related side effects, and postoperative analgesia requirements were assessed and recorded. Significant improvement in quality and duration of analgesia occurred in treatment groups (receiving fentanyl and bupivacaine) compared with the control group (saline and bupivacaine) (P < .05). However, no improvement in analgesia occurred when the dose of fentanyl added was increased from 10 to 20, 30, or 40 microg. The data suggest that in a non-obstetric population receiving spinal anesthetic for superficial lower abdominal surgery (hernia repair), addition of 10 microg fentanyl to bupivacaine 0.5% (hyperbaric) significantly improves the quality and duration of analgesia. No further advantage occurs if the dose of fentanyl is increased up to 40 mug.