Background: 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 nonobstetric population undergoing superficial lower abdominal surgery (hernia repair).

Methods: 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 μg. 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.

Results: Significant improvement in quality and duration of analgesia ocurred 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 μg.

Conclusions: The data suggest that in a nonobstetric population receiving spinal anesthetic for superficial lower abdominal surgery (hernia repair), addition of 10 μg 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 μg.