Low-dose bupivacaine plus fentanyl for spinal anesthesia during ambulatory inguinal herniorrhaphy:: a comparison between 6 mg and 7.5 mg of bupivacaine

Background: Inguinal herniorrhaphy is commonly performed as an outpatient procedure. Spinal anesthesia offers some advantages over general anesthesia in this setting. Methods: Forty patients were randomly divided into two groups according to a double-blind protocol: Group L had spinal anesthesia with bupivacaine 6.0 mg and Group H with bupivacaine 7.5 mg; in both groups, fentanyl 25 mug was added to the spinal anesthetic. The sensory block was measured by 'pin-prick' and the motor block was evaluated by a modified Bromage scale. Results: No differences were seen in the spread, duration and regression of sensory block between the groups on the operated side. A greater number of patients required analgesics during the operation in Group L (6) compared with Group H (1) (P< 0.05). The return of the modified Bromage scale to grade 0 was earlier in Group L than in Group H (P< 0.05) but the time to mobilization and discharge was similar. Seven patients (17%) needed to be catheterized and two had the catheter retained overnight. Times to home discharge (median) were 350 and 445 min, respectively, in Groups L and H. Postoperatively and during the first week, visual analog pain scores, analgesic requirements and side-effects were similar between the groups. In Group H, 95% of the patients and in Group L 85% would have the same anesthetic again if operated upon for a similar procedure. Conclusions: Spinal anesthesia with bupivacaine 7.5 mg and fentanyl offers an alternative to general or local anesthesia for ambulatory inguinal herniorrhaphy. However, the long discharge times and risk for urinary retention restrict its routine use in all patients.