Fentanyl does not improve the nerve block characteristics of axillary brachial plexus anaesthesia performed with ropivacaine

Background: The aim of this prospective, randomized, double-blind study was to evaluate the effects of adding 1 mug.kg(-1) fentanyl to ropivacaine 7.5 mg.ml(-1) for axillary brachial plexus anaesthesia. Methods: With Ethics Committee approval and written consent, 30 ASA physical status I-LI in-patients, scheduled for orthopaedic hand procedures were randomly allocated to receive axillary brachial plexus block with 20 mi of either ropivacaine 7.5 mg.ml(-1) (n=15) or ropivacaine 7.5 mg.ml(-1)+1 mug.ml(-1) fentanyl (n=15). Nerve blocks were placed using a nerve stimulator with the multiple injection technique. A blinded observer recorded the time to onset of surgical block (loss of pinprick sensation in the innervation areas of the hand (C-6-C-8) With concomitant inability to flex the wrist against gravity and move the fingers when squeezing the hand) and first request for pain medication after surgery. Results: No differences in demography, degree of sedation or peripheral oxygen saturation were observed between the two groups. Median (range) time required to achieve readiness for surgery was 15 min (5-36 min) with ropivacaine alone and 15 min (5-40 min) with the ropivacaine-fentanyl mixture. No differences in the intraoperative quality of nerve block were reported between the two groups. Four patients receiving ropivacaine plain and two patients receiving the ropivacaine-fentanyl mixture did not require analgesics during the first 24 h after surgery (P=0.62). The degree of pain experienced at first analgesic request in those patients asking for pain medication, as well as median consumption of postoperative analgesics, were similar in the two soups. First postoperative analgesic request was made at 11 h (25th-75th percentiles: 9.1-14 h) in patients receiving ropivacaine alone and at 11.8 h (25th-75th percentiles: 9.8-15 h) in patients receiving the ropivacaine-fentanyl mixture (P=0.99). Conclusion: The addition of fentanyl 1 mug.ml(-1) to ropivacaine 7.5 mg.ml(-1) does not improve the nerve block characteristics of axillary brachial plexus anaesthesia for orthopaedic procedures involving the hand.