Effect of warming bupivacaine 0.5% on ultrasound-guided axillary plexus block. Randomized prospective double-blind study.

OBJECTIVE: To evaluate the effect of warming bupivacaine 0.5% on ultrasound-guided axillary brachial plexus block.

STUDY DESIGN: Prospective, randomized, double-blind.

PATIENTS AND METHODS: Eighty patients undergoing elective or emergency surgery beyond the distal third of the upper limb were divided into two groups of 40 patients: the warm group received 15mL bupivacaine 0.5% heated to 37°C; the cold group received 15mL 0.5% bupivacaine stored for at least 24hours in the lower compartment of a refrigerator at 13-15°C. Onset and duration of sensory and motor blocks were evaluated every 5minutes for 40minutes. Postoperative pain was evaluated at 1, 3, 6, 12 and 24hours. Effective analgesia time was recorded as the interval between anesthetic injection and the first analgesia requirement (VAS>30mm).

RESULTS: Time to onset of sensory and motor block was significantly shorter in the warm group, and mean duration of sensory and motor block and of postoperative analgesia significantly longer.

CONCLUSION: Warming bupivacaine 0.5% to 37°C accelerated onset of sensory and motor block and extended action duration.