Background and Objectives. The study examined the effects of adding fentanyl to mepivacaine supraclavicular blocks on block characteristics and postoperative analgesia.

Methods. Twenty patients undergoing upper extremity surgery with supraclavicular blocks were prospectively randomized to receive 75 μg fentanyl either added to the local anesthetic (30 mL mepivacaine 1.5% with epinephrine 5 μg/mL) or given intramuscularly. An equivalent volume of normal saline was given in one of the two sites as a control in a double-blind fashion. Sensory and motor block onset, time to completion, and duration were measured. After the operation, patient-controlled analgesia with morphine was administered and the total dose used over 24 hours recorded. Visual analog pain scale (VAS: 0 = no pain, 10 cm = worst pain) was measured at 0, 1, 2, 3, 4, and 12 hours after the operation.

Results. There was no statistically significant difference between the two groups in sensory or motor block characteristics. There was a significantly lower VAS score among the patients with fentanyl added to their blocks within the first hour after the operation (1.3 ± 1.5 cm versus 3.8 ± 3.1 cm; P < .05), but subsequent VAS scores and total 24-hour patient-controlled analgesia requirements were no different.

Conclusions. Adding fentanyl 75 μg to mepivacaine supraclavicular blocks has no significant effects on block characteristics. It may enhance postoperative analgesia, but the duration of this effect is too brief to be clinically useful.