No anesthetic or analgesic benefit of neostigmine 1 mg added to intravenous regional anesthesia with lidocaine 0.5% for hand surgery

BACKGROUND AND OBJECTIVES: Neostigmine has shown analgesic benefit when used as an adjunct to epidural or intrathecal anesthesia and analgesia, but evidence of benefit in the peripheral nervous system is controversial. This study aimed to determine if neostigmine 1 mg added to intravenous regional anesthesia (IVRA) provided any advantage in terms of intraoperative anesthesia or postoperative analgesia. METHODS: We recruited 54 patients booked for hand surgery into this randomized, double-blind study. For the IVRA technique, patients were administered 3 mg/kg of 0.5% lidocaine (maximum 45 mL). The treatment group (group N) had 1 mg neostigmine added to lidocaine before dilution. The control group (group C) had no additives to the IVRA solution. At the completion of surgery and after transfer to the recovery room, patients had verbal response pain scores measured at 30 minutes, 1 hour, and 2 hours after cuff deflation. Time to first request for analgesic, side effects, and analgesic consumption at 24 hours were also recorded. RESULTS: Significantly more patients in group N had motor block at 5 and 10 minutes after injection of study solution. There were no other significant differences in sensory block onset, intraoperative anesthesia, postoperative analgesia, or adverse effects between groups. CONCLUSIONS: Neostigmine 1 mg provides no anesthetic or analgesic advantage when added to IVRA for upper limb surgery.