Efficacy of Neostigmine as an Adjuvant to Ropivacaine in Axillary Brachial Plexus Block for Hand and Forearm Surgery: A Randomized, Double-Blind Clinical Trial

Abstract

Background: Neostigmine, an acetylcholinesterase inhibitor, has been investigated as an adjuvant to local anesthetics to potentially prolong the duration of regional anesthesia. However, its role in peripheral nerve blocks such as the axillary brachial plexus block remains debated due to mixed clinical outcomes. Objectives: This study aimed to evaluate the effect of adding neostigmine to ropivacaine on the onset time, intensity, and duration of sensory and motor blockade in patients undergoing hand and forearm surgery. Methods: This randomized, double-blind clinical trial included 40 patients undergoing elective hand and forearm surgeries under axillary brachial plexus block. Participants were randomly allocated (1:1) to receive either 30 mL of 0.5% ropivacaine with 500 µg neostigmine (neostigmine group, n = 20) or 30 mL of 0.5% ropivacaine with 1 mL normal saline (placebo group, n = 20). The random sequence was computer-generated, and blinding was maintained for participants and outcome assessors. A sample size of 20 patients per group (total N = 40) was determined. Primary outcomes were the onset and duration of sensory and motor block. Secondary outcomes were hemodynamic stability, opioid consumption, and incidence of adverse events. Data were analyzed using SPSS version 22, with significance set at P < 0.05. Results: There were no significant differences between the neostigmine and placebo groups in terms of the onset of sensory and motor block, pain intensity during the procedure and recovery, or opioid consumption (P > 0.05 for all comparisons). Additionally, no significant differences were observed in heart rate, systolic and diastolic blood pressure, or incidence of complications between the two groups (P > 0.05). Conclusions: The addition of neostigmine to ropivacaine provides no clinically significant benefit for axillary brachial plexus blocks in hand and forearm surgery. It neither significantly shortens block onset nor extends analgesia duration. Given its trend toward higher nausea rates and lack of therapeutic advantage, neostigmine should not be recommended as an adjuvant in this clinical context.