The Effects of Intrathecal Neostigmine Added to Bupivacaine on Postoperative Analgesic Requirement in Patients Undergoing Lower Limb Orthopedic Surgery.

BACKGROUND Several additives have been suggested to enhance analgesic effect of local anesthetic agents to decrease the adverse effects of them and increase the degree of satisfaction. We designed this randomized double-blind controlled study to evaluate the analgesic efficacy of the neostigmine added to bupivacaine using spinal anesthesia in patients undergoing lower limb orthopedic surgery. METHODS Sixty patients 18-80 yr old American Society of Anesthesiologists (ASA) physical status I or II, scheduled for femur surgery under spinal anesthesia, were recruited in a prospective, double-blinded, randomized way. The patients were randomly allocated to one of two groups of 30 each. The neostigmine group (group N) received bupivacaine 20 mg combined with 25 µg neostigmine, and the placebo group (group C) received bupivacaine 20 mg combined with 0.5ml distilled water (intrathecally) 5 minutes prior to surgery. The time to the first analgesic request, analgesic requirement in the first 12 hours after surgery, the duration of sensory and motor blockade, the incidence of adverse effects such as nausea,vomiting,hypotension, ephedrine requirements, bradycardia, and hypoxemia were recorded. RESULTS Patients receiving neostigmine had a significantly prolonged duration of motor block (C95% CI 30.27 to 87.65; P < 0.001) and sensory block (C95% CI 101.04 to 224.64; P < 0.001) compared to the control group. The difference of the mean time to the first analgesic request was also significantly longer in neostigmine group (C95% CI 83.139 to 208.526; P < 0.001). The total analgesic consumption during the first 12 hours after surgery was devoid of any significant difference between groups N and C (p = 0.41).The two groups were not significantly different in terms of intraoperative and postoperative side effects. CONCLUSION Intrathecal neostigmine 25 µg with bupivacaine caused a prolonged time to the first analgesic request and its use was not associated with any side effects.