The Analgesic Efficacy of Intrathecal Bupivacaine and Fentanyl with Added Neostigmine or Magnesium Sulphate

BACKGROUND: An appropriate anesthesia duration with minimal side effects and prolonged postoperative analgesia are the ideal characteristics of an intrathecal drug used during spinal anesthesia. Neostigmine and magnesium sulphate have been used as spinal anesthetic additives with narcotics and local anesthetics. OBJECTIVES: This study aimed to assess the analgesic properties of intrathecal neostigmine and magnesium sulphate by adding them to intrathecal bupivacaine-fentanyl. METHODS: : In total, 210 patients undergoing tibial fracture surgery were enrolled in a double-blinded clinical trial study. Patients were randomly allocated to one of three groups: group F received 10 mg of bupivacaine and 25 µg of fentanyl as intrathecal drug for spinal anesthesia, group N received 150 µg of neostigmine added to 10 mg of bupivacaine and 25 µg of fentanyl, and group M received 50 mg of magnesium sulphate added to 10 mg of bupivacaine and 25 µg of fentanyl. Analgesia duration, motor blockade scores, postoperative pain scores 6 and 12 hours after surgery, postoperative voiding time, and the incidence of hypotension, bradycardia, respiratory depression, and nausea and vomiting were recorded. RESULTS: Group M showed significantly longer analgesia duration (330.76 ± 80.98 minutes) than group F (280.98 ± 60.33 minutes). The pain scores in group M 6 hours (NRS: 2.44 ± 0.98) and 12 hours (NRS: 4.10 ± 0.88) after surgery were significantly lower than those of the other two groups. Before discharge from recovery, motor blockade scores and voiding time were not significantly different between the three groups. Hypotension (40%), bradycardia (25%), and nausea and vomiting (70%) were more obvious among group N patients. Respiratory depression did not occur in any patients. CONCLUSIONS: The addition of 50 mg of magnesium sulfate to a bupivacaine–fentanyl solution for intrathecal anesthesia improved the efficacy and duration of the analgesia without any significant side effects. The addition of 150 µg of neostigmine increased the incidence of hypotension, bradycardia, and nausea and vomiting. Moreover, neostigmine failed to prolong analgesia duration.