The Effect of Magnesium Sulfate on Postoperative Pain in Upper Limb Surgeries by Supraclavicular Block Under Ultrasound Guidance

BACKGROUND: Previous studies have been conducted to evaluate the effect of different adjuvants on brachial plexus block. OBJECTIVES: This study investigated the effect of adding magnesium sulfate to lidocaine on postoperative pain in upper limb surgeries by supraclavicular brachial plexus block under ultrasound guidance. METHODS: This study was carried out on patients who were candidate for upper limb surgeries. This was a controlled double-blind study conducted on a number of 52 patients aged 18 - 75 years with ASA class I or II. The first group (M) received lidocaine 1% (4 mg/kg) plus fentanyl 50 micg and magnesium sulfate 20% (5 mL) while the second group (N) received lidocaine 1% (4 mg/kg) plus fentanyl 50 micg and normal saline (5 mL) to supraclavicular brachial plexus block under ultrasound guidance. Postoperative pain was evaluated by visual analog scale (VAS) until 24 hours. Sensory and motor blocks onset and duration, rescue analgesics, hemodynamic variables, and side effects were recorded for all the patients. RESULTS: Postoperative VAS values at 24 hours were significantly lower in group M than group N (P < 0.0001). Sensory and Motor blocks onset and duration were statistically longer in group M than group N (P < 0.0001). CONCLUSIONS: The addition of magnesium sulfate to lidocaine decreased the postoperative pain and increased the onset and duration of sensory and motor blocks in supraclavicular brachial plexus block under ultrasound guidance in upper limb surgeries.