The effect of magnesium sulfate as an adjuvant to 0.5% bupivacaine on motor and sensory supraclavicular brachial plexus blockade.

ABSTRACT

Background: Magnesium is a physiologic cation that blocks neuromuscular transmission and does not allow the nerve to be stimulated. This study investigates the effect of adding magnesium sulfate to 0.5% bupivacaine to extend the duration of sensory and motor blocks of the supraclavicular brachial plexus in orthopedic surgeries of the upper extremities. Methods: This controlled randomized double-blind study was performed on patients who were candidates for orthopedic surgery of the upper extremities. A total of 60 patients between 18 and 60 years with ASA Class 1 or 2 participated in the study. One Group M received 0.5% bupivacaine (1.5 mg/kg) with magnesium sulfate 20% (3 ml) as the case group, while the second Group P received 0.5% bupivacaine (1.5 mg/kg) with normal saline (3 ml) as a placebo to block the supraclavicular brachial plexus using nerve locator. The duration of the sensory and motor block of the supraclavicular brachial plexus was monitored and evaluated using the pinprick and modifi ed Bromage scale. Results: A total of 60 patients were included in the study with 30 patients having received 0.5% bupivacaine plus magnesium and the other 30 patients having received 0.5% bupivacaine plus normal saline. The mean sensory block duration in the case Group M was 249±9.36 and in control Group P was 160±5.62 (p<0.39). The mean motor block duration in the case Group M was 232±9.64 and in control Group P was 147±26.52 (both p<0.32). The mean onset of sensory block in case Group M was 15.5±2.16 and the onset block in control Group P was 12.73±1.18 (p<0.49; statistically not signifi cant). The mean onset of motor block in case Group M was 23.5±1.1 and the onset block in control Group P was 41±3 (p<0.53; statistically not signifi cant). Conclusions: The addition of magnesium sulfate to 0.5% bupivacaine increased the duration of motor and sensory supraclavicular brachial block in the upper extremities during surgeries when compared to the use of 0.5% bupivacaine alone, though statistically not signifi cant, but defi nitely in clinically signifi cant proportions.