Efficacy of Magnesium Sulfate as Adjuvant to Ropivacaine 0.4% for Supraclavicular Brachial Plexus Block in Patients undergoing Upper Limb Surgery: A Randomized Controlled Trial

Abstract

Objectives: To prolong the duration of brachial plexus block, different adjuvants have been used. We evaluated the effect of adding magnesium sulfate to local anesthetic ropivacaine 0.4% for institution of supraclavicular brachia plexus block. Onset of sensory and motor block, duration of motor block, and rescue analgesia were observed. Materials and methods: Total 120 patients (20–50 years) scheduled for elective surgeries of upper limb under supraclavicular brachial plexus block were randomized into two groups. Group I received 24 mL 0.5% ropivacaine (120 mg) + 6.0 mL normal saline (NS) to make total volume of 30 mL. Group II received 24 mL 0.5% ropivacaine (120 mg) + 150 mg magnesium sulfate + 5.5 mL NS to make total volume of 30 mL. Results: Onset of sensory block in group I was 16.63 ± 2.79 min and in group II was 17.33 ± 2.25 min (statistically not significant, p < 0.05). Onset of motor block in group I was 18.63 ± 2.79 min and in group II was 19.76 ± 2.18 min (statistically significant, p < 0.05). The duration of motor block was significantly longer in group II; 322.00 ± 81.35 min than group I; 260.25 ± 66.79 min (p < 0.05). Similarly, time of rescue analgesia was significantly prolonged in group II; 491 ± 100.22 min than group I; 377.67 ± 73.31 min (p < 0.05). Conclusion: From our study, we concluded that the addition of 150 mg magnesium sulfate as adjuvant to 30 mL of 0.4% ropivacaine in comparison to 30 mL of 0.4% ropivacaine provides longer duration of analgesia. Although the onset of sensory block is not affected, onset of motor block is delayed. Motor block lasts for longer duration.