Analgesic Efficacy of Addition of Magnesium Sulfate to Bupivacaine in Wound Infiltration Technique in Perianal Surgeries

BACKGROUND: In peripheral nerve blocks, magnesium sulfate is an excellent adjuvant to local anesthetics. The use of magnesium sulfate as an adjuvant in wound infiltration for postoperative analgesia needs to be investigated. AIMS: This study was conducted to evaluate the analgesic efficacy of magnesium sulfate as an adjuvant when added to bupivacaine in wound infiltration technique in perianal surgeries. SETTINGS AND DESIGN: This was a prospective, randomized, double-blind study. MATERIALS AND METHODS: Sixty patients undergoing perianal surgeries were randomly divided into two groups, Group M and Group C. Following perianal surgery, Group M patients received a local wound infiltration of injection magnesium sulfate 750 mg (1.5 mL of injection 50% magnesium sulfate) added to 0.5% bupivacaine 13.5 mL making a total volume of 15 mL, whereas Group C patients received a local wound infiltration of injection 0.5% bupivacaine 13.5 mL and 1.5 mL normal saline. Postoperative vitals and pain scores were assessed. STATISTICAL ANALYSIS USED: Student's t-test for normally distributed continuous data, Mann–Whitney U-test for ordinal data, and Chi-square test or Fisher's exact test, whichever is appropriate for categorical data, were used. RESULTS: The magnesium sulfate group had a lower postoperative pain score, a longer duration of postoperative analgesia, and a lesser number of rescue analgesic doses in the first 24 h. CONCLUSION: We conclude that magnesium sulfate is an effective adjuvant to bupivacaine for wound infiltration in terms of postoperative analgesia quality and duration following perianal surgeries.