Comparison of Magnesium Sulfate and Ketamine with Ropivacaine in Supraclavicular Brachial Plexus Block: A Randomized Controlled Trial

BACKGROUND: Supraclavicular brachial plexus block offers good operating conditions with limited postoperative analgesia. Magnesium sulfate (MgSO(4)) and ketamine block peripheral nociception mediated via N-methyl-D-aspartate receptors. AIMS: The aim of this study was to evaluate the effect of MgSO(4) and ketamine on the duration of analgesia in brachial block. SETTINGS AND DESIGN: This was a prospective, randomized, controlled double-blind study. MATERIALS AND METHODS: One hundred and five adult patients were randomly divided into three groups: Group I = 27 mL of 0.5% ropivacaine; Group II = 27 mL of 0.5% ropivacaine + 250 mg MgSO(4); and Group II = 27 mL of 0.5% ropivacaine + 2 mg.kg(−1) ketamine. Normal saline was added to make a total volume of 30 mL. The onset and duration of the sensorimotor blockade, quality and duration of postoperative analgesia, and adverse effects were assessed. STATISTICAL ANALYSIS: Statistical analysis was performed using SPSS, version 17.0 software (SPSS, Inc., Chicago, IL, USA). Chi-square test was used for nonparametric and ANOVA for parametric data. Post hoc Student's paired t-test was applied wherever indicated. The results were expressed as mean and standard deviation or numbers (%). P < 0.05 was considered as statistically significant. RESULTS: The duration of analgesia was significantly longer in Group II (8.78 ± 0.97 h) compared to Group I (6.76 ± 0.92 h; P < 0.001) and Group III (7.1 ± 0.89 h; P < 0.001). Intervention groups had lower postoperative visual analog scores at 8, 12, and 24 h compared to the control group. Sedation, nystagmus, and hallucinations were observed in Group III. CONCLUSION: The addition of MgSO(4) to ropivacaine in supraclavicular brachial plexus block significantly prolongs the duration of analgesia. MgSO(4) improves the quality of postoperative analgesia with lesser incidence of side effects when compared to ketamine.