A Comparative Analysis of Magnesium Sulfate Administered Intravenously Versus Perineurally as an Additive to Ropivacaine in Supraclavicular Brachial Plexus Block Under Ultrasound Guidance: A Randomized Clinical Trial

Background and objective Ultrasound-guided supraclavicular brachial plexus block has revolutionized the anesthesia practice, and a single injection can facilitate the rapid onset of anesthesia. Ropivacaine has replaced bupivacaine due to its enhanced cardiovascular and neurological safety profile. Several clinical investigations have demonstrated that magnesium sulfate administration during peripheral nerve blocks can reduce the anesthetic requirements and postoperative analgesic consumption. In this study, we aimed to compare the analgesic efficacy of perineural magnesium sulfate versus intravenous (IV) magnesium sulfate as an adjuvant to ropivacaine in patients undergoing upper limb orthopedic surgeries under supraclavicular brachial plexus block. The secondary objectives included analyzing the duration and onset of sensorimotor blockade, total doses of rescue analgesic administered, hemodynamic profile, and adverse effects. Methodology We conducted a prospective randomized study involving 50 patients with the American Society of Anaesthesiologists (ASA) grade I and II who were aged 18-60 years and scheduled for elective upper limb orthopedic surgeries to treat both-bone forearm fractures. We adopted a single-blinded study design and patients were randomly allocated into two groups based on a sealed opaque envelope technique. Both groups received 0.75% ropivacaine 20 ml; in addition, Group IV Mg received 2 mL of normal saline and Group perineural Mg received 150 mg of magnesium sulfate (2 ml) as additives, amounting to a total of 22 ml for supraclavicular brachial plexus block. Group IV Mg received an injection of magnesium sulfate 150 mg in 100 ml of isotonic saline IV whereas Group perineural Mg received 100 ml of isotonic saline IV 30 minutes before the administration of supraclavicular brachial plexus block. Results Both groups were statistically comparable in terms of all demographic variables, ASA grading, and duration of surgery. Duration of analgesia was prolonged in Group perineural Mg (616.48 ± 92.396 min) vs. Group IV Mg (459.81 ± 82.984 min) (p = 0.001). The duration of sensory and motor blockade was significantly higher in Group perineural Mg when compared to Group IV Mg (p<0.001). Intraoperative hemodynamic parameters were comparable between the groups, and no side effects were reported in either of the groups. Conclusions Based on our findings, magnesium sulfate administered perineurally as an additive in the supraclavicular brachial plexus block is associated with a superior duration of analgesic effect when compared to the IV route. Perineural magnesium sulfate is also more effective in increasing the duration of sensorimotor blockade.