The Use of Magnesium Sulfate and Peripheral Nerve Blocks

Objectives: With the popularization of ultrasound, nerve blocks have been widely implemented in current clinical practice. Although, they have seen limited success due to their shorter duration and suboptimal analgesia. Magnesium sulfate as a local anesthetic adjuvant for peripheral nerve blocks could enhance the effects of local anesthetics. However, previous investigations have not thoroughly investigated the analgesic efficacy of magnesium sulfate as an adjunct to local anesthetics for peripheral nerve blocks. Thus, we attempted to fill the gap in the existing literature by conducting a meta-analysis. Materials and Methods: We performed of a quantitative systematic review of randomized controlled trials published between May 30, 2011 and November 1, 2018. Inclusion criteria were: (1) magnesium sulfate used as adjuvant mixed with local anesthetic for nerve blockade, (2) complete articles and published abstracts of randomized controlled trials, (3) English language. Primary and Secondary Outcome Measures: The primary outcome measures were time of onset, total duration of the sensory blockade, and Visual Analog Scale pain scores. The secondary outcomes were postoperative oral and intravenous analgesics consumption and the incidence of nausea and vomiting. Results: The 21 trials analyzed in this study included 1323 patients. Magnesium sulfate effectively prolonged the total duration of sensory blockade (mean difference [MD]=114.59 min, 95% confidence interval [CI]: 89.31-139.88), reducing Visual Analog Scale pain scores at 6 hours (MD=1.36 points, 95% CI: −2.09 to −0.63) and 12 hours (MD=1.54 points, 95% CI: −2.56 to −0.53) postsurgery. Magnesium sulfate also effectively reduced postoperative analgesic use within 24 hours postsurgery (standard MD=−2.06, 95% CI: −2.67 to −1.35). Furthermore, adjuvant magnesium sulfate significantly reduced the incidence of nausea and vomiting after transversus abdominis plane blockade (odds ratio: 0.39, 95% CI: 0.18-0.81). Conclusion: Adjuvant magnesium sulfate enhanced the anesthetic effects of local anesthetics and improved postoperative analgesia following the perineural blockade.