Magnesium Sulfate as an Adjuvant to Local Anesthetic in Erector Spinae Plane Block: A Systematic Review of Randomized Controlled Trials

Background: Magnesium sulfate (MgSO4) added to local anesthetics has been investigated as an adjuvant in regional anesthesia, but its role in ultrasound-guided erector spinae plane block (ESPB) remains uncertain. Methods: We conducted a PRISMA 2020-compliant systematic review of randomized controlled trials evaluating MgSO4 added to the local anesthetic solution in ESPB. In the predefined core comparison (MgSO4 added to local anesthetic vs. local anesthetic alone in adult postoperative surgery), four trials (225 participants enrolled; 160 contributing to the comparison) informed the qualitative synthesis. Results: Eight randomized controlled trials were included. In the predefined core comparison, 24 h pain intensity was reported heterogeneously and was frequently not extractable as continuous data, precluding pooling. Opioid consumption or rescue analgesia more often favored MgSO4; however, outcome metrics, analgesic drugs, and assessment windows were not harmonized, and these effects were not consistently accompanied by reductions in pain intensity at 24 h, limiting their interpretation as true analgesic benefit. Safety reporting was frequently incomplete and often lacked structured adverse event tabulation. Risk of bias varied across domains, and GRADE certainty for all core outcomes was very low. Conclusions: Current randomized evidence does not support routine use of MgSO4 as an adjuvant in ESPB. Future trials using standardized ESPB techniques, harmonized magnesium dosing strategies, and core outcome sets are required to determine whether magnesium provides clinically meaningful incremental analgesic benefit.