Magnesium sulfate versus dexmedetomidine as adjuvants for peribulbar block: a GRADE-assessed systematic review and meta-analysis.

BACKGROUND

Regional anesthesia is widely used for ophthalmic surgery, but peribulbar block may have slower onset and variable akinesia. Dexmedetomidine and magnesium sulfate are used as adjuvants, yet their comparative effects remain uncertain.

METHODS

This systematic review and meta-analysis followed PRISMA 2020 and Cochrane guidance (PROSPERO CRD420261435378). PubMed, Embase, Scopus, ScienceDirect, Cochrane and Google Scholar were searched from inception to May 2026 for randomized controlled trials comparing magnesium sulfate with dexmedetomidine as adjuvants to peribulbar local anesthetic. Random-effects meta-analysis used REML, conventional and Hartung-Knapp confidence intervals, prediction intervals, leave-one-out sensitivity analyses, dosage and surgery-based subgroup analyses, and GRADE assessment.

RESULTS

Six randomized controlled trials were included. Most pooled outcomes showed no statistically significant between-group differences, including sensory-block onset (MD - 0.04 min, 95% CI - 0.15 to 0.06), globe-akinesia onset (MD - 0.33 min, 95% CI - 1.61 to 0.96), globe-akinesia duration (MD - 11.46 min, 95% CI - 29.68 to 6.77), time to block adequacy (MD 0.10 min, 95% CI - 0.92 to 1.12), IOP at 5 and 10 min, akinesia scores, supplementary injection, and satisfaction. Dexmedetomidine was associated with faster lid-akinesia onset in the conventional analysis (MD 0.32 min, 95% CI 0.15 to 0.50; P = 0.0003), but the HK-adjusted CI crossed the null (- 0.31 to 0.95). Conventional analyses also favored dexmedetomidine for lid-akinesia duration (MD - 12.20 min, P = 0.0188) and time to first analgesia (MD - 18.22 min, P = 0.0101), but both lost statistical significance after HK adjustment. Heterogeneity was substantial for several outcomes, and GRADE certainty ranged from high to very low, with most outcomes rated very low.

CONCLUSION

Current evidence does not establish a clear efficacy or safety advantage of magnesium sulfate or dexmedetomidine as a peribulbar adjuvant. Apparent benefits for lid-akinesia onset, lid-akinesia duration, and time to first analgesia are sensitive to conservative statistical adjustment and should not be interpreted as definitive. The evidence base is small, heterogeneous, geographically concentrated, and generally low or very low certainty; adequately powered multicenter trials with standardized dosing and outcome assessment are needed.