Comparison of Equiosmolar Hypertonic Saline and Mannitol for Brain Relaxation During Craniotomies: A Meta-analysis of Randomized Controlled Trials

There is a controversy about the effects of hypertonic saline (HS) used for brain relaxation in patients requiring craniotomies. We conducted a meta-analysis to compare the efficacy of equiosmolar hypertonic saline with mannitol on intraoperative brain relaxation in patients undergoing craniotomies. We searched PubMed, EMBASE, Cochrane Library databases, and Web of Science for randomized controlled trials (RCTs). The outcome indicators included brain relaxation, hemodynamic status, fluid volume, and blood chemistry. A total of nine RCTs involving 665 patients were identified and included. There was a greater increase in the odds of good intraoperative brain relaxation in the HS group (odds ratio (OR) 2.05, 95% confidence interval (CI) 1.40~3.01; P = 0.0002) compared with mannitol. In comparison with HS, mannitol slightly reduced the central venous pressure (CVP) (mean difference (MD) 1.03, 95% CI 0.03~2.03; P = 0.04) as well as significantly increasing the diuretic effect regardless of the dosage of HS (standardized mean difference (SMD) -0.86, 95% CI -1.35~-0.37; P = 0.0006). HS increased the plasma sodium level significantly (MD 7.86, 95% CI 2.78 ~ 12.95, P = 0.002) but reduced the intraoperative fluid intake (SMD -0.56, 95% CI -0.98~-0.15, P = 0.008). However, there were no significant differences in plasma osmolality and mean arterial pressure (MAP). Our results suggest that there appears to be better brain relaxation without a significant increase in urine volume in the HS group compared with mannitol in patients requiring craniotomies. High-quality RCTs with larger sample sizes will be required in the future to confirm the conclusions.