Intraoperative methylene blue administration and postoperative delirium: a meta-analysis of surgical patients

BACKGROUND: This meta-analysis aimed to determine the effect of intraoperative intravenous methylene blue administration on the incidence of postoperative delirium in adult surgical patients. METHODS: This systematic review and meta-analysis was reported in accordance with PRISMA guidelines and registered in PROSPERO. A comprehensive search of seven electronic databases was performed from inception to January 2026 to identify randomized controlled trials evaluating intraoperative intravenous methylene blue administration and postoperative delirium in adult surgical populations. Study selection, data extraction, and methodological quality assessment were independently conducted by two reviewers using predefined eligibility criteria. Risk of bias was assessed using the Cochrane Risk of Bias 2 tool. Pooled odds ratios with 95% confidence intervals were calculated using a fixed-effect model due to the absence of between-study heterogeneity. Publication bias was evaluated using funnel plot inspection, Egger's regression test, and Kendall's tau test. RESULTS: = 0%). CONCLUSIONS: Intraoperative methylene blue administration was associated with a reduction in postoperative delirium in surgical patients. However, given the limited number of included studies, further large-scale randomized controlled trials are required.