Impact of Intraoperative Hyperoxia Versus Normoxia on Mortality and Organ Injury in Cardiac Surgery: A Systematic Review and Meta-analysis of Randomized Clinical Trials

Objective To compare mortality and organ injury associated with intraoperative hyperoxia and normoxia in cardiac surgery patients. Design Systematic review and meta-analysis of randomized clinical trials (RCTs). Setting Tertiary care. Participants Patients who underwent cardiac surgery with cardiopulmonary bypass (CPB) or off-pump procedures. Interventions Intraoperative hyperoxia or normoxia. Measurements and main results A systematic search of PubMed, Embase, and the Cochrane Library identified RCTs comparing hyperoxia versus normoxia in cardiac surgery. Primary outcomes were in-hospital and 30-day mortality; secondary outcomes included postoperative clinical and biochemical measures. Risk ratios (RRs), mean differences (MDs) and standardized mean differences (SMDs) with 95% confidence intervals (CIs) were calculated. Trial sequential analysis (TSA) and subgroup analysis based on the variable used to define oxygenation (PaO₂-based vs. FiO₂-based thresholds) were performed to address heterogeneity in oxygenation strategies. Nineteen RCTs (2,001 patients) were included, with 982 patients (49.1%) experiencing hyperoxia. In-hospital (9/798 [1.1%] vs. 10/799 [1.3%]; RR 0.84; 95% CI 0.36 to 1.94; p=0.684) and 30-day mortality (1/282 [0.4%] vs. 4/280 [1.4%]; RR 0.41; 95% CI 0.08 to 2.28; p=0.311) was not different between the groups. However, the normoxia group had a higher postoperative PaO 2 /FiO 2 ratio (MD -31.49; 95% CI -47.13 to -15.85; p<0.01), whereas creatine kinase-MB (CK-MB) (SMD 1.65; 95% CI 0.12 to 3.18; p=0.03) and malondialdehyde (MDA) (SMD 3.77; 95% CI 2.99 to 4.55; p<0.01) were higher in the hyperoxia group. Conclusions Compared with normoxia, hyperoxia during cardiac surgery does not impact in-hospital or 30-day mortality but is associated with worsening physiological and biochemical parameters.