Central and Mixed Venous Oxygen Saturation in Cardiac Surgery: A Systematic Review and Meta-analysis.

Central venous oxygen saturation (ScvO2) and mixed venous oxygen saturation (SvO2) are widely used markers of tissue perfusion. Their role in cardiac surgery remains uncertain. This study conducted a systematic review and meta-analysis to evaluate the prognostic significance of ScvO2 or SvO2 in this setting. PubMed, Embase, and the Cochrane Library were searched from inception to March 31, 2025. Included studies enrolled adult or pediatric cardiac surgery patients reporting associations between ScvO2 and/or SvO2 values and clinical outcomes. Exclusion criteria were noncardiac surgery populations, case reports, editorials, and studies without outcome data. Quantitative synthesis was performed for studies reporting mortality data across different ScvO2 or SvO2 strata. Of 11,037 records screened, 29 studies (38,217 patients) were included in the qualitative synthesis and 9 studies in the meta-analysis. Most were observational, with heterogeneous measurement timing and thresholds. In particular, most studies performed measurement at a single time point. Low ScvO2 or SvO2 (<60%-65%) was significantly associated with increased mortality compared with normal values (risk ratio, 5.23; 95% confidence interval, 2.82-9.69; p < 0.00001; I2 = 79%). No significant difference was observed between normal and supranormal (>77.4%-80%) values. Risk of bias was generally low to moderate, with confounding the main concern. Low ScvO2 or SvO2 identified patients at higher risk after cardiac surgery. However, most data were derived from single-time-point observational studies, and evidence regarding trends, repeated measurements, or study-defined high or supranormal values is limited.