Central Venous Oxygen Saturation for Estimating Mixed Venous Oxygen Saturation and Cardiac Index in the ICU: A Systematic Review and Meta-Analysis

Objectives: The objectives of our systematic review and meta-analyses were to determine the diagnostic accuracy of central venous oxygen saturation (Scv o 2 ) in estimating mixed venous oxygen saturation (Sv o 2 ) and cardiac index in critically ill patients. Data Sources: A systematic search using MEDLINE, Cochrane Central Register of Controlled Trials, and Embase was completed on May 6, 2024. Study Selection: Studies of patients in the ICU for whom Scv o 2 and at least one reference standard test was performed (thermodilution and/or Sv o 2 ) were included. Data Extraction: Individual patient data were used to calculate the pooled intraclass correlation coefficient (ICC) for Sv o 2 and Spearman correlation for cardiac index. The Quality Assessment of Diagnostic Accuracy Studies-2 and Grading Recommendations Assessment, Development, and Evaluation tools were used for the risk of bias and certainty of evidence assessments. Data Synthesis: Of 3427 studies, a total of 18 studies with 1971 patients were identified. We meta-analyzed 16 studies (1335 patients) that used Sv o 2 as a reference and three studies (166 patients) that used thermodilution as reference. The ICC for reference Sv o 2 was 0.83 (95% CI, 0.75–0.89) with a mean difference of 2.98% toward Scv o 2 . The Spearman rank correlation for reference cardiac index is 0.47 (95% CI, 0.46–0.48; p < 0.0001). Conclusions: There is moderate reliability for Scv o 2 in predicting Sv o 2 in critical care patients with variability based on sampling site and presence of sepsis. There is limited evidence on the independent use of Scv o 2 in predicting cardiac index.