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 (Scvo2) in estimating mixed venous oxygen saturation (Svo2) 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 Scvo2 and at least one reference standard test was performed (thermodilution and/or Svo2) were included. DATA EXTRACTION: Individual patient data were used to calculate the pooled intraclass correlation coefficient (ICC) for Svo2 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 Svo2 as a reference and three studies (166 patients) that used thermodilution as reference. The ICC for reference Svo2 was 0.83 (95% CI, 0.75-0.89) with a mean difference of 2.98% toward Scvo2. 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 Scvo2 in predicting Svo2 in critical care patients with variability based on sampling site and presence of sepsis. There is limited evidence on the independent use of Scvo2 in predicting cardiac index.