Comparison of central venous minus arterial carbon dioxide pressure to arterial minus central venous oxygen content ratio and lactate levels as predictors of mortality in critically ill patients: a systematic review and meta-analysis - Critical Care Science (CCS)

ABSTRACT

Objective:

The central venousarterial carbon dioxide pressure to arterial-central venous oxygen content ratio (P_cv-aCO₂/C_a-cvO₂) is frequently used as a surrogate for tissue oxygenation. We aimed to identify and synthesize literature and quality of evidence supporting P_cv-aCO₂/C_a-cvO₂ as a predictor of mortality in critically ill patients compared with lactate.

Methods:

We searched several databases for studies measuring P_cv-aCO₂/C_a-cvO₂ in critically ill patients. Independent investigators performed the article screening and data extraction. A random-effects metaanalysis was performed. Pooled standardized mean differences (SMD) were used to compare the prognostic ability of P_cv-aCO₂/C_a-cvO₂ and lactate.

Results:

We initially retrieved 172 studies; 17 were included for qualitative description, and 10 were included for quantitative synthesis. The mean P_cv-aCO₂/C_a-cvO₂ was higher in nonsurvivors than in survivors (pooled SMD = 0.75; 95%CI 0.34 – 1.17; I = 83%), as was the case with lactate levels (pooled SMD = 0.94; 95%CI 0.34 – 1.54; I = 92%). Both tests were statistically significant predictors of mortality, albeit with overlapping 95%CIs between them.

Conclusion:

Moderate-quality evidence showed little or no difference in the ability of P_cv-aCO₂/C_a-cvO₂, compared with lactate, to predict mortality. Nevertheless, our conclusions are limited by the considerable heterogeneity among the studies.