Utility of venous-to-arterial carbon dioxide changes to arteriovenous oxygen content ratios in the prognosis of severe sepsis and septic shock: A systematic review and meta-analysis

Background: Sepsis patients with insufficient tissue perfusion and hypoxia should be identified and resuscitated immediately. Recently, venous-to-arterial carbon dioxide pressure changes and the arteriovenous oxygen content difference ratio (Pcv-aCO2/Ca-vO2) as a predictor of tissue perfusion recovery and poor prognosis. Objectives: Pcv-aCO2/Ca-vO2 is a substitute for respiratory entropy, the elevation of which indicates a lack of tissue perfusion. Pcv-aCO2/Ca-vO2 can be used as an indicator to predict the prognosis of patients with sepsis or septic shock, but its prognostic value has not been fully evaluated. Here, we have performed a meta-analysis to assess its predictive value for mortality. Methods: Meta-analysis of Observational Studies in Epidemiology group guidelines were followed for this meta-analysis. We searched the comprehensive electronic databases of PubMed, EMBASE, Web of Science, and Cochrane libraries from inception to March 2019, using the terms including “venous-arterial,” “carbon dioxide,” “Shock, Septic,” and related keywords. The Newcastle-Ottawa scale was used for quality evaluation of the literature. A meta-analysis was performed using RevMan 5.3 and Stata 14.0 software to evaluate the effects of Pcv-aCO2/Ca-vO2 on short-term mortality, sequential organ failure assessment, and acute physiology and chronic health evaluation scores in patients with sepsis or septic shock. Results: The final analysis included 13 clinical studies involving a total of 940 subjects. The results of the meta-analysis showed that non-surviving patients had higher Pcv-aCO2/Ca-vO2 than survivors after fluid resuscitation (standardized mean difference = 0.68, 95% confidence interval = 0.24–1.12) and blood samples taken 6 h after resuscitation showed a greater risk of mortality (risk ratio = 1.89, 95% confidence interval = 1.48–2.41) and sequential organ failure assessment scores (mean difference = 1.58, 95% confidence interval = 0.88–2.28, P < 0.01) in patients with high Pcv-aCO2/Ca-vO2. These differences were statistically significant. Conclusion: This meta-analysis indicates that Pcv-aCO2/Ca-vO2 has predictive value for mortality in patients with sepsis or septic shock. Further studies are now required to determine the optimal threshold for predicting sepsis mortality. Prospero Registration: The protocol for this systematic review was registered on PROSPERO (CRD 42019128134).