Several studies reported Pv-aCO₂/Ca-vO₂ ratio as a surrogate of VCO₂/VO₂ to detect global tissue hypoxia. The present study aimed to evaluate the prognostic value of Pv-aCO₂/Ca-vO₂ ratio combined with lactate levels during the early phases of resuscitation in septic shock.

A retrospective study was conducted in 144 septic shock patients in a 30-bed mixed ICU. A Pv-aCO₂/Ca-vO₂ ratio>1.4 was considered abnormal. Patients were classified into four predefined groups according to lactate levels and Pv-aCO₂/Ca-vO₂ ratio after the first 6h of resuscitation. Sequential Organ Failure Assessment (SOFA) score at day 3 was assessed. A Kaplan-Meier curve showed the survival probabilities at day 28 using a log-rank test to evaluate the differences between groups. A receiver operating characteristics (ROC) curve evaluated the ability of lactate, Pv-aCO₂/Ca-vO₂ ratio and Pv-aCO₂/Ca-vO₂ ratio combined with lactate to predict mortality at day 28.

Combination of hyperlactatemia and high Pv-aCO₂/Ca-vO₂ ratio was associated with poor SOFA scores and low survival rates at day 28 (P<0.001). The Cox multivariate survival analysis demonstrated that Pv-aCO₂/Ca-vO₂ ratio and lactate at T6 were independent predictors of mortality at day 28. The area under the ROC curve of the Pv-aCO₂/Ca-vO₂ ratio combined with lactate for predicting mortality at day 28 was highest and superior to that of lactate and Pv-aCO₂/Ca-vO₂ ratios.

Combination of Pv-aCO₂/Ca-vO₂ ratio and lactate at early stages of resuscitation of septic shock can better predict the prognosis of patients. The Pv-aCO₂/Ca-vO₂ ratio may become a useful parameter supplementary to lactate in the resuscitation of septic shock.