Objective To analyze the relationship between the ratio of difference of venous-arterial blood carbon dioxide differential pressure(Pv-aCO₂) to difference of arterial-venous blood oxygen content(Ca-vO₂)(Pv-aCO₂/Ca-vO₂) and lactic acid clearance in cardiac surgery patients after cardiopulmonary bypass, and evaluate its therapy value.

Methods A total of 119 CPB post-cardiac patients were selected, the central vein and arterial blood gas analysis at the time of transferring to ICU and after 3 h of surgery were detected, and the corresponding Pv-aCO₂/Ca-vO₂ ratio was calculated.The general conditions, hemodynamic indexes, oxygen metabolism indexes, lactic acid, peripheral perfusion index(PI), SOFA score and vasoactive drug dose were collected to calculate the 3 h lactate clearance rate(LCR).According to the 3 h LCR, the patients were divided into the LCR < 10% group(21 cases) and LCR≥10% group(98 cases).The hemodynamic indexes, oxygen metabolism indexes, PI, PPV and Pv-aCO₂/Ca-vO₂ were compared between two groups.

Results There was no statistical significance in the gender, body temperature, SOFA score, PH, PI, PPV, hemoglobin, norepinephrine, epinephrine dose and hemodynamic parameters between two groups(P>0.05).At the time of transferring to ICU, the Pv-aCO₂/Ca-vO₂ in the LCR≥10% group was lower than that in LCR < 10%(P < 0.05).After 3 h of surgery, the lactic acid in the LCR≥10% group was significantly lower than that in LCR < 10%(P < 0.01).

Conclusions After CPB cardiac surgery, the Pv-aCO₂/Ca-vO₂ can be used to assist the guidance of postoperative lactic acid clearance, and the lower level of Pv-aCO₂/Ca-vO₂ is conducive to postoperative lactic acid clearance.