Lactate and CO2-Derived Parameters are not Predictive Factors of Major Postoperative Complications after Cardiac Surgery with Cardiopulmonary Bypass: A Diagnostic Accuracy Study

Xiaofen Zhou ^1,2 Han Chen ¹ Jun Ke ¹ Shirong Lin ¹ Ting-Feng Huang ¹ Bing- Ying Chen ¹ Xin-Da Jiang ¹ Feng Chen ^1,2*

• ¹ Shengli Clinical Medical College, Fujian Medical University, Fuzhou, Fujian Province, China
• ² Fujian Provincial Hospital, Fuzhou, China

Purpose: This study aimed to compare the performance of lactate and CO2-derived parameters in predicting major postoperative complications (MPC) after cardiac surgery with cardiopulmonary bypass.Methods: Lactate and CO2-derived parameters, including the venous-arterial difference in CO2 partial pressure (Pv-aCO2), the venous-arterial difference in CO2 partial pressure to arterial-venous O2 content ratio (Pv-aCO2/Ca-vO2), and the venous-arterial difference in CO2 content to arterial-venous O2 content ratio (Cv-aCO2/Ca-vO2) at ICU admission, 3 h, 6 h, and 12 h later were collected. Receiver-operating characteristics (ROC) curve analysis was carried out to assess the predictive performance. Univariate and multivariate logistic regression analyses were performed to identify independent predictors of MPC.Results: MPC occurred in 77 (54.2%) of 142 patients. No significant difference was observed between the MPC and no-MPC groups regarding lactate and CO2-derived parameters. The area under the curves (AUCs) were 0.532 (0.446 to 0.616) for lactate, 0.559 (0.473 to 0.642) for Pv-aCO2, 0.617 (0.532 to 0.697) for Pv-aCO2/Ca-vO2, and 0.625 (0.540 to 0.705) for Cv-aCO2/Ca-vO2, respectively, and there was no significant difference between the parameters. In the post-hoc analysis, all parameters’ AUCs were lower than 0.75 in predicting acute renal failure, and there was no significant difference between these parameters. Cv-aCO2/Ca-vO2 at 12 h yielded the highest AUC of 0.853 (0.784 to 0.907) in predicting mortality and the highest AUC of 0.808 (0.733 to 0.869) in predicting delirium. In multivariate analysis, hypertension, surgery duration, and PaO2/FiO2 were identified as independent predictors of MPC, while lactate and CO2-derived parameters lost statistical significance after adjustment for covariates.Conclusions: Lactate and CO2-derived parameters cannot be used as reliable indicators to predict the occurrence of MPC after cardiopulmonary bypass. Instead, traditional clinical factors such as hypertension, extended surgical duration, and impaired oxygenation emerged as the most reliable risk indicators.