Abstract: Objective To analyze the changes of serum procalcitonin (PCT), N-terminal natriuretic peptide precursor (NT-proBNP) and mitochondrial DNA (mtDNA) levels in patients undergoing cardiopulmonary bypass (CPB) and to explore its value in predicting early complications. 
Methods A total of 108 patients undergoing cardiac surgery involving CPB were selected as the observation group, and 108 healthy people undergoing physical examination during the same period were selected as the control group. The levels of serum PCT, NT-proBNP and mtDNA were measured by enzyme-linked immunosorbent assay (ELISA) and compared. The incidence of early complications after surgery was calculated and the general data of patients with or without complications were compared. The factors affecting early complications after surgery were analyzed by logistic regression analysis. The value of serum PCT, NT-proBNP and mtDNA in predicting early complications was analyzed by receiver operating characteristic (ROC) curve, and the interaction among the three was evaluated by additive model. 
Results The serum levels of PCT, NT-proBNP and mtDNA in patients undergoing cardiac surgery involving CPB were higher than those in healthy people (P＜0.05), and the complication rate of 108 patients was 37.96%. There were significant differences in emergency surgery, preoperative cardiac function classification, duration of operation, duration of cardiopulmonary bypass, duration of aortic block, serum PCT, NT-proBNP, and mtDNA levels between patients undergoing cardiac surgery involving CPB with early complications and those without early complications (P＜0.05). The levels of serum PCT, NT-proBNP and mtDNA were the influencing factors of early complications in patients undergoing cardiac surgery involving CPB (P＜0.05). ROC curve showed that area under the ROC curve (AUC) of PCT, NT-proBNP and mtDNA in combination to predict early complications in patients undergoing cardiac surgery involving CPB was the largest, the corresponding sensitivity was 77.61%, and the specificity was 82.98%. Serum PCT, NT-proBNP and mtDNA had a synergistic effect on the occurrence of early complications in patients. 
Conclusion Serum PCT, NT-proBNP, and mtDNA are highly expressed in patients undergoing cardiac surgery involving CPB. The high levels of the three are independent risk factors for early postoperative complications, and there is a synergistic effect among them, which is of high value in predicting early complications. In addition, it has a positive effect on guiding clinical intervention measures as soon as possible. 

Key words: extracorporeal circulation, procalcitonin, N-terminal natriuretic peptide precursor