Intraoperative partial pressure of arterial carbon dioxide levels and adverse outcomes in patients undergoing lung transplantation

Abstract

Objective: Patients undergoing lung transplantation (LTx) often experience abnormal hypercapnia or hypocapnia. This study aimed to investigate the association between intraoperative PaCO₂ and postoperative adverse outcomes in patients undergoing LTx.

Methods: We retrospectively reviewed the medical records of 151 patients undergoing LTx. Patients' demographics, perioperative clinical factors, and pre- and intraoperative PaCO₂ data after reperfusion were collected and analyzed. Based on the PaCO₂ levels, patients were classified into three groups: hypocapnia (≤35 mmHg), normocapnia (35.1-55 mmHg), and hypercapnia (>55 mmHg). Univariate and multivariable logistic regressions were used to identify independent risk factors for postoperative composite adverse events and in-hospital mortality.

Results: Intraoperative hypercapnia occurred in 69 (45.7%) patients, and hypocapnia in 17 (11.2%). Patients with intraoperative PaCO₂ of 35.1-45 mmHg showed a lower incidence of composite adverse events (53.3%) and mortality (6.2%) (P < 0.001). There was no significant difference in composite adverse events and mortality among preoperative PaCO₂ groups (P > 0.05). Compared with intraoperative PaCO₂ at 35.1-45 mmHg, the risk of composite adverse events in hypercapnia group increased: the adjusted OR was 3.07 (95% confidence interval [CI]: 1.36-6.94; P = 0.007). The risk of death was significantly higher in hypocapnia group than normocapnia group, the adjusted OR was 7.69 (95% CI: 1.68-35.24; P = 0.009). Over ascending ranges of PaCO₂, PaCO₂ at 55.1-65 mmHg had the strongest association with composite adverse events, the adjusted OR was 6.40 (95% CI: 1.18-34.65; P = 0.031).

Conclusion: These results demonstrate that intraoperative hypercapnia independently predicts postoperative adverse outcomes in patients undergoing LTx. Intraoperative hypocapnia shows predictive value for postoperative in-hospital mortality in LTx.

Keywords: Adverse events; Lung transplantation; Mortality; Partial pressure of arterial carbon dioxide; Prognosis.