Low intraoperative end-tidal carbon dioxide levels are associated with improved recurrence-free survival after elective colorectal cancer surgery.

Study Objective: Higher levels of carbon dioxide (CO ₂ ) increase the invasive abilities of colon cancer cells in vitro. Studies assessing target values for end-tidal CO ₂ concentrations (EtCO ₂ ) to improve surgical outcome after colorectal cancer surgery are lacking. Therefore, we evaluated whether intraoperative EtCO ₂ was associated with differences in recurrence-free survival after elective colorectal cancer (CRC) surgery.
Design: Single center, retrospective analysis.
Setting: Anesthesia records, surgical databases and hospital information system of a tertiary university hospital.
Patients: We analyzed 528 patients undergoing elective resection of colorectal cancer at Heidelberg University Hospital between 2009 and 2018.
Interventions: None.
Measurements: Intraoperative mean EtCO ₂ values were calculated. The study cohort was equally stratified into low-and high-EtCO ₂ groups. The primary endpoint measure was recurrence-free survival until last known follow-up. Groups were compared using Kaplan-Meier analysis. Cox-regression analysis was used to control for covariates. Sepsis, reoperations, surgical site infections and cardiovascular events during hospital stay, and overall survival were secondary outcomes.
Main Results: Mean EtCO ₂ was 33.8 mmHg ±1.2 in the low- EtCO ₂ group vs. 37.3 mmHg ±1.6 in the high-EtCO ₂ group. Median follow-up was 3.8 (Q1-Q3, 2.5-5.1) years. Recurrence-free survival was higher in the low-EtCO ₂ group (log-rank-test: p = .024). After correction for confounding factors, lower EtCO ₂ was associated with increased recurrence-free survival (HR = 1.138, 95%-CI:1.015-1.276, p = .027); the hazard for the primary outcome decreased by 12.1% per 1 mmHg decrease in mean EtCO ₂ . 1-year and 5-year survival was also higher in the low-EtCO ₂ group. We did not find differences in the other secondary endpoints.
Conclusions: Lower intraoperative EtCO ₂ target values in CRC surgery might benefit oncological outcome and should be evaluated in confirmative studies.
Competing Interests: Declaration of competing interest None.
(Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)