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) increase the invasive abilities of colon cancer cells in vitro. Studies assessing target values for end-tidal CO concentrations (EtCO) to improve surgical outcome after colorectal cancer surgery are lacking. Therefore, we evaluated whether intraoperative EtCO 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 values were calculated. The study cohort was equally stratified into low-and high-EtCO 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 was 33.8 mmHg ±1.2 in the low- EtCO group vs. 37.3 mmHg ±1.6 in the high-EtCO group. Median follow-up was 3.8 (Q1-Q3, 2.5-5.1) years. Recurrence-free survival was higher in the low-EtCO group (log-rank-test: p = .024). After correction for confounding factors, lower EtCO 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. 1-year and 5-year survival was also higher in the low-EtCO group. We did not find differences in the other secondary endpoints.

CONCLUSIONS

Lower intraoperative EtCO target values in CRC surgery might benefit oncological outcome and should be evaluated in confirmative studies.