The association of intraoperative end-tidal carbon dioxide with the risk of postoperative nausea and vomiting.

PURPOSE: Patients undergoing gynecological surgery are considered to be a high-risk cohort for postoperative nausea and vomiting (PONV). The purpose of this study was to assess the association of intraoperative end-tidal carbon dioxide (EtCO2 ) with risk of PONV in patients underwent gynecological open surgery.

METHODS: In this single-center retrospective observational study, we included patients aged 20-60 years who underwent elective gynecological open surgery. We obtained data for the incidence of PONV within 24 h after operation. We collected EtCO2 every minute during the operation, and determined the lowest value of EtCO2 . We compared the lowest EtCO2 between patients with and without PONV. Multivariate logistic regression analysis was performed to assess the independent association of EtCO2 with the risk of PONV.

RESULTS: A total of 146 patients were included in the current study. There were 81 patients with PONV within 24 h after the operation. The median lowest value of EtCO2 in patients with PONV was significantly lower than that in patients without PONV (31 vs 33 mmHg, p = 0.02). In the multivariate logistic regression model, we found that lowest EtCO2  ≤ 31 mmHg was independently associated with increase in the risk of PONV (adjusted odds ratio = 3.37, p = 0.02).

CONCLUSION: In this retrospective observational study, low intraoperative EtCO2 was shown to be independently associated with increased risk of PONV. However, this result may be skewed by uncollected information including previous PONV, motion sickness or other unknown bias, so future studies should be conducted to refute or confirm our findings.