Association Between Intraoperative End-Tidal Carbon Dioxide and Postoperative Organ Dysfunction in Major Abdominal Surgery: A Cohort Study

Li Dong, Chikashi Takeda, Tsukasa Kamitani, Miho Hamada, Akiko Hirotsu, Yosuke Yamamoto, Toshiyuki Mizota



Data on the effects of intraoperative end-tidal carbon dioxide (EtCO2) levels on postoperative organ dysfunction are limited. Thus, this study was designed to investigate the relationship between the intraoperative EtCO2 level and postoperative organ dysfunction in patients who underwent major abdominal surgery under general anesthesia.


Although high-risk surgeries account for only 12.5% of all surgical procedures, they account for more than 80% of surgery-related deaths [1]. Intraoperative organ hypoperfusion is a cause of poor outcomes and may lead to high postoperative mortality [2]. Therefore, markers that can be used to monitor intraoperative organ hypoperfusion and predict postoperative organ injury are essential to improve postoperative outcomes.

Materials and Methods

Study design, setting, and population

In this single-center cohort study, we used data from the IMProve Anesthesia Care and ouTcomes (Kyoto-IMPACT) database of Kyoto University Hospital. The Kyoto-IMPACT database aims to clarify the relationship between intraoperative respiratory and cardiovascular parameters and postoperative outcomes. We continuously selected patients who underwent surgery under the care of anesthesiologists at Kyoto University Hospital (1,121 beds). Several studies have been published using the Kyoto-IMPACT database [14, 15]. We included consecutive patients aged 18 years or older who underwent major abdominal surgery under general anesthesia at Kyoto University Hospital between March 2008 and December 2017. We included individuals who underwent abdominal surgery because major abdominal surgeries involve many cases, a long duration of surgery, and a high rate of postoperative organ dysfunction as outcomes.


Baseline patient characteristics

Among the 4,781 patients who underwent major abdominal surgeries between 2008 and 2017, 4,772 met the inclusion criteria and were included in the analyses (4,171 were complete cases) (Fig 1). Low EtCO2 (defined as a mean EtCO2 of < 35 mmHg) occurred in 28% of the patients included. Table 1 displays the characteristics of the study participants. The median EtCO2 level was 36 mmHg (IQR, 34–39 mmHg) for the entire population, 33 mmHg (IQR, 31–34 mmHg) for patients with low EtCO2, and 38 mmHg (IQR, 36–40 mmHg) for patients with normal EtCO.


As for the mechanism of the association between intraoperative EtCO2 and postoperative organ dysfunction, we interpreted that low cardiac output is associated with hypotension and low EtCO2, resulting in intraoperative hypoperfusion and postoperative organ dysfunction, when ventilation is constant during surgery. Additionally, even if blood pressure is stabilized by increasing peripheral vascular resistance to compensate for low cardiac output, low EtCO2 because of low cardiac output is associated with postoperative organ dysfunction, regardless of blood pressure. As an alternative to markers of cardiac output, such as cardiac output from pulmonary artery catheters or noninvasive cardiac output monitors, EtCO2 levels may provide an objective assessment of cardiac output and organ perfusion status.


In conclusion, in patients undergoing major abdominal surgery, intraoperative low EtCO2 levels of less than 35 mmHg were associated with increased postoperative organ dysfunction, suggesting that intraoperative EtCO2 is a predictor of postoperative organ dysfunction.


Assistance with the study: We are grateful to Mr. Yoshihiro Kinoshita, Ms. Tomoko Hosoya, and Mr. Yohei Taniguchi (Medical Information Systems Section, Management Division, Kyoto University Hospital, Kyoto, Japan) for their assistance in data collection for this study.

Citation: Dong L, Takeda C, Kamitani T, Hamada M, Hirotsu A, Yamamoto Y, et al. (2023) Association between intraoperative end-tidal carbon dioxide and postoperative organ dysfunction in major abdominal surgery: A cohort study. PLoS ONE 18(3): e0268362.

Editor: Jörn Karhausen, Duke University, UNITED STATES

Received: April 26, 2022; Accepted: February 1, 2023; Published: March 10, 2023

Copyright: © 2023 Dong et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: The Institutional Review Board did not permit the sharing of our raw data (email: In this paper, there are ethical reasons for restricting the data. To minimize the risk of leaking personal information, the data extracted from medical records does not include information that directly identifies individuals such as name and date of birth. However, when submitting an ethical application to the ethics committee, we stated that we will not provide samples or information to other research institutions regarding the provision of samples or information used in the research, and regarding records related to the provision of samples or information.

Funding: This work was supported in part by the Japan Society for the Promotion of Science KAKENHI program (grant number: 20K09242; principal investigator: Toshiyuki Mizota) and the 2019 Kyoto University ISHIZUE Research Development Program (principal investigator: Toshiyuki Mizota). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

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