An observational study of end-tidal carbon dioxide trends in general anesthesia

Purpose Despite growing evidence supporting the potential benefits of higher end-tidal carbon dioxide (ETCO 2 ) levels in surgical patients, there is still insufficient data to formulate guidelines for ideal intraoperative ETCO 2 targets. As it is unclear which intraoperative ETCO 2 levels are currently used and whether these levels have changed over time, we investigated the practice pattern using the Multicenter Perioperative Outcomes Group database. Methods This retrospective, observational, multicentre study included 317,445 adult patients who received general anesthesia for non-cardiothoracic procedures between January 2008 and September 2016. The primary outcome was a time-weighted average area-under-the-curve (TWA-AUC) for four ETCO 2 thresholds (< 28, < 35, < 45, and > 45 mmHg). Additionally, a median ETCO 2 was studied. A Kruskal-Wallis test was used to analyse differences between years. Random-effect multivariable logistic regression models were constructed to study variability. Results Both TWA-AUC and median ETCO 2 showed a minimal increase in ETCO 2 over time, with a median [interquartile range] ETCO 2 of 33 [31.0–35.0] mmHg in 2008 and 35 [33.0–38.0] mmHg in 2016 ( P