Hypocapnia measured by end-tidal carbon dioxide tension during anesthesia is associated with increased 30-day mortality rate

To evaluate the relationship between intraoperative end-tidal carbon dioxide (etco2) values and clinical outcomes with special attention on 30-day postoperative mortality and secondarily on hospital length of stay (LOS).Retrospective, observational study.Surgical theaters of the University Hospital Center of Charleroi.Five thousand three hundred seventeen patients ASA I-IV undergoing various surgical procedures (except pediatric and cardiac surgery) under general anesthesia.No intervention on the patients.The mean etco2 level measured during anesthesia was secondarily extracted from an electronic information management system. Patients were divided into 2 separate groups based on etco2 values less than or greater than or equal to 35 mm Hg. The primary end point was the in- and outhospital mortality in the 30-day period after surgery. The second was the LOS more than 6 days.Hypocapnia occurred in 66% of the patients. Mortality rate at 30-day was 84 of 3554 (2.4%) in the low etco2 group vs 15 of 1763 (0.9%) in the other (odds ratio, 2.99 [1.69-5.28]; P<.001). In multivariate analysis, age and ASA scores had significant independent associations with mortality rate. Adjusting for these factors had an effect on the relative odds ratio of etco2 on mortality of 1.99 ([1.11-3.56]; P<.001). Patients with low etco2 experienced higher LOS (14.1±9.4 vs 13.1±8.9 days; P<.001). Thirty five percent of the patients in the low etco2 group were still hospitalized more than 6 days compared with 30% in the other (P<.001).Low etco2 level during anesthesia is associated with an increase in postoperative mortality rate and LOS. These results emphasize the importance of preventing hypocapnia during anesthesia to improve surgical outcomes.