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.