To the Editor:
We read with great interest the recent study by Canet et al. 1In this investigation, based on 2,464 surgical patients, the incidence of postoperative pulmonary complications (PPCs) was 5%, with a related mortality rate at Day 30 of 19.5% (95% CI, 12.5–26.5%).
Predicting risk factors for PPCs is a cornerstone of better patient management. However, reliable knowledge of PPC incidence in a broad, heterogeneous surgical population remains difficult because of nonrepresentative samples and statistical flaws. Furthermore, definitions of PPC are often not explicit and differ among studies. The recent study of Canet et al. 1has similarities with that of McAlister et al. 2Both investigations were built with a strong statistical methodology and included a large representative surgical population. Yet, the 5% incidence of PPC reported by Canet et al. 1is almost double the 2.7% reported by McAlister et al. 2This higher rate of complications observed by Canet et al. 1could be explained, in part, by the inclusion of emergency cases (14.2%), whereas McAlister et al. 2included only scheduled cases. The risk of PPC increases significantly in emergency cases.3In addition, Canet et al. 1included some thoracic surgical cases. Another major difference is related to the use of different PPC definitions. The diagnostic criteria used by McAlister et al. 2were stricter, including supplementary therapeutic action, such as mechanical ventilation for respiratory failure, percutaneous intervention for treatment of pleural effusion, and bronchoscopic intervention for atelectasis.2
Nevertheless, the most striking result reported by Canet et al. 1is not the high incidence of PPC per se but the high percentage of mortality (19.5%) associated with these cases. It seems difficult to conceive that PPC alone can explain this finding. A previous study by Lawrence et al. 4showed that, in a cohort of patients undergoing major abdominal surgery, 33% who developed PPC also had cardiovascular complications. This result suggests that a significant proportion of patients studied by Canet et al. 1also had cardiovascular complications that were not evaluated and that these complications may have been the cause of death in these patients.
In conclusion, further studies are necessary to examine prospectively comparative incidence, outcomes, and predictors of both types of complications.
*Hôpital Foch, Suresnes, France. firstname.lastname@example.org