Association of Hospital Altitude and Postoperative Infectious Complications After Major Operations

The relationship between altitude during treatment and common postoperative infections remains to be established. Based on the inverse relationship between oxygen partial pressure and altitude, we hypothesized that hospital elevation would correlate positively with postoperative infectious complication rates, including surgical site infection (SSI), urinary tract infection (UTI), and pneumonia. We used an event-enriched population of general, urologic, vascular, plastic-reconstructive, orthopedic, and thoracic patients within the 2016 ACS National Surgical Quality Improvement Program (NSQIP) dataset who underwent procedures with high risk of infectious complications. This yielded 82,172, 175,409, and 88,856 patients from 571, 577, and 570 hospitals for the study of 30-day postoperative SSI, UTI, and pneumonia outcomes respectively. Hospital altitudes were determined using Google Maps. Data were analyzed using univariate (altitude) and multivariate logistic regression, with altitude forced into the model, and forward-selection of NSQIP variables, with adjustment for clustering by hospital. When compared in 1000-foot increments above sea level, hospital altitude had no significant effect on SSI or UTI (odds ratio [OR] = 1.0, p > 0.05). The risk of postoperative pneumonia decreased with increased altitude (OR = 0.93, 95% confidence interval: 0.87-0.99, p = 0.03). Patients and providers should be reassured that there is no increased risk of SSI or UTI at higher altitudes. The decreased risk of postoperative pneumonia was surprising and there exist potential explanations warranting future investigation.