Hypoxemia adds to the CURB-65 pneumonia severity score in hospitalized patients with mild pneumonia

BACKGROUND: Hypoxemia may influence the prognosis of patients with mild pneumonia, regardless of the initial CURB-65 score (confusion, blood urea nitrogen > 20 mg/dL, respiratory rate > 30 breaths/min, blood pressure < 90/60 mm Hg, and age ≥ 65 y). OBJECTIVE: To determine the risk factors associated with hypoxemia and the influence of hypoxemia on clinical outcomes in hospitalized patients with mild pneumonia. METHODS: We performed a multicenter prospective cohort study of 585 consecutive hospitalized patients with mild pneumonia (CURB-65 groups 0 and 1). We stratified the patients according to the presence of hypoxemia, defined as a P_aO2/F_IO2 < 300 mm Hg on admission. We assessed the risk factors associated with hypoxemia, hypoxemia's influence on the course of pneumonia, and clinical outcomes (mortality, hospital stay, and need for intensive care unit admission), with multivariable regression. RESULTS: Fifty percent of the patients (294 cases) had hypoxemia on admission. The risk factors independently associated with hypoxemia were: bilateral radiological involvement (odds ratio 2.8, 95% CI 1.1-7.5), history of COPD (odds ratio 2.5, 95% CI 1.4-4.3), and hypoalbuminemia (odds ratio 2.0, 95% CI.1-3.5). The hypoxemic patients had longer hospital stay, higher intensive care unit admission rate, higher rate of severe sepsis, and higher mortality than the non-hypoxemic patients. CONCLUSIONS: Hypoxemia in patients with mild pneumonia is independently associated with several adverse clinical and radiological variables, and the hypoxemic patients had worse clinical outcomes than the non-hypoxemic patients. Therefore, additional attention should be paid to the presence of hypoxemia, regardless of a low CURB-65 score.