Reaching Stability in Community-Acquired Pneumonia: The Effects of the Severity of Disease, Treatment, and the Characteristics of Patients

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Abstract
Background. The natural history of the resolution of infectious parameters in patients with community-acquired pneumonia (CAP) is not completely known. The aim of our study was to identify those factors related to host characteristics, the severity of pneumonia, and treatment that influence clinical stability. Methods. In a prospective, multicenter, observational study, we observed 1424 patients with CAP who were admitted to 15 Spanish hospitals. The main outcome variable was the number of days needed to reach clinical stability (defined as a temperature of ⩽37.2°C, a heart rate of ⩽100 beats/min, a respiratory rate of ⩽24 breaths/min, systolic blood pressure of ⩾90 mm Hg, and oxygen saturation ⩾90% or arterial oxygen partial pressure of ⩾60 mm Hg). Results. The median time to stability was 4 days. A Cox proportional hazard model identified 6 independent variables recorded during the first 24 h after hospital admission related to the time needed to reach stability: dyspnea (hazard ratio [HR], 0.76), confusion (HR, 0.66), pleural effusion (HR, 0.67), multilobed CAP (HR, 0.72), high pneumonia severity index (HR, 0.73), and adherence to the Spanish guidelines for treatment of CAP (HR, 1.22). A second Cox model was performed that included complications and response to treatment. This model identified the following 10 independent variables: chronic bronchitis (HR, 0.81), dyspnea (HR, 0.79), confusion (HR, 0.61), multilobed CAP (HR, 0.84), initial severity of disease (HR, 0.73), treatment failure (HR, 0.31), cardiac complications (HR, 0.66), respiratory complications (HR, 0.77), empyema (HR, 0.57), and admission to the intensive care unit (HR, 0.57). Conclusions. Some characteristics of CAP are useful at the time of hospital admission to identify patients who will need a longer hospital stay to reach clinical stability. Empirical treatment that follows guidelines is associated with earlier clinical stability. Complications and treatment failure delay clinical stability.