ICU-acquired pneumonia with or without etiologic diagnosis: a comparison of outcomes.

Giunta, Valeria; Ferrer, Miquel; Esperatti, Mariano; Ranzani, Otavio T; Saucedo, Lina Maria; Li Bassi, Gianluigi; Blasi, Francesco; Torres, Antoni

OBJECTIVES The impact of ICU-acquired pneumonia without etiologic diagnosis on patients' outcomes is largely unknown. We compared the clinical characteristics, inflammatory response, and outcomes between patients with and without microbiologically confirmed ICU-acquired pneumonia. DESIGN Prospective observational study. SETTING ICUs of a university teaching hospital. PATIENTS We prospectively collected 270 consecutive patients with ICU-acquired pneumonia. Patients were clustered according to positive or negative microbiologic results. INTERVENTIONS None. MEASUREMENTS AND MAIN RESULTS We compared the characteristics and outcomes between both groups. Negative microbiology was found in 82 patients (30%). Both groups had similar baseline severity scores. Patients with negative microbiology presented more frequently chronic renal failure (15 [18%] vs 11 [6%]; p=0.003), chronic heart disorders (35 [43%] vs 55 [29%]; p=0.044), less frequently previous intubation (44 [54%] vs 135 [72%]; p=0.006), more severe hypoxemia (PaO2/FIO2: 165±73 mm Hg vs 199±79 mm Hg; p=0.001), and shorter ICU stay before the onset of pneumonia (5±5 days vs 7±9 days; p=0.001) compared with patients with positive microbiology. The systemic inflammatory response was similar between both groups. Negative microbiology resulted in less changes of empiric treatment (33 [40%] vs 112 [60%]; p=0.005) and shorter total duration of antimicrobials (13±6 days vs 17±12 days; p=0.006) than positive microbiology. Following adjustment for potential confounders, patients with positive microbiology had higher hospital mortality (adjusted odds ratio 2.96, 95% confidence interval 1.24-7.04, p=0.014) and lower 90-day survival (adjusted hazard ratio 0.50, 95% confidence interval 0.27-0.94, p=0.031), with a nonsignificant lower 28-day survival. CONCLUSIONS Although the possible influence of previous intubation in mortality of both groups is not completely discarded, negative microbiologic findings in clinically suspected ICU-acquired pneumonia are associated with less frequent previous intubation, shorter duration of antimicrobial treatment, and better survival. Future studies should corroborate the presence of pneumonia in patients with suspected ICU-acquired pneumonia and negative microbiology.