Bacteremia is an independent risk factor for mortality in nosocomial pneumonia: a prospective and observational multicenter study

Abstract

Introduction: Since positive blood cultures are uncommon in patients with nosocomial pneumonia (NP), the responsible pathogens are usually isolated from respiratory samples. Studies on bacteremia associated with hospital-acquired pneumonia (HAP) have reported fatality rates of up to 50%. The purpose of the study is to compare risk factors, pathogens and outcomes between bacteremic nosocomial pneumonia (B-NP) and nonbacteremic nosocomial pneumonia (NB-NP) episodes.

Methods: This is a prospective, observational and multicenter study (27 intensive care units in nine European countries). Consecutive patients requiring invasive mechanical ventilation for an admission diagnosis of pneumonia or on mechanical ventilation for > 48 hours irrespective of admission diagnosis were recruited.

Results: A total of 2,436 patients were evaluated; 689 intubated patients presented with NP, 224 of them developed HAP and 465 developed ventilation-acquired pneumonia. Blood samples were extracted in 479 (69.5%) patients, 70 (14.6%) being positive. B-NP patients had higher Simplified Acute Physiology Score (SAPS) II score (51.5 ± 19.8 vs. 46.6 ± 17.5, P = 0.03) and were more frequently medical patients (77.1% vs. 60.4%, P = 0.01). Mortality in the intensive care unit was higher in B-NP patients compared with NB-NP patients (57.1% vs. 33%, P < 0.001). B-NP patients had a more prolonged mean intensive care unit length of stay after pneumonia onset than NB-NP patients (28.5 ± 30.6 vs. 20.5 ± 17.1 days, P = 0.03). Logistic regression analysis confirmed that medical patients (odds ratio (OR) = 5.72, 95% confidence interval (CI) = 1.93 to 16.99, P = 0.002), methicillin-resistant Staphylococcus aureus (MRSA) etiology (OR = 3.42, 95% CI = 1.57 to 5.81, P = 0.01), Acinetobacter baumannii etiology (OR = 4.78, 95% CI = 2.46 to 9.29, P < 0.001) and days of mechanical ventilation (OR = 1.02, 95% CI = 1.01 to 1.03, P < 0.001) were independently associated with B-NP episodes. Bacteremia (OR = 2.01, 95% CI = 1.22 to 3.55, P = 0.008), diagnostic category (medical patients (OR = 3.71, 95% CI = 2.01 to 6.95, P = 0.02) and surgical patients (OR = 2.32, 95% CI = 1.10 to 4.97, P = 0.03)) and higher SAPS II score (OR = 1.02, 95% CI = 1.01 to 1.03, P = 0.008) were independent risk factors for mortality.

Conclusions: B-NP episodes are more frequent in patients with medical admission, MRSA and A. baumannii etiology and prolonged mechanical ventilation, and are independently associated with higher mortality rates.