Mortality risk factors in patients with Acinetobacter baumannii ventilator: associated pneumonia

Ventilator-associated pneumonia (VAP) caused by Acinetobacter baumannii has contributed to high mortality rate, prolonged stays in the intensive care unit, and the rapid development of antimicrobial resistance to commonly used antimicrobials. This study sought to determine predictors of mortality and carbapenem resistance for patients with A baumannii VAP.

We retrospectively reviewed 541 adult patients with A baumannii pneumonia, who were admitted to a medical center between 2005 and 2007; of which 180 (33.3%) had been treated with mechanical ventilation. Of the 180 patients, 98 (54.4%) who survived were categorized as the survivor group, and 82 (45.6%) who died as the mortality group. Eighty-seven (48.3%) with imipenem-sensitive A baumannii VAP were categorized as the IS-AB group, and the remaining 93 (51.7%) with imipenem-resistant VAP as the IR-AB group.

Compared with the survivor group, the mortality group had significantly higher Charlson comorbidity index scores, and more neoplastic disease, other sites of infection, bloodstream infections, altered mental status, confusion, urea >7 mmol/L, respiratory rate >30/min, low blood pressure (systolic <90 mmHg or diastolic <60 mmHg), age >65 years (CURB-65) ≥ 3, creatinine > 1.6 mg/dL, C-reactive protein ≥ 100 mg/L, and imipenem resistance. The survivor group had more cases of tracheostomy and diabetes mellitus than the mortality group had. Compared with the IS-AB group, the IR-AB group had higher Charlson comorbidity index scores, longer stays before VAP onset, an increase in other sites of infection, white blood cell count <4/μL or >1.1 × 10(4)/μL, and higher hospital mortality rates.

Inadequate initial empiric antimicrobial therapy and higher disease severity scores, including CURB ≥ 3 and C-reactive protein ≥ 120 mg/L, were independent risk factors associated with higher mortality rates for A baumannii pneumonia. Length of stay before VAP and white blood cell count <4/μL or >1.1 × 10(4)/μL were independent risk factors for carbapenem resistance.