Descriptive epidemiology and attributable morbidity of ventilator-associated events

Abstract

Objective: The Centers for Disease Control and Prevention implemented new surveillance definitions for ventilator-associated events (VAEs) in January 2013. We describe the epidemiology, attributable morbidity, and attributable mortality of VAEs.

Design: Retrospective cohort study.

Setting: Academic tertiary care center.

Patients: All patients initiated on mechanical ventilation between January 1, 2006, and December 31, 2011.

Methods: We calculated and compared VAE hazard ratios, antibiotic exposures, microbiology, attributable morbidity, and attributable mortality for all VAE tiers.

Results: Among 20,356 episodes of mechanical ventilation, there were 1,141 (5.6%) ventilator-associated condition (VAC) events, 431 (2.1%) infection-related ventilator-associated complications (IVACs), 139 (0.7%) possible pneumonias, and 127 (0.6%) probable pneumonias. VAC hazard rates were highest in medical, surgical, and thoracic units and lowest in cardiac and neuroscience units. The median number of days to VAC onset was 6 (interquartile range, 4-11). The proportion of IVACs to VACs ranged from 29% in medical units to 42% in surgical units. Patients with probable pneumonia were more likely to be prescribed nafcillin, ceftazidime, and fluroquinolones compared with patients with possible pneumonia or IVAC-alone. The most frequently isolated organisms were Staphylococcus aureus (29%), Pseudomonas aeruginosa (14%), and Enterobacter species (7.9%). Compared with matched controls, VAEs were associated with more days to extubation (relative rate, 3.12 [95% confidence interval (CI), 2.96-3.29]), more days to hospital discharge (relative rate, 1.46 [95% CI, 1.37-1.55]), and higher hospital mortality risk (odds ratio, 1.98 [95% CI, 1.60-2.44]).

Conclusions: VAEs are common and morbid. Prevention strategies targeting VAEs are needed.