Ventilator-Associated Events: What They Are and What They Are Not

In 2013, the United States Centers for Disease Control and Prevention redefined surveillance for quality of care in ventilated patients by shifting from ventilator-associated pneumonia (VAP) definitions to ventilator-associated event (VAE) definitions. VAE definitions were designed to overcome many of the limitations of VAP definitions, including their complexity, subjectivity, limited correlation with outcomes, and incomplete capture of many important and morbid complications of mechanical ventilation. VAE definitions broadened the focus of surveillance from pneumonia alone to the syndrome of nosocomial complications in ventilated patients, as marked by sustained increases in ventilator settings after a period of stable or decreasing ventilator settings. Qualitative studies suggest that most VAEs are caused by pneumonia, fluid overload, ARDS, and atelectasis. Only about 40% of clinically diagnosed VAPs meet VAE criteria, likely because the VAE requirement for a sustained increase in ventilator settings sets a threshold effect that selects for patients with severe disease. VAEs are associated with a doubling of the risk of death compared to patients without VAEs and compared to patients who meet traditional VAP criteria. Risk factors for VAEs include sedation with benzodiazepines or propofol, volume overload, high tidal-volume ventilation, high inspiratory driving pressures, oral care with chlorhexidine, blood transfusions, stress ulcer prophylaxis, and patient transport. Potential strategies to prevent VAEs include minimizing sedation, paired daily spontaneous awakening and breathing trials, early mobility, conservative fluid management, conservative transfusion thresholds, and low tidal-volume ventilation. A limited number of studies that have tested subsets of these interventions have reported substantial decreases in VAEs; no group, however, has thus far assessed the impact of a fully optimized VAE prevention bundle that includes all of these interventions upon VAE rates and other outcomes.