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Risk Factors for Ventilator-Associated Events: A Case-Control Multivariable Analysis*

Lewis, Sarah C. MD1; Li, Lingling PhD2; Murphy, Michael V. BA2; Klompas, Michael MD, MPH2,3; for the CDC Prevention Epicenters

doi: 10.1097/CCM.0000000000000338
Clinical Investigations

Objectives: The Centers for Disease Control and Prevention recently released new surveillance definitions for ventilator-associated events, including the new entities of ventilator-associated conditions and infection-related ventilator-associated complications. Both ventilator-associated conditions and infection-related ventilator-associated complications are associated with prolonged mechanical ventilation and hospital death, but little is known about their risk factors and how best to prevent them. We sought to identify risk factors for ventilator-associated conditions and infection-related ventilator-associated complications.

Design: Retrospective case-control study.

Setting: Medical, surgical, cardiac, and neuroscience units of a tertiary care teaching hospital.

Patients: Hundred ten patients with ventilator-associated conditions matched to 110 controls without ventilator-associated conditions on the basis of age, sex, ICU type, comorbidities, and duration of mechanical ventilation prior to ventilator-associated conditions.

Interventions: None.

Measurements: We compared cases with controls with regard to demographics, comorbidities, ventilator bundle adherence rates, sedative exposures, routes of nutrition, blood products, fluid balance, and modes of ventilatory support. We repeated the analysis for the subset of patients with infection-related ventilator-associated complications and their controls.

Main Results: Case and control patients were well matched on baseline characteristics. On multivariable logistic regression, significant risk factors for ventilator-associated conditions were mandatory modes of ventilation (odds ratio, 3.4; 95% CI, 1.6–8.0) and positive fluid balances (odds ratio, 1.2 per L positive; 95% CI, 1.0–1.4). Possible risk factors for infection-related ventilator-associated complications were starting benzodiazepines prior to intubation (odds ratio, 5.0; 95% CI, 1.3–29), total opioid exposures (odds ratio, 3.3 per 100 μg fentanyl equivalent/kg; 95% CI, 0.90–16), and paralytic medications (odds ratio, 2.3; 95% CI, 0.79–80). Traditional ventilator bundle elements, including semirecumbent positioning, oral care with chlorhexidine, venous thromboembolism prophylaxis, stress ulcer prophylaxis, daily spontaneous breathing trials, and sedative interruptions, were not associated with ventilator-associated conditions or infection-related ventilator-associated complications.

Conclusions: Mandatory modes of ventilation and positive fluid balance are risk factors for ventilator-associated conditions. Benzodiazepines, opioids, and paralytic medications are possible risk factors for infection-related ventilator-associated complications. Prospective studies are needed to determine if targeting these risk factors can lower ventilator-associated condition and infection-related ventilator-associated complication rates.

1Division of Infectious Disease, University of California San Francisco, San Francisco, CA.

2Department of Population Medicine, Harvard Medical School and Harvard Pilgrim Health Care Institute, Boston, MA.

3Department of Medicine, Brigham and Women’s Hospital, Boston, MA.

* See also p. 1949.

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Dr. Lewis is employed by University of California at San Francisco Infectious Disease Division. Dr. Li received reseach support from the Centers for Disease Control and Prevention (CDC). Dr. Klompas has received grant support from CDC and honoraria for lectures on ventilator-associated pneumonia surveillance from Premier Healthcare Alliance. He lectured for Infectious Disease Association of California and received support for travel from Infectious Diseases Society of America, Society for Healthcare Epidemiology of America, and American Society of Microbiologists. His institution received grant support from the CDC. Mr. Murphy has disclosed that he does not have any potential conflicts of interest.

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© 2014 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins