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Acute Respiratory Distress Syndrome Secondary to Influenza A(H1N1)pdm09: Clinical Characteristics and Mortality Predictors.

BACKGROUND
Acute respiratory distress syndrome secondary to influenza A(H1N1)pdm09 virus is the leading cause of death among this patient population. Expanding the knowledge of its course and predictors of mortality is relevant to decision making. We aimed to describe the clinical characteristics and identify factors associated with mortality in patients with acute respiratory distress syndrome secondary to influenza A(H1N1)pdm09 during the 2013-2014 influenza season.


METHODS
This is an observational study of a prospective cohort of 70 patients with acute respiratory distress syndrome and influenza A(H1N1) pdm09 seen in an academic medical center. Multivariate logistic regression was used to identify the independent mortality predictors. Bootstrap was used for internal model validation.


RESULTS
This cohort was represented by young adults (43 ± 11 years old). Obesity was present in 62.5% and was not associated with mortality. Mortality at 28 days and at discharge from the respiratory intensive care unit was 14 and 20%, respectively. All patients met the criteria for acute respiratory distress syndrome, 73% had vasodilatory shock, and 27.1% had acute kidney injury on respiratory intensive care unit admission. We observed a high incidence of intensive care unit-acquired weakness (81.4%). Ventilator-associated pneumonia developed in 47.1% and was not associated with mortality. In multivariate analysis, independent risk factors for intensive care unit mortality were age (odds ratio [OR] = 1.102), white blood cell count (OR = 1.22), and lactate dehydrogenase levels (OR = 1.004) on admission to the intensive care unit.


CONCLUSIONS
We described the clinical characteristics and course of a cohort of patients with acute respiratory distress syndrome secondary to influenza A(H1N1)pdm09, and developed a predictive model of mortality based on the covariates age, levels of lactate dehydrogenase, and white cell count on admission to the respiratory intensive care unit.