title: Acute Respiratory Distress Syndrome Secondary to Influenza A(H1N1)pdm09: Clinical Characteristics and Mortality Predictors.
abstract: 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.
authors.affiliation: Respiratory Intensive Care Unit, Instituto Nacional de Enfermedades Respiratorias Ismael Cosío Villegas, Mexico City, Mexico.
authors.forename: Carmen Margarita
authors.initials: CM
authors.lastname: Hernández-Cárdenas
authors.affiliation: Respiratory Intensive Care Unit, Instituto Nacional de Enfermedades Respiratorias Ismael Cosío Villegas, Mexico City, Mexico.
authors.forename: Héctor
authors.initials: H
authors.lastname: Serna-Secundino
authors.affiliation: Respiratory Intensive Care Unit, Instituto Nacional de Enfermedades Respiratorias Ismael Cosío Villegas, Mexico City, Mexico.
authors.forename: José Guadalupe
authors.initials: JG
authors.lastname: García-Olazarán
authors.affiliation: Respiratory Intensive Care Unit, Instituto Nacional de Enfermedades Respiratorias Ismael Cosío Villegas, Mexico City, Mexico.
authors.forename: Cristina Leticia
authors.initials: CL
authors.lastname: Aguilar-Pérez
authors.affiliation: Respiratory Intensive Care Unit, Instituto Nacional de Enfermedades Respiratorias Ismael Cosío Villegas, Mexico City, Mexico.
authors.forename: Jesús
authors.initials: J
authors.lastname: Rocha-Machado
authors.affiliation: Respiratory Intensive Care Unit, Instituto Nacional de Enfermedades Respiratorias Ismael Cosío Villegas, Mexico City, Mexico.
authors.forename: Luis Fernando
authors.initials: LF
authors.lastname: Campos-Calderón
authors.affiliation: Respiratory Intensive Care Unit, Instituto Nacional de Enfermedades Respiratorias Ismael Cosío Villegas, Mexico City, Mexico.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Lugo-Goytia
mesh_terms: D000046:Academic Medical Centers; D000328:Adult; D015331:Cohort Studies; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000150:complications* / Q000401:mortality; D007362:Intensive Care Units / Q000706:statistics & numerical data; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D015999:Multivariate Analysis; D009765:Obesity / Q000453:epidemiology; D053717:Pneumonia, Ventilator-Associated / Q000453:epidemiology; D011446:Prospective Studies; D012128:Respiratory Distress Syndrome / Q000209:etiology* / Q000401:mortality / Q000821:virology; D012307:Risk Factors