title: Severe H1N1-Associated acute respiratory distress syndrome: A case series.
abstract: BACKGROUND
  Acute respiratory distress syndrome resulting from novel influenza A virus (H1N1) infection remains uncommon.
  
  
  METHODS
  We describe the clinical profiles of adult patients with acute respiratory distress syndrome due to microbiologically confirmed H1N1 admitted to a medical intensive care unit in San Francisco, California over a 2-month period.
  
  
  RESULTS
  Between June 1 and July 31, 2009, 7 patients (age range: 25-66 years; 4 patients under the age of 40 years; 6 male; 1 pregnant) were diagnosed with H1N1, with 5 of 6 (83%) having initial false-negative rapid testing. All developed respiratory failure complicated by acute respiratory distress syndrome, with 4 additionally developing multiorgan dysfunction. All were managed with a lung protective ventilator strategy (average number of days on the ventilator: 16), and 4 patients also required additional rescue therapies for refractory hypoxemia, including very high positive end-expiratory pressure, inhaled epoprostenol, recruitment maneuvers, and prone positioning. Despite these measures, 3 patients (43%) ultimately died.
  
  
  CONCLUSIONS
  Clinicians should be vigilant for the potential of H1N1 infection to progress to severe acute respiratory distress syndrome in a variety of patient demographics, including younger patients without baseline cardiopulmonary disease. A high degree of suspicion is critical, especially with the relative insensitivity of rapid testing, and should prompt empiric antiviral therapy.
authors.affiliation: University of California, San Francisco, 94143-0131, USA. alai@medicine.ucsf.edu
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Lai
authors.forename: Kevin
authors.initials: K
authors.lastname: Keet
authors.forename: Celina M
authors.initials: CM
authors.lastname: Yong
authors.forename: Janet V
authors.initials: JV
authors.lastname: Diaz
mesh_terms: D000328:Adult; D000368:Aged; D000956:Antigens, Viral / Q000032:analysis; D001706:Biopsy; D004279:DNA, Viral / Q000032:analysis; D003937:Diagnosis, Differential; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D007251:Influenza, Human / Q000150:complications* / Q000175:diagnosis / Q000821:virology; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious; D011379:Prognosis; D013902:Radiography, Thoracic; D012128:Respiratory Distress Syndrome / Q000175:diagnosis / Q000209:etiology* / Q000821:virology; D012189:Retrospective Studies
chemical_list: D000956:Antigens, Viral; D004279:DNA, Viral