title: Critical illness associated with 2013-2014 influenza A (H1N1): Postpandemic characteristics, presentation and outcomes.
abstract: BACKGROUND
  The United States experienced a postpandemic outbreak of H1N1 influenza in 2013-2014. Unlike the pandemic in 2009 clinical course and outcomes associated with critical illness in this postpandemic outbreak has been only sparsely described.
  
  
  METHODS
  We conducted a retrospective analysis of all patients admitted to the Medical Intensive Care Unit with H1N1 influenza infection in 2009-2010 (pandemic) and 2013-2014 (postpandemic).
  
  
  RESULTS
  Patients admitted in the postpandemic period were older (55 ± 13 vs. 45 ± 12, P = 0.002), and had a higher incidence of underlying pulmonary (17 vs. 7, P = 0.0007) and cardiac (16 vs. 8, P = 0.005) disease. Mechanical ventilation was initiated in most patients in both groups (27 vs. 21, P = 1.00). The PaO2/FiO2 ratio was significantly higher in the pandemic group on days 1 (216 vs. 81, P = 0.0009), 3 (202 ± 99 vs. 100 ± 46, P = 0.002) and 7 (199 ± 103 vs. 113 ± 44, P = 0.019) but by day 14 no difference was seen between the groups. Rescue therapies were used in more patients in the postpandemic period (48% vs. 20%, P = 0.028), including more frequent use of prone ventilation (10 vs. 3, P = 0.015), inhaled vasodilator therapy (11 vs. 4, P = 0.015) and extracorporeal membrane oxygenation (ECMO) (4 vs. 2, P = NS). No significant differences in mortality were seen between the two cohorts.
  
  
  CONCLUSIONS
  Compared to the 2009-2010 pandemic, the 2013-2014 H1N1 strain affected older patients with more underlying co-morbid cardio-pulmonary diseases. The patients had worse oxygenation indices and rescue modalities such as prone ventilation, inhaled epoprostenol and ECMO, were used more consistently as compared to the 2009 pandemic.
authors.affiliation: Department of Pulmonary Critical Care, Cleveland Clinic, Respiratory Institute, Cleveland, Ohio, USA.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Wiesen
authors.affiliation: Department of Pulmonary Critical Care, Cleveland Clinic, Respiratory Institute, Cleveland, Ohio, USA.
authors.forename: Dhruv
authors.initials: D
authors.lastname: Joshi
authors.affiliation: Department of Pulmonary Critical Care, Cleveland Clinic, Respiratory Institute, Cleveland, Ohio, USA.
authors.forename: Jorge A
authors.initials: JA
authors.lastname: Guzman
authors.affiliation: Department of Pulmonary Critical Care, Cleveland Clinic, Respiratory Institute, Cleveland, Ohio, USA.
authors.forename: Abhijit
authors.initials: A
authors.lastname: Duggal
keywords: Acute respiratory distress syndrome; influenza A; mechanical ventilation