Critical illness associated with 2013-2014 influenza A (H1N1): Postpandemic characteristics, presentation and outcomes

Abstract

Introduction: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.

Epidemiology and Outcomes of HIN1 Pneumonia in ICU

“…The differences could possibly be due to the exclusion of the pediatric age group in our study. 8 , 9 Linderman et al found that the H1N1 virus mutated in later years which might explain the high susceptibility seen in middle-aged adults during 2013–2014. 10 In the post-pandemic years, the afflicted patients were noted to be older with a higher prevalence of pulmonary and cardiac disease.…”