2009 pandemic influenza A (H1N1) in critically ill children in Cincinnati, Ohio.

Objective: To compare the clinical features, management, and outcome of critically ill children with H1N1 to children with seasonal influenza from the previous three influenza seasons.

Design: The overall number of hospitalizations and the proportion cared for in the pediatric intensive care unit during the H1N1 epidemic period and the three previous influenza seasons (2007-2009) were determined. Medical records of patients admitted to the pediatric intensive care unit with H1N1 and seasonal influenza infection were reviewed.

Setting: Cincinnati Children's Hospital Medical Center, a large, 523-bed hospital located in Cincinnati.

Patients: Hospitalized children with laboratory-confirmed seasonal or H1N1 infection.

Measurements: Study variables included demographic data (age, gender), clinical factors (weight, Pediatric Risk of Mortality III scores, presenting signs and symptoms, comorbid conditions), management (length of mechanical ventilation, other treatments, including high-frequency oscillatory ventilatory support, inhaled nitric oxide, or extracorporeal membrane oxygenation), and outcome (overall and pediatric intensive care unit length of stay and mortality).

Main Results: Overall, 312 children were hospitalized with H1N1 and 222 with seasonal influenza from the three previous seasons. Children with H1N1 infection were significantly less likely to require pediatric intensive care unit care compared to children with seasonal influenza infection (14% vs. 24%, p = .02). Compared to children with seasonal influenza, children in the pediatric intensive care unit with H1N1 were older (median age in months 107 vs. 68, p = .05) and significantly more likely to have comorbid conditions (64% vs. 40%, p = .03), especially respiratory conditions. While there were no significant differences in severity of illness by Pediatric Risk of Mortality III scores or pediatric intensive care unit length of stay, children with H1N1 were significantly less likely to have acute respiratory failure (p = .04) or die compared to children with seasonal influenza infection (p = .03).

Conclusions: In contrast to other studies, we found that critically ill children with H1N1 had a significantly lower morbidity and mortality compared to children with seasonal influenza.