Influenza A (pH1N1) infection in children admitted to a pediatric intensive care unit: differences with other respiratory viruses.

OBJECTIVES: To describe the clinical features of patients admitted to the pediatric intensive care unit (PICU) with acute lower respiratory tract infection (LRTI) attributable to influenza A pH1N1 virus and compare them with those admitted with LRTI due to other viral pathogens.

DESIGN: Retrospective, observational, comparative study.

SETTING: PICU in a university-affiliated, tertiary-care, pediatric hospital.

PATIENTS: Patients aged >1 month with acute viral LRTI admitted to the PICU who met the following criteria: 1) influenza A pH1N1 virus infection detected between June 1, 2009 and July 16, 2009; and 2) patients with LRTI due to other viral pathogens infection detected in the same period of the year 2008 plus patients with 2009 influenza A non-pH1N1 infection.

INTERVENTIONS: None.

MEASUREMENTS AND MAIN RESULTS: We evaluated age, weight, gender, length of hospital stay before PICU admission, length of PICU stay, underlying disease, clinical diagnosis, severity, complications, treatment, risk of death, mortality, and cause of death. We identified 30 patients with acute LRTI due to influenza A pH1N1 virus (group 1) and 62 patients with LRTI due to other viral pathogens (group 2). Relevant characteristics in group 1: 59% of patients were aged >2 yrs. Median length of PICU stay was 15 days. An underlying condition was present in 83% of the patients. None of them had bronchiolitis on PICU admission; 12 (40%) had bilateral pneumonia; 15 (50%) had acute respiratory distress syndrome; and nine (30%) had shock. Twenty-nine patients required mechanical ventilation (96.6%); only one required extracorporeal membrane oxygenation; and 19 (63%) had respiratory complications. Six (20%) children died. When both groups were compared, patients with influenza A pH1N1 infection were older; pneumonia, acute respiratory distress syndrome, and shock were more frequently seen at the time of PICU admission, although length of stay and mortality were similar.

CONCLUSIONS: Patients with influenza A pH1N1 respiratory virus infection presented with more severe illness. Outcomes were similar in both groups.