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.