Severe cases of pandemic H1N1 pneumonia and respiratory failure requiring intensive care.

Background: The objective of our study is to analyze the clinical data of patients with pandemic H1N1 2009 infection admitted to the intensive care unit (ICU) and to report key features observed among these patients.

Methods: A total of 18 patients were admitted to our ICU between July and November 2009, with a primary diagnosis of influenza. Clinical data were analyzed to identify potential risk factors and characteristics thought to affect outcomes.

Results: Our patients were between ages 23 and 62 (mean 41). In all, 10 were obese. Two had no other comorbid conditions and 6 had obesity as their only comorbid condition. The most common symptoms were fever, shortness of breath, and cough. Laboratory data were notable for elevated creatine kinase levels, transaminitis, and lack of leukocytosis. The rapid influenza detection test (RIDT) had a 76% false negative result. Patients with a negative RIDT had their infection confirmed with real-time reverse transcriptase polymerase chain reaction (rRT-PCR). A total of 12 patients required invasive mechanical ventilation, with over half of whom responded only to nonconventional modes of ventilation. Most patients received high-dose (150 mg twice daily) oseltamivir. In all, 3 patients died and 11 were discharged without any long-term sequalae.

Conclusions: Unlike seasonal influenza, our patients were not in the extremes of age. Most were obese and presented with severe respiratory distress and hypoxia in the summer months. A negative RIDT did not exclude pandemic H1N1 2009. Using a higher dose of oseltamivir and nonconventional modes of ventilation may have improved the outcome in our subset of patients. Hence, patients with a high clinical suspicion of severe influenza infection should be treated early and aggressively, even before confirmatory results are available.