Severe virus influenza A H1N1 related pneumonia and community-acquired pneumonia: differences in the evolution

To analyze the clinical, laboratory and evolution data of patients with severe influenza A H1N1 pneumonia and compare the data with that of patients with severe community-acquired bacterial pneumonia.

Cohort and retrospective study. All patients admitted to the intensive care unit between May 2009 and December 2010 with a diagnosis of severe pneumonia caused by the influenza A H1N1 virus were included in the study. Thirty patients with severe community-acquired pneumonia admitted within the same period were used as a control group. Severe community-acquired pneumonia was defined as the presence of at least one major severity criteria (ventilator or vasopressor use) or two minor criteria.

The data of 45 patients were evaluated. Of these patients, 15 were infected with H1N1. When compared to the group with community-acquired pneumonia, patients from the H1N1 group had significantly lower leukocyte counts on admission (6,728±4,070 versus 16,038±7,863; p<0.05) and lower C-reactive protein levels (Day 2: 15.1±8.1 versus 22.1±10.9 mg/dL; p<0.05). The PaO2/FiO2 ratio values were lower in the first week in patients with H1N1. Patients who did not survive the H1N1 severe pneumonia had significantly higher levels of C-reactive protein and higher serum creatinine levels compared with patients who survived. The mortality rate was significantly higher in the H1N1 group than in the control group (53% versus 20%; p=0.056, respectivelly).

Differences in the leukocyte count, C-reactive protein concentrations and oxygenation profiles may contribute to the diagnosis and prognosis of patients with severe influenza A H1N1 virus-related pneumonia and community-acquired pneumonia.