Outcomes of severe H1N1 pneumoniae: A retrospective study at intensive care units

The incidence of acute respiratory distress syndrome (ARDS) and the mortality rate of H1N1 influenza pneumonia are unclear. The aim of this study is to investigate the clinical features and outcomes of adult patients admitted to intensive care units (ICUs) with H1N1 pneumonia related ARDS.

This retrospective study included patients with confirmed H1N1 influenza pneumonia admitted to the ICUs of a medical center between July 2009 and May 2014. We investigated the patients' characteristics, clinical presentations, illness severities, and outcomes.

Sixty-six patients were confirmed to have H1N1 influenza pneumonia requiring mechanical ventilation. Fifty-four of those patients (82%) developed ARDS, while their hospital mortality rate was 33% (22/66). There were no significant differences in the ICU and hospital mortality rates of the ARDS and non-ARDS patients. Among the ARDS patients, there were higher rates of solid malignant disease (22.8% vs. 2.8%, p = 0.038) and sepsis (66.7% vs. 33.3%, p = 0.020) and a higher mean tidal volume (8.9 ± 1.8 vs. 7.8 ± 1.9 ml/kg, p = 0.032) in the non-survivors than the survivors. Logistic regression analysis revealed that a high tidal volume (odds ratio = 1.448, 95 % CI = 1.033-2.030; p = 0.032) and sequential organ failure assessment (SOFA) score (odds ratio = 1.233, 95% CI = 1.029-1.478; p = 0.023) were the risk factors of hospital mortality.

For H1N1 influenza pneumonia patients admitted to ICUs with mechanical ventilation, there is a high probability of developing ARDS with a modest mortality rate. For patients with ARDS due to H1N1 influenza pneumonia, the tidal volume and SOFA score are the predictors of hospital mortality.