2009 H1N1 Influenza and Experience in Three Critical Care Units

Teke, Turgut; Coskun, Ramazan; Sungur, Murat; Guven, Muhammed; Bekci, Taha T; Maden, Emin; Alp, Emine; Doganay, Mehmet; Erayman, Ibrahim; Uzun, Kursat

Our data of critically ill patients with Influenza A 2009 (H1N1) reveals that relatively younger patients are affected by the disease. Fever and respiratory symptoms were cardinal symptoms of disease in all patients. There was a relatively long period of illness prior to presentation to the hospital, followed by a short period of acute and severe respiratory deterioration. These patients had severe hypoxia requiring high FiO2, PEEP, and ventilator pressures. Within 30 days, 51% of critically ill patients had died. Previously published reports have highlighted cases of severe viral pneumonia affecting patients younger than the expected age of patients affected during a normal influenza season (11) . The low mean age is different from seasonal influenza, in which older patients appear more susceptible to severe diseases (12) . Our findings are consistent with these reports. In our data and in other studies, death was occurred mostly young critically ill patients (1, 13, 14) . But, the risk of death increased with increasing age. Importantly, severity of illness and mortality in our cohort are similar to that demonstrated previously with novel H1N1. The first data from Mexico showed that most of the patients were previously healthy (1). In our study, the most of critically ill patients had comorbidities and there was no difference according to comorbidities between survived and died patients. A history of lung diseases, obesity, diabetes, hypertension, neurological diseases, malignancy, and heart diseases were the most common comorbidities in our study (83.6%). Among critically ill patients, obesity has been shown to be a risk factor for increased morbidity, but not consistently with mortality (15) . In our study, there was no statistically significant difference due to obesity between survivors and nonsurvivors. We did not find a significant difference in BMI between survivors and nonsurvivors. An early 2009 meta-analysis indicated that obesity was not associated with increased ICU mortality (16) . A recent, large cohort study by Gong et al. (17) prior to 2009 novel H1N1 infection, noted an association of obesity with ARDS but not with mortality. The Canadian novel H1N1 experience likewise suggests that BMI did not differ between survivors and non-survivors (18) . Patients with H1N1 infection-related critical illness experienced symptoms for an average of 6 days prior to hospital presentation, but rapidly worsened and required care in the ICU within 1 to 2 days (1). In our study, this duration was higher than other studies (1, 18, 19) . The tendency of females to develop severe 2009 influenza A (H1N1) infection in this series is striking. A general female susceptibility has been observed in other influenza case series of variable severity including reports of H1N1 infections (18, 19) . In this report, death was higher in males than females. The explanation for increased risk of death among males in this report may be due to existence of more frequent comorbidities in man. In most of infectious diseases and related conditions such as sepsis and septic shock, males represent a larger proportion of cases and have a higher mortality (20, 21) . Importantly, we found in this cohort that APACHE II score may help to identify patients at high risk of death.