[Analysis of inpatients with pneumonia due to influenza (H1N1) 2009--clinical aspects based on the presence or absence of respiratory complications].

We retrospectively analyzed the clinical aspects of inpatients with pneumonia caused by influenza (H1N1) 2009 after classifying them into two groups based on the presence or absence of respiratory complications. The study population--121 (5.6%) of 1,777 subjects diagnosed with influenza (H1N1) 2009 using a rapid influenza diagnostic kit or real-time reverse-transcription PCR-were hospitalized from August 2009 to May 2010 as detailed from admission to discharge in hospital medical charts. Of these, 72 had respiratory symptoms and most -56, or 3.2%, of the total-were diagnosed with pneumonia in chest radiography. The mean age of those with pneumonia was 6.9 years, 35.7% had a history of bronchial asthma and 80.4% were admitted within three days of onset. Some 75% of those with pneumonia, or 42, had respiratory distress (SpO2 < or = 93%) requiring supplementary oxygen. Significant lymphopenia and neutrophil increase were observed in blood tests of those admitted within three days of onset. Almost all were given an antiviral agent for 5 days. Among pneumonia cases, 14 (25%) also had severe respiratory complications such as pneumomediastinum and atelectasis, designated the complications group. They also had significantly lower oxygen saturation and significantly more elevated non-specific IgE on admission than those in the non-complications group (n = 42). Those with complications were hospitalized for significantly longer, and were administered isopretenol. All inpatients with influenza (H1N1) 2009 were discharged as healthy. Based on our retrospectively analyzed results in those with influenza (H1N1) 2009 pneumonia, we concluded that the following medical circumstances covered by the Japanese insurance system help lead to good outcomes: i) visiting the hospital soon after onset, ii) being diagnosed early using a rapid identification kit, iii) under-going systemic whole-body management, and iv) being administered antiviral and antibacterial agents.