摘要IntroductionCommunity-acquired pneumonia (CAP) is a common respiratory disease and is considered to be the leading cause of mortality among various infectious diseases.[1,2] A large population-based study showed that among hospitalized patients diagnosed with pneumonia,21％ of them required the intensive care unit (ICU) admission,6％ required invasive mechanical ventilation,and 2％ died.[3] Although therapeutic strategies have been significantly improved over recent years,the morbidity and mortality of CAP,especially severe CAP (SCAP),remain high.Mortality of SCAP has been reported to range from 17％ to 49％ by different multi-center cohort studies.[4] The Infectious Diseases Society of America (IDSA),American Thoracic Society (ATS) and the Infectious Disease Assembly,Chinese Thoracic Society,have published consensus guidelines for CAP (IDSMATS 2007,CTS 2016),which clearly defined SCAP criteria.[5] According to IDSA/ATS SCAP criteria,patients with SCAP requiring ICU admission should have at least one major criteria (invasive mechanical ventilation or septic shock with the need for vasopressors) or at least three minor criteria (respiratory rate ≥30 breaths/min,oxygenation index (PaO2/FiO2) ratio ≤250,multi-lobe infiltrates,hypothermia (core temperature ＜36℃),leukopenia (white blood cell count ＜4000 cells/mm3),thrombocytopenia (platelet count ＜100,000 cells/mm3),hypotension requiring aggressive fluid resuscitation,confusion/disorientation,and uremia (blood urea nitrogen (BUN) ≥20 mg/dL).