Article Abstract

Surveillance of community-acquired pneumonia in critically ill patients

Authors: Kam Wah Lam


Background: In this study, we aimed to investigate the epidemiology, causative agents and outcomes of severe community-acquired pneumonia (CAP) in Hong Kong. Also, the risk factors for mortality would be identified.
Methods: This is a retrospective cohort study of patients with severe CAP admitted to an adult ICU in a tertiary hospital. The study period was from January 2010 to December 2014. The following patient data were extracted from the medical records: (I) demographic data; (II) comorbidities; (III) the APACHE IV scores; (IV) probable causative agents; (V) laboratory results; (VI) use of invasive interventions; (VII) outcomes in term of mortality and length of stay. Multivariate regression analysis was used to assess the impact of independent variables on hospital mortality.
Results: Totally 390 patients were admitted to ICU for severe CAP. We were able to obtain the causative pathogens in about 60% of patients. Bacterial infection was identified in 154 patients and 88 patients suffered from viral infection. Twenty-seven of them suffered from co-infection of bacteria and viruses. Streptococcus pneumoniae was the most commonly isolated organism and accounted for almost 40% of the bacterial pneumonia. Gram-negative organisms constituted about 45% of bacterial chest infection. The common agents included Pseudomonas aeruginosa, Klebsiella pneumoniae and Acinetobacter baumannii. Approximately 70% of viral infection was caused by influenza A infection, followed by influenza B and parainfluenza. Atypical pneumonia only contributed to a minority of CAP, of about 2%. Legionella pneumophila was the most common organism. The overall ICU and hospital mortality rate was 23.1% and 34.6%, respectively, with mean ICU stay of 11.3 days and mean hospital stay of 28.7 days. The hospital survivors had shorter ICU and hospital length of stay. The mortality rates for CAP caused by bacteria, viruses and atypical organisms were 44.3%, 24.4% and 10.0%, respectively (P<0.05). Significant factors identified to be associated with mortality included age, low platelet count, presence of metastatic carcinoma, need of renal replacement therapy and use of nitric oxide therapy.
Conclusions: CAP is an important cause of admission to our ICU with significant mortality. Etiological organisms could be identified in about 60% of CAP. Streptococcus pneumoniae was the most common bacterial agent and most viral infections were caused by influenza A. Atypical bacteria accounted for only a minority of CAP. Pneumococcal and influenza immunization may be effective to reduce the incidence and severity of CAP.