Control of Bacterial Pneumonia during Mechanical Ventilation Juranko Kolak , Hendrick K.F. van Saene 1 , Miguel A. de la Cal 2 , Luciano Silvestre 3 , Mladen Periæ Department of Anesthesiology and Intensive Care, Sisters of Mercy University Hospital, Zagreb, Croatia; 1 Department of Medical Microbiology, University of Liverpool and Royal Liverpool Children’s NHS Trust, Liverpool, UK; 2 Department of Critical Care Medicine, Hospital Universario de Getafe, Madrid, Spain; and 3 Emergency Department, Unit of Anesthesia and Intensive Care, Presidio Ospedaliero di Gorizia, Gorizia, Italy Abstract Pneumonia complicates the course of 50% of patients on mechanical ventilation, requiring three or more days of mechanical ventilation and potentially increasing the relative risk of mortality by 20-40%. The predominant potentially pathogenic micro-organisms are Streptococcus pneumoniae, Staphylo- coccus aureus (sensitive to methicillin in the previously healthy host), Pseudomonas aeruginosa (aero- bic gram-negative bacilli), and methicillin-resistant Staphylococcus aureus in the host with underlying disease. Approximately 85% of pneumonias are endogenous, caused by bacteria present in the pa- tient’s oropharyngeal flora. Bacteria present on admission cause primary endogenous pneumonia (55%), whereas bacteria acquired in the unit lead to supercarriage or secondary carriage and subse- quently secondary endogenous pneumonia (30%). The remaining 15% are exogenous, ie the bacteria causing pneumonia are not carried by the patient. The diagnosis is usually based on clinical, radiologi- cal, and microbiological criteria, using the non-invasive method of tracheal aspirate, which yields ³10 5 micro-organisms. Seven randomized trials have evaluated three non-antibiotic prophylactic maneu- vers: hygiene (1 trial), subglottic drainage (4 trials), and semirecumbent position (2 trials). The impact on pneumonia was mixed, whereas mortality was unchanged. Selective digestive decontamination, using parenteral and enteral antimicrobials to control the three types of pneumonia, has been evaluated in 54 trials and showed an absolute mortality reduction of 8%. The therapy of pneumonia relies on six basic principles: (a) surveillance and diagnostic cultures to identify micro-organisms; (b) immediate and ade- quate antibiotic treatment to sterilize the lower airways, (c) the source of potential pathogens requires elimination for recovery of the original infection and prevention of relapses and/or superinfections; (d) aerosolized antimicrobials; (e) removal or replacement of the endotracheal tube; and (f) surveillance samples are indispensable to monitor efficacy of treatment. The aim of our review was to evaluate up to date facts regarding control of bacterial pneumonias during mechanical ventilation in intensive care unit settings. This review aims to summarize the present knowledge of pneumonia in patients re- quiring mechanical ventilation, using evidence from randomized controlled trials (RCT) where possible. The scope of the article includes inci- dence, causative micro-organisms, pathogenesis, diagnosis, prevention, and treatment. We include pneumonias presenting as the prime indication for ventilation and those developing during treat- ment in the intensive care unit (ICU). Terminol- ogy such as “ventilator associated” or “nosoco- mial” pneumonia can cause confusion. We pro- pose definitions of pneumonia, presenting in the ICU based on the origin of causative micro-organ- isms, using surveillance cultures to detect micro- bial carrier states. 183 www.cmj.hr REVIEW Croat Med J 2005;46(1):183-196