Nonantibiotic measures in the prevention of ventilator-associated pneumonia

Aspiration of oropharyngeal and/or gastrointestinal (GI) contents is the main cause of ventilator-associated pneumonia. A number of nonantibiotic measures have been proposed to prevent aspiration eg, drainage of subglottic secretions or the semirecumbent position or to prevent gastric microbial overgrowth by stress-ulcer prophylaxis with sucralfate or early enteral feeding. Critical review of the studies shows that subglottic drainage does not prevent colonization or infection of the respiratory tract with intensive care unit-acquired Enterobacteriaceae or Pseudomonas aeruginosa. The effect of subglottic drainage on primary endogenous infections caused by Staphalococcus aureus and Streptococcus spp in patients not receiving antibiotics is only found in a post-hoc subgroup analysis and might reflect differences in carriage of community-acquired potentially pathogenic microorganisms (PPM) caused by previous antibiotic treatment, rather than a true treatment effect. The semirecumbent position may reduce the incidence of aspiration, particularly in patients without a nasogastric tube, but the aspiration rate remains high even in the short observation periods of the studies. There is no evidence that it reduces the ventilator-associated pneumonia rate. Sucralfate may reduce the increased pneumonia rate caused by H2-antagonists and/or antacids, but it remains to be proven whether it is superior to placebo. Sucralfate has no effect on the oropulmonary route of infection and has therefore no effect on early-onset (primary endogenous) pneumonia, which is characteristically caused by PPM carried in the oropharynx. Early enteral feeding is preferable to total parenteral feeding. However, there is limited evidence that it prevents ventilator-associated pneumonia. The studies showing a benefit of early enteral feeding were relatively small studies, partly in nonventilated patients, and used poorly defined criteria for pneumonia. The oropulmonary route is the most important route in the pathogenesis of pneumonia. Preventive strategies (both antibiotic and nonantibiotic strategies) have to block both the oropulmonary route and the gastropulmonary route to be fully effective. Because microaspiration cannot be fully prevented in critically ill patients, preventive strategies should attempt to eliminate PPM from the oropharynx and GI-tract.