Risk Factors and Common Preventive Measures for Ventilator Associated Pneumonia in Patients With Severe Traumatic Brain Injury

Ventilator-associated pneumonia (VAP) is a type of nosocomial pneumonia that occurs in patients who receive >48 h of mechanical ventilation (MV). Early onset VAP occurs during the first 4 days of MV and is usually caused by antibiotic-sensitive bacteria. The increased systemic inflammatory response in patients with a head trauma may predispose them to develop early-onset VAP1,2. Late-onset VAP develops 5 days after initiating MV and is caused by multidrug resistant (MDR) pathogens3,4.

Patients with traumatic brain injury (TBI) are at high risk of infection, particularly nosocomial infections, during treatment in the intensive care unit (ICU) 5-7, where the incidence of VAP can be as high as 50%. The duration of MV usually influences the type of organism that causes VAP8. Early-onset VAP is caused by antibiotic-sensitive pathogens, whereas late-onset VAP is caused by MDR bacteria, which are more difficult to treat. The microbiological environment can have a marked influence on VAP isolates, particularly during late-onset VAP, but it also influences early-onset VAP9. Patients who acquire VAP have longer ICU stays, higher morbidity and mortality, and a greater number of infectious agents10,11. The risk factors for developing VAP are diverse, and the pathogenesis of intra-hospital infections is complex. Common VAP preventive measures such as early mobility, the daily interruption of sedation, and a readiness-to-extubate assessment may not be applicable because of associated injuries such as severe chest trauma, intra-abdominal bleeding, and other organ damage. Hence, VAP diagnosis can be difficult in a setting of multiple trauma, and significant variations in the diagnosis and management of VAP remain8.

The upper respiratory tract of the majority of mechanically-ventilated patient is colonized with potentially pathogenic microorganisms. This was first established in a study in 1969 that reported the presence of enteric gram-negative bacteria in the oropharynx of 75 percent of critically ill patients8. A proposed explanation is bacterial overgrowth of the upper gastrointestinal tract and retrograde movement. Aspiration of secretions containing these pathogens provides a means for infection of the sterile bronchial tree. Another study published in 2007 confirmed the presence of similar pathogenic microorganisms in the lower respiratory tract of intubated patients by comparing DNA samples from bacteria on the tongue and obtained from bronchoalveolar lavage (BAL)12.

Prevention of VAP:

The use of Non-invasive positive pressure ventilation NPPV has been shown to significantly lower the risk of VAP and has also demonstrated a mortality benefit in randomized studies conducted using patients with a variety of illnesses10, daily weaning trials and sedation holidays have been repeatedly described and validated as strategies that limit the time of mechanical ventilation13,14.