Ventilator-associated pneumonia (VAP)

Ventilator-associated pneumonia is the most common hospital-acquired infection among critically ill patients in the intensive care units., with a mortality rate ranging between 20%-60%. Usually occurs within 48-72 hours of the initiation of mechanical ventilation. The main risk factors for developing ventilator-associated pneumonia are: needs of mechanical ventilation, nasogastric intubation, frequent manipulation of ventilators tubing devices, gastrointestinal prophylaxis using H-2 blockers and/or proton-pump inhibitors (PPI's), pre-pyloric enteral feeding, underlying chronic pulmonary diseases, immunosuppressive states, etc. The risk of developing ventilator-associated pneumonia increases with the duration of mechanical ventilation: the risk increased 3% per day for the first 3-5 days of mechanical ventilation, etc.
For practical purposes, it is important to differentiate between early-onset ventilator-associated pneumonia (within the first 5 days of the onset of mechanical ventilation) and late-onset ventilator-associated pneumonia (occurring after 5 days of the initiation of mechanical ventilation), since the causative organisms are different and may help to lead the physicians in establishing an appropriate empiric antimicrobial therapy. In early-onset ventilator-associated pneumonia, the most frequent isolated organisms are gram-positive cocci (Streptococcus spp, methicillin-sensitive Staphylococcus aureus, and sensitive gram-negative bacilli). On the other hand, late-onset ventilator-associated pneumonia is usually caused by resistant gram-positive bacteria (methicillin-resistant Staphylococcus aureus or MRSA) and multidrug-resistant gram-negative bacteria (Pseudomonas aeruginosa, Klebsiella pneumonaiae, Acinetobacter baumannii, Stenotrophomonas malthophillia, Escherichia coli, Enterobacter cloacae, etc). Critical Care Medicine physicians should suspect the diagnosis based on clinical (fevers, leukocytosis, purulent secretions throughout the endotracheal tube, increased FIO2 requirements), radiographic (new pulmonary infiltrates or worsening of pre-existing infiltrates), and microbiologic findings (growth of bacteria in blood and/or respiratory cultures). The gold-standard diagnosis method for the diagnosis of ventilator-associated pneumonia is the bronchoscopy with broncho-alveolar lavage (BAL) with quantitative cultures. In general, the duration of treatment for ventilator-associated pneumonia is 7-10 days, but varies depending on clinical cases.
The most important measures to prevent the development of ventilator-associated pneumonia are: elevated head of bed 45 degrees), avoid nasogastric intubation (also decreased the risk of developing sinusitis), gastrointestinal prophylaxis using sucralfate (controversial), weaning and extubation as soon as possible, post-pyloric enteral feeding, avoid frequent manipulation of ventilator devices (change tubing only when defective), subglotic aspiration of endotracheal tubes, and general universal measures of infection control (hand washing, use of gloves, etc).