Alameda County Medical Center / Highland General Hospital
The two most
important risk factors for ICU-acquired pneumonia are the duration of
mechanical ventilation and prior administration of broad spectrum
antibiotics. The other risk factors include age, coma, burn, trauma, acute
lung injury (ARDS, pulmonary contusion), and severity of illness. The risk of
ICU-acquired pneumonia peaks around day 5 of mechanical ventilation. After 15
days, the incidence plateaus and then declines, such that pneumonia rates are
quite low in chronically ventilated patients.
The most common
mechanism by which pneumonia occurs is aspiration of organisms from the upper
respiratory or gastrointestinal tract. Less common are direct inhalation and
hematogenous spread. Pneumonia can result when the inoculum is large, the
microbes are virulent, or host defenses are impaired. Organisms that are seen
early (<72 hours) in a patient’s stay in the ICU vary markedly from those seen
later. “Early” organisms are largely S. aureus, S. pneumoniae, other
Streptococci and H. influenzae, while “late” pathogens reflect resistant
nosocomial pathogens, particularly Pseudomonas aeruginosa, MRSA, and
The diagnosis of
ICU-acquired pneumonia can be very difficult to establish. Various
combinations of clinical, radiographic, and laboratory criteria are frequently
used to make the diagnosis. These criteria include fevers, leukocytosis or
leukopenia, purulent secretions, and the presence of a new and persistent
radiographic infiltrate. Quantitative cultures of tracheal aspirate,
bronchoalveolar lavage, and protected specimen brush can aid in the
diagnosis. However, no combination of clinical diagnostic criteria has been
identified to reliably diagnose pneumonia.
ventilated patients should be placed in a semi-recumbent position (head
elevated 30-45º), especially when enterally fed, to decrease the occurrence
of aspiration of gastric contents. At least three prospective studies
and one randomized controlled trial have identified supine positioning to be
associated with pneumonia.
parenteral nutrition as soon as possible. The incidence of ICU-acquired
pneumonia is lower in patients who receive enteral nutrition versus those
receiving parenteral nutrition.
indiscriminate use of stress ulcer prophylaxis. Drugs which raise
gastric pH such as the histamine-2 receptor blockers may encourage bacterial
overgrowth and predispose to pneumonia. The current recommendation is
to limit stress ulcer prophylaxis to high-risk patients (septic,
mechanically ventilated, head injured, burned, history of GI bleeding) since
the benefit of H-2 blockade outweighs the risk of pneumonia in these
patients. Stress ulcer prophylaxis is unnecessary in low risk
indiscriminate use of antibiotics, as these may eradicate susceptible
organisms and encourage the emergence of resistant organisms later.
Use general preventive measures such as strict hand washing and use of
gloves when dealing with specific antibiotic-resistant pathogens.
antibiotics as soon as a threshold for suspicion of pneumonia is exceeded.
Obtain blood and respiratory secretions for culture before starting
antibiotic therapy. The choice of antibiotics depends largely on the local
antibiogram and the patterns of antibiotic resistance and may be tailored to
the result of the culture of respiratory secretions.
The decision to
withdrawn antibiotics should be based both on culture results and patient’s
serial clinical evaluation. In general, patients infected with sensitive
organisms may be treated for 7-10 days. Patients infected with
multi-resistant pathogens may require 14-21 days of treatment.
Hungness ES, Campbell RS, et al. Ventilator-Associated Pneumonia in the
Surgical Intensive Care Unit. JTrauma
Diagnosis and Management of Pneumonia in the Intensive Care Unit.
Chest Surg Clin N Am 2002, 12:379-395.
Chaste J, Fagon
JY. Ventilator-Associated Pneumonia. Am J Respir Crit Care Med
Statement of the 4th International Consensus Conference in
Critical Care on ICU-Acquired Pneumonia – Chicago, Illinois, May 2002.
Intensive Care Med 2002,
- protocols & guidelines
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