Supine positioning may contribute to the development of NP, likely due to an increased risk of gastric reflux and subsequent aspiration. Studies of semi-recumbent positioning (elevation of the head of the bed >45 degrees) have shown less reflux, less aspiration, and in one recent randomized control trial, a significant reduction in the rate of VAP (12). Elevation of the head of the bed is clearly indicated in mechanically ventilated patients and is also likely to benefit all patients at risk for aspiration and subsequent NP, although this technique has not been well studied in non-ventilated patients.
Subglottic secretion drainage (SSD) involves the removal of pooled secretions above the cuff of a specialized endotracheal tube that might otherwise leak into the lung. A meta-analysis of five studies evaluating this new technology showed significant reductions in the incidence of VAP. The use of SSD should be considered for use in patients requiring more than 3 days of mechanical ventilation (13).
Medications used for stress ulcer prophylaxis that increase gastric pH-such as H2 antagonists and antacids-allow for colonization of the upper gastrointestinal tract by potentially pathogenic organisms and therefore increase the risk for NP. The use of sucralfate instead of H2 antagonists is felt to lead to less alkalinization of the stomach and less bacterial overgrowth. The ability of sucralfate to prevent nosocomial pneumonia, however, has not been well demonstrated and its routine use is not recommended (14). Instead, efforts should be targeted at limiting use of stress ulcer prophylaxis to populations at high risk for clinically significant bleeding, namely patients with coagulopathy and prolonged ventilatory failure. Most patients who are not in the ICU should not receive stress ulcer prophylaxis. The risk of NP related to use of proton pump inhibitors has not been well studied.
Selective digestive decontamination (SDD) involves sterilization of the oropharynx and gastrointestinal tract in mechanically ventilated patients in order to prevent aspiration of large numbers of potentially pathogenic organisms and subsequent VAP. Most evaluations of SDD have involved oral (and sometimes gastric) application of topical polymixin, aminoglycoside, and amphotericin. In many cases, short courses of IV antibiotics have been added. At least 10 meta-analyses have shown a reduction in the risk of VAP with the use of SDD. The addition of IV antibiotics may also provide a mortality benefit. However, the long-term risk for emergence of resistant organisms, and insufficient data on the cost-effectiveness of SDD prevent its recommendation for routine use (14).
There are several preventive strategies targeted at reducing aspiration of contaminants in ventilator circuits, filters, and tubing. Recommended strategies, listed in Table III, page 16, include avoidance of routine ventilator circuit changes (change the tubing only when visibly contaminated or for a new patient), use of heat and moisture exchangers rather than heated humidifiers, and reduction in the frequency of changes of the heat and moisture exchangers (1,11,14).
Discharge/Follow-up Plans
Patients should be followed in the hospital until it is clear they are responding to therapy and clinically improving. There has been limited evaluation of strategies to rapidly transition patients to oral therapy. However, if patients are improving, are tolerating oral therapy, have a functional GI tract, and have an organism isolated that is sensitive to available oral antibiotics, the switch to oral therapy can be made. If no organism is isolated, but a patient definitely was felt to have NP, the oral antibiotics selected should have the same spectrum of activity as the previously administered IV antibiotics. In many cases, patients will have an infection with an organism that is only susceptible to IV antibiotics. These patients are likely to be ill enough to complete a full one week IV course in the hospital, but if they have no active co-morbid illness and have improved, they can have a PICC line placed (or other long-term IV access) and receive the remainder of their therapy at home or in another lower acuity setting.