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CHAPTER 59: Ventilator-Associated Pneumonia 533

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maintain a database that describes endemic rates of nosocomial infection. OSCILLATING AND ROTATING BED
Awareness of the endemic rates enables the recognition of the onset of an Immobility in critically ill patients treated with mechanical ventilation
epidemic when infection rates rise above a calculated threshold. results in atelectasis, impaired secretions drainage, and potentially pre-
Adoption of an antibiotic policy restricting the prescription
of broad-spectrum agents and useless antibiotics is of major impor- disposes to pulmonary complications including VAP. Oscillating and
rotating beds may help in preventing pneumonia. Six randomized trials,
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tance. 36,173,243,248,249,340 Better use of antibiotics in the ICU can be achieved by which included mostly surgical and trauma patients, ventilated or not,
implementing strict guidelines, avoiding the treatment of patients who do and summarized in a meta-analysis by Choi and Nelson have compared
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not have bacterial infections, using narrow-spectrum antibiotics whenever continuous lateral rotational therapy with standard beds. The meta-
possible, and reducing the duration of treatment. Similarly, transfusion of analysis found a significant reduction in the risk for pneumonia, principally
red blood cells and other allogenic blood products should follow a strict concerning early-onset (<5 days) pneumonia and a decreased duration of
policy, because several studies have identified exposure to allogenic blood ICU stay. Notably, the only randomized, controlled trial—not included in
products as a risk factor for postoperative infection and pneumonia. 341-346 the meta-analysis—conducted on a general ICU population did not show
Some very simple, safe, inexpensive, and logical measures may have major any differences in pneumonia rates but showed a significantly shorter
effects on the frequency of VAP in ventilated patients. These include length of ICU stay. Some adverse events have been described with these
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avoiding nasal insertion of endotracheal and gastric tubes, maintaining the beds including disconnection of catheters or pressure ulceration; in addi-
endotracheal tube cuff pressure above 20 cm H O to prevent leakage of bac- tion, nursing care is potentially complicated with oscillating beds. Finally,
2
teria around the cuff into the lower respiratory tract, prompt reintubation despite the cost of such beds, cost-benefit analyses suggested favorable
of patients who are likely to fail extubation, removing tubing condensate, results, mainly caused by the reduction of ICU length of stay.
and providing adequate oral hygiene with tooth brushing. 109,128,145,347,348
■ SPECIFIC PROPHYLAXIS AGAINST VAP ■ ORAL DECONTAMINATION WITH ANTISEPTICS

Specific strategies aimed at reducing the duration of mechanical ventilation Topical application of chlorhexidine or other antiseptics to the oral
(a major risk factor for VAP), such as improved methods of sedation, use mucosa may decrease respiratory pathogen colonization and secondary
of protocols to facilitate and accelerate weaning, using low tidal volume and lung infection in ventilated patients. Randomized, controlled trials, how-
adequate levels of PEEP, and use of intensive insulin therapy to control blood ever, have reported mixed results: some showed little effect whereas others
glucose should be considered as integral parts of any infection-control pro- found a reduction in the incidence of VAP. 375-387 Combining the results of
gram. 349-354 All are based on the application of strict protocols. Noninvasive the seven randomized controlled trials that evaluated the potential efficacy
ventilation is an alternative approach to the use of artificial airways to avoid of chlorhexidine, a 30% relative reduction in the risk of VAP was observed,
infectious complications and injury of the trachea in patients with acute but no effect of chlorhexidine on reduction of mortality or duration of
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respiratory failure. Many observational studies and seven randomized tri- mechanical ventilation could be demonstated. The varying concentra-
als suggest that patients who tolerate noninvasive ventilation have a lower tion of the chlorhexidine solutions used in these studies may have affected
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incidence of pneumonia than those tracheally intubated. 349,355-363 the results. In the study by Koeman et al, a 2% solution of chlorhexidine
Apart from protocols aimed at reducing the duration of mechanical was used, a much higher concentration than in the other published stud-
ventilation, eight prophylactic approaches have been studied: semirecum- ies, most of which used a 0.12% or 0.2% solution; this may partially explain
bent positioning, oscillating and rotating beds, continuous or intermit- the benefit of chlorhexidine for reducing VAP in this study. Reported
tent aspiration of subglottic secretions, ventilator circuits management, adverse effects of oral use of chlorhexidine include staining of the teeth,
methods of enteral feeding, stress ulcer prophylaxis, oral decontamina- which is reversible with professional cleaning, and a transient abnormality
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tion with antiseptics, and selective digestive decontamination. of taste. The optimal concentration, frequency of application, effect on
■ SEMIRECUMBENT POSITIONING chlorhexidine should be addressed in future studies.
promoting resistance among oropharyngeal flora, and cost-effectiveness of
VAP. Placing ventilated patients in a semirecumbent position to mini- ■ ASPIRATION OF SUBGLOTTIC SECRETIONS AND USE
Supine positioning is independently associated with the development of
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mize reflux and aspiration of gastric contents is a simple measure, although OF SPECIALIZED ENDOTRACHEAL TUBES
some practical problems can occur in unstable patients. Only a few trials Repeated micro-inhalations of colonized oro-pharyngeal (subglottic) secre-
have evaluated the efficacy of semirecumbent positioning. 120-122,125,364-366 tions are the major mechanism of VAP. Continuous or intermittent suction-
In a randomized trial based on a small number of patients, Drakulovic et ing of oropharyngeal secretions has been proposed as a means to avoid
al observed lower rates of both clinically suspected and bacteriologically chronic aspiration of secretions through the tracheal cuff of intubated
confirmed VAP, and identified supine positioning as an independent patients. Aspiration of subglottic secretions requires the use of specially
risk factor for VAP with enteral nutrition, ventilation for >7 days and designed endotracheal tube with a separate lumen that opens into the
a Glasgow Coma Score of <9 points. The feasibility and efficacy of this subglottic region. Thirteen randomized controlled trials have studied aspi-
intervention in a larger patient population, however, remain unknown, ration of subglottic secretions for the prevention of VAP for a total of 2442
all the more since its efficacy was not confirmed in a subsequent trial that randomized patients. 389-397 Of the 13 studies, 12 reported a reduction in VAP
included 221 ventilated patients or in two recent meta-analyses. 125,126,364 rates in the subglottic secretion drainage arm. When the results were com-
Raising the head of bed to 30° or higher may also have some detrimental bined in a meta analysis, the overall risk ratio for VAP was 0.55 (95% CI,
skin effects and may increase the incidence of pressure ulcer forma- 0.46-0.66; p <.00001) with no heterogeneity, and the use of subglottic secre-
tion. Pending additional studies, most experts currently recommend tion drainage was associated with reduced ICU length of stay, decreased
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maintaining the head of the bed elevated to at least 20° to 30° in all ven- duration of mechanical ventilation, and increased time to first episode of
tilated patients who are hemodynamically stable, particularly when they VAP. No effect, however, on hospital or ICU mortality could be demon-
397
are receiving enteral nutrition. 143,328,367-372 strated. Some experimental data in sheep and ICU patients suggest the
397
New insights from laboratory experimentation suggest that the possibility of tracheal damage with the use of this type of tube. 393,398,399
lateral-Trendelenburg position in patients requiring mechanical ventila- Bacterial aggregates in biofilm dislodged during suctioning might
tion could fully prevent gravity-driven translocation of pathogens from not be eradicated by antibiotics or effectively cleared by host immune
the oropharynx into the lung. Nevertheless, clinical application of these defenses, thereby constituting dangerous inoculums for the lung.
new concepts could be challenging and the efficacy and safety of the Preliminary data obtained in animal models and from small randomized
lateral-Trendelenburg position need to be thoroughly assessed in large human studies support the hypothesis that an endotracheal tube coated
clinical trials before being used on a day-to-day practice. externally and internally with a potent antiseptic product such as silver

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