Should We Be Using Oral Decontamination with Ventilated Patients?

Abstract & Commentary

By Andrew M. Luks, MD

Synopsis: This systematic review and meta-analysis demonstrates that oral decontamination with antiseptic preparations decreases the risk of ventilator-associated pneumonia but has no effect on mortality, duration of mechanical ventilation or length of stay in the ICU.

Source: Chan EY, et al. Oral decontamination for prevention of pneumonia in mechanically ventilated adults: Systematic review and meta-analysis. BMJ. 2007;334:889.

Previous work demonstrates that selective gut decontamination decreases the risk of ventilator-associated pneumonia (VAP), but the practice has been limited by concerns about promoting antibiotic resistance. Oral decontamination alone has been proposed as an alternative, but the data on its efficacy have been mixed. Chan and colleagues conducted a meta-analysis to further investigate this issue and to determine whether oral decontamination with antibiotic or antiseptic preparations decreases the risk of VAP.

Two reviewers searched the literature for published and unpublished randomized trials testing the effects of oral decontamination on the incidence of pneumonia and evaluated the quality of these trials. Studies were grouped into two broad categories including those that tested oral antibiotics vs placebo and those that tested oral antiseptics against placebo. No trials compared oral antibiotics with oral antiseptics or selective gut decontamination. The primary outcome measures in their meta-analysis were the incidence of VAP and mortality. They used each included study's definition of pneumonia rather than applying their own standard definition across the included studies. Secondary outcomes included the duration of mechanical ventilation and duration of stay in the intensive care unit.

Eleven trials including a total of 3242 patients were included in the meta-analysis. Four trials (1098 patients) examined oral antibiotics while the remaining seven trials (2144 patients) looked at oral antiseptic solutions. While the oral antibiotic solutions had no effect on the risk of VAP, oral antiseptic solution was, in fact, associated with decreased risk (RR = 0.56, 95% confidence interval 0.39-0.81). When the 11 trials were combined in a single analysis, the relative risk of pneumonia with oral decontamination was 0.61 (95% confidence interval 0.45-0.82) and the number needed to treat to prevent one case of pneumonia was 14 (95% confidence interval 10-31). Oral decontamination with either antibiotics or antiseptics had no effect on mortality, duration of mechanical ventilation or duration of stay in the intensive care unit.

Commentary

Given the high morbidity and mortality associated with VAP, identifying effective strategies for preventing this complication should be a high priority. The study by Chan and colleagues suggests that oral decontamination with antiseptic solution may be effective for this purpose but does not provide strong enough evidence of benefit or low risk to justify widespread adoption of the practice.

There are several issues that prevent broad application of these results. First, there were important methodological differences between the trials included in the meta-analysis, such as the manner in which they defined VAP and the manner in which they did or did not control for important variables, which may make comparison between the included studies difficult. Second, although the meta-analysis examines a large number of patients and points to a benefit for oral antiseptic solutions, important clinical questions remain unanswered. For example, with the exception of one trial that examined the use of povidone iodine, the remaining trials used chlorhexidine, but in varying concentrations. As a result, we have no idea which is the best antiseptic preparation or its optimum concentration for use in decontamination.

More importantly, we still lack information about perhaps the most important question of all regarding this practice: what role, if any, will it have on rates of antibiotic resistance in the ICU? We may prevent VAP, but if we end up concurrently creating resistant bacteria that will make ICU care more problematic in the future, have we really done ourselves or our patients any favors? Until this issue is resolved, we should focus on other proven techniques for preventing VAP, such as elevating the head of the bed, that do not pose this risk.