Prevention of ventilator-associated pneumonia by use of oral chlorhexidine.

To the Editor—We read with interest the article by Tantipong et al. on the use of oral decontamination with 2% chlorhexidine solution for the prevention of ventilator-associated pneumonia (VAP). We believe that their study has some important limitations and that the authors' conclusion that oral chlorhexidine is an effective and safe method for VAP prevention is not supported by the results. In their study, some patients received ventilation for less than 48 hours, the population was not homogeneous, and the randomization procedure was not adequate. The mean duration of mechanical ventilation was approximately 5 days, but only 43% of patients in the test group and 50% of patients in the control group received ventilation for more than 48 hours, a period that, if not completed, is usually considered an exclusion criterion in the majority of trials on VAP prevention. Approximately 60% of patients admitted to their study were adults who received ventilation in intensive care units (ICUs) (mainly surgical ICUs), whereas 40% received ventilation in general medical wards. Although the mean Acute Physiology and Chronic Health Evaluation II score was not significantly different among the 2 arms, it is highly likely that patients who received ventilation in general medical wards were in less "critical" condition than those treated in ICUs. Moreover, the care of a patient who receives ventilation may be different in the general ward than in the ICU, all wards did not change their regular protocols, parenteral antibiotic policy was not reported, semirecumbency was maintained only "if possible," and the degree of semirecumbency was not assessed. Therefore, the study results seem to not be generalizable to the high-risk ICU population. Finally, randomization according to patient sex is not an adequate method of randomization, the study was not blinded, and it is not clear whether consecutive patients were enrolled. All these issues may have influenced the results and should be acknowledged by the authors. The authors' claim that oral decontamination with 2% chlorhexidine solution is an effective method for reducing VAP is not supported by the results and may be misleading for the reader. Although use of chlorhexidine reduced the risk of VAP by approximately 55% in the overall population and among patients who received mechanical ventilation for more than 2 days, this reduction was not statistically significant, because both relative-risk (RR) calculations had large 95% confidence intervals (CIs) (RR, 0.43 [95% CI, 0.16-1.17] for study patients who received mechanical ventilation and oral decontamination and RR, 0.45 [95% CI, 0.16-1.23] for patients who received mechanical ventilation for more than 2 days). The study showed a significant, albeit borderline (P = .04), reduction in the number of episodes of pneumonia per 1,000 ventilator-days, but this reduction was not statistically significant (P = .06) when the authors evaluated only patients who received mechanical ventilation for more than 48 hours, which is an acceptable period for the diagnosis of VAP.