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A large proportion of patients who remain in ICUs for more than a few days develop hospital-acquired infections, including bloodstream infections. Indwelling urinary or venous catheters, gut translocation, aspiration and impaired host defenses can all be causative.
Bloodstream infection incidence has been reduced over time, but remains persistently ineradicable. One enticing method of prevention has been to "decontaminate" patients by cleaning their mouths or bodies with chlorhexidine, or with a gastrointestinal antibiotic delivered into the mouth or via enteral tube.
This was recently tried among 8,665 mechanically ventilated patients in 13 European ICUs with high rates of multidrug resistant gram-negative bacteremia. The ICUs (not the patients) were randomized to either usual care (chlorhexidine body washes), chlorhexidine mouthwash, antibiotic mouthpaste (colistin, tobramycin, nystatin), or gastrointestinal suspension (same antibiotics).
After six months, there were no statistically significant differences between groups in bloodstream infections with drug resistant bacteria. There was a tendency toward reduced risk with the gastrointestinal mouthpaste and suspension.
The study contrasted with previous work in the Netherlands showing reduction in infection rates with selective gut decontamination.
In the U.S., chlorhexidine mouthwash is a standard component of so called "VAP bundles," but as with the other common-sense bundle elements (e.g., head-of-bed elevation), there is little to no evidence for chlorhexidine's efficacy. Reductions in reported rates of VAP should invite some healthy skepticism, as they are influenced by hospitals' financial disincentives to report VAP, which prompted a frustrated CDC to invent a strange new epidemiologic entity, "ventilator-associated events," according to criteria that have low or no utility clinically or epidemiologically.
Interestingly, indiscriminate use of intravenous broad spectrum antibiotics, given to all mechanically ventilated ICU patients shortly after arrival, has consistently been shown to reduce rates of ventilator associated pneumonia and mortality, in randomized trials and a meta-analysis. This strategy has not been implemented widely, due to concerns about instigating antibiotic resistance on a massive scale.