The Institute of Healthcare Improvement's (IHI) guidelines for preventing ventilator-associated pneumonia (VAP) are, by now, well-known. But there are many more tactics that health professionals could be using to prevent the illness, according to Keith S. Kaye, FACP, associate professor of medicine at Duke University Medical Center in Durham, N.C.
“There is quite an evolving literature regarding novel and innovative VAP prevention methods that offer hope for the future—maybe the near future,” Dr. Kaye said during a talk at the recent Infectious Diseases Society of America's annual conference in San Diego.
The CDC has guidelines which, though not a formal part of the IHI “VAP bundle,” offer a few basic prevention modalities, he said. One is to use endotracheal tubes that have dorsal drainage mechanisms to prevent aspiration; another is to change a ventilator circuit only when it is malfunctioning or visibly contaminated.
“There is absolutely no data supporting routine changing of the circuits,” Dr. Kaye said. “If anything, when we get our hands on things and in the middle of things, we actually increase the risk for contamination and infections.”
Still another CDC-recommended modality is the use of noninvasive ventilation (NIV), which reduces the need for and duration of intubation and mechanical ventilation, he said.
“Randomized studies have shown up to threefold decreases in pneumonia and mortality, and decreased durations of ICU stays, in patients who receive noninvasive ventilation,” Dr. Kaye said. “Patient populations in which NIV has been effective include those with chronic obstructive pulmonary disease, pulmonary edema, community-acquired pneumonia and hypoxemic respiratory failure.”
While NIV doesn't apply to all intubated and respiratory failure patients in the ICU, it certainly covers a large proportion, he said.
“The cost of preventing infections can be difficult to justify to administration, but certainly, by preventing intubation and mechanical ventilation, you are decreasing the single greatest risk for hospital-acquired pneumonia,” Dr. Kaye said.
New ways of using antibiotics
One area that's really changed in the last five years is the use of antibiotics, Dr. Kaye noted. Intravenous antibiotics have fallen out of favor as a way to prevent VAP in a unit, due to fears that the drugs will progressively alter the host gastrointestinal flora and lead to superinfections with multidrug-resistant organisms.
Newer strategies focus on antimicrobial stewardship and preventing resistance. The goal is to eliminate or reduce the burden of pathogens and microbes of the mouth, and thus decrease aspiration risk that might lead to VAP, Dr. Kaye said. This is done either via oral antibiotics or antiseptics.
While many studies haven't shown a significant decrease in VAP via oral antibiotics, a 2001 study in the American Journal of Respiratory and Critical Care Medicine found a threefold decrease in VAP using triamcinolone (Orabase) dental paste compared with placebo. Colonization rates of bacteria in the stomach and rectum weren't affected by triamcinolone, the study found.
Meanwhile, most of the newest literature on antiseptics focuses on oral chlorhexidine, Dr. Kaye said. A 2007 meta-analysis in the British Medical Journal found that chlorhexidine decontamination is associated with a relative risk of 0.70 for VAP, Dr. Kaye noted.
“Antiseptic methods are important and are being used in some institutions, but I don't think they are widely used or widely appreciated as an effective method that will do no harm,” Dr. Kaye said. “Further trials are needed to show the impact on mortality and hospitalization, because administrators will ask about this, but I think this is a very exciting and promising modality.”
Aerosolized antibiotics is another area for both treatment and prevention of VAP that has “somewhat taken off,” Dr. Kaye said. While older studies using polymyxins alone or in combination with gentamicin didn't show a clear effect on prevention, ceftazidime has shown promise, he said. A 2002 study in Pharmacotherapy found ceftazidime decreased the incidence of VAP, and lowered the length of ICU stay, in trauma patients, while having no adverse effects on flora.
“I would like to see similar results in different sites and patient populations, but again it is exciting data. Whenever you can use antibiotic prophylaxis without using it systemically and without showing harm, it is always favorable,” Dr. Kaye said.
One bit of fairly new technology that hasn't caught on as much as expected is subglottic suctioning—that is, continuous aspiration of subglottic secretion through an endotracheal tube, Dr. Kaye said. A 2005 American Journal of Medicine meta-analysis found that, compared to a standard endotracheal tube, subglottic suctioning was associated with a risk ratio for VAP of 0.51, 1.8 fewer days of mechanical ventilation and 1.4 fewer days in the ICU. Mortality, however, was not significantly affected.
“Most people are not routinely using subglottic suctioning, and I'm not sure why. It does cost more, about 25% more than standard [endotracheal] tubes, but obviously if you are preventing more cases of VAP, you are probably paying for your [endotracheal] tubes,” Dr. Kaye said. “I have heard some nurses say they think it's more labor-intensive, though others say it's fairly easy once you get used to it….if you can clearly show a mortality benefit from subglottal suctioning, you'll see it used more.”
Continuous lateral rotation bed therapy is another alternative to help prevent VAP, though it's rarely used, Dr. Kaye said. The aim is to prevent aspiration, which can occur when patients are left immobilized in bed. A meta-analysis in the 2007 American Journal of Critical Care found that, while many individual studies showed a preventive effect for rotating patients that failed to reach statistical significance, the summary risk ratio was 0.5 for VAP reduction.
There are limitations to bed rotation, however. For one, there is no standard method for how the patients are rotated or for the frequency of turning. As well, patients may not like the rotation; some may get motion sick, or even fall out of bed.
“There is not a rotation standard, like you put the patient on a turntable and set them at 78,” Dr. Kaye said. “But the biggest limitation is patient tolerance. I think generally this type of modality might best be used when patients are sedated or not terribly awake or cognizant.”
Other novel methods that have received a fair amount of press are chest physical therapy, using heat- and moisture-exchange filters instead of conventional humidifiers, and intermittent—versus continuous—enteral feeding. None of these have shown clear superiority in clinical trials, however, Dr. Kaye said.
“I think we're still looking for that major step forward in terms of technology,” Dr. Kaye said. “Overall, though, I am still excited about some of these existing modalities.”