What's new in critical illness and injury science? Pneumonia prevention in the ICU remains a challenge.

Hospital acquired pneumonia (HAP) and particularly Ventilator associated pneumonia (VAP) remain a difficult problem to tackle in modern day health care. The estimated cost of one episode of HAP is about $20,000.[1] The proposed mechanisms for HAP and VAP include micro aspirations of bacteria from the mouth and throat into the airways and in case of mechanically ventilated patients this happens alongside the endotracheal tube. A number of studies have been performed over the years that have looked into a number of strategies of prevent or reduce the HAP and VAP events.

The Institute for Healthcare Improvement (IHI) recommends a bundled approach for VAP prevention including head elevation, deep vein thrombosis and stress ulcer prophylaxis, daily sedation vacations and finally selective oral decontamination (OD) with chlorhexidine mouth-rinse. In 2010 the Institute for Healthcare Improvement instituted the regular use of chlorhexidine for OD as they had deemed “support in the evidence.” These recommendations have resulted in a swift and resounding incorporation of daily OD at most institutions around the globe. Each of these elements has been shown to reduce the incidence of VAP although the evidence is questionable at best. Trials implementing these practices have failed to show benefit, with pre-post studies frequently being the only design consistently showing benefit of this bundled approach.[2] The inherent flaw in this approach is the inability to account for any additional interventions occurring, given the heightened focus on an ongoing problem, increased attention has been shown to account for rates of VAP.[3] Finally the overall pool of literature in this area introduces a very high risk of publication bias, given the lack of publication of negative outcomes. In fact depending on the population in which this approach is utilized, there may even introduce an increase in the incidence of VAP.[4]

Additional flaws in studying a bundled approach is the inability to determine what component provides the greatest impact, and does this impact transcend all populations. Interestingly the evidence utilized to establish the recommendation of chlorhexadine stems from a single cardiothoracic surgery study carried out by Deriso and colleagues in 1996.[5] Since this time the evidence has been all but robust, with wavering support in regards to regular OD, with multiple studies failing to identify benefit in this practice. While other groups support this practice, such as the surviving sepsis campaign, there rationale even endorses the lack of evidence in existence claiming a lack of risk thus preferring it to alternative slightly riskier practices.[6] The impact does appear to waver in relation to the population at hand, supporting this practice more commonly in the cardiothoracic surgery population, were this benefit has been identified most consistently.[7] A recently published meta-analysis by Roquilly et al. identified a reduction in the development of HAP through the use of selective OD, use of sub-glottic suctioning, post-pyloric feeding as well as selective digestive decontamination (SDD). However these interventions failed to change duration of mechanical ventilation or mortality, with only SDD as predictor of significantly changing these endpoints.[8] This raises the question of the true impact of these interventions.

The authors of the article “Impact of Chlorhexidine Mouthwash Prophylaxis on Ventilator-Associated Events in a Surgical Intensive Care Unit” have done a good job of evaluating the impact of OD on Ventilator associated events. Even though on the surface it would seem like the number of events were reduced, selecting only patients who had a BAL done may have limited and biased the data. Additionally it is difficult to ascertain if the effects are solely attributable to OD or due to combination of OD with other measures incorporated into their protocol over the years.

While the importance of preventing complications of health care such as VAP is a high priority, especially in the economic environment of today's healthcare systems. The literature supporting current common practices truly need re-evaluation and heightened scrutiny.