Home Q&A Ventilator-associated pnenumonia guidelines take new view of evidence

Ventilator-associated pnenumonia guidelines take new view of evidence

October 2004

Published in the October 2004 issue of Today’s Hospitalist

When new guidelines were published this summer assessing strategies to prevent ventilator-associated pneumonia, they likely raised a few eyebrows. While the guidelines confirm standard practice in some areas “the timing of ventilator circuit changes, for example “they give a less-than-glowing assessment of other therapies.

The guidelines, which were published in the Aug. 17 Annals of Internal Medicine, address three types of interventions “physical, positional and pharmacologic “to prevent VAP. While portions of the guidelines may be of greater interest to respiratory therapists than physicians, some of their recommendations are sure to get the attention of physicians.

While several studies have shown that topical and IV antibiotics can help prevent VAP, for example, the guidelines made no recommendation on this strategy. Similarly, while there is a plethora of evidence both supporting and opposing early tracheostomies to prevent VAP, the guidelines abstain from making any recommendation at all on the topic.

If the guidelines counter the conventional wisdom on some strategies to prevent VAP, it’s probably because of the unique process used to create them.

Peter Dodek, MD, chair of the clinical practice guidelines committee of the Canadian Critical Care Society and Canadian Critical Care Trials Group, says that a panel of nine intensivists was asked to examine nearly 100 clinical trials focusing on VAP strategies. More specifically, they were asked to score the validity of trials, the effect size and confidence intervals, the homogeneity of the results, and other issues like safety and feasibility.

Dr. Dodek, who is an intensivist at St. Paul’s Hospital in Vancouver, British Columbia, says that asking reviewers to use a very explicit set of criteria to rank the evidence helped panel members focus on the results of pertinent trials. Because some of the panelists have strong opinions on the issue and had even worked on some of the trials being examined, he says the process helped people “leave their opinions at the door.”

The reviewers also examined more than just a specific treatment’s efficacy and looked at safety and feasibility and, to a lesser extent, the economic impact of the strategies. That explains why a strategy like prophylactic antibiotics to prevent VAP received a “no recommendation” from the group. Despite evidence showing that the strategy can be effective, reviewers thought there were unanswered questions about antibiotic resistance and cost effectiveness.

Today’s Hospitalist talked to Dr. Dodek about aspects of the guidelines that might affect “and surprise “hospitalists.

Which of the recommendations will come as a surprise to hospitalists?

The evidence regarding recommendations for heat and moisture exchangers has not been taken up as quickly as the evidence on other issues. As a result, it may come as something of a surprise that we’re recommending health and moisture exchangers, because people are so used to using heated humidifiers.

While these exchangers were associated with a slightly decreased incidence of VAP when compared to heated humidifiers, it’s a newer technology that may not have been adopted as widely as the heated humidifier.

Some physicians are going to wonder why the guidelines do not recommend either topical or IV antibiotics to prevent VAP. Hasn’t the evidence shown that the drugs can help prevent VAP?

It’s true that there have been more than 10 meta-analyses and at least 40 randomized trials that have been quite promising. The problem is that many of them were done in a single unit that had very distinct antibiotic resistance patterns.

The strategy has been shown to decrease VAP in units in the Netherlands, for example, but the units have a very low incidence of MRSA. We don’t know how well that research will translate into areas that have a higher incidence of MRSA.

That explains our hesitance to make a recommendation. We were encouraged by the findings that antibiotics could decrease the incidence of VAP, but we were also concerned about the additional consequences. This is one of the big strengths of our guidelines, which is that we looked at issues like safety and feasibility, and in a rudimentary way economic issues.

It’s possible that we’ll see more studies that will show that antibiotics are indeed safe in units with a higher antibiotic resistance. We’re open to changing our recommendations should new evidence become available.

How popular are antibiotics as a strategy to prevent VAP?

The strategy is not as popular in North America as it is in Europe. That explains why many of the studies we examined were done in Europe. I don’t think we’re going to be upsetting an existing pattern of practice in North America, but we might inject some controversy into an area where people were thinking of adopting what has been an increasing weight of evidence in favor of prophylactic antibiotics.

Why did the panel decide to refrain from making any recommendations about the timing of tracheostomy?

The issue of tracheostomy is another highly debated topic that is still unsettled. There are some studies that have shown you can wean patients earlier who have had tracheostomies, but there are biases that are introduced because you can’t really blind a study like that.

For example, it’s difficult to randomize subjects into groups that will receive late vs. early tracheostomy because you can’t predict which patients will remain intubated at 14 days. That’s when they become candidates for late tracheostomy.

Because the studies have these problems in their design, the evidence is problematic, and it was difficult for us to make any recommendations. The evidence did not help us guide physicians to say here’s a reason to do an early vs. a late tracheostomy.

How did the panel assess treatment strategies in terms of costs?

A good example is subglottic secretion drainage tubes. A recent trial found that the number needed to treat is eight. The incremental cost of that tube is about $5 Canadian, which will vary depending on location. If we had to use eight of those tubes to prevent a single VAP, the strategy would cost an additional $40.

We know from other studies that the attributed ICU length of stay for one episode of VAP is 4.3 days. That means that by preventing a case of ventilator-associated pneumonia, you would expect to decrease length of stay in one patient by 4.3 days. A conservative estimate of ICU costs is $1,500 per day, so it’s a no-brainer to compare spending $40 to saving $6,450.

Which of the strategies were less clear in terms of a cost benefit?

Cost is one reason we said consider, but didn’t recommend, strategies like kinetic beds. These beds are expensive, which is why some facilities rent them and others buy them.

Other recommendations automatically produce cost savings because they suggest doing things less often and reducing costs. For example, if you change ventilator circuits and suction systems less frequently, you’re doing something that automatically saves money. It’s not like you have to spend money on the intervention.

Still others cost nothing, like putting patients in a semi-recumbeant position. That’s a nursing practice that doesn’t add any cost. But if you prevent a case of VAP, you’ve just saved that patient an average of 4.3 days in the ICU.

These guidelines don’t address areas that for many physicians represent the bread and butter of managing ventilator patients: weaning, the use of noninvasive ventilators, and nutritional strategies. How are the issues outlined in the guidelines important to physicians?

Because respiratory therapists in North America handle issues like ventilator circuit management and chest physiotherapy, some of these issues have slipped into the background for many physicians. While physicians may not even think about some of those issues, once the patient is put on a ventilator, they are all important decisions.

As the paper points out, there’s a large burden of disease. The incidence of pneumonia acquired in the ICU is between 10 and 65 percent, and attributable mortality ranges between 0 and 50 percent.

As physicians, if we explain the impact that ventilator-associated pneumonia has in terms of morbidity and mortality, and we show that there are some inexpensive and effective solutions to prevent it, it’s amazing how well people get on board.

Most of the strategies that we have recommended are pretty straightforward, but overcoming the inertia of standard practice is not easy. Once people understand the rationale, however, it’s amazing how quickly they buy into it.