Bronchiolitis: The Rationale Behind the New AAP Guideline

Dr Quinonez: The guidelines state that viral testing for respiratory syncytial virus (RSV) is only indicated for children on palivizumab prophylaxis with suspected breakthrough disease. The purpose of testing is to determine whether prophylaxis can be discontinued, and it should be discontinued for infants who test positive. What is the harm of testing, though?

Dr Ralston: That's a good question. I think there's an obvious financial harm in testing. Many of these tests are polymerase chain reaction tests and approach $700-$800. The question is, what are you going to do with that information? That said, however, it is not meant to imply that there won't be settings where a viral test may be done for very good reasons—for example, when there is a large amount of parental distress or confusion or diagnostic uncertainty. I think it's important to remember that a guideline should serve as a shared baseline and a recommendation for what to do in the typical patient. That does not mean that it makes recommendations for what will be done in every single patient case. That said, I can think of very few settings where I really need to know which virus is causing the viral lower respiratory tract infection that I'm treating, given that knowing the specific virus does not lead me down a particular therapeutic course.

Dr Quinonez: The guideline is equally clear that albuterol, epinephrine, corticosteroid, antibiotics, and chest physiotherapy should not be used. However, in practice (and supported by the 2006 guidelines), it is fairly common to treat a child with bronchiolitis with albuterol and assess response. Why the significant change in this guideline regarding bronchodilators? In particular, can you address some of the issues regarding first-time-wheezing infants and those with atopy or a family history of asthma?

Dr Ralston: Absolutely. I think this is the burning question that most clinicians have about this particular guideline. There are multiple ways to address this issue. One is the epidemiology of wheezing in the young child. We know from the Tucson Children's Respiratory Study^[2] that 30% of children—a huge number—are going to wheeze before the age of 3 years. We also know that well less than 10%, probably closer to 5%, of children go on to have asthma. We feel like we should be able to predict which of those children are asthmatic the first time they wheeze. I can tell you that you can't. There isn't anything that helps us very clearly when the patient presents for the first time. Certainly a family history of wheezing and atopy seem to be important and potentially predictive. But these factors don't perform very well in practice. Even recurrent wheezing doesn't perform well in predicting who will respond to albuterol. This is discussed in the guideline.

You have a large cohort of patients who wheeze and you have no ability to predict who is likely to respond. We cannot mandate a trial of bronchodilators, a medication that, in clinical trials, clearly has no impact on any meaningful outcome, such as risk for hospitalization, duration of illness, length of stay—all of those things. There is a large volume of literature supporting this conclusion that these medications don't prevent these negative outcomes. And these findings probably will not change with further study. Ultimately, if we mandated a trial, we'd be exposing a large number of children to a medication with a significant amount of side effects. Certainly the majority of nebulized medications given to babies are deposited in the back of the mouth and throat and systemically absorbed. Babies get significant tachycardia, irritability, and all of the side effects from albuterol, when only a very small percentage might benefit.

The other set of literature that we looked at as we sought to determine whether this type of trial was a rational approach was the physiology literature. Although this body of research was not in the guideline, we certainly considered it. When people assiduously assess the physiologic response of infants, in particular, to bronchodilators, only a very small percentage physiologically respond to bronchodilators, just as is the case with adults. The guideline committee concluded that the harm of exposing the larger cohort of patients to a trial of bronchodilators far outweighed the potential benefit when applied across the entire population.

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