Hypoxia & Overtreatment in Bronchiolitis

“Treat the patient, not the number” works for many things in medicine – asymptomatic hypertension, hyperglycemia, and anemia, among others.  However, hypoxia is less frequently dismissed as clinically irrelevant.

And, that perfectly explains the results in this study, which evaluated clinician dependence on oxygen saturation to guide disposition in pediatric bronchiolitis.

Bronchiolitis, a viral process of large airway inflammation, can be challenging to treat.  For the most part, the disease simply must run its course, and it’s a matter of the secondary effects of the infection determining need for admission – work of breathing and hydration status.  Clinicians have been encouraged to accept low oxygen saturations (>90%) in the absence of other sequelae as part of their decision-making process leading to safe discharge home.

But, apparently, we’re still married to “normal” numbers.  In this study, researchers in Ontario randomized patients to the pulse oximeter providing either a true oxygen saturation, or an “altered oxygen saturation” – altered, specifically, to display 3% higher than the true value.  Over four years, 345 patients in respiratory distress with a clinical diagnosis of bronchiolitis met screening criteria, although only 213 agreed to participate.  As you might expect, patients with the true oxygen saturation were much more likely to be hospitalized than the patients with the falsely elevated oxygen saturation – 41% vs 25%.  Patients whose true oxygen saturation was displayed also tended to have increased resource utilization within 72-hours.  Zero adverse patient-oriented outcomes were observed in either group.

This is a small, single-center study, so, strictly speaking, its generalizability is limited.  However, it probably accurately reflects practice in many settings – where hypoxia, independent of more important clinical factors, is inappropriately sufficient cause for admission or observation.  This is a worthy reminder of such a flaw in our practice as respiratory viral season begins to ramp up this fall.

“Effect of Oximetry on Hospitalization in Bronchiolitis: A Randomized Clinical Trial”
http://jama.jamanetwork.com/article.aspx?articleid=1896981

7 thoughts on “Hypoxia & Overtreatment in Bronchiolitis”

  1. Ryan,

    What a clever and unique article. Thanks for bringing it to our attention. Probably a good one for journal club discussion with the pediatric team. I wonder how they got ethical approval for this one…

    Keep up the good work.

    Brian

  2. Canadians!

    But, yes, somehow demonstrating to the IRB the safety of a trial in which children in respiratory distress with hypoxia might be discharged home based on false pulse oximetry … very interesting, indeed.

    Thanks for the kind words!

  3. Hmmm. Interesting concept and study, but I am not really sure what this is supposed to show.
    I do not think we need a study to tell us that hypoxia is not the only factor in admitting kids with bronchiolitis.
    All this is telling me is that whatever the trigger point for admitting the kids they used is of no clinical benefit. None of the kids came to harm, there were no patient oriented adverse outcomes, they did not even measure any, apart from the return in 72h. The primary outcome was a purely doctor related decision and the majority got admitted on day 1. All this is SUGGESTING is that we can send kids with low O2 sats home. But how low? would 85% be OK, maybe 80%? Or were they just lucky? With not a single adverse outcome I do not know which kid I should keep- from this study they could probably all have gone home and there would have been no clinically significant adverse outcomes, none ended up on CPAP, or ICU or suffered any permanent damage. As Jerry Hoffman would have put it this was a study of 213 kids but 0 sick kids.
    Normally I like to make my decisions based on whether I feel the patients is likely to come to harm if I do nothing. Unfortunately I do not know the natural history of bronchiolitis well enough to be able to tell which kid is not going to deteriorate over night, when no one is watching. Even more unfortunately this study does not tell me.

  4. You're correct – this study does not inform any particular breakpoint is regarding true pulse oximetry in the safe disposition of children with bronchiolitis. There are general recommendations – I'm not familiar with the evidence behind them – to be more tolerant of low oxygen saturations, as low as 90% with the AAP.

    As you say, it sounds like a study of 213 kids by 0 sick kids – but even in those circumstances, we're swayed by an apparently objective measure of illness severity over our own clinical evaluation.

  5. I'm not quite as unimpressed by the study. It does show that our original arbitrary cutoff for admission based on pulse ox is at least 3% too high. There does need to be further study to show what number we should consider too high risk to send home.
    Or maybe we shouldn't check it at all. I can mark "respiratory distress" on my chart without a pulse ox, a chest x ray, a blood gas, or even a stethoscope.

  6. To Justin
    I am not really sure it is quite like that. What you are forgetting is that the pulse oximetry is one of the factors we all use in our clinical assessment. I am pretty sure that those kids who got admitted did not have resp rate of 25, no accessory muscle use and were feeding perfectly well. The low sats were likely “the last drop in the bucket”. You see if I have a 6 month old kid with bronch with a RR of 40, some accessory use and decreased eating, but sats of 95% I will send them home. If the same kid has sats of 88 though, I will admit them. If I have a kid with NO resp distress and has sats of 88, well then I would be wondering if they have some kind of cardiac condition but I am not all that likely to admit him/her. You have to remember that parents do not take their kids in because they have low sats, but because they seem sick. To me sats are part of my clinical assessment. I can assure you that if they repeated the study with someone somehow giving them a false resp rate by 10 the results would be identical.

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