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Podcast 142 - EBM Guide To RSV w/ Natalie May

I reached out to @medtwitter asking for help finding a guest to talk about the respiratory syncytial virus (RSV). It may seem weird to be talking about RSV when everyone is thinking about the current pandemic, but I find the virology and mechanism of symptoms of RSV exciting.

Twitter did not let me down, my friend Ashley Liebig recommended Natalie May from Sydney, HEMS. Natalie is an EM, and Pediatric-EM trained UK doctor working in Prehospital & Retrieval Medicine in Australia. I was very excited to have a chance to speak with Dr. May regarding RSV & Bronchiolitis and what the current evidence suggests for treatment.

Topics Discussed

  • Routine viral testing and chest imaging are not recommended for patients with presumed RSV bronchiolitis. What are you using to differentiate RSV from other causes?

  • The American Academy of Pediatrics states that "Bronchodilators, systemic or inhaled corticosteroids, and epinephrine should not be administered to infants and children with bronchiolitis." Why do you think these interventions do not work in RSV?

  • Do you think ultrasound has an application in differentiating various pathology?

The Mechanism of RSV

RSV is spread by viral droplets that make their way down to a nice cozy spot in the smallest part of the airway - the bronchioles.

Here is a great infographic Brian King created after reviewing this episode.

Once it reaches the bronchioles it will attach to the epithelial layer of the bronchioles, hi-jack the cell, and begin to replicate. As this process occurs, the neighboring epithelium will be invaded or destroyed as well. This process creates something called multinucleated syncytia. This is essentially connecting all the cells to create one gigantic viral replicating factory. The natural killer cells will trigger a chemokine release that increases mucous production and inflammation.

Things Referenced:

In the episode, Dr. May discusses how often these patients are hypovolemic from poor feeding (due to dyspnea and secretions). Fluid resuscitation may be needed (20cc/kg/10 minutes) and Sam mentions the 4,2,1 rule with maintenance fluids.

Infographic by Sam Ireland

At the beginning of this episode, I mention a book Authored by Dr. May titled, 101 Lesson Learned from Sydney HEMS. Here is the link for the free download here

Huge thanks again to Dr. Natalie May for coming on the podcast! Check out a lot more of her work at


American Academy of Pediatrics., & American Heart Association. (2016). Pediatric advanced life support.

Cunningham S, Rodriguez A, Adams T, Boyd KA, Butcher I, Enderby B, MacLean M, McCormick J, Paton JY, Wee F, Thomas H, Riding K, Turner SW, Williams C, McIntosh E, Lewis SC; Bronchiolitis of Infancy Discharge Study (BIDS) group. Oxygen saturation targets in infants with bronchiolitis (BIDS): a double-blind, randomized, equivalence trial. Lancet. 2015 Sep 12;386(9998):1041-8. DOI: 10.1016/S0140-6736(15)00163-4. PMID: 26382998; PMCID: PMC4673090.

Kallappa C, Hufton M, Millen G, Ninan TK. Use of high flow nasal cannula oxygen (HFNCO) in infants with bronchiolitis on a pediatric ward: a 3-year experience. Arch Dis Child. 2014;99(8):790–791

Malla D, Rathi V, Gomber S, Upreti L. Can lung ultrasound differentiate between bacterial and viral pneumonia in children? J Clin Ultrasound. 2021 Feb;49(2):91-100. doi: 10.1002/jcu.22951. Epub 2020 Nov 16. PMID: 33196108.

Smith DK, Seales S, Budzik C. Respiratory Syncytial Virus Bronchiolitis in Children. Am Fam Physician. 2017 Jan 15;95(2):94-99. PMID: 28084708.

Walsh, E. E., & Hall, C. B. (2015). Respiratory Syncytial Virus (RSV). Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, 1948–1960.e3.

Not ready for the fun to end? Click on this picture below to learn how to up your game as a clinician!👇🏼


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