David and Goliath: Inhalational anesthetics and dexmedetomidine

John Fiadjoe MD and Amy Vinson MD

The PAAD is back from the SPA/ASA interlude! The meetings and the ability to see and hug old and new friends in person was simply fabulous and life affirming. I can only hope that this portends to great things to come.

One of the very best lectures I’ve ever attended was the Rovenstine lecture at ASA. Entitled Ever Eger: My Love Affair with Anesthesia, presented by: Steven Shafer, MD is the story of the late Ted Eger and the development of MAC. It is something every anesthesiologist should or really must see. I’m certain it was taped and over the next couple of days I’ll try to get a link to post in the PAAD. Additionally, at the meetings we formed a PAAD editorial board and several new reviewer/writers joined. More information about some of the changes will be forthcoming in the next week or 2. OK, back to business. I hope you recall a recent PAAD discussed MRIs and how to anesthetize children for them. Lynne Maxwell and I questioned the need for so many MRIs and the use of dexmedetomidine in the anesthetic management. Dr. Amy Vinson, an absolute rising star from THE Boston Children’s Hospital and the senior author of the reviewed paper and Dr. John Fiadjoe sent the following response. Myron Yaster MD

John Fiadjoe : I was thrilled as always to have Drs. Yaster and Maxwell analyze a paper from Boston Children’s Hospital (my new home) for the PAAD (Trends in Pediatric MRI sedation/anesthesia at a tertiary medical center over time. Paediatr Anaesth. 2021 Sep;31(9):953-961. PMID: 34036674). The line “This absolutely makes no sense to us” got my ears perked up. So in the spirit of good old scientific banter, I asked Amy Vinson, the author of the paper, wellness expert, researcher, and superior singer, to help me respond to two of the Giants in our field… enter analogies of David vs Goliath. Goliath was thought to have acromegaly and suffered from blindness…there is an analogy there about the blindness of Drs. Yaster and Maxwell to some important points.

Amy Vinson: Indeed, many of the concerns being raised regarding the necessity of diagnostic imaging and the inherent frustrations of these tests requiring anesthetics, all amongst the backdrop of financial drivers within institutions, are shared among pediatric anesthesiologists.

 The point that was not clear was our speculation that dexmedetomidine was added to propofol because of concerns about anesthetic effects on the developing brain. Drs. Yaster and Maxwell are right about the results of the GAS study but one thing that they didn’t acknowledge is that many MRIs take much longer than 1 hr and in fact some complex MRIs at our institution can be as long as 3+ hours. Furthermore, many of the children presenting for MRI are not normal healthy children and receive serial scanning, thus increasing their anesthetic exposure. So the extrapolation of results from healthy children receiving an hour long anesthetic to children who may not be healthy receiving very long or repeated scans is not appropriate.

Specifically, the point being raised resided in the speculated etiology of an organic change in practice: that anesthesiologists at our institution were trending away from propofol-only anesthetic techniques and towards a balanced technique of (lower dose) propofol infusion with a (low-dose) dexmedetomidine bolus. Our data demonstrated strong safety within both techniques with frankly similar time to discharge. It is hard to know exactly why this occurred, but we attempted to honestly speculate. 

A couple of points.  A balanced technique with a low-dose dexmedetomidine bolus plus a propofol infusion has been shown to decreased required airway interventions during diagnostic imaging, and this data likely influenced many of our anesthesiologists.1

But that wasn’t the focus of concern – the focus was our supposition that some practitioners may have transitioned to this balanced technique because of a concern for neurotoxicity and the insinuation that we at Boston Children’s Hospital should “know better” since it was the “epicenter” of the GAS study.2  We discussed the findings of this landmark study in the original manuscript, but also recommend that there are more factors at play in the entire studied population receiving MRIs than in the more narrow/controlled population studied in the GAS study. Granted, there are many other high-quality retrospective, population-based and prospective studies of neurotoxicity in children that are reassuring. I (Vinson) recently authored a review of the issue of neurotoxicity of anesthesiology in children, so feel equipped to address these caveats directly.3 

1.       Children undergoing MRI under anesthesia are often requiring anesthetics well in excess of an hour.

2.       These children often require multiple scans, not single episode anesthetics due to complex medical conditions

3.       These anesthetics are IV based, not inhalational anesthetic based, so straight extrapolation is dubious

4.       Dexmedetomidine has been shown to be neuroprotective in multiple animal models, so at worst equivocal and at best helpful in mitigating any possible neurotoxic effects of anesthesia.

John Fiadjoe: A second point made was about the use of inhalational anesthetics for IV placement. In my opinion many children tolerate awake IV placement just fine. The practice of inhalational induction for IV placement is a historical, cultural one based on clinician comfort rather than one that is based on evidence. Most children presenting in the ED have IV’s placed without inhaled anesthetics. Distraction and topical anesthetics using needless systems (e.g. J-tip) make this much easier these days. In fact placing an IV awake can be much less traumatic than forcing a mask over the face of a reluctant child although I know there are ways to do this less traumatically. We should spend time teaching the next generation how to place IV’s awake.

Amy Vinson: And while we are on the topic of distraction & child-life services, the Radiology and Child-Life departments at Boston Children’s Hospital ought to be applauded for the “Try Without” efforts they have partnered with our team to facilitate children being able to try their scan without anesthesia, without risking losing their anesthetic slot. To quote our original manuscript: “During the queried time period there was a consistent drop in percentage of MRI cases requiring sedation/anesthesia (from 24.6% in 2013 to 17.3% in 2019). (Supplemental Figure 2)”4

Hopefully we have cleared up any blind spots Drs. Yaster and Maxwell. We should start virtual PAAD beer rounds to discuss some of these interesting PAADS. Keep em coming and thank you!

1 Nagoshi M, Reddy S, Bell M, Cresencia A, Margolis R, Wetzel R, et al. Low‐dose dexmedetomidine as an adjuvant to propofol infusion for children in MRI: A double‐cohort study. Pediatr Anesth. 2018;28(7):639–46.

2 MD DAJD, MD ND, PhD JC de G, BM DEW, DClinPsy LD, MBChB GB, et al. Neurodevelopmental outcome at 2 years of age after general anaesthesia and awake-regional anaesthesia in infancy (GAS): an international multicentre, randomised controlled trial. The Lancet. 2016 Jan 16;387(10015):239–50.

3 Vinson AE, Houck CS. Neurotoxicity of Anesthesia in Children: Prevention and Treatment. 2018 Nov 15;1–10.

4 Vinson AE, Peyton J, Kordun A, Staffa SJ, Cravero J. Trends in Pediatric MRI sedation/anesthesia at a tertiary medical center over time. Pediatr Anesth. 2021;

PS: Readers: What are your thoughts? And for those readers who are members of SPA’s education committee: a PEDx talk or debate on some of these issues would, in Goliath’s opinion be great and warranted. MY