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Rural Medicine - A Mysterious Case of Methemoglobinemia
Vanessa Cardy and Louis Yu
Case: Syncope in a 15-year-old with cold symptoms, including sore throat and runny nose × 3 days. He has been tired and weak × 1 day. He collapsed as he was walking to his grandmother’s room. NRB 15L, O2 saturation (%) in mid-70s, tired; temperature: 96.6°F, BP: 103/59, heart rate: 134, respiration rate: 26. Exam: notable for central cyanosis, clear lungs. No past medical history, no family history, and no history of heart problems.
Case continued: Central cyanosis and O2 saturation not improving with high-flow nasal cannula. The blood, when drawn, appeared chocolate brown.
Case continued: Grandparents offered more history. The patient was given Vicks Vapo cool sore throat spray and it helped with symptoms, so he drank about 30 mL of it. It is 5% benzocaine. There were issues obtaining the methylene blue, the flight was delayed, and the patient was getting more fatigued, more short of breath, and now has an expiratory wheeze. He is responding to the nebulizer.
Dallas H. - February 7, 2023 5:54 PM
Patients in rural areas should always be encouraged to carry flight insurance.
Unfortunately, the staffing crisis in healthcare has also impacted EMS crews. I've sat on STEMIs and LVOs for hours, waiting for transport, begging and pleading. It's heartbreaking and probably the worst aspect of rural, critical access medicine.
Vanessa C. - February 9, 2023 7:43 AM
I totally agree that holding onto critically ill patients while the medevac companies scramble to find crews is so challenging and disheartening.
The idea of flight insurance is intriguing but I know that most of my patients living in rural and remote areas could not afford it. Even if they could afford it, the 2 or 3 planes that they would potentially access with insurance are the same ones used by our hospital system, which would then divert resources way from our public needs. So tricky and so complicated on every front. Thanks for listening and writing in!
Preston W. - February 16, 2023 6:45 AM
Did you consider NAC while looking for the Methylene blue?
Louis Y. - February 20, 2023 8:37 PM
I didn't, but there is some interesting literature regarding the use of NAC. NAC has been shown to reduce MetHgb levels in vitro, however, there is a very small study from 2000 that showed no effect in human subjects. The authors performed a randomized controlled trial using 9 adult physician and compared NAC (at a similar dose used to treat acetaminophen poisoning) with dextrose infusions. There was no difference in the MetHgb levels. They induced methemoglobinemia using intravenous sodium nitrate. There really doesn't seem to be a lot of good alternatives to good old methylene blue for acute methemoglobinemia. I did find that Cimetidine can be used specifically for Dapsone induced methemoglobinemia. Ascorbic acid works too slowly. Second line treatment for refractory cases include exchange transfusion and hyperbaric oxygen.
Sara M. - February 19, 2023 6:25 AM
Any utility in transfusing the patient in a bind in hopes of oxygenating? Presuming/hoping we’re far enough out and circulating offending agent causing hemoglobinopathy is metabolized.
Louis Y. - February 20, 2023 8:50 PM
Good question. Ultimately methemoglobinemia is a hemoglobinopathy and by adding functional Hgb you might be able to improve tissue oxygenation. The toxicologists I spoke with didn't think there was much utility given that the small amount of transfused blood would likely be oxidized based on the timing of the ingestion. Exchange transfusion is occasionally used in refractory cases, and gets around the issue of persistent circulating offending agent.
Evan M. - March 1, 2023 9:04 AM
Did you consider transferring to San Juan Regional ER for them to administer the methylene blue? If they had the drug, it would be an appropriate transfer per EMTALA.
Louis Y. - March 1, 2023 7:25 PM
Thanks for the question Evan. From what I remember (and this case was many months ago so I could be wrong) SJR did not have any PICU beds. It was tremendously difficult to transfer that winter due to severe staffing shortages everywhere and the delta wave was filling up hospitals. An ER to ER transfer was theoretically possible, but the patient would have been stuck in their ER without an inpatient bed. Although more complicated, we decided the best option would be to get the antidote and transfer to a PICU. Both Phoenix and Salt Lake City also had access to hyperbaric oxygen should it be required.