Episode 164: Keywords part 9: Fentanyl and Breathing Circuits

Anesthesia and Critical Care Reviews and Commentary (ACCRAC) Podcast
Anesthesia and Critical Care Reviews and Commentary (ACCRAC) Podcast
Episode 164: Keywords part 9: Fentanyl and Breathing Circuits

In this 164th episode I welcome back Dr. Gillian Isaac to do another ABA keywords episode. We discuss fentanyl and breathing systems (Mapleson and Circle systems).

CME: https://earnc.me/delVJ8

Great info from Aaron Sandock:

The toxicity was reported in rats and research was published in the early-mid 90’s. 

Gonsowski, C., Laster, M., Eger, E., Ferrell, L. and Kerschmann, R. Toxicity of Compound A in Rats: Effect of a 3-Hour Administration

Anesthesiology. 1994;80(3):566-573. 


It is actually the case that follow up studies were done in the US on volunteer patients through University of Arizona and Medical College of Wisconsin in the later 1990’s.Ebert, T., Frink, E. and Kharasch, E. Absence of Biochemical Evidence for Renal and Hepatic Dysfunction after 8 Hours of 1.25 Minimum Alveolar Concentration Sevoflurane Anesthesia in Volunteers. Anesthesiology. 1998;88(3):601-610.


Kharasch, E. and Jubert, C. Compound A Uptake and Metabolism to Mercapturic Acids and 3,3,3-Trifluoro-2-fluoromethoxypropanoic Acid during Low-flow Sevoflurane Anesthesia. 

Anesthesiology. 1999;91(5):1267-1278.


The key point of the final article concludes that humans are nearly devoid of renal beta lyase, the key enzyme in directing biodegradation of compound A to the toxic renal thiol. Essentially, this research was done in the late 90’s but the original possibility of renal toxicity in humans from just a few years prior has stuck in peoples’ minds (and therefore textbooks). 

More recent studies agree:

Ong Sio LDela Cruz R,  and Bautista A. Sevoflurane and renal function: a meta-analysis of randomized trials.

Med Gas Res. 2017 Oct 17;7(3):186-193.


Gillian’s random recommendation: Born a Crime by Trevor Noah

Circle C Farm: https://www.circlecfarmfl.com

3 thoughts on “Episode 164: Keywords part 9: Fentanyl and Breathing Circuits”

  1. In episode 164, there seems to be a math/conversion mistake in the question at 19:57. The question states that the woman received 3000mcg of fentanyl, and it was stated by your guest and by you in your answer that she received 3 grams of fentanyl. 3000mcg of fentanyl is equal to 3mg of fentanyl, not 3 grams.

    As a side note, I am a certified veterinary technician studying for my Veterinary Technician Specialist exam in anesthesia and analgesia. I find these podcasts to be an excellent review of information for my exam. Thank you for doing all that you do to produce these podcasts.

  2. For the question:

    ” Which of the following statements concerning the use of a Bain circuit is true?

    o A) Fresh gas flow can be as low as the patient’s minute ventilation
    o B) Heat conservation is better than with a circle system
    o C)Lower flows can be used with controlled ventilation than spontaneous ventilation
    o D) Lower fresh gas flows can be used than with the Jackson Rees circuit
    o E) the concentration of inhaled vapors can be changed rapidly using high flows, so can change concentration faster

    We said that “E” was the correct answer, which I agree. However, why isn’t “C” correct? Is there possibly two correct answers?

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