In this 154th episode I welcome Dr. Emery Brown to the show to discuss how we monitor the depth of anesthesia. We discuss the drawbacks to BIS and why Dr. Brown thinks the EEG itself is the best way to go.
CME: https://earnc.me/fbGYsk
References:
EEG reading tutorials: https://eegforanesthesia.iars.org/
Purdon et al: The Ageing Brain: Age-dependent changes in the electroencephalogram during propofol and sevoflurane general anaesthesia
Brown et al: General Anesthesia and Altered States of Arousal: A Systems Neuroscience Analysis. Annu. Rev. Neurosci. 2011.
Brown et al: General Anesthesia, Sleep, and Coma. NEJM. 2010.
Brown et al: Multimodal General Anesthesia: Theory and Practice. A&A 2018.
Purdon et al: Clinical Electroencephalography for Anesthesiologists. Part I: Background and Basic Signatures. Anesthesiology 2015.
Dental Anesthesia info:
Contacts:
Thomas Whitmer: thomas.whitmer.tw@gmail.com
Mana saraghi: msaraghi@gmail.com
References:
https://www.ada.org/en/ncrdscb/dental-specialties/specialty-definitions
http://www.ada.org/~/media/CODA/Files/anes.ashx
American Society of Dentist Anesthesiologists website: https://www.asdahq.org
Virtual tour https://www.youtube.com/watch?v=ZJ1Mo65ah4w&feature=youtu.be
I think there are some misconceptions about MAC value in this episode.
MAC is reffered as value for monoanesthesia with a volatile anesthetic, which is rare now, so I wouldn’t say it is wrong, but rather outdated for modern anesthesia practice, would you agree on that? Moreover, modern books (referring to Morgan) provide with MAC value for preventing movement in 95% of patients, but still as a monoanesthetic.
Still an amazing episode as usual, thank you for your work!
Thanks for the thoughts Dimitri. I think Dr. Brown’s point was that some people see 1 MAC as a goal and, at least for a sole anesthetic, that would mean 50% of patients would move. But your point that we rarely use single agent anesthesia is true, and that makes MAC hard to interpret. I think that’s why Dr. Brown prefers EEG monitoring.
The tutorial is quite fun and I would encourage everybody to give it a go (it takes a few hours, but you can get CME). Inferring mixed agents from the spectrograms I found tricky at first but after a bit of practice it is quite doable . It’s pretty amazing how well you can say : its propofol and there they gave some ketamine there, purely based on the spectrogram after a short amount of time!
We do not have spectral EEG monitoring in my current (non academic) hospital.But even from the EEG alone you can get quite a bit more info I have learned.
I always preferred to have the EEG showing when using a BIS monitor as I felt it’s easier to see depth of anaesthesia trends on the EEG earlier than the BIS number which frankly does a bad job at quick unanticipated emergence.
I think this is a very important part of anaesthesia practice as the goal is not to achieve a target MAC or TCI (there machines that can do a very good job of that), but to achieve adequate anaesthesia.
There are centres were they just do Sevo closed loop target MAC 1.6, Remi 0.5 mcg.kg.min and everybody got a norepi perfusor to get blood pressure back on target. I do not think that is a optimal strategy and reduces physiology to only blood pressure.
We all had cases that required copious amounts of everything . Likewise patients that respond profoundly to anaesthesia with a blood pressure drop while not actually adequately under, something that will show with a BIS but more effectively with EEG.