In today’s Pediatric Anesthesia Article of the Day, we will continue to present another article on the use of EEG monitoring to guide anesthetic vapor and propofol administration in the pediatric operating rooms. We have one more in the pipeline which will be posted in the next week or two. In that PAAD we will close the loop and discuss how one institution, the Children’s Hospital of Philadelphia, implemented this “new” monitoring technology into their clinical practice. So stayed tuned!
And one more favor. The new calendar year for residents, fellows, SRNAs, AA students, and new faculty and partners is now well underway. Please pass on the PAADs to them so they can join us and please also encourage them to join our parent sponsor, the Society for Pediatric Anesthesia. And of course, have them download the PediCrisis App v 2! Myron Yaster MD
Original observational article
Yuan I, Xu T, Skowno J, et al. Isoelectric Electroencephalography in Infants and Toddlers during Anesthesia for Surgery: An International Observational Study. Anesthesiology. Aug 1 2022;137(2):187-200. PMID: 35503999 1
“Electroencephalography (EEG) provides a noninvasive method to monitor changes in brain electrical activity that can reflect brain drug levels, as EEG waveforms change predictably with propofol and sevoflurane dose”.1, 2 Because there is no practical way to monitor the target effect site concentration (Ce) of anesthetics, under- or over-dosing may be common. Why should we care? “Increasing sevoflurane or propofol dose leads to an initial increase in EEG amplitude and progressively decreased frequency, until isoelectric EEG occurs where amplitude and frequency are close to zero, indicating an electrically inactive neocortex. In adults, isoelectric EEG has been associated with intraoperative hypotension, postoperative delirium, and poor outcomes”.3, 4 Whether this happens in children is not so clear and, in fact may not happen at all.5 Thus, the authors wondered what is the prevalence of isoelectric events in infants and children and does it have perioperative adverse effects?
This was a large multi-institutional and multi-national study (708 enrolled, 648 completed patients, approximately 50 from each of the 15 sites in USA, Europe, Australia, and China). Isoelectric events occurred in 32% of children under 3 years old, with higher occurrence in 0–3-month infants (59%) and large variation amongst the sites. Most isoelectric events occurred during pre-incision and surgical maintenance, particularly in the 0-3 month group. Most interestingly, isoelectric events occurred most commonly when a propofol bolus was given after a sevoflurane mask induction and was less likely if a neuromuscular blocking agents (NMBAs) was used. I (MY) found this incredible and supports one of my recurrent teaching themes: “if you live long enough, what was once truth, turns out to false, only to return to being truth, usually in a 10-20 year time period”. Having grown up in the era when NMBAs were always used for intubation and maintenance of anesthesia, then discarded with the introduction of propofol, I (MY) find it somewhat satisfying to learn that the use of NMBAs following a sevoflurane induction may come back as a safer and better method of providing anesthesia. But I digress.
Unlike in adults where isoelectric EEGs and post operative are bad (maybe deadly), does it matter in children? Intraoperatively, isoelectric EEGs, which essentially mean an over-anesthetized brain, were associated with hypotension and higher sevoflurane dose, particularly in the 0-3 month age group. It was not associated with emergence delirium behaviors or with significant differences in Pediatric Quality of Life scores up to 30 days after anesthesia and surgery although the study was not powered to examine this question. Interesting, Pediatric Quality of Life scores pre-operatively were lower in infants that had isoelectric EEG intraoperatively, suggesting a brain sensitivity to anesthesia associated with the surgical disease.
So, does isoelectric EEG matter? If we think intraoperative hypotension, particularly in the very young, is bad then absolutely. Is overdosing our patients with sevoflurane and/or propofol bad? Then yes, we are overdosing about a third of our patients. If we want to prevent over-dosing, then we have to use EEG to guide the dose in the individual patient. Vital signs and expired agent monitoring will not prevent over-dosing the brain. Should we reconsider the propofol bolus dose following a sevoflurane induction and switch to a NMBA? We think yes. When the autonomic response to surgery and surgical incision indicates light anesthesia and pain, the response should be to give opioids and other analgesics and not increase the doses of hypnotics.
Regardless, the use of EEG as a monitor of the depth of hypnosis (not anesthesia or analgesia) is going to change how we all practice anesthesia. Please send me (myasterster@gmail.com) your comments and thoughts.
References
1. Yuan I, Xu T, Skowno J, et al. Isoelectric Electroencephalography in Infants and Toddlers during Anesthesia for Surgery: An International Observational Study. Anesthesiology. Aug 1 2022;137(2):187-200. doi:10.1097/aln.0000000000004262
2. Purdon PL, Sampson A, Pavone KJ, Brown EN. Clinical Electroencephalography for Anesthesiologists: Part I: Background and Basic Signatures. Anesthesiology. Oct 2015;123(4):937-60. doi:10.1097/aln.0000000000000841
3. Shanker A, Abel JH, Schamberg G, Brown EN. Etiology of Burst Suppression EEG Patterns. Frontiers in psychology. 2021;12:673529. doi:10.3389/fpsyg.2021.673529
4. Fritz BA, Kalarickal PL, Maybrier HR, et al. Intraoperative Electroencephalogram Suppression Predicts Postoperative Delirium. Anesthesia and analgesia. Jan 2016;122(1):234-42. doi:10.1213/ane.0000000000000989
5. Koch S, Stegherr AM, Rupp L, et al. Emergence delirium in children is not related to intraoperative burst suppression - prospective, observational electrography study. BMC anesthesiology. Aug 8 2019;19(1):146. doi:10.1186/s12871-019-0819-2