Optimal Sevoflurane Dosage for Intraoperative Localization of the Epileptogenic Zone
Abstract number :
2.441
Submission category :
9. Surgery / 9B. Pediatrics
Year :
2024
Submission ID :
714
Source :
www.aesnet.org
Presentation date :
12/8/2024 12:00:00 AM
Published date :
Authors :
Presenting Author: Hiroshi Uda, MD/PhD – Wayne State University
Naoto Kuroda, MD – Wayne State University
Ethan Firestone, MD-PhD Candidate – Wayne State University
Keisuke Hatano, MD/PhD – Wayne State University
Mio Maeda, MD Candidate – Kagoshima University
Tomoko Maehara, MD Candidate – Kagoshima University
Dominik Choromanski, MD – Children’s Hospital of Michigan
Michael Cools, MD – Children's Hospital of Michigan
Aimee F. Luat, MD – Central Michigan University
Eishi Asano, MD/PhD – Wayne State University
Rationale: We assessed dynamic changes in intraoperative intracranial EEG (iEEG) biomarkers under Sevoflurane anesthesia to determine the optimal dosage for localizing the epileptogenic zone in the operating room.
Methods: This retrospective observational study included 10 children (aged 6-16 years, including four girls) with drug-resistant epilepsy who achieved an ILAE class-1 outcome following focal resection after intraoperative and extraoperative iEEG recordings. Since all patients achieved postoperative seizure control, the seizure onset zone (SOZ) identified in the extraoperative recordings was used as a proxy for the epileptogenic zone. Our routine anesthesia procedures for intraoperative iEEG consist of maintaining Isoflurane levels at 1% or below, incrementally increasing Sevoflurane from 2% to 3%, and then to 4%. We analyzed iEEG biomarkers every 30 seconds during each three-minute period of the recordings under 2%, 3%, or 4% Sevoflurane anesthesia. Using open-source toolboxes, we quantified two iEEG biomarkers: the rate of high-frequency oscillation (HFO) at ≥80 Hz and the modulation index (MI), which quantifies the coupling strength between HFO and slow waves at 3-4 Hz. We employed a mixed model analysis for each 30-second iEEG epoch to determine differences in iEEG biomarker values between the SOZ and non-epileptic sites. Fixed effect predictor variables included SOZ, age, sex, number of anti-seizure medications, sampled lobe, and sampled hemisphere, with patient intercept as a random effect.
Results: We analyzed 92 SOZ artifact-free electrode sites and 517 non-epileptic artifact-free electrode sites. The mixed-model analysis indicated that HFO rates were higher in the SOZ than in non-epileptic sites (p< 0.001), specifically by 5.25 per minute (95% CI: 4.39 to 6.10) during 30-60 seconds after switching to 2% Sevoflurane, by 5.24 per minute (95% CI: 4.23 to 6.26) 90-120 seconds after switching to 3%, and by 5.17 per minute (95% CI: 3.81 to 6.52) 30-60 seconds after switching to 4%. MI values were also significantly higher (p< 0.001), specifically by 0.21 (95% CI: 0.16 to 0.26) during 150-180 seconds after switching to 2% Sevoflurane, 0.29 (95% CI: 0.22 to 0.37) during 150-180 seconds after switching to 3%, and 0.11 (95% CI: 0.05 to 0.17) during 150-180 seconds after switching to 4%.
Conclusions: Optimal localization of the epileptogenic zone by HFO rate and MI is achievable with 2-3% Sevoflurane anesthesia. Increasing the dosage to 4% may not enhance the diagnostic value of these iEEG biomarkers. Additionally, our results suggest that a dose increase of Sevoflurane rapidly activates HFO in the epileptogenic zone, whereas it augments the phase-amplitude coupling between HFO and slow waves more gradually.
Funding: NIH NS064033 (E.A.); JSPS JP22J23281 and JP22KJ0323 (N.K.).
Surgery