Title: Can depth of anesthesia (DoA) monitors be used to predict intra-operative convulsions? Lessons learned from a Case Report using the Narcotrend® Monitor.

Authors: Berger-Estilita J, Vetter C, Kaiser H, Krejci V.
Department of Anesthesiology and Pain Therapy, Inselspital, Bern University Hospital,
University of Bern, Switzerland

Background: The Narcotrend ® (MonitorTechnik, Bad Bramstedt, Germany) is an EEG monitor designed to measure the DoA. Besides an arbitrary number of DoA it also displays raw and quantitative EEG for further clinical interpretation. 

Case report: We present the case of an ASA I, 30-year-old man undergoing craniotomy for glioblastoma resection under general anesthesia who suffered tonic-clonic seizures captured by intraoperative EEG (Narcotrend®). Eight to ten minutes before the seizure this device recorded a progressive increase of relative power in the Beta-wave range accompanied by a reduction of relative power in the Delta-wave range in a distinct pattern (Figure 1). These was no change in the propofol/remifentanil dosage before the seizure. This pattern was repeated before the second seizure, while on induction levels of Propofol and after the administration of Levetiracetam 1000mg IV. The patient had no previous history of seizures and following surgery no further seizures were recorded. Patient written consent was obtained.

Discussion: Intraoperative electroencephalographic seizures under general anesthesia are rare1,2 and our observation is the first to describe a “typical” EEG pattern on a DoA monitor. We also discuss the differential diagnosis for intraoperative seizures in patients undergoing large head tumour resection.

References: 
1. Burbridge MA, Jaffe RA, Doufas AG, Lopez JR. Intraoperative Tonic-Clonic Seizure Under General Anesthesia Captured by Electroencephalography: A Case Report. A&A Case Rep. 2017 Jul 1;9(1):9-12.
2. Van der Linde HJ, Van Deuren B, Somers Y, Teisman A, Drinkenburg WH, Gallacher DJ.
EEG in the FEAB model: measurement of electroencephalographical burst suppression and seizure liability in safety pharmacology. Pharmacol Toxicol Methods. 2011 Jan-Feb;63(1):96-101. 
3. Howe J, Lu X, Thompson Z, Peterson GW, Losey TE. Intraoperative seizures during craniotomy under general anesthesia. Seizure. 2016 May;38:23-5. 

Learning points: An attentive analysis of the EEG trends using the Narcotrend® display may be useful in anticipating convulsive activity during head tumour resection. 

04 / Can depth of anesthesia (DoA) monitors be used to predict intra-operative convulsions? Lessons learned from a case report using the Narcotrend® monitor.
