Letter to the Editor. Is the total propofol dose associated with false-positive motor evoked potentials?

AbstractFor high-risk spinal surgeries, intraoperative neurophysiological monitoring (IONM) is used to detect and prevent intraoperative neurological injury. The motor tracts are monitored by recording and analyzing muscle transcranial electrical stimulation motor evoked potentials (mTc-MEPs). A mTc-MEP amplitude decrease of 50–80% is the most common warning criterion for possible neurological injury. However, these warning criteria often result in false positive warnings. False positives may be caused by inadequate depth of anesthesia and blood pressure on mTc-MEP amplitudes. The aim of this paper is to validate the study protocol in which the goal is to investigate the effects of depth of anesthesia (part 1) and blood pressure (part 2) on mTc-MEPs. Per part, 25 patients will be included. In order to investigate the effects of depth of anesthesia, a processed electroencephalogram (pEEG) monitor will be used. At pEEG values of 30, 40 and 50, mTc-MEP measurements will be performed. To examine the effect of blood pressure on mTc-MEPs the mean arterial pressure will be elevated from 60 to 100 mmHg during which mTc-MEP measurements will be performed. We hypothesize that by understanding the effects of depth of anesthesia and blood pressure on mTc-MEPs, the mTc-MEP monitoring can be interpreted more reliably. This may contribute to fewer false positive warnings. By performing this study after induction and prior to incision, this protocol provides a unique opportunity to study the effects of depths of anesthesia and blood pressure on mTc-MEPs alone with as little confounders as possible.Trial registration number NL7772.

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Bilateral and Optimistic Warning Paradigms Improve the Predictive Power of Intraoperative Facial Motor Evoked Potentials during Vestibular Schwannoma Surgery

Cancers ◽

10.3390/cancers13246196 ◽

2021 ◽

Vol 13 (24) ◽

pp. 6196

Author(s):

Tobias Greve ◽

Liang Wang ◽

Sophie Katzendobler ◽

Lucas L. Geyer ◽

Christian Schichor ◽

...

Keyword(s):

Evoked Potentials ◽

Vestibular Schwannoma ◽

False Positive ◽

Motor Evoked Potentials ◽

False Positive Rate ◽

Tumor Resection ◽

Outcome Variable ◽

Facial Muscle ◽

Threshold Method ◽

Warning Criteria

Facial muscle corticobulbar motor evoked potentials (FMcoMEPs) are used to monitor facial nerve integrity during vestibular schwannoma resections to increase maximal safe tumor resection. Established warning criteria, based on ipsilateral amplitude reduction, have the limitation that the rate of false positive alarms is high, in part because FMcoMEP changes occur on both sides, e.g., due to brain shift or pneumocephalus. We retrospectively compared the predictive value of ipsilateral-only warning criteria and actual intraoperative warnings with a novel candidate warning criterion, based on “ipsilateral versus contralateral difference in relative stimulation threshold increase, from baseline to end of resection” (BilatMT ≥ 20%), combined with an optimistic approach in which a warning would be triggered only if all facial muscles on the affected side deteriorated. We included 60 patients who underwent resection of vestibular schwannoma. The outcome variable was postoperative facial muscle function. Retrospectively applying BilatMT, with the optimistic approach, was found to have a significantly better false positive rate, which was much lower (9% at day 90) than the traditionally used ipsilateral warning criteria (>20%) and was also lower than actual intraoperative warnings. This is the first report combining the threshold method with an optimistic approach in a bilateral multi-facial muscle setup. This method could substantially reduce the rate of false positive alarms in FMcoMEP monitoring.

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Letter to the Editor: Threshold criterion in transcranial motor evoked potentials

Journal of Neurosurgery ◽

10.3171/2016.11.jns162664 ◽

2017 ◽

Vol 126 (5) ◽

pp. 1744-1746

Author(s):

Jose L. Sanmillan ◽

Gerard Plans ◽

Andreu Gabarrós ◽

Isabel Fernández-Conejero

Keyword(s):

Evoked Potentials ◽

Motor Evoked Potentials ◽

Letter To The Editor ◽

Threshold Criterion ◽

Transcranial Motor Evoked Potentials

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Test occlusion under monitoring of motor-evoked potentials for a giant distal anterior cerebral artery aneurysm: letter to the editor

Acta Neurochirurgica ◽

10.1007/s00701-015-2570-x ◽

2015 ◽

Vol 157 (11) ◽

pp. 1841-1842 ◽

Cited By ~ 1

Author(s):

Kampei Shimizu ◽

Shoichi Tani ◽

Hirotoshi Imamura ◽

Nobuyuki Sakai

Keyword(s):

Evoked Potentials ◽

Cerebral Artery ◽

Anterior Cerebral Artery ◽

Motor Evoked Potentials ◽

Artery Aneurysm ◽

Letter To The Editor ◽

Anterior Cerebral Artery Aneurysm ◽

Distal Anterior Cerebral Artery ◽

Cerebral Artery Aneurysm

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Impact of total propofol dose during spinal surgery: anesthetic fade on transcranial motor evoked potentials

Journal of Neurosurgery Spine ◽

10.3171/2018.10.spine18322 ◽

2019 ◽

Vol 30 (5) ◽

pp. 705-713 ◽

Cited By ~ 2

Author(s):

Hiroki Ushirozako ◽

Go Yoshida ◽

Sho Kobayashi ◽

Tomohiko Hasegawa ◽

Yu Yamato ◽

...

Keyword(s):

Body Temperature ◽

Blood Loss ◽

Evoked Potentials ◽

False Positive ◽

Spinal Surgery ◽

Motor Evoked Potentials ◽

High Rate ◽

Team Approach ◽

Estimated Blood Loss ◽

Transcranial Motor Evoked Potentials

OBJECTIVEIntraoperative neuromonitoring may be valuable for predicting postoperative neurological complications, and transcranial motor evoked potentials (TcMEPs) are the most reliable monitoring modality with high sensitivity. One of the most frequent problems of TcMEP monitoring is the high rate of false-positive alerts, also called “anesthetic fade.” The purpose of this study was to clarify the risk factors for false-positive TcMEP alerts and to find ways to reduce false-positive rates.METHODSThe authors analyzed 703 patients who underwent TcMEP monitoring under total intravenous anesthesia during spinal surgery within a 7-year interval. They defined an alert point as final TcMEP amplitudes ≤ 30% of the baseline. Variations in body temperature (maximum − minimum body temperature during surgery) were measured. Patients with false-positive alerts were classified into 2 groups: a global group with alerts observed in 2 or more muscles of the upper and lower extremities, and a focal group with alerts observed in 1 muscle.RESULTSFalse-positive alerts occurred in 100 cases (14%), comprising 60 cases with global and 40 cases with focal alerts. Compared with the 545 true-negative cases, in the false-positive cases the patients had received a significantly higher total propofol dose (1915 mg vs 1380 mg; p < 0.001). In the false-positive cases with global alerts, the patients had also received a higher mean propofol dose than those with focal alerts (4.5 mg/kg/hr vs 4.2 mg/kg/hr; p = 0.087). The cutoff value of the total propofol dose for predicting false-positive alerts, with the best sensitivity and specificity, was 1550 mg. Multivariate logistic analysis revealed that a total propofol dose > 1550 mg (OR 4.583; 95% CI 2.785–7.539; p < 0.001), variation in body temperature (1°C difference; OR 1.691; 95% CI 1.060–2.465; p < 0.01), and estimated blood loss (500-ml difference; OR 1.309; 95% CI 1.155–1.484; p < 0.001) were independently associated with false-positive alerts.CONCLUSIONSIntraoperative total propofol dose > 1550 mg, larger variation in body temperature, and greater blood loss are independently associated with false-positive alerts during spinal surgery. The authors believe that these factors may contribute to the false-positive global alerts that characterize anesthetic fade. As it is necessary to consider multiple confounding factors to distinguish false-positive alerts from true-positive alerts, including variation in body temperature or ischemic condition, the authors argue the importance of a team approach that includes surgeons, anesthesiologists, and medical engineers.

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