Analgesic efficacy of surgeon placed paravertebral catheters compared with thoracic epidural analgesia after Ivor Lewis esophagectomy: a retrospective non-inferiority study.

Background: The Ivor Lewis esophagectomy is an operation that involves a laparotomy and a right thoracotomy, both of which are associated with severe postoperative pain and subsequent impairment of respiratory function. Currently, the accepted "gold standard" for postoperative analgesia for laparotomies and thoracotomies is the thoracic epidural. A systematic review has shown paravertebral blocks to be equivalent to epidural analgesia for post-thoracotomy pain control and have decreased incidence of nausea and vomiting, hypotension and respiratory depression. To our knowledge, the use of the paravertebral catheter (PVC) in open Ivor Lewis esophagectomy has not been formally studied. The primary outcome is the area under the curve (AUC) pain scores in the first 48 hours after surgery. Methods: We performed a retrospective chart review of the open Ivor Lewis esophagectomy patients at our local institution, with local research ethics board (REB) approval. Results: A total of 92 patients were included in this study: 43 patients had a PVC and 49 had a thoracic epidural for postoperative pan control. Overall, the PVC group was non-inferior and statistically equivalent to the epidural group. Time to ambulation in the PVC group was non-inferior compared to epidurals. The PVC group was superior when comparing total opioid consumption. Conclusions: Our retrospective study continues to challenge the role of epidurals as the gold standard of pain control post thoracotomy and laparotomy. Further prospective studies with a larger population are needed to better compare the two modalities.

Analyzing the value of IONM as a complex intervention: The gap between published evidence and clinical practice.

OBJECTIVE: Intraoperative neurophysiological monitoring (IONM) was investigated as a complex intervention (CI) as defined by the United Kingdom Medical Research Council (MRC) in published studies to identify challenges and solutions in estimating IONM's effects on postoperative outcomes. METHODS: A scoping review to April 2022 of the influence of setting on what was implemented as IONM and how it influenced postoperative outcomes was performed for studies that compared IONM to no IONM cohorts. IONM complexity was assessed with the iCAT_SR tool. Causal graphs were used to represent this complexity. RESULTS: IONM implementation depended on the surgical procedure, institution and/or surgeon. "How" IONM influenced neurologic outcomes was attributed to surgeon or institutional experience with the surgical procedure, surgeon or institutional experience with IONM, co-interventions in addition to IONM, models of IONM service delivery and individual characteristics of the IONM provider. Indirect effects of IONM mediated by extent of tumor resection, surgical approach, changes in operative procedure, shorter operative time, and duration of aneurysm clipping were also described. There were no quantitative estimates of the relative contribution of these indirect effects to total IONM effects on outcomes. CONCLUSIONS: IONM is a complex intervention whose evaluation is more challenging than that of a simple intervention. Its implementation and largely indirect effects depend on specific settings that are usefully represented in causal graphs. SIGNIFICANCE: IONM evaluation as a complex intervention aided by causal graphs and multivariable analysis could provide a valuable framework for future study design and assessments of IONM effectiveness in different settings.

Postoperative mortality risk prediction that incorporates intraoperative vital signs: development and internal validation in a historical cohort.

PURPOSE: Accurate risk reassessment after surgery is crucial for postoperative planning for monitoring and disposition. Existing postoperative mortality risk prediction models using preoperative features do not incorporate intraoperative hemodynamic derangements that may alter risk stratification. Intraoperative vital signs may provide an objective and readily available prognostic resource. Our primary objective was to derive and internally validate a logistic regression (LR) model by adding intraoperative features to established preoperative predictors to predict 30-day postoperative mortality. METHODS: Following Research Ethics Board approval, we analyzed a historical cohort that included patients aged ≥ 45 undergoing noncardiac surgery with an overnight stay at two tertiary hospitals (2013 to 2017). Features included intraoperative vital signs (blood pressure, heart rate, end-tidal carbon dioxide partial pressure, oxygen saturation, and temperature) by threshold and duration of exposure, as well as patient, surgical, and anesthetic factors. The cohort was divided temporally 75:25 into derivation and validation sets. We constructed a multivariable LR model with 30-day all-cause mortality as the outcome and evaluated performance metrics. RESULTS: There were 30,619 patients in the cohort (mean [standard deviation] age, 66 [11] yr; 50.2% female; 2.0% mortality). In the validation set, the primary LR model showed a c-statistic of 0.893 (99% confidence interval [CI], 0.853 to 0.927), a Nagelkerke R-squared of 0.269, a scaled Brier score of 0.082, and an area under precision-recall curve of 0.158 (baseline 0.017 for an uninformative model). The addition of intraoperative vital signs to preoperative factors minimally improved discrimination and calibration. CONCLUSION: We derived and internally validated a model that incorporated vital signs to improve risk stratification after surgery. Preoperative factors were strongly predictive of mortality risk, and intraoperative predictors only minimally improved discrimination. External and prospective validations are needed. STUDY REGISTRATION: www. CLINICALTRIALS: gov (NCT04014010); registered on 10 July 2019.

RéSUMé: OBJECTIF: Une réévaluation précise des risques après la chirurgie est cruciale pour la planification postopératoire du monitorage et du congé. Les modèles existants de prédiction du risque de mortalité postopératoire utilisant des caractéristiques préopératoires n'intègrent pas les perturbations hémodynamiques peropératoires, lesquelles pourraient modifier la stratification du risque. Les signes vitaux peropératoires peuvent fournir une ressource pronostique objective et facilement disponible. Notre objectif principal était de dériver et de valider en interne un modèle de régression logistique (RL) en ajoutant des caractéristiques peropératoires aux prédicteurs préopératoires établis pour prédire la mortalité postopératoire à 30 jours. MéTHODE: À la suite de l'approbation du Comité d'éthique de la recherche, nous avons analysé une cohorte historique qui comprenait des patients âgés de ≥ 45 ans bénéficiant d'une chirurgie non cardiaque avec un séjour d'une nuit dans deux hôpitaux tertiaires (2013 à 2017). Les caractéristiques comprenaient les signes vitaux peropératoires (tension artérielle, fréquence cardiaque, pression télé-expiratoire en CO2, saturation en oxygène et température) par seuil et durée d'exposition, ainsi que des facteurs propres au patient, chirurgicaux et anesthésiques. La cohorte a été divisée temporellement 75:25 en ensembles de dérivation et de validation. Nous avons élaboré un modèle de RL multivariée avec la mortalité toutes causes confondues à 30 jours comme critère, et évalué les mesures de performance. RéSULTATS: Il y avait 30 619 patients dans la cohorte (âge moyen [écart type], 66 [11] ans; 50,2 % de femmes; 2,0 % de mortalité). Dans l'ensemble de validation, le modèle de RL primaire a montré une statistique c de 0,893 (intervalle de confiance [IC] à 99 %, 0,853 à 0,927), un R carré de Nagelkerke de 0,269, un score de Brier mis à l'échelle de 0,082 et une aire sous la courbe de rappel et précision de 0,158 (ligne de base 0,017 pour un modèle non informatif). L'ajout de signes vitaux peropératoires aux facteurs préopératoires a amélioré de façon minimale la discrimination et l'étalonnage. CONCLUSION: Nous avons dérivé et validé en interne un modèle qui incorporait des signes vitaux pour améliorer la stratification des risques après la chirurgie. Les facteurs préopératoires étaient fortement prédictifs du risque de mortalité, et les prédicteurs peropératoires n'ont que que très peu amélioré la discrimination. Une validation externe et prospective est nécessaire. ENREGISTREMENT DE L'éTUDE: www.ClinicalTrials.gov (NCT04014010); enregistrée le 10 juillet 2019.

Neurophysiology during epilepsy surgery.

Intraoperative neuromonitoring (IONM) complements modern presurgical investigations by providing information about the epileptic focus as well as real-time identification of critical functional tissue and assessment of ongoing neural integrity during resective epilepsy surgery. This chapter summarizes current IONM methods for mapping the epileptic focus and for mapping and monitoring functionally important structures with direct brain stimulation and evoked potentials. These techniques include electrocorticography, computerized high-frequency oscillation mapping, single-pulse electric stimulation, cortical and subcortical motor evoked potentials, somatosensory evoked potentials, visual evoked potentials, and cortico-cortical evoked potentials. They may help to maximize epileptic tissue resection while avoiding permanent postoperative neurologic deficits.

Monitoring scoliosis and other spinal deformity surgeries.

Surgery to correct a spinal deformity incurs a risk of injury to the spinal cord and roots. Injuries include postoperative paraplegia. Surgery for cervical myelopathy also incurs risk for postoperative motor deficits, as well as nerve injury most commonly at the C5 root. Risks can be mitigated by monitoring the nervous system during surgery. Ideally, monitoring detects an impending injury in time to intervene and correct the impairment before it becomes permanent. Monitoring includes several modalities of testing. Somatosensory evoked potentials measure axonal conduction in the spinal cord posterior columns. This can be checked almost continuously during surgery. Motor evoked potentials measure conduction along the lateral corticospinal tracts. Because motor pathway stimulation often produces a patient movement on the table, these often are tested periodically rather than continuously. Electromyography observes for spontaneous discharges accompanying injuries, and is useful to assess misplacement of pedicle screws. Literature demonstrates the usefulness of these techniques, their association with reducing motor adverse outcomes, and the relative value of the techniques. Neurophysiologic monitoring for scoliosis, kyphosis, and cervical myelopathy surgery are addressed, along with background information about those conditions.

Intraoperative evoked potential techniques.

There are many recent advances in intraoperative evoked potential techniques for mapping and monitoring neural function during surgery. In particular, somatosensory evoked potential optimization speeds surgical feedback, motor evoked potentials provide selective motor system information, and new visual evoked potential methods promise reliable visual system monitoring. This chapter reviews these advances and provides a comprehensive background for understanding their context and importance.

Frailty for Perioperative Clinicians: A Narrative Review.

Frailty is a multidimensional syndrome characterized by decreased reserve and diminished resistance to stressors. People with frailty are vulnerable to stressors, and exposure to the stress of surgery is associated with increased risk of adverse outcomes and higher levels of resource use. As Western populations age rapidly, older people with frailty are presenting for surgery with increasing frequency. This means that anesthesiologists and other perioperative clinicians need to be familiar with frailty, its assessment, manifestations, and strategies for optimization. We present a narrative review of frailty aimed at perioperative clinicians. The review will familiarize readers with the concept of frailty, will discuss common and feasible approaches to frailty assessment before surgery, and will describe the relative and absolute associations of frailty with commonly measured adverse outcomes, including morbidity and mortality, as well as patient-centered and reported outcomes related to function, disability, and quality of life. A proposed approach to optimization before surgery is presented, which includes frailty assessment followed by recommendations for identification of underlying physical disability, malnutrition, cognitive dysfunction, and mental health diagnoses. Overall, 30%-50% of older patients presenting for major surgery will be living with frailty, which results in a more than 2-fold increase in risk of morbidity, mortality, and development of new patient-reported disability. The Clinical Frailty Scale appears to be the most feasible frailty instrument for use before surgery; however, evidence suggests that predictive accuracy does not differ significantly between frailty instruments such as the Fried Phenotype, Edmonton Frail Scale, and Frailty Index. Identification of physical dysfunction may allow for optimization via exercise prehabilitation, while nutritional supplementation could be considered with a positive screen for malnutrition. The Hospital Elder Life Program shows promise for delirium prevention, while individuals with mental health and or other psychosocial stressors may derive particular benefit from multidisciplinary care and preadmission discharge planning. Robust trials are still required to provide definitive evidence supporting these interventions and minimal data are available to guide management during the intra- and postoperative phases. Improving the care and outcomes of older people with frailty represents a key opportunity for anesthesiologists and perioperative scientists.

Optimal frequency of scans for patients on cancer therapies: A population kinetics assessment.

BACKGROUND: Optimal frequency of follow-up scans for patients receiving systemic therapies is poorly defined. Progression-free survival (PFS) generally follows first-order kinetics. We used exponential decay nonlinear regression analysis to calculate half-lives for 887 published PFS curves. METHOD: We used the Excel formula x = EXP(-tn *0.693/t1/2 ) to calculate proportion of residual patients remaining progression-free at different times, where tn is the interval in weeks between scans (eg, 6 weeks), * indicates multiplication, 0.693 is the natural logarithm of 2, and t1/2 is the PFS half-life in weeks. RESULTS: Proportion of residual patients predicted to remain progression-free at each subsequent scan varied with scan intervals and regimen PFS half-life. For example, with a 4-month half-life (17.3 weeks) and scans every 6 weeks, 21% of patients would progress by the first scan, 21% of the remaining patients would progress by the second scan at 12 weeks, etc With 2, 6- and 12-month half-lives (for example), the proportion of remaining patients progressing at each subsequent scan if repeated every 3 weeks would be 21%, 8% and 4%, respectively, while with scans every 12 weeks it would be 62%, 27% and 15%, respectively. Furthermore, optimal scan frequency can be calculated for populations comprised of distinct rapidly and slowly progressing subpopulations, as well as with convex curves arising from treatment breaks, where optimal scan frequency may differ during therapy administration vs during more rapid progression after therapy interruption. CONCLUSIONS: A population kinetics approach permits a regimen- and tumor-specific determination of optimal scan frequency for patients on systemic therapies.

Personalized perioperative medicine: a scoping review of personalized assessment and communication of risk before surgery.

BACKGROUND: Personalized medicine aims to improve outcomes through application of therapy directed by individualized risk profiles. Whether personalized risk assessment is routinely applied in practice is unclear; the impact of personalized preoperative risk prediction and communication on outcomes has not been synthesized. Our objective was to perform a scoping review to examine the extent, range, and nature of studies where personalized risk was evaluated preoperatively and communicated to the patient and/or healthcare professional. METHODS: A systematic search was developed, peer-reviewed, and applied to Embase, Medline, CINAHL, and Cochrane databases to identify studies of individuals having or considering surgery, where a process to assess personalized risk was applied and where these estimates were communicated to a patient and/or healthcare professional. All stages of the review were completed in duplicate. We narratively synthesized and described identified themes. RESULTS: We identified 796 studies; 24 underwent full-text review. Seven studies were included; one communicated personalized risk to patients, four to a healthcare professional, and two to both. Cardiac (n = 2) and orthopedic surgery (n = 2) were the most common surgical specialties. Four studies used electronic risk calculators, and three used paper-based tools. Personalized preoperative risk assessment and communication may improve accuracy of information provided to patients, improve consent processes, and influence length of stay. Methodologic weaknesses in study design were common. CONCLUSIONS: Personalized preoperative risk assessment and communication may improve patient and system outcomes. This evidence is limited, however, by weaknesses in study design. Appropriately powered, low risk of bias evaluation of personalized risk communication before surgery is needed.

Diagnostic Accuracy of Attenuation Difference and Iodine Concentration Thresholds at Rapid-Kilovoltage-Switching Dual-Energy CT for Detection of Enhancement in Renal Masses.

OBJECTIVE. The objective of our study was to evaluate iodine concentration and attenuation change in Hounsfield unit (ΔHU) thresholds to diagnose enhancement in renal masses at rapid-kilovoltage-switching dual-energy CT (DECT). MATERIALS AND METHODS. We evaluated 30 consecutive histologically confirmed solid renal masses (including nine papillary renal cell carcinomas [RCCs]) and 27 benign cysts (17 simple and 10 hemorrhagic or proteinaceous cysts) with DECT December 2016 and May 2018. A blinded radiologist measured iodine concentration (in milligrams per milliliter) and ΔHU (attenuation on enhanced CT - attenuation on unenhanced CT) using 70-keV corticomedullary (CM) phase virtual monochromatic and 120-kVp nephrographic (NG) phase images. The accuracies of previously described enhancement thresholds were compared by ROC curve analysis. RESULTS. An iodine concentration of ≥ 2.0 mg/mL and an iodine concentration of ≥ 1.2 mg/mL achieved sensitivity, specificity, and the area under the ROC curve (AUC) of 73.3%, 100.0%, and 0.87 and 86.7%, 100.0%, and 0.93, respectively. On 70-keV CM phase images, ΔHU ≥ 20 HU and ΔHU ≥ 15 HU yielded sensitivity, specificity, and AUC of 80.0%, 100.0%, and 0.90 and 90.0%, 100.0%, and 0.95, respectively. The numbers of incorrectly classified papillary RCCs were as follows: iodine concentration of ≥ 2.0 mg/mL, 77.8% (7/9; range, 0.7-1.6 mg/mL); iodine concentration of ≥ 1.2 mg/mL, 44.4% (4/9; range, 0.7-0.9 mg/mL); ΔHU ≥ 20 HU on 70-keV CM phase images, 66.7% (6/9; range, 4-17 HU); and ΔHU ≥ 15 HU on 70-keV DECT images, 33.3% (3/9; 4-12 HU). No cyst pseudoenhancement occurred on DECT. For 120-kVp NG phase DECT, ΔHU ≥ 20 HU and ΔHU ≥ 15 HU yielded sensitivity, specificity, and AUC of 93.3%, 96.3%, and 0.95 and 100.0%, 88.9%, and 0.94, respectively. With ΔHU ≥ 20 HU, 22.2% (2/9) (range, 15-18 HU) of papillary RCCs were misclassified and there was one pseudoenhancing cyst. With ΔHU ≥ 15 HU, no papillary RCCs were misclassified but 11.1% (3/27) of cysts showed pseudoenhancement. Only an iodine concentration of ≥ 2.0 mg/mL showed significantly lower accuracy than other measures (p = 0.031-0.045). CONCLUSION. DECT applied in the CM phase performed best using an iodine concentration of ≥ 1.2 mg/mL or a 70-keV ΔHU ≥ 15 HU; these parameters improved sensitivity for the detection of enhancement in renal masses without instances of cyst pseudoenhancement.

Correction to: Is the new ASNM intraoperative neuromonitoring supervision "guideline" a trustworthy guideline? A commentary.

The article Is the new ASNM intraoperative neuromonitoring supervision "guideline" a trustworthy guideline? A commentary, written by Stanley A. Skinner, Elif Ilgaz Aydinlar, Lawrence F. Borges, Bob S. Carter, Bradford L. Currier, Vedran Deletis, Charles Dong, John Paul Dormans, Gea Drost, Isabel Fernandez­Conejero, E. Matthew Hoffman, Robert N. Holdefer, Paulo Andre Teixeira Kimaid, Antoun Koht, Karl F. Kothbauer, David B. MacDonald, John J. McAuliffe III, David E. Morledge, Susan H. Morris, Jonathan Norton, Klaus Novak, Kyung Seok Park, Joseph H. Perra, Julian Prell, David M. Rippe, Francesco Sala, Daniel M. Schwartz, Martín J. Segura, Kathleen Seidel, Christoph Seubert, Mirela V. Simon, Francisco Soto, Jeffrey A. Strommen, Andrea Szelenyi, Armando Tello, Sedat Ulkatan, Javier Urriza and Marshall Wilkinson, was originally published electronically on the publisher's internet portal (currently SpringerLink) on 05 January 2019 without open access. With the author(s)' decision to opt for Open Choice the copyright of the article changed on 30 January 2019 to © The Author(s) 2019 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, duplication, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made. The original article has been corrected.

Attenuation and Degree of Enhancement With Conventional 120-kVp Polychromatic CT and 70-keV Monochromatic Rapid Kilovoltage-Switching Dual-Energy CT in Cystic and Solid Renal Masses.

OBJECTIVE: The purpose of this study was to compare attenuation values (in Hounsfield units) and degree of enhancement (attenuation change) in renal masses using 120-kVp polychromatic (conventional) CT and 70-keV monochromatic dual-energy CT (DECT). MATERIALS AND METHODS: Twenty-two patients with 39 renal masses (24 Bosniak category I and II cysts and 15 solid masses under active surveillance) underwent conventional CT (120-kVp unenhanced and contrast-enhanced CT) and rapid kilovoltage-switching DECT (120-kVp unenhanced CT and 70-keV contrast-enhanced CT). The mean (± SD) time between scans was 648 ± 943 days. A radiologist measured attenuation on matched image sets coregistered between examinations. Absolute attenuation and attenuation change were compared using independent t tests, Pearson correlation, and Bland-Altman analysis. RESULTS: There was no difference in attenuation on 120-kVp versus 70-keV contrast-enhanced CT images for cysts (9.5 ± 5.5 HU [range, -2 to 20 HU] vs 10.1 ± 4.6 HU [range, -2 to 16 HU]; p = 0.33) and solid masses (110.1 ± 72.9 HU [range, 35-267 HU] vs 119.1 ± 73.7 HU [range, 33-265 HU]; p = 0.04). There also was no difference in attenuation change for 120-kVp contrast-enhanced CT minus 120-kVp unenhanced CT (cysts, 3.5 ± 3.9 HU [range, -2 to 13 HU]; solid masses, 80.7 ± 73.3 HU [range, 9-227 HU]; p = 0.45) or for 70-keV contrast-enhanced CT minus 120-kVp unenhanced CT (cysts, 4.3 ± 4.1 HU [range, -3 to 12 HU]; solid masses, 89.8 ± 74.1 HU [range, 7-226 HU]; p = 0.04). The correlation was strong to almost perfect (ß = 0.83-0.98) with substantial agreement. There was no difference in attenuation of cysts and solid masses comparing 120-kVp acquisitions acquired at different time points (p = 0.20-0.92). The correlation was strong to almost perfect (ß = 0.72-0.95) with substantial agreement. CONCLUSION: There are no differences in absolute attenuation or degree of enhancement comparing 70-keV monochromatic CT to conventional 120-kVp CT in renal cysts and solid masses.

Intraoperative direct cortical stimulation motor evoked potentials: Stimulus parameter recommendations based on rheobase and chronaxie.

OBJECTIVE: To determine optimal interstimulus interval (ISI) and pulse duration (D) for direct cortical stimulation (DCS) motor evoked potentials (MEPs) based on rheobase and chronaxie derived with two techniques. METHODS: In 20 patients under propofol/remifentanil anesthesia, 5-pulse DCS thenar MEP rheobase and chronaxie with 2, 3, 4 and 5ms ISI were measured by linear regression of five charge thresholds at 0.05, 0.1, 0.2, 0.5 and 1msD, and estimated from two charge thresholds at 0.1 and 1msD using simple arithmetic. Optimal parameters were defined by minimum threshold energy: the ISI with lowest rheobase2×chronaxie, and D at its chronaxie. Near-optimal was defined as threshold energy <25% above minimum. RESULTS: The optimal ISI was 3 or 4 (n=7 each), 2 (n=4), or 5ms (n=2), but only 4ms was always either optimal or near-optimal. The optimal D was ∼0.2 (n=12), ∼0.1 (n=7) or ∼0.3ms (n=1). Two-point estimates closely approximated five-point measurements. CONCLUSIONS: Optimal ISI/D varies, with 4ms/0.2ms being most consistently optimal or near-optimal. Two-point estimation is sufficiently accurate. SIGNIFICANCE: The results endorse 4ms ISI and 0.2msD for general use. Two-point estimation could enable quick individual optimization.

Standardized computer-based organized reporting of EEG: SCORE - Second version.

Standardized terminology for computer-based assessment and reporting of EEG has been previously developed in Europe. The International Federation of Clinical Neurophysiology established a taskforce in 2013 to develop this further, and to reach international consensus. This work resulted in the second, revised version of SCORE (Standardized Computer-based Organized Reporting of EEG), which is presented in this paper. The revised terminology was implemented in a software package (SCORE EEG), which was tested in clinical practice on 12,160 EEG recordings. Standardized terms implemented in SCORE are used to report the features of clinical relevance, extracted while assessing the EEGs. Selection of the terms is context sensitive: initial choices determine the subsequently presented sets of additional choices. This process automatically generates a report and feeds these features into a database. In the end, the diagnostic significance is scored, using a standardized list of terms. SCORE has specific modules for scoring seizures (including seizure semiology and ictal EEG patterns), neonatal recordings (including features specific for this age group), and for Critical Care EEG Terminology. SCORE is a useful clinical tool, with potential impact on clinical care, quality assurance, data-sharing, research and education.

Overview on Criteria for MEP Monitoring.

Intraoperative motor evoked potentials include the D-wave as a surrogate for long-term motor outcome and muscle motor evoked potentials as a surrogate for early outcome. Their efficacy depends on excluding confounding factors and on warning criteria; insufficiently sensitive criteria could result in unpredicted deficits, whereas excessively sensitive ones could cause false alarms deterring surgical treatment and jading surgeons to alerts, eventually leading to deficits through failure to intervene. Although D-waves have few indications, they are nonsynaptic, linear, and stable-properties that support amplitude reduction criteria: >50% for intramedullary spinal cord tumor surgery and >30% to 40% for peri-Rolandic brain surgery. Muscle motor evoked potentials have many indications but are polysynaptic, nonlinear, and unstable-properties that challenge warning criteria and make them unusually capricious and sensitive. Disappearance is a remarkably frequent pathologic sign compared with other evoked potentials and is always a major criterion. Marked (>80%) amplitude reduction may be a minor or moderate spinal cord criterion, depending on the surgical circumstance. Modest (>50%) reduction may be a major criterion for brain, brainstem, and facial nerve monitoring, if justified by sufficient preceding stability. Acute ≥100-V threshold elevation may be a minor or moderate spinal cord criterion, depending on the surgical circumstance and on adherence to reported methodology. Morphology criteria lack support. Tailoring warning criteria to different monitoring situations based on anatomy, surgical goals, and published evidence seems advisable.