Neuroanesthesia Guidelines for Optimizing Transcranial Motor Evoked Potential Neuromonitoring During Deformity and Complex Spinal Surgery: A Delphi Consensus Study

Remimazolam in neurosurgery

PURPOSE OF REVIEW

Remimazolam represents a novel intravenous anesthetic agent whose use began in 2020. As a new ultrashort-acting benzodiazepine, it has unique pharmacokinetic properties, such as remifentanil, designed to be active and easily transformed into inactive metabolites by tissue esterases. The purpose is to search the literature and evidences to use this new medication in neurosurgery.

RECENT FINDINGS

Currently, it is allowed for procedural sedation and general anesthesia in a few countries. More advantages of this new drug are predictable onset, short duration, rapid recovery profile, low liability for respiratory depression, cardiovascular depression, lack of injection pain, and known reversible agent, flumazenil. A literature search led to the conclusions that remimazolam may maintain better hemodynamic stability and reduce the episodes of hypotension during coil embolization of cerebral aneurysm and that general anesthesia with remimazolam does not alter cerebral metabolism, cerebral blood flow, and cerebral blood volume. Also, because it facilitates safe and quick arousal, it can be a suitable medication for awake craniotomy.

SUMMARY

With more desirable properties such as reduced risk of prolonged sedation and reliable safety margin, it is expected to increase the safety of sedation and general anesthesia in future.

Delphi-Based Survey for Surgical Indications in Biopsy Proven Active Adult Spinal Tuberculosis

STUDY DESIGN

Delphi survey.

OBJECTIVES

To obtain an expert consensus on various dilemmas in the surgical treatment of adult spinal tuberculosis (TB) patients.

METHODS

Stage I included a literature review, stage II the identification of 40 Key Opinion leaders (KOLs) and a set of 46 questions, stage III included analysis of 3 rounds of the Delphi survey, and stage IV had final analysis and recommendations. For each question, the level of agreement needed to reach a consensus was set at greater than or equal to 70.0%.

RESULTS

The first and second Delphi survey rounds received 62 and 58 responses, respectively, with 16 questions having more than 70% and two questions having 100% agreement in the first stage. The second stage saw a 70% agreement on six questions. Thus, a consensus was obtained on 22 questions. The recommendations that emerged were as follows: neurodeficit with corresponding radiology and neurological deficit appearing/deteriorating while on anti-tubercular chemotherapy(ATT) are absolute indications for surgery, duration of ATT before neurological deterioration need not be considered, epidural abscess does not need decompression unless concordant clinical neurological findings are present, pain not responding to medical management is not a surgical indication, active pulmonary TB, drug-resistant TB, and tubercular sacroiliitis are not considered as surgical indications, and hemoglobin and other health markers have little contribution to surgical indications.

CONCLUSION

In order to resolve several conundrums in the surgical treatment of adult spinal TB, this Delphi survey is the first to achieve a national consensus from spine experts. The final recommendations cover the serological, radiographic, and clinical aspects of spinal TB.

Co-administration of dexmedetomidine with total intravenous anaesthesia in carotid endarterectomy reduces requirements for propofol and improves haemodynamic stability: A single-centre, prospective, randomised controlled trial

BACKGROUND

Total intravenous anaesthesia guided by electroencephalography and neurophysiological monitoring may be used for carotid endarterectomy. Reduction of brain metabolic demand during cross-clamping of the internal carotid artery with propofol titrated to burst suppression requires effect-site concentrations that may delay emergence and interfere with intraoperative neurophysiological monitoring.

OBJECTIVE

To test the hypothesis that dexmedetomidine decreases the effect-site concentration of propofol required for burst-suppression in patients undergoing carotid endarterectomy.

DESIGN

Randomised controlled trial.

PARTICIPANTS

Patients undergoing carotid endarterectomy.

SETTING

University Hospital of Berne, Switzerland, from October 2018 to September 2024.

INTERVENTIONS

Patients were randomised into a control ( n  = 23) and a dexmedetomidine groups ( n  = 22). Total intravenous anaesthesia was administered to both groups. Patients in the dexmedetomidine group received an intravenous bolus of dexmedetomidine (0.4 μg kg -1 over 10 min) before induction, followed by a continuous intravenous infusion (0.4 μg kg -1  h -1 ). The effect-site concentrations of propofol were titrated against frontal electroencephalography parameters. Burst suppression was induced with propofol during cross-clamping of the internal carotid artery.

OUTCOME MEASURES

The primary outcome was the effect-site concentration of propofol required for burst-suppression. The secondary outcomes were the requirement for vasoactive substances, neurophysiological monitoring parameters, and postoperative delirium.

RESULTS

The effect-site concentration of propofol required for burst suppression was 4.0 μg ml -1 [3.50 to 4.90] (median [interquartile range]) in the dexmedetomidine group compared with 6.0 μg ml -1 [5.5 to 7.3] in the control group ( P  < 0.001). Less norepinephrine was required in the dexmedetomidine group (total 454 μg [246 to 818] compared with 1000 μg [444 to 1326] ( P  = 0.015) in the control group). Dexmedetomidine did not affect intraoperative neurophysiological monitoring.

CONCLUSION

Co-administration of dexmedetomidine to total intravenous anaesthesia for carotid endarterectomy decreased the effect-site concentrations of propofol required for burst suppression by 33%. The propofol-sparing effect and peripheral alpha-agonism of dexmedetomidine may explain the reduced requirement for vasopressors.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT04662177.

Sensitivity of intraoperative electrophysiological monitoring for scoliosis correction in identifying postoperative neurological deficits: a retrospective chart review of the Scoliosis Research Society morbidity and mortality database

BACKGROUND

Surgical intervention is the ultimate treatment for scoliosis, but iatrogenic spinal cord injury is one of the major concerns. Although intraoperative electrophysiological monitoring can aid in detecting and reducing postoperative neurological complications, its use is still controversial.

METHODS

A retrospective chart review of 6,577 scoliotic patients who underwent surgery for curve correction with a reported complication was conducted. Our dataset was sourced from the morbidity and mortality database of the Scoliosis Research Society spanning the period from 2013 to 2023. The sensitivity of intraoperative monitoring was evaluated.

RESULTS

Intraoperative monitoring was used in 60% of surgeries, while 26% of the reported complications in the study cohort were new postoperative neurologic deficits. The overall monitoring performance indicated a sensitivity of 45%. Neurogenic motor evoked potential showed the best outcomes among the individual monitoring methods. The highest sensitivity (60.4%) was achieved using four monitoring methods, demonstrating significantly better results than one, two, and three methods.

CONCLUSIONS

The monitoring practice benefits in distinguishing postoperative neurologic deficits within the scoliosis population. Employing four monitoring techniques yielded the most favourable outcomes.

Anesthesia and Pain Management for Scoliosis Surgery: A Narrative Review

STUDY DESIGN

This was a narrative review.

OBJECTIVE

The objective of this review was to summarize the current evidence and knowledge gaps regarding anesthesia and pain management for scoliosis surgery, including multimodal analgesia, and identify the best anesthetic approach to scoliosis surgery that ensures patient safety and pain relief even in the postoperative period, with minimal influence on SSEP monitoring.

SUMMARY OF BACKGROUND DATA

Spinal surgeries and fusions for scoliosis are associated with high pain levels. Inadequate analgesia can cause patient dissatisfaction, delay recovery, and increase the risk of chronic pain. Despite serious side effects, opioids are the mainstay of pain medication after scoliosis surgery. However, increasing emphasis on minimizing opioids and accelerating recovery has increased the adoption of multimodal analgesic therapy.

MATERIALS AND METHODS

The literature review was performed on standards of care, a pain management protocol, current therapeutic options, and innovative treatment options for patients undergoing scoliosis surgery. The literature was reviewed through 4 electronic databases: PubMed, Cochrane Library, Google Scholar, and Embase.

RESULTS

The initial search yielded 994 articles. Forty-seven relevant articles were selected based on relevance, recentness, search quality, and citations. Ten studies described the influence of different methods of anesthesia on neuromonitoring. Twenty-one researchers studied the effect of analgesics and coanalgesics on pain relief protocol. Nine studies treated regional anesthesia and its influence on pain management.

CONCLUSIONS

The most suitable anesthetic approach that does not disturb the neuromonitoring is obtained by combining total intravenous anesthesia (TIVA) with remifentanil and propofol with regional anesthesia, particularly erector spinae plane block (ESPB), as a part of a multimodal analgesia protocol.

LEVEL OF EVIDENCE

Level II.

Does an improvement in cord-level intraoperative neuromonitoring data lead to a reduced risk for postoperative neurologic deficit in spine deformity surgery?

PURPOSE

To determine if an improvement in cord-level intraoperative neuromonitoring (IONM) data following data loss results in a reduced risk for new postoperative motor deficit in pediatric and adult spinal deformity surgery.

METHODS

A consecutive series of 1106 patients underwent spine surgery from 2015 to 2023 by a single surgeon. Cord alerts were defined by Somatosensory-Evoked Potentials (SSEP; warning criteria: 10% increase in latency or > 50% loss in amplitude) and Motor-Evoked Potentials (MEP; warning criteria: 75% loss in amplitude without return to acceptable limits after stimulation up 100 V above baseline level). Timing of IONM loss and recovery, interventions, and baseline/postoperative day 1 (POD1) lower extremity motor scores were analyzed.

RESULTS

IONM Cord loss was noted in 4.8% (53/11,06) of patients and 34% (18/53) with cord alerts had a POD1 deficit compared to preoperative motor exam. MEP and SSEP loss attributed to 98.1% (52/53) and 39.6% (21/53) of cord alerts, respectively. Abnormal descending neurogenic-evoked potential (DNEP) was seen in 85.7% (12/14) and detected 91.7% (11/12) with POD1 deficit. Abnormal wake-up test (WUT) was seen in 38.5% (5/13) and detected 100% (5/5) with POD1 deficit. Most cord alerts occurred during a three-column osteotomy (N = 23/53, 43%); decompression (N = 12), compression (N = 7), exposure (N = 4), and rod placement (N = 14). Interventions were performed in all 53 patients with cord loss and included removing rods/less correction (N = 11), increasing mean arterial pressure alone (N = 10), and further decompression with three-column osteotomy (N = 9). After intervention, IONM data improved in 45(84.9%) patients (Full improvement: N = 28; Partial improvement: 17). For those with full and partial IONM improvement, the POD1 deficit was 10.7% (3/28) and 41.2% (7/17), respectively. For those without any IONM improvement (15.1%, 8/53), 100% (8/8) had a POD1 deficit, P < 0.001.

CONCLUSION

A full or partial improvement in IONM data loss after intraoperative intervention was significantly associated with a lower risk for POD1 deficit with an absolute risk reduction of 89.3% and 58.8%, respectively. All patients without IONM improvement had a POD1 neurologic deficit.

The Influence of Anesthesia on Neuromonitoring During Scoliosis Surgery: A Systematic Review

BACKGROUND

Intraoperative neuromonitoring (IONM) is crucial for the safety of scoliosis surgery, providing real-time feedback on the spinal cord and nerve function, primarily through motor-evoked potentials (MEPs). The choice of anesthesia plays a crucial role in influencing the quality and reliability of these neuromonitoring signals. This systematic review evaluates how different anesthetic techniques-total intravenous anesthesia (TIVA), volatile anesthetics, and regional anesthesia approaches such as Erector Spinae Plane Block (ESPB), spinal, and epidural anesthesia-affect IONM during scoliosis surgery.

METHODS

A systematic review was conducted following PRISMA guidelines. PubMed, MEDLINE, EMBASE, and Cochrane databases were searched for studies published between 2017 and 2024 that examined the impact of anesthetic techniques on neuromonitoring during scoliosis surgery. The focus was on studies reporting MEP outcomes, anesthetic protocols, and postoperative neurological and analgesic effects.

RESULTS

The search initially identified 998 articles. After applying inclusion criteria based on relevance, recency, methodological quality, and citation frequency, 45 studies were selected for detailed review.

CONCLUSION

The erector Spinae Plane Block (ESPB) provides distinct benefits over spinal and epidural anesthesia in scoliosis surgery, particularly in maintaining neuromonitoring accuracy, reducing hemodynamic instability, and minimizing complications. The ESPB's ability to deliver effective segmental analgesia without compromising motor function makes it a safer and more efficient option for postoperative pain management, enhancing patient outcomes.

Comparison of dexmedetomidine versus fentanyl-based total intravenous anesthesia technique on the requirement of propofol, brain relaxation, intracranial pressure, neuronal injury, and hemodynamic parameters in patients with acute traumatic subdural hematoma undergoing emergency craniotomy: A randomized controlled trial

BACKGROUND

Propofol is one of the most used intravenous anesthetic agents in traumatic brain injury (TBI) patients undergoing emergency neurosurgical procedures. Despite being efficacious, its administration is associated with dose-related adverse effects. The use of adjuvants along with propofol aids in limiting its consumption, thereby mitigating the side effects related to propofol usage. This study aims to compare the safety and efficacy of dexmedetomidine-propofol versus fentanyl-propofol-based total intravenous anesthesia (TIVA) in adult TBI patients.

METHODS

A hundred patients posted for emergency evacuation of acute subdural hematoma were enrolled, and they were randomized into two groups of 50 each. Propofol-based TIVA with a Schneider target-controlled infusion model was used for induction and maintenance. Patients in Group F received fentanyl, and those in Group D received dexmedetomidine infusions as adjuvants. Advanced hemodynamic parameters were monitored. Intracranial pressure (ICP) and brain relaxation were measured after dural opening. The mean propofol consumption, number of additional fentanyl boluses, and blood samples for S100b (a biomarker of neuronal injury) were also collected.

RESULTS

The mean propofol consumption in Group D (88.7 ± 31.8 μg/kg/min) was lower when compared to Group F (107.9 ± 34.6 μg/kg/min), (P = 0.005). The mean intraoperative fentanyl requirement and postoperative S100b were significantly reduced in Group D. Subdural ICPs and brain relaxation scores were comparable. Hemodynamic parameters were well maintained in both groups.

CONCLUSION

In TBI, dexmedetomidine as an adjunct to propofol-based TIVA results in a greater reduction in total propofol consumption and intraoperative opioid requirements while maintaining hemodynamic stability when compared to fentanyl.

Dexmedetomidine Versus Fentanyl in Intraoperative Neuromuscular Monitoring Using A Propofol-based Total Intravenous Anaesthesia Regimen in Spine Surgeries

Objective

This prospective, double-blind, randomized study aimed to compare the effects of dexmedetomidine and fentanyl on the latency and amplitude of transcranial motor evoked potentials (TcMEPs) under propofol-based total intravenous anaesthesia (TIVA) in spine surgery. Secondarily, intraoperative hemodynamics, total propofol consumption, recovery profile, and surgical field quality were compared.

Methods

TcMEP amplitude and latency recordings of bilateral abductor pollicis brevis and abductor hallucis muscles posted for elective lumbar spine surgery under TcMEP monitoring randomly divided into two study groups. Throughout the surgery, TIVA was administered using intravenous propofol (100-150 μg kg-1 min-1) and dexmedetomidine (0.5-0.7 μg kg-1 h-1) in group D and intravenous propofol (100-150 μg kg-1 min-1) and fentanyl (1 μg kg-1 h-1) in group F. TcMEPs were recorded at various time points during the surgery. Immediately after extubation recovery from anaesthesia was noted. Additionally, hemodynamic parameters, total propofol consumption, and surgical field quality were assessed.

Results

Latency and amplitude were comparable between the groups. Time to extubation was significantly longer in group D, but the mean (standard deviation) duration of stay in recovery was shorter in group D [47.55 (7.51) 95% confidence interval (CI) (44.863-50.237)] (P=0.046). Total propofol consumption was reduced in group D [220 (38) 95% CI (206.402-233.598)] (P=0.025) and surgical field condition was better in group D.

Conclusions

Dexmedetomidine and fentanyl do not have any effect on TcMEP amplitude and latency. However, dexmedetomidine provides the additional advantage of reduced total propofol consumption, shorter stay in recovery, and better surgical field quality.

Effect of Remimazolam on Transcranial Electrical Motor-evoked Potential in Spine Surgery: A Prospective, Preliminary, Dose-escalation Study

BACKGROUND

Some anesthetic drugs reduce the amplitude of transcranial electrical motor-evoked potentials (MEPs). Remimazolam, a new benzodiazepine, has been suggested to have little effect on MEP amplitude. This prospective, preliminary, dose-escalation study aimed to assess whether remimazolam is associated with lower MEP amplitude in a dose-dependent manner.

METHODS

Ten adult patients scheduled for posterior spinal fusion were included in this study. General anesthesia was induced with a continuous infusion of remifentanil and remimazolam. After the patient lost consciousness, the infusion rate of remimazolam was set to 1 mg/kg/h, and the patient underwent tracheal intubation. Baseline MEPs were recorded under 1 mg/kg/h of remimazolam in a prone position. Thereafter, the infusion rate of remimazolam was increased to 2 mg/kg/h, with a bolus of 0.1 mg/kg. Ten minutes after the increment, the evoked potentials were then recorded again. The primary endpoint was the MEP amplitude recorded in the left gastrocnemius muscle at 2 time points.

RESULTS

There was no difference in MEP amplitude recorded from the left gastrocnemius muscle before and after increasing remimazolam (median [interquartile range]: 0.93 [0.65 to 1.25] mV and 0.70 [0.43 to 1.26] mV, respectively; P=0.08). The average time from the cessation of remimazolam administration to neurological examination after surgery was 4 minutes using flumazenil.

CONCLUSIONS

This preliminary study suggests that increasing remimazolam from 1 to 2 mg/kg/h might have an insignificant effect on transcranial electric MEPs.

Effect of remimazolam versus propofol anesthesia on postoperative delirium in neurovascular surgery: study protocol for a randomized controlled, non-inferiority trial

BACKGROUND

Remimazolam is a short-acting benzodiazepine newly approved for the induction and maintenance of general anesthesia. Remimazolam emerges as an ideal drug for the neurosurgical population due to its rapid emergence, enabling early neurological assessment, and its ability to maintain perfusion pressure, which is crucial for preventing cerebral ischemia. However, the use of benzodiazepine has been associated with an increased risk of postoperative delirium (POD). There is currently limited evidence about the relationship between remimazolam-based total intravenous anesthesia (TIVA) and POD.

METHODS

In this double-blind, randomized, non-inferiority trial, we plan to include 696 adult patients with American Society of Anesthesiologists physical status class I to III, undergoing elective neurovascular surgery under general anesthesia. After informed consent, the patients will be randomized to receive either remimazolam or propofol-based TIVA with a 1:1 ratio. The primary outcome is the incidence of POD within 5 days after surgery. Secondary outcomes include subtypes, number of positive assessments and severity of POD, emergence agitation, intraoperative awareness and undesirable patient movement, intraoperative hypotension, and postoperative cognitive function. The data will be analyzed in modified intention to treat.

DISCUSSION

This trial will evaluate the effect of remimazolam on the development of POD compared to propofol anesthesia. The results of this trial will provide evidence regarding the choice of optimal anesthetics to minimize the risk of POD in neurosurgical patients.

TRIAL REGISTRATION

The study protocol was prospectively registered at the Clinical trials ( https://clinicaltrials.gov , NCT06115031, principal investigator: Jiseon Jeong; date of first registration: November 2, 2023, before the recruitment of the first participant.

Second-degree atrioventricular block induced by electrical stimulation of transcranial motor-evoked potential: a case report

BACKGROUND

Although several complications of transcranial motor-evoked potentials (Tc-MEPs) have been reported, reports of arrhythmias during Tc-MEP are very rare.

CASE PRESENTATION

A 71-year-old woman underwent transforaminal lumbar interbody fusion under general anesthesia, with intraoperative Tc-MEP monitoring. Preoperative electrocardiography showed an incomplete right bundle branch block but no cardiovascular events in her life. After induction of anesthesia, Tc-MEP was recorded prior to the surgery. During the Tc-MEP monitoring, electrocardiography and arterial blood pressure showed a second-degree atrioventricular block, but it improved rapidly at the end of the stimulation, and the patient was hemodynamically stable. Tc-MEP was recorded seven times during surgery; the incidence of P waves without QRS complexes was significantly higher than before stimulation. The surgery was uneventful, and she was discharged eight days postoperatively without complications.

CONCLUSIONS

Our case suggests that electrical stimulation for Tc-MEP can cause arrhythmia. Electrocardiography and blood pressure must be closely monitored during Tc-MEP monitoring.

Descending Neurogenic Evoked Potentials Monitoring Is an Effective Alternative in Spinal Deformity Surgery Under Inhaled Anesthesia

BACKGROUND

To evaluate the reliability of descending neurogenic evoked potentials (DNEP) monitoring in spinal deformity surgery under inhaled anesthesia.

METHODS

A total of 180 consecutive patients who underwent spinal deformity surgery in our scoliosis center from July 2014 to August 2016 were reviewed. Intraoperative monitoring including somatosensory evoked potentials (SEP), motor evoked potentials (MEP), and DNEP was conducted routinely throughout operation. Patients were divided into 2 groups according to anesthesia methods: group A (n = 72, inhaled anesthesia, SEP/DNEP) and group B (n = 108, total intravenous anesthesia, SEP/MEP/DNEP). Intraoperative monitoring data were collected and analyzed.

RESULTS

Positive alerts were observed in 26 patients (14.5%), of whom 18 (10%) were confirmed as true-positive events in the study population. No false-negative events were recorded. In group A, the sensitivity and specificity of SEP and DNEP were 100% and 93.8% and 100% and 98.5%, respectively. For group B, the sensitivity and specificity of SEP/MEP and DNEP were 100% and 95.9% and 100% and 98%, respectively.

CONCLUSIONS

DNEP monitoring seemed to be effective for the detection and prevention of iatrogenic neurologic deficits during spinal deformity surgery. This study indicates that DNEP was an effective alternative in spinal deformity surgery under inhaled anesthesia.

The effects of dexmedetomidine on intraoperative neurophysiologic monitoring modalities during corrective scoliosis surgery in pediatric patients: A systematic review

BACKGROUND

During scoliosis surgery, motor evoked potentials (MEP), and somatosensory evoked potentials (SSEP) have been reported to be affected by the use of higher doses of anesthetic agents. Dexmedetomidine, a sympatholytic agent, an alpha-2 receptor agonist, has been used as an adjunctive agent to lower anesthetic dose. However, there is conflicting evidence regarding the effects of dexmedetomidine on the intraoperative neurophysiological monitoring of MEP and SSEP during surgery, particularly among pediatric patients.

OBJECTIVES

This systematic review aimed to determine whether, during spinal fusion surgery in pediatric patients with scoliosis, dexmedetomidine alters MEP amplitude or SSEP latency and amplitude and, if so, whether different doses of dexmedetomidine display different effects (PROSPERO registration number CRD42022300562).

METHODS

We searched PubMed, Scopus, and Cochrane Library on January 1, 2022 and included randomized controlled trials, observational cohort and case-control studies and case series investigating dexmedetomidine in the population of interest and comparing against a standardized anesthesia regimen without dexmedetomidine or comparing multiple doses of dexmedetomidine. Animal and in vitro studies and conference abstracts were excluded.

RESULTS

We found substantial heterogeneity in the risk of bias (per Cochrane-preferred tools) of the included articles (n = 5); results are summarized without meta-analysis. Articles with the lowest risk of bias indicated that dexmedetomidine was associated with MEP loss and that higher doses of dexmedetomidine increased risk. In contrast, articles reporting no association between dexmedetomidine and MEP loss suffered from higher risk of bias, including suspected or confirmed problems with confounding, outcome measurement, participant selection, results reporting, and lack of statistical transparency and power.

CONCLUSION

Given the limitations of the studies available in the literature, it would be advisable to conduct rigorous randomized controlled trials with larger sample sizes to assess the effects of dexmedetomidine use of in scoliosis surgery in pediatric patients.

Effect of intraoperative muscle relaxation reversal on the success rate of motor evoked potential recording in patients undergoing spinal surgery: a randomized controlled trial

BACKGROUND

Partial neuromuscular blockade (NMB) has been applied for some surgeries to reduce bleeding and prevent patient movement for spinal surgery. Sugammadex selectively binds to rocuronium in the plasma and consequently lowers the rocuronium concentration at the neuromuscular junction. In this study, we aimed to observe whether the success rate of transcranial motor-evoked potential (TceMEP) can be increased by sugammadex compared with partial NMB during spinal surgery.

METHODS

Patients who underwent elective spinal surgery with TceMEP monitoring were randomly assigned to the sugammadex group and control group. Rocuronium was continuously infused to maintain the train of four counts (TOFc) = 2. The sugammadex group discontinued rocuronium infusion at the time of TceMEP monitoring and was infused with 2 mg/kg sugammadex; the control group was infused with the same dose of saline.

RESULTS

A total of 171 patients were included. The success rate of TceMEP monitoring in the sugammadex group was significantly higher than that in the control group. TceMEP amplitudes were greater in the sugammadex group than in the control group at 5 min, 10 min, and 20 min after the start of motor-evoked potential monitoring. The latencies of upper extremity TceMEPs monitoring showed no difference between groups. TOF ratios were greater in the sugammadex group at 5 min, 10 min, and 20 min after the start of motor-evoked potential monitoring. There were no adverse effects caused by sugammadex.

CONCLUSIONS

Sugammadex can improve the success rate of motor-evoked potential monitoring compared with moderate neuromuscular blockade induced by continuous infusion of rocuronium in spinal surgery.

TRIAL REGISTRATION

The study was registered on clinicaltrials.gov.cn on 29/10/2020 (trial registration number: NCT04608682).

Effect of Sugammadex During Transcranial Electrical Motor Evoked Potentials Monitoring in Spinal Surgery: A Randomized Controlled Trial

INTRODUCTION

Neuromuscular blockade suppresses transcranial electrical motor evoked potential (TceMEP) amplitude and is usually avoided during TceMEP monitoring. In this randomized controlled trial, we investigated whether rocuronium-induced suppression of TceMEP amplitude could be reversed by sugammadex in patients undergoing spine surgery.

METHODS

Seventy-six patients undergoing spinal surgery were randomly allocated into sugammadex and control groups. In the sugammadex group, a rocuronium infusion was titrated to maintain moderate neuromuscular blockade (2 twitches on train-of-four) until dural opening when the rocuronium infusion was discontinued and 2 mg/kg sugammadex administered. In the control group, no neuromuscular blockade was administered after induction of anesthesia. The primary outcome was a comparison between sugammadex and control groups of mean TceMEP amplitudes in the abductor pollicis brevis muscles of both upper extremities 5 minutes after dural. Secondary outcomes included TceMEP amplitudes at 10, 20, 30, and 60 minutes after dural opening.

RESULTS

Sixty-six patients were included in the analysis. TceMEP amplitudes were significantly greater in the sugammadex group (629 μV, interquartile range: 987 μV) than in the control group (502 μV, interquartile range: 577 μV; P =0.033) at 5 minutes after dural opening. TceMEP amplitudes were also greater in the sugammadex group at 10 minutes ( P =0.0010), 20 minutes ( P =0.003), 30 minutes ( P =0.001), and 60 minutes ( P =0.003) after dural opening.

CONCLUSIONS

Moderate neuromuscular blockade induced by continuous infusion of rocuronium was effectively reversed by sugammadex. This suggests that sugammadex could be used to enhance TceMEP waveform monitoring during spine surgery requiring muscle relaxation.

Comparison of Dexmedetomidine Versus Fentanyl-Based Anesthetic Protocols Under Patient State Index Guidance in Patients Undergoing Elective Neurosurgical Procedures with Intraoperative Neurophysiological Monitoring

Objectives The study was designed to elucidate the effects of dexmedetomidine as an anesthetic adjunct to propofol in total intravenous anesthesia (TIVA) on anesthetic dose reduction, the quality of intraoperative neurophysiological monitoring (IONM) recordings, analgesic requirements, and recovery parameters in patients undergoing neurosurgical procedures with neurophysiological monitoring. Methods A total of 54 patients for elective neurosurgical procedures with IONM were randomized to group D (dexmedetomidine) and group F (fentanyl). A loading dose of the study drug of 1µg/kg followed by 0.5 µg/kg/h infusion was used in two groups. Propofol-based TIVA with a Schneider target-controlled infusion model was used for induction and maintenance with effect site concentration of 4-5 and 2.5-4 µg/mL, respectively, titrated to a Patient State Index (PSI) of 25-40. Baseline IONM recordings were obtained after induction. The mean propofol consumption, number of patient movements, quality of IONM recordings, number of fentanyl boluses, hemodynamic characteristics, and recovery parameters were recorded. Results The mean propofol consumption was significantly lower in group D when compared to group F (101.4 ± 13.5 µg/kg/min vs 148.0 ± 29.8 µg/kg/min). Baseline IONM recordings were acquired in all patients without any difficulty. The two groups were comparable with respect to the number of additional boluses of fentanyl, patient movements, and recovery characteristics. Conclusion Dexmedetomidine as an adjuvant to propofol in TIVA reduces the requirement of the latter, without affecting the IONM recordings. The addition of dexmedetomidine also ensures stable hemodynamics and decreases the requirement of opioids with similar recovery characteristics.

The intraoperative motor-evoked potential when propofol was changed to remimazolam during general anesthesia: a case series

Remimazolam is a short-acting benzodiazepine that was approved for clinical use in 2020. We report three patients who underwent surgery for cerebral and spinal cord tumors, in whom transcranial electrical stimulation-motor-evoked potential (TES-MEP) was successfully monitored under general anesthesia with remimazolam. During total intravenous anesthesia with propofol at a target concentration of 2.7 - 3.5 µg/mL and 0.1 - 0.35 µg/kg/min of remifentanil, delayed awakening, bradycardia, and hypotension during propofol anesthesia were expected in all three cases. With patient safety as the top priority, we considered changing the anesthetic agent. Propofol was replaced with remimazolam at a loading dose of 12 mg/kg/h for a few seconds (case 3), followed by 1 mg/kg/h for maintenance (cases 1-3). TES-MEP was recorded during propofol and remimazolam administration in all three patients. Amplitudes of TES-MEP during anesthesia with propofol and remimazolam were 461.5 ± 150 µV and 590.5 ± 100.9 µV, 1542 ± 127 µV and 1698 ± 211 µV, and 581.5 ± 91.3 µV and 634 ± 82.7 µV sequentially from Case 1. Our findings suggest that intraoperative TES-MEP could be measured when anesthesia was managed with remimazolam at 1 mg/kg/h.

Effects of dexmedetomidine on evoked potentials in spinal surgery under combined intravenous inhalation anesthesia: a randomized controlled trial

OBJECTIVE

We aimed to investigate the effects of different doses of dexmedetomidine (Dex) on evoked potentials in adult patients undergoing spinal surgery under intravenous anesthesia with low-concentration desflurane.

METHODS

Ninety patients were divided into three groups at random. To maintain anesthesia in the control group (group C), desflurane 0.3 MAC (minimal alveolar concentration), propofol, and remifentanil were administered. Dex (0.5 μg·kg^-1) was injected for 10 min as a loading dose in the low-dose Dex group (group DL), then adjusted to 0.2 μg·kg^-1·h^-1 until the operation was completed. Dex (1 μg·kg^-1) was injected for 10 min as a loading dose in the high-dose Dex group (group DH), then adjusted to 0.7 μg·kg^-1·h^-1 until the operation was completed. The additional medications were similar to those given to group C. The perioperative hemodynamics, body temperature, intraoperative drug dosages, fluid volume, urine volume, blood loss, the latency and amplitude of somatosensory evoked potentials (SEPs) at four different time points, the incidence of positive cases of SEPs and transcranial motor evoked potentials (tcMEPs), and perioperative adverse reactions were all recorded.

RESULTS

Data from 79 patients were analyzed. The MAP measured at points T2-T4 in group DH was higher than at corresponding points in group C (P < 0.05). The MAP at point T4 in group DL was higher than at corresponding points in group C (P < 0.05). The remifentanil dosage in group DH was significantly lower than in group C (P = 0.015). The fluid volume in group DL was significantly lower than in group C (P = 0.009). There were no significant differences among the three groups in the amplitude and latency of SEP at different time points, nor in the incidence of warning SEP signals. The incidence of positive tcMEP signals did not differ significantly between groups C and DL (P > 0.05), but was significantly higher in group DH than in groups DL (P < 0.05) or C (P < 0.05). The incidence of intraoperative hypertension was significantly higher in group DH than in group C (P = 0.017).

CONCLUSIONS

Low-dose Dex has no effect on the SEPs and tcMEPs monitoring during spinal surgery. High-dose Dex has no effect on SEPs monitoring, but it may increase the rate of false positive tcMEPs signals and the incidence of intraoperative hypertension.

TRIAL REGISTRATION

This study has completed the registration of the Chinese Clinical Trial Center at 11/09/2020 with the registration number ChiCTR2000038154.

Developing consensus for the management of pediatric cervical spine disorders and stabilization: a modified Delphi study

OBJECTIVE

Cervical spine disorders in children are relatively uncommon; therefore, paradigms for surgical and nonsurgical clinical management are not well established. The purpose of this study was to bring together an international, multidisciplinary group of pediatric cervical spine experts to build consensus via a modified Delphi approach regarding the clinical management of children with cervical spine disorders and those undergoing cervical spine stabilization surgery.

METHODS

A modified Delphi method was used to identify consensus statements for the management of children with cervical spine disorders requiring stabilization. A survey of current practices, supplemented by a literature review, was electronically distributed to 17 neurosurgeons and orthopedic surgeons experienced with the clinical management of pediatric cervical spine disorders. Subsequently, 52 summary statements were formulated and distributed to the group. Statements that reached near consensus or that were of particular interest were then discussed during an in-person meeting to attain further consensus. Consensus was defined as ≥ 80% agreement on a 4-point Likert scale (strongly agree, agree, disagree, strongly disagree).

RESULTS

Forty-five consensus-driven statements were identified, with all participants willing to incorporate them into their practice. For children with cervical spine disorders and/or stabilization, consensus statements were divided into the following categories: A) preoperative planning (12 statements); B) radiographic thresholds of instability (4); C) intraoperative/perioperative management (15); D) postoperative care (11); and E) nonoperative management (3). Several important statements reaching consensus included the following recommendations: 1) to obtain pre-positioning baseline signals with intraoperative neuromonitoring; 2) to use rigid instrumentation when technically feasible; 3) to provide postoperative external immobilization for 6-12 weeks with a rigid cervical collar rather than halo vest immobilization; and 4) to continue clinical postoperative follow-up at least until anatomical cervical spine maturity was reached. In addition, preoperative radiographic thresholds for instability that reached consensus included the following: 1) translational motion ≥ 5 mm at C1-2 (excluding patients with Down syndrome) or ≥ 4 mm in the subaxial spine; 2) dynamic angulation in the subaxial spine ≥ 10°; and 3) abnormal motion and T2 signal change on MRI seen at the same level.

CONCLUSIONS

In this study, the authors have demonstrated that a multidisciplinary, international group of pediatric cervical spine experts was able to reach consensus on 45 statements regarding the management of pediatric cervical spine disorders and stabilization. Further study is required to determine if implementation of these practices can lead to reduced complications and improved outcomes for children.

Effect of low-dose lidocaine on MEPs in patients undergoing intracranial tumor resection with propofol anesthesia: A randomized controlled trial

OBJECTIVE

To investigate the effect of low-dose lidocaine on motor evoked potentials (MEPs) in patients undergoing intracranial tumor resection with propofol anesthesia.

METHODS

Forty patients who underwent intracranial tumor resection and required MEP monitoring were selected. They were randomly divided into the lidocaine group (group L, n = 20) and the control group (group C, n = 20) by computer-generated randomization. All patients were given propofol anesthesia under the guidance of the bispectral index. In group L, 1 mg/kg of lidocaine was injected intravenously during anesthesia induction. Then, lidocaine was continuously pumped at a speed of 1 mg/kg/h until the operation started. Group C was given an equal volume of normal saline. Heart rate (HR), mean artery pressure (MAP), and bispectral index were recorded before anesthesia induction (T0), 2 minutes after tracheal intubation (T1), and 35 minutes (T2), and 50 minutes (T3) after anesthesia induction. The amplitude and latency of MEP at T2 and T3, the total dosage of propofol after anesthesia induction, and adverse events before T3 were recorded.

RESULTS

Compared with those in group C, HR and MAP were significantly decreased at T1 in group L. No significant differences were observed in HR and MAP at T0, T2, and T3 between group L and group C. The total dosage of propofol and the incidence of adverse events were significantly lower in group L than in group C before T3. There were no significant differences in the amplitude and latency of MEP between the 2 groups at each time point.

CONCLUSIONS

Low-dose lidocaine has no obvious effect on MEP in patients undergoing intracranial tumor resection. However, it increased hemodynamic stability, reduced propofol use, and decreased the incidence of adverse events.

Effect of intraoperative muscle relaxation reversal on the success rate of motor-evoked potential recording in patients undergoing spinal surgery: study protocol for a randomised controlled trial

INTRODUCTION

Transcranial motor-evoked potentials (TceMEPs) is conventionally performed without neuromuscular blockade (NMB) because of its potential interference with neuromuscular junction and signal interpretation. Sugammadex is the first highly selective antagonist that binds to rocuronium and can rapidly and effectively reverse NMB. This study aims to evaluate the success rate of intraoperative muscle relax reversal by sugammadex on intraoperative TceMEP recording.

METHODS AND ANALYSIS

We will conduct a single-centre randomised controlled study. In total, 162 patients undergoing thoracic or lumbar spinal surgery will be randomly divided into the sugammadex group or control group at a ratio of 1:1. Total intravenous anaesthesia by propofol and remifentanil will be performed in both groups. In the sugammadex group, patients will receive continuous infusion of rocuronium to produce a blockade maintained for at least two twitches in train-of-four, rocuronium infusion will be discontinued and 2 mg/kg sugammadex will be given while performing TceMEPs monitoring. In the control group, rocuronium infusion will be discontinued and the same volume of saline will be infused while performing TceMEPs monitoring. The primary aim of this study is to evaluate the success rate of TceMEPs recording between two groups.

ETHICS AND DISSEMINATION

The approval for the study was certificated by the Ethical Committee of Beijing Tiantan Hospital, Capital Medical University on, 16 July 2021 (KY2021-082-02). The study was registered on clincaltrials.gov on 25 October 2020. Our study might guide neuromuscular blockade plans in TceMEPs monitoring undergoing spinal surgery. The findings of the study will be published in peer-reviewed journals and will be presented at national or international conference.

TRIAL REGISTRATION NUMBER

NCT04608682.

A Loading Dose of Dexmedetomidine With Constant Infusion Inhibits Intraoperative Neuromonitoring During Thoracic Spinal Decompression Surgery: A Randomized Prospective Study

Background: The effect of a bolus dose of dexmedetomidine on intraoperative neuromonitoring (IONM) parameters during spinal surgeries has been variably reported and remains a debated topic. Methods: A randomized, double-blinded, placebo-controlled study was performed to assess the effect of dexmedetomidine (1 μg/kg in 10 min) followed by a constant infusion rate on IONM during thoracic spinal decompression surgery (TSDS). A total of 165 patients were enrolled and randomized into three groups. One group received propofol- and remifentanil-based total intravenous anesthesia (TIVA) (T group), one group received TIVA combined with dexmedetomidine at a constant infusion rate (0.5 μg kg-1 h-1) (D1 group), and one group received TIVA combined with dexmedetomidine delivered in a loading dose (1 μg kg-1 in 10 min) followed by a constant infusion rate (0.5 μg kg-1 h-1) (D2 group). The IONM data recorded before test drug administration was defined as the baseline value. We aimed at comparing the parameters of IONM. Results: In the D2 group, within-group analysis showed suppressive effects on IONM parameters compared with baseline value after a bolus dose of dexmedetomidine. Furthermore, the D2 group also showed inhibitory effects on IONM recordings compared with both the D1 group and the T group, including a statistically significant decrease in SSEP amplitude and MEP amplitude, and an increase in SSEP latency. No significance was found in IONM parameters between the T group and the D1 group. Conclusion: Dexmedetomidine delivered in a loading dose can significantly inhibit IONM parameters in TSDS. Special attention should be paid to the timing of a bolus dose of dexmedetomidine under IONM. However, dexmedetomidine delivered at a constant speed does not exert inhibitory effects on IONM data.

Application of Triggered EMG in the Intraoperative Neurophysiological Monitoring of Posterior Percutaneous Endoscopic Cervical Discectomy

OBJECTIVE

To describe the rationale and application of triggered EMG (T-EMG) in intraoperative neurophysiological monitoring, and to explore the efficacy and safety of posterior percutaneous endoscopic cervical discectomy (PPECD) in the treatment of cervical spondylotic radiculopathy (CSR) under multimodal intraoperative neurophysiological monitoring (IOM).

METHODS

This study was a retrospective cohort control study. The clinical data of 74 patients with single-segment CSR from June 2015 to August 2018 were analyzed retrospectively, of whom 35 underwent IOM-assisted PPECD with triggered EMG (T-EMG group), while 39 were subjected to IOM-assisted PPECD alone (IOM group). Operation time, hospital stay, and complications were recorded for both groups. The curative effect was evaluated according to the Visual Analog Scale (VAS) of neck and arm pain, Japanese Orthopaedic Association (JOA) score, and modified MacNab scale.

RESULTS

Operations were successful and all patients were followed up for at least 24 (average 31.77 ± 9.51) months with no patient lost to follow-up. No significant difference was found in preoperative baseline data between the T-EMG and the IOM group (P > 0.05). Also, no significant difference was found in the operation time between the T-EMG (108.29 ± 11.44 min) and the IOM (110.13 ± 12.70 min) (P > 0.05) group, but the difference in hospital stay (T-EMG: 5.66 ± 0.99 days; IOM: 7.10 ± 1.43 days) was statistically significant (P < 0.05). The VAS for the neck and upper limbs in the two groups at 1 month post-operation (T-EMG: 2.09 ± 1.07, 2.26 ± 0.92; IOM:2.18 ± 1.05, 2.31 ± 0.77) and the last follow-up (T-EMG: 0.83 ± 0.62, 0.86 ± 0.55; IOM: 0.90 ± 0.50, 0.87 ± 0.61) were significantly different from the preoperative scores (T-EMG: 6.14 ± 1.09, 7.17 ± 1.04; IOM: 6.18 ± 1.28, 7.15 ± 1.23) (P < 0.05). However, no significant difference was found between the two groups (P > 0.05). The 1-month postoperative JOA scores for the two groups (12.69 ± 0.76; 12.59 ± 0.82) and those at the last follow-up (14.60 ± 0.77; 14.36 ± 0.78) were significantly different from the preoperative scores (11.09 ± 0.98; 11.05 ± 0.89) (P < 0.05), but the difference between the two groups was not significant (P > 0.05). One patient in the T-EMG group developed a transient aggravation of symptoms on the first day after surgery. In the IOM group, three patients had intraoperative cerebrospinal fluid leakage, and symptoms of C5 nerve root paralysis were presented in four patients following surgery. Compared with the IOM group, the T-EMG group had fewer complications (1/35; 7/39, P < 0.05). At the last follow-up, the modified MacNab criteria were 91.43% (32/35) and 89.7% (35/39) for the T-EMG group and IOM group, respectively.

CONCLUSIONS

Triggered EMG prevents the occurrence of neurological complications, which not only aids PPECD for CSR treatment in achieving satisfactory results, but also reduces average hospital stay and complication rates.

Impact of inhalational anesthetic agents on the baseline monitorability of motor evoked potentials during spine surgery: a review of 22,755 cervical and lumbar procedures

BACKGROUND CONTEXT

During spine surgery, motor evoked potentials (MEPs) are often utilized to monitor both spinal cord function and spinal nerve root or plexus function. While there are reports evaluating the impact of anesthesia on the ability of MEPs to monitor spinal cord function, less is known about the impact of anesthesia on the ability of MEPs to monitor spinal nerve root and plexus function.

PURPOSE

To compare the baseline monitorability and amplitude of MEPs during cervical and lumbar procedures between two cohorts based on the maintenance anesthetic regimen: a total intravenous anesthesia (TIVA) versus a regimen balanced with volatile inhalational and intravenous agents.

STUDY DESIGN

Baseline MEP data from a total of 16,559 cervical and 6,196 lumbar extradural spine procedures utilizing multimodality intraoperative neuromonitoring (IONM) including MEPs between January 2017 and March 2020 were obtained from a multi-institutional database. Two cohorts for each region of spine surgery were delineated based on the anesthetic regimen: a TIVA cohort and a Balanced anesthesia cohort.

PATIENT SAMPLE

Age 18 and older. Fellowship support for 65,000 for year 2021.

OUTCOME MEASURES

Percent monitorability and amplitudes of baseline MEPs.

METHODS

The baseline monitorability of each muscle MEP was evaluated by the IONM team in real-time and recorded in the patient's electronic medical record. The relation between anesthetic regimen and baseline monitorability was estimated using mixed effects logistic regression, with distinct models for cervical and lumbar procedures. Subsets of cervical and lumbar procedures from each anesthesia cohort in which all MEPs were deemed monitorable were randomly selected and the average peak-to-trough amplitude of each muscle MEP was retrospectively measured. Mixed-effects linear regression models were estimated (one each for cervical and lumbar procedures) to assess possible differences in average amplitude associated with anesthesia regimen.

RESULTS

At the time of surgery, baseline MEPs were reported monitorable from all targeted muscles in 86.8% and 83.0% of cervical and lumbar procedures, respectively, for the TIVA cohort, but were reported monitorable in just 59.3% and 61.0% of cervical and lumbar procedures, respectively, in the Balanced cohort, yielding disparities of 27.5% and 22.0%, respectively. The model-adjusted monitorability disparity between cohorts for a given muscle MEP ranged from 0.2% to 16.6% but was smallest for distal intrinsic hand and foot muscle MEPs (0.2%-1.1%) and was largest for proximal muscle MEPs (deltoid: 10.8%, biceps brachii: 8.8%, triceps: 13.0%, quadriceps: 16.6%, gastrocnemius: 7.8%, and tibialis anterior: 3.7%) where the monitorability was significantly decreased in the Balanced cohort relative to the TIVA cohort (p<.0001). Relative to the TIVA cohort, the model-adjusted amplitude of an MEP in the Balanced cohort was smaller for all muscles measured, ranging from 27.5% to 78.0% smaller. Relative to the TIVA cohort, the model-adjusted amplitude of an MEP was significantly decreased (p<.01) in the Balanced cohort for the most proximal muscles (Percent smaller: deltoid: 74.3%, biceps: 78.0%, triceps: 54.9%, quadriceps: 54.8%).

CONCLUSIONS

TIVA is the preferred anesthetic regimen for optimizing MEP monitoring during spine surgery. Inhalational agents significantly decrease MEP monitorability and amplitudes for most muscles, and this effect is especially pronounced for proximal limb muscles such as the deltoid, biceps, triceps, and quadriceps.

Effects of desflurane and sevoflurane on somatosensory-evoked and motor-evoked potential monitoring during neurosurgery: a randomized controlled trial

Background

Better protection can be provided during neurosurgery due to the establishment of somatosensory-evoked potential (SEP) and motor-evoked potential (MEP) monitoring technologies. However, some studies have showed that inhaled halogenated anesthetics have a significant impact on neurophysiological monitoring.

Methods

A total of 40 consecutive patients undergoing neurosurgery were randomly assigned to two groups receiving inhaled anesthetics, either desflurane or sevoflurane. Multiples levels (concentrations of 0.3, 0.6 and 0.9) of anesthetics were administered at minimum alveolar concentration (MAC), and then the latencies and amplitudes of SEPs and MEPs were recorded.

Results

SEP and MEP signals were well preserved in patients who underwent neurosurgery under general anesthesia supplemented with desflurane or sevoflurane at concentrations of 0.3, 0.6 and 0.9 MAC. In each desflurane or sevoflurane group, the amplitudes of SEPs and MEPs decreased and the latencies of SEPs were prolonged significantly as the MAC increased (P < 0.05). The SEP latencies of both the upper and lower limbs in the desflurane group were significantly longer, and the SEP amplitudes were significantly lower than those in the sevoflurane group (P < 0.05). The MEP amplitudes in the desflurane group were significantly lower than those in the sevoflurane group (P < 0.05), only the amplitudes of the upper limbs at 0.3 MAC did not vary significantly.

Conclusions

SEPs and MEPs were inhibited in a dose-dependent manner by both desflurane and sevoflurane. At the same MAC concentration, desflurane appeared to have a stronger inhibitory effect than sevoflurane. All patients studied had normal neurological examination findings, hence, these results may not be applicable to patients with preexisting deficits.

Trial registration

The study registered on the Chinese Clinical Trial Registry (www.chictr.org.cn), Clinical Trials identifier ChiCTR2100045504 (18/04/2021).

Roadmap for Motor Evoked Potential (MEP) Monitoring for Patients Undergoing Lumbar and Lumbosacral Spinal Fusion Procedures

MEPs are recommended for patients undergoing lumbar and lumbosacral procedures in which intraoperative neuromonitoring (IONM) is being utilized. While electromyography (EMG) provides critical nerve root proximity information, spontaneous EMG discharges are relatively poor at reliably diagnosing spinal nerve root dysfunction. In contrast, research indicates that MEPs are both sensitive and specific in diagnosing evolving spinal nerve root dysfunction. There is conflicting evidence, however, and it must be emphasized that the value of adding MEPs is only realized when practices and techniques are optimized. The ideal anesthetic plan is an optimized total intravenous anesthetic (TIVA) regimen. Selection of appropriate anesthetics and dosing is important for optimizing baseline response amplitudes and promoting diagnostic confidence in analyzing signal changes. An adaptive set of alert criteria that account for baseline amplitude and morphology fluctuations should guide the determination of significant signal change. The therapeutic impact of accurate diagnostic information depends on the timeliness of diagnosis and intervention. Prior to the start of surgery, a plan to obtain MEPs at least once every 10 minutes during the active part of the procedure and after every significant surgical maneuver should be agreed upon, and the intervention plan should include but not be limited to possible removal of hardware and release of retraction or distractive forces. In summary, MEPs can improve monitoring of at-risk nerve root function, but the accuracy and therapeutic impact of such monitoring depend on perioperative planning and communication that optimize use of this modality.