Influence of muscle relaxation on neuromonitoring of the recurrent laryngeal nerve during thyroid surgery

A study on the appropriate dose of rocuronium for intraoperative neuromonitoring in Da Vinci robot thyroid surgery: a randomized, double-blind, controlled trial

Background

This study was to explore the effect of different doses of rocuronium bromide on neuromonitoring during Da Vinci robot thyroid surgery.

Methods

This was a prospective, randomized, double-blind, controlled trial that included 189 patients who underwent Da Vinci robot thyroidectomy with intraoperative neuromonitoring(IONM). Patients were randomly divided into three groups and given three different doses of rocuronium (0.3mg/kg, 0.6mg/kg, 0.9mg/kg). Outcome measurements included IONM evoked potential, postoperative Voice Handicap Index-30(VHI-30), intraoperative body movement incidence rate, Cooper score, and hemodynamic changes during anesthesia induction.Results: The difference in IONM evoked potentials at various time points between the three groups was not statistically significant (P>0.05). The difference in Cooper scores and intraoperative body movement incidence rate between 0.6 and 0.9mg/kg groups was statistically significant compared with the 0.3mg/kg group (both P<0.001). There was no statistically significant difference in VHI-30 score and hemodynamic changes during anesthesia induction among the three groups (both P>0.05).

Conclusions

For patients undergoing Da Vinci robot thyroidectomy, a single dose of rocuronium at 0.6 and 0.9mg/kg during anesthesia induction can provide stable IONM evoked potential. Additionally, compared to 0.3 mg/kg, it can offer better tracheal intubation conditions and lower incidence of body movements during surgery. It is worth noting that the use of higher doses of rocuronium should be adjusted based on the duration of IONM and local practices.

Deep Neuromuscular Block for Endolaryngeal Surgery: A Systematic Review and Meta-Analysis

OBJECTIVES

To determine the safety and efficacy of deep neuromuscular block (NMB) for endolaryngeal surgery.

DATA SOURCES

PubMed, Web of Science, Cochrane Library, Ovid Medline, Embase, China National Knowledge Infrastructure, Wanfang, VIP databases, and trial registry database.

METHODS

Inclusion criteria followed the PICOS principles: Participants, adults undergoing endolaryngeal surgery; Intervention, deep NMB performed during the surgery; Control, no-deep NMB performed; Outcomes, primary outcome: the incidence of clinically acceptable surgical conditions.

SECONDARY OUTCOME

the incidence of intraoperative complications (including vocal fold movement and coughing) and total incidence of postoperative complications [including postoperative residual curarization (PORC), postoperative sore throat (POST), and postoperative nausea and vomiting (PONV)]. Study design, randomized controlled trials (RCTs). Duplicate publications, editorials, letters, abstracts, and reviews were excluded.

RESULTS

Four articles with 242 patients were identified for analysis. The results indicated that compared with no-deep NMB, deep NMB provides a higher incidence of clinically acceptable surgical conditions (98.36% vs. 76.67%; relative ratio [RR] = 1.29, 95% CI: 1.07-1.56), a lower incidence of intraoperative complications (10.83% versus 37.16%; RR = 0.32; 95% CI: 0.21-0.49) (lower incidence of vocal fold movement [1.85% vs. 34%; RR = 0.08, 95% CI: 0.02-0.41] and coughing [15.53% vs. 38.78%; RR = 0.42, 95% CI: 0.27-0.66]). There were no differences in the overall incidence of postoperative complications (RR = 2.10, 95% CI: 0.12-36.40).

CONCLUSIONS

Based on current published evidence, deep NMB provides better surgical conditions with a higher incidence of clinically acceptable surgical conditions and a lower incidence of intraoperative complications (lower incidence of vocal fold movement and coughing) without increasing the overall incidence of postoperative complications.

LEVEL OF EVIDENCE

1 Laryngoscope, 133:2055-2065, 2023.

The TOFr of 0.75 to 0.85 is the optimal timing for IONM during thyroid surgery: a prospective observational cohort study

BACKGROUD

Recurrent laryngeal nerve (RLN) injury is one of the serious complications of thyroid tumour surgery, surgical treatment of thyroid cancer requires careful consideration of the RLN and its impact on glottis function. There has been no unified standard for precise neuromuscular block monitoring to guide the monitoring of RLN in thyroid surgery. This study aimed to investigate the correlation between Train-of-four stabilization ratio (TOFr) and neural signal values of intraoperative neurophysiological monitoring (INOM) during thyroid operation, and further to determine the optimal timing for INOM during thyroid operation.

METHODS

Patients scheduled for thyroid tumour resection with INOM and RLN monitoring from April 2018 to July 2018 in our center were recruited. Electromyography (EMG) signals and corresponding TOFr were collected. All nerve stimulation data were included in group VR. Vagus nerve stimulation data were included in Subgroup V. RLN stimulation data were included in Subgroup R. The timing of recording was as follows: Vagus nerve EMG amplitude after opening the lateral space between the thyroid and carotid sheath and before the initiation of thyroid dissection, RLN EMG amplitude at first recognition, RLN EMG amplitude after complete thyroid dissection (Repeat three times), and Vagus nerve EMG amplitude after resection of the thyroid (Repeat three times). Correlation analysis of continuous variables was described by a scatter diagram. Pearson correlation analysis or Spearman correlation analysis was used for the two groups of variables.

RESULTS

Finally, 134 vagus nerve signals and 143 RLN signals were analysed after matching with TOFr. The EMG amplitude in the VR group and subgroups after nerve stimulation was positively correlated with TOFr (p < 0.05). In the VR, V and R group, the incidence of EMG ≥ 500 µV in the 0.75 < TOFr ≤ 0.85 interval was significantly higher than the 0 < TOFr ≤ 0.75 interval (P = 0.002, P = 0.013 and P = 0.029), and has no statistical difference compared to 0.85 < TOFr ≤ 0.95 interval (P > 0.05).

CONCLUSIONS

The EMG signals of the RLN and vagus nerve stimulation during thyroid surgery were positively correlated with TOFr. TOFr > 0.75 could reflect more than 50% of the effective nerve electrophysiological signals, 0.75 < TOFr ≤ 0.85 interval was the optimal timing for IONM during thyroid surgery.

TRIAL REGISTRATION

Chinese Clinical Trial Registry (ChiCTR1800015797) Registered on 20/04/2018. https://www.chictr.org.cn .

Monitoring surgery around the cranial nerves

Intraoperative neurophysiologic monitoring (IONM) of cranial nerve (CN) function is an essential component in multimodality monitoring of surgical procedures where CNs are at risk for injury. In most cases, IONM consists of localizing and mapping CNs and their pathways, and monitoring of CN motor function during surgery. However, CN VIII, which has no motor function, and is at risk for injury in many surgical procedures, can be easily and accurately monitored using brainstem auditory evoked potentials. For motor CNs, the literature is clear that function can be safely and adequately performed using basic electromyographic (EMG) techniques, such as recording of continuous EMG activity and electrically evoked compound muscle actions potentials. Newer techniques, such as corticobulbar motor evoked potentials and reflex studies, show good potential for a greater degree of functional assessment but require further study to determine their clinical utility. EMG remains the basic clinical neurophysiologic technique with the greatest clinical research supporting its utility in IONM of motor CN function and should be used as part of a comprehensive multimodality IONM protocol. Understanding the physiologic basis of EMG and the changes associated with altered motor function will allow the practitioner to alter surgical course to prevent injury and improve patient safety.

Optimization of Intraoperative Neural Monitoring of the Recurrent Laryngeal Nerve in Thyroid Surgery

The application of intraoperative neural monitoring (IONM) has been widely accepted to improve surgical outcomes after thyroid surgery. The malfunction of an IONM system might interfere with surgical procedures. Thus, the development of anesthesia modalities aimed at ensuring functional neuromonitoring is essential. Two key issues should be taken into consideration for anesthetic management. Firstly, most patients undergo recurrent laryngeal nerve monitoring via surface electrodes embedded in an endotracheal tube. Thus, advanced video-assisted devices might optimize surface electrode positioning for improved neuromonitoring signaling accuracy. Secondly, neuromuscular blocking agents are routinely used during thyroid surgery. The ideal neuromuscular block should be deep enough for surgical relaxation at excision and recovered enough for an adequate signal f nerve stimulation. Proper neuromuscular block management could be achieved by titration doses of muscle relaxants and reversal agents.

A Surgeon-Centered Neuromuscular Block Protocol Improving Intraoperative Neuromonitoring Outcome of Thyroid Surgery

BACKGROUND

Neuromuscular blocking agents provide muscular relaxation for tracheal intubation and surgery. However, the degree of neuromuscular block may disturb neuromuscular transmission and lead to weak electromyography during intraoperative neuromonitoring. This study aimed to investigate a surgeon-friendly neuromuscular block degree titrated sugammadex protocol to maintain both intraoperative neuromonitoring quality and surgical relaxation during thyroid surgery.

METHODS

A total of 116 patients were enrolled into two groups and underwent elective thyroid surgery with intraoperative neuromonitoring. All patients followed a standardized intraoperative neuromonitoring protocol with continuous neuromuscular transmission monitoring and received 0.6 mg/kg rocuronium for tracheal intubation. Patients were allocated into two groups according to the degree of neuromuscular block when the anterior surface of the thyroid gland was exposed. The neuromuscular block degree was assessed by the train-of-four (TOF) count and ratio. Patients in group I received sugammadex 0.25 mg/kg for non-deep neuromuscular block degree (TOF count = 1~4). Patients in group II were administered sugammadex 0.5 mg/kg for deep neuromuscular block degree (TOF count = 0). The quality of the intraoperative neuromonitoring was measured using the V₁ electromyography (EMG) amplitude. An amplitude less than 500 μV and greater than 500 μV was defined as weak and satisfactory, respectively.

RESULTS

The quality of the intraoperative neuromonitoring was not different between groups I and II (satisfactory/weak: 75/1 vs. 38/2, P = 0.14). The quality of surgical relaxation was acceptable after sugammadex injection and showed no difference between groups [55/76 (72.3%) in group I vs. 33/40 (82.5%) in group II, P = 0.23].

CONCLUSIONS

This surgeon-centered sugammadex protocol guided by neuromuscular block degree (0.5 mg/kg for deep block and 0.25 mg/kg for others) showed comparably high intraoperative neuromonitoring quality and adequate surgical relaxation. The results expanded the practicality of sugammadex for precise neuromuscular block management during monitored thyroidectomy.

Dosage effect of cisatracurium on intubation and intraoperative neuromonitoring during thyroidectomy: a randomized controlled trial

Background

Intraoperative neuromonitoring (IONM) reduces the risk of recurrent laryngeal nerve (RLN) injury during thyroid surgery. However, the use of neuromuscular blocking agents (NMBAs), which are essential to improve intubation conditions, may hinder the electromyographic response during IONM. The aim of this prospective, double-blind, randomized controlled trial was to explore the optimal dosage of cisatracurium to produce adequate muscle relaxation for tracheal intubation without significantly affecting evoked potentials of IONM during thyroidectomy.

Methods

Patients undergoing thyroidectomy with IONM in our institution, with an American Society of Anesthesiologists grade of I-II, aged 18-75 years, and with a body mass index below 32 kg/m² were enrolled and randomly assigned (by random numbers) to receive 1× (group C1) or 2× (group C2) the effective dose (ED₉₅) of cisatracurium for tracheal intubation. The patients, surgeons, and anesthesiologists in charge were blinded to group assignment. Anesthesia was induced with sufentanil, propofol, and cisatracurium (0.05 mg/kgin group C1, 0.1 mg/kg in group C2). Ease of intubation was evaluated with the intubation condition score (Cooper score) and the intubation difficulty scale (IDS). Amplitudes of evoked potentials during intermittent IONM were compared between groups. The primary outcomes were the Cooper score, the IDS score, and the evoked potentials of IONM.

Results

Fifty-three patients were randomized from October 2019 to November 2020, and 52 were analyzed (with 26 patients in each group). The Cooper score was significantly lower in group C1 [median, 8.0 (interquartile range, 7.0-8.3)] than in group C2 [9.0 (9.0-9.0), P<0.001]. The rate of difficult laryngoscopy without external laryngeal pressure was significantly higher in group C1 than in group C2 (61.5% vs. 11.5%, P<0.001). More patients in group C1 required assistance to complete tracheal intubation (16 vs. 4, P=0.001). The IDS score was significantly higher in group C1 [3.0 (0.0-4.0) vs. 1.0 (0.0-1.0), P=0.045]. There were no significant differences between groups in amplitudes of evoked potentials. No serious adverse events were observed.

Conclusions

A dose of 2× ED₉₅ of cisatracurium provided better intubation conditions and easier tracheal intubation than 1× ED₉₅, without disturbing IONM.

Trial Protocol

Chinese Clinical Trial Registry (No. ChiCTR1900022884).

Sinus pause during nerve integrity monitoring tube insertion following anesthetic induction with a low-dose neuromuscular blocking agent: A CARE-compliant case report

RATIONALE

Nerve integrity monitoring (NIM) tubes are commonly used in thyroid surgery to prevent recurrent laryngeal nerve injury. To achieve the optimal electromyographic signal for NIM as intraoperative neural monitoring (IONM), the neuromuscular blocking agent (NMBA) dose should be low. The use of a low-dose NMBA increases the anesthetic and analgesic agent dose required to attenuate the laryngeal reflex during intubation. In addition, since the NMBA onset time is delayed, depending on the situation, anesthesia may become excessively deep or shallow before intubation.

PATIENTS CONCERN

A 51-year-old woman scheduled for thyroid lobectomy received 0.3 mg/kg of rocuronium. Three minutes later, when the NIM tube was inserted through the vocal cord, the patient's heart rate (HR) was undetectable for 2 seconds.

DIAGNOSIS

We suspected that the use of a high-dose anesthetic agent and remifentanil or the laryngocardiac reflex induced the sinus pause.

INTERVENTIONS

To maintain the anesthetic depth, we administered 6 vol% of desflurane. Because the patient's systolic blood pressure was 70 mmHg and HR was 30 beats/min, we discontinued the remifentanil infusion and administered 8 mg of ephedrine.

OUTCOMES

The patient's vital signs recovered to normal levels. Subsequently, there were no episodes of bradycardia or arrhythmia.

CONCLUSION

Sinus pause or severe bradycardia may occur due to the laryngocardiac reflex or the administration of a high-dose anesthetic and analgesic agent during tracheal intubation in patients who received a low-dose NMBA for IONM induction using an NIM tube. Anesthesiologists should be aware of these risks and take precautions to maintain adequate anesthesia, be prepared to administer vasoactive drugs to increase the blood pressure and HR if needed, and, if possible, intravenously administer lidocaine to attenuate the laryngeal reflex during intubation.

Impact of rocuronium on intraoperative neuromonitoring vagal amplitudes during thyroidectomy

PURPOSE

Neuromuscular blocking agents (NMBA) facilitate endotracheal intubation and reduce related laryngeal morbidity. However, NMBA interfere with intraoperative neuromonitoring amplitudes during thyroidectomy. The goal of this study was to evaluate the impact of rocuronium used for tracheal intubation on early intraoperative neuromonitoring vagal amplitudes observed during first thyroid lobe dissection.

METHODS

This is an observational pharmacoepidemiological study with prospective data collection and retrospective analysis. During the study period, all consecutive patients who underwent thyroid surgery with neuromonitoring were included. Patients underwent endotracheal intubation either using a single dose of rocuronium (NMBA group) or without NMBA (NMBA-free group) according to the anesthesiologist's preference.

RESULTS

Six hundred six patients were included (213 NMBA and 393 NMBA-free group patients). At V1, 39 patients (18%) in the NMBA group had an amplitude < 100 µV (need for curarization reversal in 30 patients) and 13 patients (3.3%) in the NMBA-free group (p < 0.001). In the remaining 554 patients, the mean V1 amplitude was significantly decreased in the NMBA group (544 versus 685 µV; p < 0.001). After exclusion of 25 patients with loss of signal types 1 and 2 during dissection, the difference between mean V1 and mean V2 was significantly lower in NMBA group patients (- 22 versus - 86 µV; p = 0.016).

CONCLUSION

This study provides new data showing how NMBA used for tracheal intubation significantly decrease V1 amplitude baseline and modify amplitude variations from V1 to V2 values during the first thyroid lobe dissection.

LEVEL OF EVIDENCE

Pharmacoepidemiological study.

Lidocaine Infusion Improves the Functionality of Intraoperative Nerve Monitoring During Thyroid Surgery: A Prospective, Randomized, Double-Blinded Study

BACKGROUND

Intraoperative nerve monitoring (IONM) to assess the recurrent laryngeal nerve function during thyroid surgery is becoming the standard of care across many institutions. The successful deployment and data analysis from the IONM require complete laryngeal relaxation and reflex suppression. We investigated the role of intravenous lidocaine infusion (IVLI) to provide such operating conditions, under a lighter plane of anesthesia and fewer hemodynamic fluctuations.

METHODS

Sixty-five patients were randomly assigned to lidocaine group (LG) or placebo group (PG) based on the computer-generated coding developed by the pharmacy department. The study medication (SM) was delivered by the pharmacist in a pre-filled coded syringe to the investigator 30 min prior to the surgery. All the patients were anesthetized by narcotic and inhalation based general anesthesia. The SM was administered at the rate of 1.5mg/kg/h following a loading dose of 1 mg/kg. Dragonfly® laryngeal surface electrode and Nerveana® nerve locator system were used for IONM during surgery.

RESULTS

The proportion of patients requiring lower strength stimulating current (StMC) at 0.5 mA was significantly higher in the LG than in the PG (X2 (1, N = 61) = 10.1615, P = 0.001434). Similarly, the proportion of patients with the drop in the aggregate impedance level (DAIL) by < 50% at the end of surgery was significantly higher in the LG than in the PG (X2 (1, N = 61) = 15.982, P = 0.000064). In addition, the proportion of patients with the hypotensive episodes requiring rescue medications more than twice during surgery was significantly lower in the LG than in the PG (X2 (1, N = 61) = 0.0183, P < 0.05).

CONCLUSIONS

The enhanced laryngeal relaxation and the reflex suppression afforded by the IVLI could have enabled a lower StMC to elicit a positive signal. The lower StMC promotes less intense laryngeal alterations as evidenced by the lower DAIL in the LG. IVLI can enhance the functionality of the IONM during prolonged operating time and the resultant increased number of IONM stimulations, while providing a stable hemodynamic environment.

[Maximum dose of continuous infusion of mivacurium for thyroid surgery under total intravenous anesthesia: a sequential trial of monitoring neurological function in 30 patients]

OBJECTIVE

To investigate the maximum dose of continuous mivacurium infusion for intraoperative neuromonitoring (IONM) and observe the adverse reactions during thyroid surgery under total intravenous anesthesia (TIVA).

METHODS

Thirty patients undergoing IONM during thyroid surgery received continuous infusion of mivacurium at the initial rate of 14.97 μg · kg^-1 · min^-1. The infusion rate was adjusted in the next patient based on the response of the previous patient in IONM. The depth of anesthesia was maintained with propofol and remifentanil during the surgery. The EC₅₀ and 95%CI of mivacurium were calculated with Brownlee's up- and-down sequential method. During the operation, body movement and skin flushing of patient was monitored, and the mean arterial pressure (MAP) and heart rate (HP) were recorded immediately (T₀) and at 5 min (T₁) after injection of muscle relaxant for anesthesia induction, immediately (T₂) and at 10 min (T₃) and 20 min (T₄) after initiation of intraoperative infusion of the muscle relaxant.

RESULTS

The EC₅₀ for continuous infusion of mivacurium without affecting IONM was 18.9 μg · kg^-1 · min^-1(95%CI: 17.3-20.5 μg · kg^-1 · min^-1) during thyroid surgery under TIVA. One patient (3.3%) developed transient facial skin redness after induction. Intubation difficulties or body motions occurred in none of the patients during the surgery. Pair-wise comparison showed no significant variations in MAP or HR of the patients at the 5 time points (P>0.05).

CONCLUSIONS

In patients undergoing thyroid surgery under TIVA, the EC₅₀ for continuous infusion of mivacurium is 18.9 μg · kg^-1 · min^-1 (95%CI: 17.3-20.5 μg · kg^-1 · min^-1), which does not affect IONM or causes serious adverse reactions during the operation.

Influence of rocuronium on achieving optimal vagal stimulation during intraoperative nerve monitoring in thyroid surgery

BACKGROUND

In the present study we determine the feasibility of intraoperative neuromonitoring following the administration of a nondepolarizing neuromuscular blocking agent during thyroid operations, as well as the influence of rocuronium on the achievement of optimal vagal stimulation during intraoperative neuromonitoring in thyroid surgery. We further investigate whether accelerometry is a reliable approach to obtaining an ipsilateral vagus signal prior to recurrent laryngeal nerve dissection.

METHODS

Included in the study were 61 thyroidectomized patients whose demographic data, indications, type of surgery, vagus, and recurrent nerve values before and after resection were obtained. We created five groups of patients based on the twitch values recorded during ipsilateral vagus stimulation prior to the recurrent laryngeal nerve dissection: (1) <10%, (2) 11-25%, (3) 26-50%, (4) 51-75% and (5) >75%.

RESULTS

The average electromyography amplitudes of the vagus nerve prior to the determination of the recurrent laryngeal nerve for each group were 552 μV, 463 μV, 543 μV, 513 μV and 551 μV, respectively. No difference between the groups was observed in this regard (p > 0.05).

CONCLUSION

It can be expected that as soon as the effects of neuromuscular blockers on the peripheral muscles begin to abate, it will be possible to obtain the ipsilateral vagus signal prior to recurrent laryngeal nerve dissection at the desired levels. It can be concluded from this study that accelerometry using the pollicis muscle is an unreliable tool for the interpretation of the proper electromyography signals of the vagus nerve prior to the determination of the recurrent laryngeal nerve.

Precision Neuromuscular Block Management for Neural Monitoring During Thyroid Surgery

INTRODUCTION

Titration of neuromuscular block (NMB) plays a key role in intraoperative recurrent laryngeal nerve monitoring during thyroid surgery. The combination of neuromuscular blocking agent and timely partial reversal of NMB was investigated in both animal experiments and clinical neuro-monitored thyroidectomy.

METHODS

In animal experiments, 8 piglets received sugammadex to assess the laryngeal EMG recovery after rocuronium-induced NMB. In clinical monitored thyroidectomy, 40 patients each were allocated to conventional group and sugammadex group. Conventional group received rocuronium 0.3 mg/kg at anesthesia induction, while sugammadex group received partial NMB recovery protocol- 0.6 mg/kg of rocuronium at anesthesia induction and 0.5 mg/kg of sugammadex. Main outcome was assessed by first (V1) and final (V2) EMG signal induced by vagal stimulation.

RESULTS

In the porcine model, 50% recovery of laryngeal EMG amplitude was achieved at 16.8 ± 1.9 and 6 ± 2.7 minutes respectively after 0.5 and 1 mg/kg of sugammadex (p < 0.01). In monitored thyroidectomy, EMG amplitudes at V1 in group S and group C were 1214 ± 623 and 915 ± 476 μV, respectively (p = 0.02). Positive and adequately high EMG amplitudes were observed at the early surgical stage for all patients. Sugammadex groups were superior to conventional group in EMG tube placement (p < 0.001).

CONCLUSION

Both porcine model and clinical application showed that precise NMB management by low-dose sugammadex was effective for intraoperative neural monitoring (IONM). The regimen ensured optimal conditions for tracheal intubation and timely neuromuscular function restoration for high-quality EMG signal.

THYROID SURGERY, IONM AND SUGAMMADEX SODIUM RELATIONSHIPS: BENEFITS IN SUGAMMADEX SODIUM USE FOR IONM

Background

It is important to protect recurrent laryngeal nerve (RLN) during thyroid surgery. Thus, intra- operative neuromonitoring (IONM) has got popularity. But, the half life of neuromuscular blocking agents used has a reverse correlation with reliability and effectiveness of IONM. This study aimed to research the effect of Sugammadex Sodium, a specific nemuromuscular blocking agent antagonist, on nerve conduction and IONM.

Materials and methods

Twenty patients who underwent thyroidectomy under IONM followed an enhanced NMB recovery protocol-rocuronium 0.6 mg/kg at anesthesia induction and sugammadex 2 mg/kg at the beginning of operation. To prevent laryngeal nerve injury during the surgical procedures, all patients underwent intraoperative monitoring. At the same time, the measurement of TOF-Watch acceleromyograph of the adductor pollicis muscle response to ulnar nerve stimulation was performed; recovery was defined as a train-of-four (TOF) ratio ≥ 0.9. Age, sex, recurrent laryngeal nerve transmission speeds prior to and after operation, BMI, duration of surgery, the change in nerve transmission after drug administration and complications were analyzed.

Results

The mean age and the mean BMI were 47.6±11.82 years and 28.74±3.20, respectively. The mean operation duration was 52.65±5.51 minutes. There was no difference in either right or left RLN monitoring values before and after surgery. Following the drug injection, the TOF guard measurements on the 1^st, 2^nd, 3^rd and 4^th minutes were 23.5±4.90; 69.5±6.86; 88±4.1 and 135.9±10.62, respectively.

Conclusion

Neuromuscular blocking antagonist use and monitoring nerve transmission speed with TOF-guard can provide a safer resection.

Influence of Sevoflurane-Based Anesthesia versus Total Intravenous Anesthesia on Intraoperative Neuromonitoring during Thyroidectomy

OBJECTIVE

To examine the influence of sevoflurane-based combined intravenous and inhaled anesthesia versus propofol-based total intravenous anesthesia (TIVA) on intraoperative neuromonitoring (IONM) during thyroidectomy.

STUDY DESIGN

A randomized controlled trial.

SETTING

The present study was conducted in a tertiary hospital.

SUBJECTS AND METHODS

Forty patients were randomly assigned to a sevoflurane-based combined intravenous and inhalation group (group S) or a propofol-based total intravenous group (group P). Anesthesia was induced with midazolam, sufentanil, propofol, and cisatracurium in both groups and was maintained with sevoflurane and remifentanil in group S and with TIVA with propofol and remifentanil in group P. IONM was performed intermittently according to the IONM formula standard.

RESULTS

The time until detection of the first positive electromyographic (EMG) signal was significantly longer in group S (median, 41.0 minutes [interquartile range, 37.5-49.3]) than in group P (37.0 minutes [33.3-41.5], P = .028). All patients in group P had a positive EMG signal at initial monitoring, whereas 8 patients (40.0%) in group S did not. The rate of positive EMG signal at initial monitoring was significantly higher in group P than in group S (P = .006). The amplitude of the evoked potentials at V1, R1, R2, and V2 were similar between the groups.

CONCLUSION

Combined intravenous and inhaled anesthesia based on sevoflurane-remifentanil prolonged the time until detection of a positive EMG signal during IONM as compared with TIVA with propofol-remifentanil in patients undergoing thyroidectomy.

Early detection of recurrent laryngeal nerve damage using intraoperative nerve monitoring during thyroidectomy

Objective

This study aimed to investigate risk factors for early recurrent laryngeal nerve (RLN) damage during thyroid surgery with intraoperative nerve monitoring (IONM) technology to avoid RLN damage during surgery.

Methods

Data were retrospectively collected from 93 patients who underwent thyroidectomy at Beijing Hospital. All operations were performed by the same surgeon. A four-step procedure of IONM was used during the operation to determine the amplitude and latency of the RLN.

Results

The majority (51.6%) of patients who underwent surgery had thyroid carcinoma. Lymphadenectomy was carried out in 55 (59.1%) patients. A strong association was observed between temporary injury of the RLN and the extent of resection. The risk of temporary injury of the RLN during total thyroidectomy was three times that during right thyroid lobectomy (odds ratio = 3.13). The results of left lobectomy were also different from those of right lobectomy because the RLN was more likely to be damaged during left lobectomy.

Conclusions

Assessment of the amplitude and latency of the RLN can help to assess the integrity of the RLN. The extent of resection affects the functional integrity of the RLN.

Effect of intraoperative neuromonitoring on efficacy and safety using sugammadex in thyroid surgery: randomized clinical trial

Purpose

The use of nondepolarizing neuromuscular blocking agents (NMBAs) may affect intraoperative neuromonitoring (IONM) during anesthesia used during thyroid and parathyroid surgery.

Methods

The use of sugammadex was evaluated in a prospective clinical study during thyroid surgery. Between July 2018 and January 2019, 129 patients were prospectively randomized to either the sugammadex group (group B) or the control group (group A). Group A patients underwent standardized IONM during thyroidectomy, while group B patients used an NMBA-reversal protocol comprised of rocuronium (0.6 mg/kg) in anesthesia induction and sugammadex (2 mg/kg) after first vagal stimulation (V0). A peripheral nerve stimulator was used to monitor the neuromuscular transmission.

Results

In our clinical study, it took 26.07 ± 3.26 and 50.0 ± 8.46 minutes to reach 100% recovery of laryngeal electromyography at injection of the sugammadex group (2 mg/kg) and the control group, respectively (P < 0.001). The train-of-four ratio recovered from 0 to >0.9 within 4 minutes after administering 2 mg/kg of sugammadex at the beginning of resection. Surgery time was significantly shorter in group B than in group A (P < 0.001). Transient recurrent laryngeal nerve (RLN) paralysis was detected in 4 patients from group A and in 3 patients from group B (P = 0.681). There was no permanent RLN paralysis in the 2 groups.

Conclusion

Our clinical study showed that sugammadex effectively and rapidly improved the inhibition of neuromuscular function induced by rocuronium. The implementation of the nondepolarizing neuromuscular block recovery protocol may lead to tracheal intubation as well as favorable conditions for IONM in thyroid surgery.

Neuromuscular blockade management for intraoperative neural monitoring

This article reviews the literature on development of neuromuscular blockade management in thyroid surgery with intraoperative neural monitoring (IONM) in the past decade. Neuromuscular blockade management includes the choice of neuromuscular blocking agents (NMBAs) and reversal of neuromuscular blockade by sugammadex. A series of animal study and clinical trials showed NMBAs effect on IONM in thyroid surgery. We summarized five NMBA regimens for IONM: (a) relaxant-free regimen, (b) depolarizing NMBA-succinylcholine, (c) titration of nondepolarizing NMBA, and (d) rocuronium combined with sugammadex. The proper management of neuromuscular blockade during IONM has greatly developed over the past decade. The misuse of NMBAs is associated with false IONM interpretations to surgeons. A detailed understanding of NMBAs and neuromuscular blockade management by sugammadex may optimize IONM quality in patients receiving monitored thyroid surgery.

Preoperative, intraoperative and postoperative anesthetic prospective for thyroid surgery: what's new

The aim of this review is to analyze what's new on anesthetic prospective to perioperative management for thyroid surgery. For recent decades intraoperative neuromonitoring (IONM) during thyroid and parathyroid surgery has obtained more and more popularity. New modality of anesthetic technique was also developed to incorporate into surgical teamwork. For example, the precise position of EMG tube and optimal use of neuromuscular blocking agents (NMBAs) play key roles in successful IONM system. Special focus is paid to following issues: (I) preoperative airway evaluation and pre-op preparation; (II) anesthetic managements including advanced intubation tools, NMBAs and sugammadex; and (III) post-op adverse events such as pain and postoperative nausea vomiting.

[Intraoperative neuromonitoring in thyroid surgery]

BACKGROUND

Intraoperative neuromonitoring of the recurrent laryngeal nerve in thyroid surgery facilitates the identification of anatomical structures in cervical endocrine surgery reducing the frequency of vocal cord paralysis.

OBJECTIVE

To study the normal electrophysiological values of the vague and recurrent laryngeal nerves before and after thyroid surgery. To compare rates of injury of recurrent nerve before and after the introduction of the intraoperative neuromonitoring in thyroid surgery.

MATERIAL AND METHODS

An observational, descriptive and prospective study in which a total of 490 patients were included. Between 2003-2010, surgery was performed on 411 patients (703 nerves at risk) with systematic identification of recurrent laryngeal nerves. Between 2010-2011 neuromonitorization was also systematically performed on 79 patients.

RESULTS

Before the introduction of intraoperative neuromonitoring of 704 nerves at risk, there were 14 recurrent laryngeal nerve injuries. Since 2010, after the introduction of the intraoperative neuromonitoring in thyroid surgery, there has been no nerve injury in 135 nerves at risk.

CONCLUSIONS

We consider the systematic identification of the recurrent laryngeal nerve is the 'gold standard' in thyroid surgery and the intraoperative neuromonitoring of nerves can never replace surgery but can complement it.

Intraoperative neural monitoring in thyroid surgery: lessons learned from animal studies

Recurrent laryngeal nerve (RLN) injury remains a significant morbidity associated with thyroid and parathyroid surgery. In the past decade, surgeons have increasingly used intraoperative neural monitoring (IONM) as an adjunct technique for localizing and identifying the RLN, detecting RLN injury, and predicting the outcome of vocal cord function. In recent years, many animal studies have investigated common pitfalls and new applications of IONM. For example, the use of IONM technology in animal models has proven valuable in studies of the electrophysiology of RLN injury. The advent of animal studies has substantially improved understanding of IONM technology. Lessons learned from animal studies have immediate clinical applications in establishing reliable strategies for preventing intraoperative RLN injury. This article gives an overview of the research progress on IONM-relevant animal models.

Reversal of rocuronium-induced neuromuscular blockade by sugammadex allows for optimization of neural monitoring of the recurrent laryngeal nerve

OBJECTIVES/HYPOTHESIS

The use of neuromuscular blocking agent may effect intraoperative neuromonitoring (IONM) during thyroid surgery. An enhanced neuromuscular-blockade (NMB) recovery protocol was investigated in a porcine model and subsequently clinically applied during human thyroid neural monitoring surgery.

STUDY DESIGN

Prospective animal and retrospective clinical study.

METHODS

In the animal experiment, 12 piglets were injected with rocuronium 0.6 mg/kg and randomly allocated to receive normal saline, sugammadex 2 mg/kg, or sugammadex 4 mg/kg to compare the recovery of laryngeal electromyography (EMG). In a subsequent clinical application study, 50 patients who underwent thyroidectomy with IONM followed an enhanced NMB recovery protocol-rocuronium 0.6 mg/kg at anesthesia induction and sugammadex 2 mg/kg at the operation start. The train-of-four (TOF) ratio was used for continuous quantitative monitoring of neuromuscular transmission.

RESULTS

In our porcine model, it took 49 ± 15, 13.2 ± 5.6, and 4.2 ± 1.5 minutes for the 80% recovery of laryngeal EMG after injection of saline, sugammadex 2 mg/kg, and sugammadex 4 mg/kg, respectively. In subsequent clinical human application, the TOF ratio recovered from 0 to >0.9 within 5 minutes after administration of sugammadex 2 mg/kg at the operation start. All patients had positive and high EMG amplitude at the early stage of the operation, and intubation was without difficulty in 96% of patients.

CONCLUSIONS

Both porcine modeling and clinical human application demonstrated that sugammadex 2 mg/kg allows effective and rapid restoration of neuromuscular function suppressed by rocuronium. Implementation of this enhanced NMB recovery protocol assures optimal conditions for tracheal intubation as well as IONM in thyroid surgery.

LEVEL OF EVIDENCE

NA.

The Effect of Routine Reversal of Neuromuscular Blockade on Adequacy of Recurrent Laryngeal Nerve Stimulation during Thyroid Surgery

Testing of the integrity of the recurrent laryngeal nerve during thyroid surgery has become routine practice for many surgeons to aid dissection and minimise the chance of inadvertent nerve injury. We hypothesised that routine reversal of an intermediate-acting, non-depolarising neuromuscular blocking agent would improve conditions for stimulation of the recurrent laryngeal nerve. We conducted a single-centre, randomised, double-blind placebo-controlled trial of patients undergoing thyroid surgery by the same surgeon. After randomisation, the participants received either neostigmine 2.5 mg with glycopyrrolate 0.4 mg or placebo, at 30 minutes after induction of anaesthesia and administration of 0.4 mg/kg of atracurium. The primary outcome was the subjective assessment by the surgeon as to whether the neuromuscular function was adequate for stimulation of the recurrent laryngeal nerve using a neuromuscular integrity monitor (NIM). Time to NIM stimulation was 44.6 minutes in the placebo group and 41.4 minutes in the intervention group ( P=0.268). Of the 21 patients who received the neuromuscular blockade reversal, 20 (95.2%) had adequate surgical conditions for NIM stimulation, compared to 9 out of 18 patients (50%) in the placebo group ( P=0.002). Three of the ten patients (30%) with inadequate reversal showed no evidence of residual blockade assessed peripherally. The routine reversal of neuromuscular blockade at 30 minutes post induction appears to result in adequate surgical conditions for safe stimulation of the recurrent laryngeal nerve. Return of neuromuscular function at a peripheral site does not guarantee adequate laryngeal muscle function for use of the NIM.

[Contribution of neuromonitoring to the safety of tracheal extubation after total thyroidectomy. Prospective study with needle electrodes]

INTRODUCTION AND OBJECTIVES

Bilateral laryngeal paralysis cause serious respiratory complications. In thyroid surgery, neuromonitoring helps in identifying the recurrent laryngeal nerve, reports on its functioning at the end of surgery, supports decision making, and may reduce the risk of bilateral paralysis. Our objective was to estimate the influence of neuromonitoring in operative strategy and extubation safety in total thyroidectomy.

METHODS

A non-randomized prospective study was conducted on 210 patients undergoing total thyroidectomy (420 laryngeal nerves stimulated included). We collected qualitative neuromonitoring variables (presence or absence of final signal after stimulation of the vagus nerve), and postoperative indirect laryngoscopy (normal motility or paralysis), performed until 3rd day after the surgery.

RESULTS

The accuracy of the test was 99.5% (95% CI 98.3 to 99.9). The positive predictive value was 100% (95% CI 99.1 to 100), which showed the high ability of neuromonitoring to predict paralysis in case of loss of signal, and the negative predictive value was 99.5% (95% CI 98.3 to 99.9), which indicated its predictive capacity for normal motility when there is a normal signal.

CONCLUSIONS

In our group of patients, recurrent laryngeal nerve monitoring was useful in total thyroidectomy as it provided information on the prognosis of laryngeal motility, and helped in making decisions during surgery when there was signal loss. Due to the risk of serious respiratory complications due to bilateral recurrent laryngeal nerve paralysis, we opted for the performing of the 2-stage total thyroidectomy in case of signal loss in the first lobectomy. Thereby, neuromonitoring contributed to the safety of the airway in tracheal extubation, aiding in the prevention of a possible bilateral laryngeal paralysis.

[Monitoring of recurrent laryngeal nerve injury using an electromyographic endotracheal tube in thyroid and parathyroid surgery. Anesthetic aspects]

Recurrent laryngeal nerve injury remains one of the main complications in thyroid and parathyroid surgery. When this injury is bilateral, an acute upper airway obstruction may occur, leading to a potentially life-threatening situation for the patient. The visual identification of the nerve during surgery is the best way to preserve its integrity. However identification of the nerves by means of electromyographic stimuli through electrodes attached to endotracheal tubes could help in decreasing nerve injury. In these cases the experience and role of the anesthetist is essential to correctly place the electromyographic endotracheal tube and ensure that the electrodes are in touch with the vocal cords during the surgery. Moreover, the results of the electromyography can be affected by the neuromuscular blocking agents. Therefore, the choice and dose must be adapted, in order to ensure a suitable anesthetic depth, and adequate response.

Intraoperative Monitoring of the Recurrent Laryngeal Nerve during Thyroidectomy: A Standardized Approach Part 2

This is the second of two articles on intraoperative neural monitoring. The aim of part one was to provide a concise overview of intraoperative nerve monitoring in thyroid surgery and its effectiveness. Part 1 included a brief review of the surgical anatomy of the recurrent laryngeal nerve and described the surgical landmarks which can be used to identify the nerve during surgery. Part 2 will describe in detail a standardized approach to intraoperative nerve monitoring during thyroid surgery. A brief review of the nerve monitoring procedure and all its requirements will be discussed. The article concludes with the description of a troubleshooting algorithm for intraoperative loss of signal.

How to cite this article

Poveda MCD, Dionigi G, Sitges- Serra A, Barczynski M, Angelos P, Dralle H, Phelan E, Randolph G. Intraoperative Monitoring of the Recurrent Laryngeal Nerve during Thyroidectomy: A Standardized Approach Part 2. World J Endocr Surg 2012;4(1):33-40.

An applied anatomical study on the recurrent laryngeal nerve and inferior thyroid artery

PURPOSE

The aim of this study was to provide some important information about the morphology and topography of the recurrent laryngeal nerve (RLN) and inferior thyroid artery (ITA), which significantly helps localize and protect the RLN in neck surgery, especially in thyroid surgery.

METHODS

Eighty adult cadavers (160 sides) fixed with formalin were dissected, analyzed and measured.

RESULTS

(1) 87.5% of the RLNs gave off multiple branches like a tree; the incidence of the RLN loop, connecting one branch to another was 3.125%; in 9.375%, one branch of RLN combined with cervical sympathetic chain (CSC) or superior laryngeal nerve (SLN). (2) A double RLN appeared in four sides, a non-recurrent inferior laryngeal nerve appeared in two cases. (3) In two cases, the RLN communicated with both of the SLN and the CSC near thyroid gland. (4) Most of the ITAs was derived from thyrocervical trunk, and divided into two or three branches before entering the thyroid gland. (5) Three ITAs gave off esophageal branch, one ITA gave off tracheal branch, one right ITA originated abnormally. (6) On the left side, the RLN was behind the ITA in 86.25% of the cases, in front of the artery in 7.5%, the nerve was between artery branches in 2.5%, the artery was between nerve branches in 1.25%, and was among the combined in 2.5%. On the right side, the RLN was in front of the artery in 75.0%, behind the artery in 10.0%, among the branches of the artery in 5.0%, 10.0% the branches of both nerves and artery were interlaced that the relationship between the branches of the nerve and the artery was uncertain.

CONCLUSIONS

Because of the variability of the RLN and ITA and the complicated relationship between them, it is necessary to dissect and recognize the RLN to avoid mistaking, ignoring, and misligating of the nerve before ligating the ITA.

Laryngeal morbidity after intubation with or without neuromuscular block in thyroid surgery using recurrent laryngeal nerve monitoring

OBJECTIVE

The avoidance of neuromuscular blocking agents (NMBA) for endotracheal intubation is associated with a higher incidence of laryngeal discomfort and lesions, but could impair effectiveness of intra operative recurrent laryngeal nerve monitoring (IONM).

METHODS

In a retrospective quality assessment study over a period of 30 months, a collective that had been intubated without NMBA was compared with a group, which had received NMBA. Endolaryngeal EMG was accomplished with a MagStim(®)-EMG-electrode.

RESULTS

Out of the 127 patients with 224 nerves at risk (NAR; NMBA 102 NAR, no NMBA 122 NAR), more than 90% received a total intravenous anaesthesia with propofol, and 88% had remifentanil. Laryngeal side effects and damage scores did not differ significantly.

CONCLUSIONS

In this special setting of IONM and thyroid surgery, avoidance of NMBA for endotracheal intubation seems not to increase the incidence of laryngeal side effects and lesions. If endotracheal intubation without NMBA is required, the authors suggest a standardized approach using induction agents as propofol and remifentanil.

Electrophysiologic recurrent laryngeal nerve monitoring during thyroid and parathyroid surgery: international standards guideline statement

Intraoperative neural monitoring (IONM) during thyroid and parathyroid surgery has gained widespread acceptance as an adjunct to the gold standard of visual nerve identification. Despite the increasing use of IONM, review of the literature and clinical experience confirms there is little uniformity in application of and results from nerve monitoring across different centers. We provide a review of the literature and cumulative experience of the multidisciplinary International Neural Monitoring Study Group with IONM spanning nearly 15 years. The study group focused its initial work on formulation of standards in IONM as it relates to important areas: 1) standards of equipment setup/endotracheal tube placement and 2) standards of loss of signal evaluation/intraoperative problem-solving algorithm. The use of standardized methods and reporting will provide greater uniformity in application of IONM. In addition, this report clarifies the limitations of IONM and helps identify areas where additional research is necessary. This guideline is, at its forefront, quality driven; it is intended to improve the quality of neural monitoring, to translate the best available evidence into clinical practice to promote best practices. We hope this work will minimize inappropriate variations in monitoring rather than to dictate practice options.

[Intraoperative neuromonitoring of thyroid gland operations : Surgical standards and aspects of expert assessment]

Intraoperative neuromonitoring (IONM) was introduced into thyroid surgery approximately 10 years ago for better identification of recurrent laryngeal nerve palsy. Since then several studies have been performed for evaluation of this new technology. IONM is superior to visual nerve identification alone for prediction of postoperative local cord function. Therefore, in bilateral procedures IONM enables intraoperative decision-making concerning resection of the second side. To avoid misinterpretation of the results of IONM a standardized approach including preoperative and postoperative laryngoscopy and preresection and postresection vagus stimulation is recommended. Trouble-shooting requires systematic checking of the device including control of electrode position (needle or tube electrodes). For expert assessment purposes documentation of the standardized application of IONM is of utmost importance.