Peripheral Nerve Stimulation in Regional Anesthesia:

The Safety of Peripheral Nerve Blocks: The Role of Triple Monitoring in Regional Anaesthesia, a Comprehensive Review

Regional anaesthesia, referred to as regional blocks, is one of the most frequently used methods of anaesthesia for surgery and for pain management. Local anaesthetic drug should be administered as close to the nerve as possible. If administered too far away, this may result in insufficient block. If it is administrated too close, severe nerve damage can occur. Neurostimulation techniques and ultrasound imaging have improved the effectiveness and safety of blockade, but the risk of nerve injury with permanent nerve disfunction has not been eliminated. Intraneural administration of a local anaesthetic damages the nerve mechanically by the needle and the high pressure generated by the drug inside the nerve. In many studies, injection pressure is described as significantly higher for unintended intraneural injections than for perineural ones. In recent years, the concept of combining techniques (neurostimulation + USG imaging + injection pressure monitoring) has emerged as a method increasing safety and efficiency in regional anaesthesia. This study focuses on the contribution of nerve identification methods to improve the safety of peripheral nerve blocks by reducing the risk of neural damage.

Consensus practice guidelines on interventions for cervical spine (facet) joint pain from a multispecialty international working group

BACKGROUND

The past two decades have witnessed a surge in the use of cervical spine joint procedures including joint injections, nerve blocks and radiofrequency ablation to treat chronic neck pain, yet many aspects of the procedures remain controversial.

METHODS

In August 2020, the American Society of Regional Anesthesia and Pain Medicine and the American Academy of Pain Medicine approved and charged the Cervical Joint Working Group to develop neck pain guidelines. Eighteen stakeholder societies were identified, and formal request-for-participation and member nomination letters were sent to those organizations. Participating entities selected panel members and an ad hoc steering committee selected preliminary questions, which were then revised by the full committee. Each question was assigned to a module composed of 4-5 members, who worked with the Subcommittee Lead and the Committee Chairs on preliminary versions, which were sent to the full committee after revisions. We used a modified Delphi method whereby the questions were sent to the committee en bloc and comments were returned in a non-blinded fashion to the Chairs, who incorporated the comments and sent out revised versions until consensus was reached. Before commencing, it was agreed that a recommendation would be noted with >50% agreement among committee members, but a consensus recommendation would require ≥75% agreement.

RESULTS

Twenty questions were selected, with 100% consensus achieved in committee on 17 topics. Among participating organizations, 14 of 15 that voted approved or supported the guidelines en bloc, with 14 questions being approved with no dissensions or abstentions. Specific questions addressed included the value of clinical presentation and imaging in selecting patients for procedures, whether conservative treatment should be used before injections, whether imaging is necessary for blocks, diagnostic and prognostic value of medial branch blocks and intra-articular joint injections, the effects of sedation and injectate volume on validity, whether facet blocks have therapeutic value, what the ideal cut-off value is for designating a block as positive, how many blocks should be performed before radiofrequency ablation, the orientation of electrodes, whether larger lesions translate into higher success rates, whether stimulation should be used before radiofrequency ablation, how best to mitigate complication risks, if different standards should be applied to clinical practice and trials, and the indications for repeating radiofrequency ablation.

CONCLUSIONS

Cervical medial branch radiofrequency ablation may provide benefit to well-selected individuals, with medial branch blocks being more predictive than intra-articular injections. More stringent selection criteria are likely to improve denervation outcomes, but at the expense of false-negatives (ie, lower overall success rate). Clinical trials should be tailored based on objectives, and selection criteria for some may be more stringent than what is ideal in clinical practice.

Consensus practice guidelines on interventions for cervical spine (facet) joint pain from a multispecialty international working group

Background

The past two decades have witnessed a surge in the use of cervical spine joint procedures including joint injections, nerve blocks and radiofrequency ablation to treat chronic neck pain, yet many aspects of the procedures remain controversial.

Methods

In August 2020, the American Society of Regional Anesthesia and Pain Medicine and the American Academy of Pain Medicine approved and charged the Cervical Joint Working Group to develop neck pain guidelines. Eighteen stakeholder societies were identified, and formal request-for-participation and member nomination letters were sent to those organizations. Participating entities selected panel members and an ad hoc steering committee selected preliminary questions, which were then revised by the full committee. Each question was assigned to a module composed of 4–5 members, who worked with the Subcommittee Lead and the Committee Chairs on preliminary versions, which were sent to the full committee after revisions. We used a modified Delphi method whereby the questions were sent to the committee en bloc and comments were returned in a non-blinded fashion to the Chairs, who incorporated the comments and sent out revised versions until consensus was reached. Before commencing, it was agreed that a recommendation would be noted with >50% agreement among committee members, but a consensus recommendation would require ≥75% agreement.

Results

Twenty questions were selected, with 100% consensus achieved in committee on 17 topics. Among participating organizations, 14 of 15 that voted approved or supported the guidelines en bloc, with 14 questions being approved with no dissensions or abstentions. Specific questions addressed included the value of clinical presentation and imaging in selecting patients for procedures, whether conservative treatment should be used before injections, whether imaging is necessary for blocks, diagnostic and prognostic value of medial branch blocks and intra-articular joint injections, the effects of sedation and injectate volume on validity, whether facet blocks have therapeutic value, what the ideal cut-off value is for designating a block as positive, how many blocks should be performed before radiofrequency ablation, the orientation of electrodes, whether larger lesions translate into higher success rates, whether stimulation should be used before radiofrequency ablation, how best to mitigate complication risks, if different standards should be applied to clinical practice and trials, and the indications for repeating radiofrequency ablation.

Conclusions

Cervical medial branch radiofrequency ablation may provide benefit to well-selected individuals, with medial branch blocks being more predictive than intra-articular injections. More stringent selection criteria are likely to improve denervation outcomes, but at the expense of false-negatives (ie, lower overall success rate). Clinical trials should be tailored based on objectives, and selection criteria for some may be more stringent than what is ideal in clinical practice.

Real-Time Injection Pressure Sensing and Minimal Intensity Stimulation Combination During Ultrasound-Guided Peripheral Nerve Blocks: An Exploratory Observational Trial

BACKGROUND

Nerve damage can occur after peripheral nerve block (PNB). Ultrasound guidance does not eliminate the risk of intraneural injection or nerve injury. Combining nerve stimulation and injection pressure (IP) monitoring with ultrasound guidance has been suggested to optimize needle tip location in PNB. In this prospective observational study, we hypothesized that measured pairs of IP and minimum intensity of stimulation (MIS) might differentiate successive needle tip locations established by high-resolution ultrasound during PNB.

METHODS

For this exploratory study, 240 observations for 40 ultrasound-guided PNBs were studied in 28 patients scheduled for orthopedic surgery. During the progression of the needle to the nerve observed by ultrasonography, the IP was measured continuously using a computerized pressure-sensing device with a low flow rate of solution. Stimulation thresholds and electrical impedance were obtained by an impedance analyzer coupled to the nerve stimulator at 6 successive needle positions. The median (quartile) or mean (95% confidence interval [CI]) was reported. A mixed model analysis was used, and the sample was also explored using a classification and regression tree (CART) algorithm.

RESULTS

Specific combinations of IP and MIS were measured for subcutaneous, epimysium contact, intramuscular, nerve contact (231 mm Hg [203-259 mm Hg] and 1.70 mA [1.38-2.02 mA]), intraneural location (188 mm Hg [152-224 mm Hg] and 0.58 mA [0.46-0.70 mA]), and subparaneural location (47 mm Hg [41-53 mm Hg] and 1.35 mA [1.09-1.61 mA]). The CART algorithm shows that the optimal subparaneural needle tip position might be defined by the lowest pressure (<81.3 mm Hg) and MIS (<1.5 mA) cutoffs.

CONCLUSIONS

Our exploratory study evaluated concepts to generate hypotheses. The combinations of IP and MIS might help the physician during a PNB procedure. A low IP and low MIS might confirm a subparaneural location, and a high IP and a low MIS might be an alert for the intraneural location of the needle tip.

Ultrasound Guidance and Nerve Stimulation Combined Versus Nerve Stimulation alone for Lumbar Plexus Block: A Randomized Controlled Trial

A nerve stimulation-guided lumbar plexus block is a well-established technique. It is not clear whether ultrasound guidance has additional value for this deep block technique. This study aimed to examine whether ultrasound guidance using a paramedian transverse scan through the intertransverse space (PMTS-ITS) approach in combination with nerve stimulation reduces the onset time of a complete sensory block. Forty-four patients who were scheduled to undergo arthroscopic knee surgery with an ultrasound visibility score (UVS) of ≥10 for the lumbar plexus were enrolled and randomly allocated to the ultrasound guidance with nerve stimulation group (group U-N) or nerve stimulation group (group N) in this prospective, randomized, parallel-group, active-controlled study. The primary outcome was the onset time of a complete sensory block. The results showed that the onset time of a complete sensory block to pinprick and cold was 10 (10-40) min and 10 (10-40) min in group U-N, respectively, and 30 (10-40) min and 20 (10-40) min in group N (P=0.005, P=0.004), respectively. The performance time was 658±87 s in group U-N and 528±97 s in group N (P<0.001). There was no (0%) patient who required 5 or more needle passes in group U-N and 6 (27.3%) in group N (P=0.028). The block failure rate was 9.1% in group U-N and 31.8% in group N (P>0.05). In conclusion, ultrasound guidance using the PMTS-ITS approach in combination with nerve stimulation led to a faster onset of a complete sensory block than nerve stimulation alone for a lumbar plexus block in patients with a UVS ≥10. Ultrasound guidance with nerve stimulation significantly decreased the number of patients who required 5 or more needle passes.

The efficacy of maxillary and mandibular nerve blockade using electrical nerve stimulation for guidance

BACKGROUND

In oral and maxillofacial surgical procedures, sometimes conventional loco-regional anesthesia techniques could be insufficient in daily clinical practice. The aim of this study was to evaluate the efficacy of analgesia using electrical nerve stimulation (ENS) for maxillary or mandibular nerve blockade, in comparison with conventional loco-regional anesthesia techniques.

METHODS

The study comprised 52 patients who were attending the department for advanced surgery of the upper and lower jaw. Patients were randomly divided into 2 groups: ENS and Local group. The predictor variable was the anesthesia technique (ENS and Local groups). The outcome variables were patient assessed pain levels (VAS scores) and total anesthetic dose.

RESULTS

Both the administered anesthetic dose and patient-assessed pain levels were significantly lower in the ENS group than in the Local group, despite there being no difference in age, sex or any hemodynamic parameters between the groups.

CONCLUSIONS

Maxillary and mandibular nerve blockade is more efficient with ENS guidance, with lower amounts of anesthetic required, compared to conventional loco-regional anesthesia.

"Triceps Brachii Muscle Response to Neurostimulation of the Radial Nerve during Axillary Plexus Blockade: Clinical, Anatomical and Histological Correlation"

Axillary plexus blockade is a common technique in clinical practice with a well-known pattern of structures around the brachial artery. Historically, the only proper response to radial nerve stimulation was considered to be extension of the hand and wrist. Twenty-five axillary blockades were assessed by ultrasound and neurostimulation; the principal objective was to correlate the needle position over the radial nerve with the anatomical and histological structure of that nerve. During the procedure, the needle was directed in two ways to reach the medial or lateral margin of the nerve: above the brachial artery or beneath it. Once the needle reached the nerve, the current was augmented gradually until a response was elicited. For the cadaveric anatomical study, eight axillae were dissected and histological samples were examined. The response of the triceps brachii muscle differed significantly between the two approaches to the radial nerve (P < 0.001), and the mean intensity of stimulation was significantly lower when the nerve was accessed above the artery (0.44 ± 0.15 mA) than below it (0.57 ± 0.17 mA) (P = 0.015). A triceps brachii motor response occurs at lower current intensity and lower needle-nerve distance when the radial nerve is accessed above the artery and over the latissimus dorsi tendon. These findings were correlated with the topography of the radial nerve in the axillary fossa. Clin. Anat. 33:578-584, 2020. © 2019 Wiley Periodicals, Inc.

Nerve stimulator for regional anaesthesia procedures with automatic interactive closed-loop control

Peripheral nerve stimulators have widespread among anaesthesiologists and remain a popular technique. However, in commercial devices, the user has to manually adjust stimulus intensity. Thus, the aim of this study is to propose a method that allows automating the current intensity control. An earlier nerve stimulator prototype was modified to add an accelerometer and an sEMG module. The choice of these two sensors is aimed at the possibility of observing the mechanical and electrical responses of the muscle contraction evoked by the stimulation. The tests were performed in two steps. The first step was to observe how the sensors behave during stimulation and muscle contraction. The second step was to implement a control algorithm and to validate the automation technique. Comparing the two methods, no significant differences were found on procedure time (manual: 12.5 ± 2.3; automatic: 11.6 ± 1.9; ρ =0.380) and blockade latency time (manual: 11.6 ± 1.1; automatic: 11.9 ± 1.2; ρ =0.524). Comparing needle-nerve distance in manual or automatic mode, no significant differences were found for 1.0 mA, 0.8 mA, 0.5 mA and 0.3 mA. We conclude that the technique for automating the current intensity update, using accelerometer and/or electromyography, is satisfactory. Furthermore, we conclude that the use of the accelerometer alone is sufficient for detection of muscle contraction.

A simple guide to regional anaesthesia

Regional anaesthesia is widely used in modern anaesthetic practice for perioperative and postoperative analgesia. In the operating theatre, regional anaesthesia is used both on its own and in combination with other techniques (general anaesthesia and sedation). Regional anaesthesia is now a core skill set in anaesthetic training. This article provides a basic outline of regional anaesthesia for surgeons and other non-anaesthetic staff working with anaesthetists, reviewing preparation, consent, basic and specialist equipment, central neuraxial blocks (spinal, epidural and caudal), trunk blocks, upper limb blocks (interscalene, supraclavicular, infraclavicular and axillary) and lower limb blocks (femoral, fascia iliaca, sciatic, popliteal and ankle). It also discusses the pharmacology of the agents used and common complications.

The role of sciatic nerve block to complement femoral nerve block in total knee arthroplasty: a meta-analysis of randomized controlled trials

INTRODUCTION

Femoral nerve block (FNB) appears to have higher postoperative analgesic benefits compared with the patient-controlled analgesia (PCA) in total knee arthroplasty (TKA). However, the role of sciatic nerve block (SNB) as a complement to FNB remains controversial. We performed a meta-analysis assessing the benefits of the SNB as a complement to FNB, as well as comparing the efficacy of single-injection versus continuous SNB in TKA.

METHODS

Our group conducted a systematic literature search in PubMed, EMBASE and Google Scholar. We retrieved randomized trials comparing either SNB versus placebo or continuous versus single-injection SNB. The intervention group was the use of SNB as a complement to FNB, while the control group was FNB alone. Pain score at rest and movement (at 4, 12, 24, 48 and 72 h), patient-controlled intravenous opioid consumption, length of hospital stay, and incidence of nausea were extracted from each study. Random-effects model was used for meta-analysis and standardized mean difference (SMD) was used as the effect size.

RESULTS

Ten articles comprising 514 patients were included to compare the effects of SNB combined with FNB versus FNB alone. Interventional group was found to significantly reduce pain score at for 4 h (SMD = - 0.94, 95% CI - 1.42 to - 0.47, P < 0.001, I² = 76.5%) compared with the control group. Pain score at rest was significantly reduced at movement for 12 h (SMD = - 0.29, 95% CI - 0.54 to - 0.04, P = 0.02, I² = 0%). Opioid consumption was significantly reduced at 24 (SMD = - 0.60, 95% CI - 1.01 to - 0.17, P = 0.01, I² = 69.1%) and 48 h (SMD = - 1.04, 95% CI - 1.46 to - 0.61, P < 0.001, I² = 43.4%) after TKA using SNB as a complement to FNB. Three articles were additionally meta-analyzed to compare the efficacy of single-injection (n = 79) versus continuous SNB (n = 79), being the latter one significantly associated with less pain score at 24 (SMD = -0.77, 95% CI - 1.10 to - 0.45, P < 0.001, I² = 0%) and 48 h (SMD = - 0.69, 95% CI - 1.01 to - 0.36, P < 0.001, I² = 0%), but not at 12 h (SMD = - 0.34, 95% CI - 0.73 to - 0.06, P = 0.10, I² = 0%).

CONCLUSIONS

This meta-analysis provides evidence-based supports to the benefits of SNB as a complement to FNB in TKA. The combination sciatic-femoral nerve block appears to be the optimal choice for patients in high risk of postoperative opioids consumption or acute pain after TKA.

The Utility of Peripheral Nerve Blocks in Interventional Radiology

OBJECTIVE

The aim of this article is to provide an overview of peripheral nerve blocks, the use of peripheral nerve block within and outside interventional radiology, and the complications of peripheral nerve block.

CONCLUSION

Interventional radiologists are often responsible for sedation and pain management in the majority of interventional radiology procedures. Peripheral nerve block is increasingly being used in interventional radiology.

The anesthetic considerations while performing supraclavicular brachial plexus block in emergency surgical patients using a nerve stimulator

Regional anesthesia is favored in patients who undergo emergency extremity (limb) surgery, and specifically so in the absence of fasting status. In the absence of ultrasonic guidance, the nerve stimulator still remains a valuable tool in performing a brachial block, but its use is difficult in an emergency surgical patient and greater cautious approach is essential. We identified the supraclavicular plexus by the nerve stimulation-motor response technique as follows. Anterior chest muscles contractions, diaphragmatic contraction, deltoid contractions, and posterior shoulder girdle muscle contractions when identified were taken as “negative response” with decreasing stimulating current. A forearm muscle contraction, especially “wrist flexion” and “finger flexion” at 0.5 mA of current was taken as “positive response.” If no positive response was identified, the “elbow flexion” was considered as the final positive response for successful drug placement. The series of patients had difficulty for administering both general and regional anesthesia and we considered them as complex scenarios. The risk of the block failure was weighed heavily against the benefits of its success. The described series includes patients who had successful outcomes in the end and the techniques, merits, and risks are highlighted.

Pathophysiology and Etiology of Nerve Injury Following Peripheral Nerve Blockade

This review synthesizes anatomical, anesthetic, surgical, and patient factors that may contribute to neurologic complications associated with peripheral nerve blockade. Peripheral nerves have anatomical features unique to a given location that may influence risk of injury. Peripheral nerve blockade-related peripheral nerve injury (PNI) is most severe with intrafascicular injection. Surgery and its associated requirements such as positioning and tourniquet have specific risks. Patients with preexisting neuropathy may be at an increased risk of postoperative neurologic dysfunction. Distinguishing potential causes of PNI require clinical assessment and investigation; a definitive diagnosis, however, is not always possible. Fortunately, most postoperative neurologic dysfunction appears to resolve with time, and the incidence of serious long-term nerve injury directly attributable to peripheral nerve blockade is relatively uncommon. Nonetheless, despite the use of ultrasound guidance, the risk of block-related PNI remains unchanged.

WHAT'S NEW

Since the 2008 Practice Advisory, new information has been published, furthering our understanding of the microanatomy of peripheral nerves, mechanisms of peripheral nerve injection injury, toxicity of local anesthetics, the etiology of and monitoring methods, and technologies that may decrease the risk of nerve block-related peripheral nerve injury.

Preoperative percutaneous nerve mapping of the mandibular marginal branch of the facial nerve

OBJECTIVE

In this study, we introduce a reliable method for mapping the location of the mandibular marginal branch of the facial nerve. The utility of preoperative percutaneous mandibular marginal branch mapping and continuous intraoperative nerve monitoring during operation with a submandibular approach is reported.

MATERIALS AND METHODS

The mapping technique was performed in 40 patients. Electromyography surface electrodes were placed on the orbicularis oris muscles. A modified bipolar probe with an adjustable distance between the 2 tips was used to apply surface stimulation at a frequency of 1 Hz to 2 Hz. The stimulating current most frequently used was 5.0 mA to 5.5 mA. By moving the electrode at right angles across the suspected path of the nerve around the marginal border of the mandible, 4 to 5 points were marked and connected, where the orbicularis oris contracted and the action potential was evoked. After general anesthesia, the mapping path was verified using needle electrodes with different needle-to-nerve distances.

RESULTS

The nerve could be mapped preoperatively in all patients and were protected in 39 patients. The thresholds of the needle electrode on the mapping path were at or below 0.5 mA, verifying the accuracy of mapping.

CONCLUSIONS

Preoperative percutaneous nerve mapping was a precise method of identifying the location of the nerve and could protect the nerve from accidental injury.

Anesthesia for Vascular access Surgery

The type of anesthesia chosen is an integral part of the decision-making process for arteriovenous access construction. We discuss the different types of anesthesia used, with emphasis on brachial plexus block, which is potentially safer than general anesthesia in this fragile patient population with end-stage renal disease. Brachial plexus block is superior to local anesthesia and enables the use of a tourniquet to minimize potential damage to the blood vessels during anastomosis using microsurgery techniques, and does not lead to the vasospasm that may be seen with local anesthesia. Regional anesthesia has a beneficial sympathectomy-like effect that causes vasodilation with increased blood flow during surgery and in the fistula postoperatively that may prevent early thrombosis and potentially improve outcome.

Blood pressure response to combined general anaesthesia/interscalene brachial plexus block for outpatient shoulder arthroscopy

BACKGROUND

Shoulder surgery is often performed in the beach-chair position, a position associated with arterial hypotension and subsequent risk of cerebral ischaemia. It can be performed under general anaesthesia or with an interscalene brachial plexus block, each of which has specific advantages but also specific negative effects on blood pressure control. It would be worthwhile to combine the advantages of the two, but the effects of the combination on the circulation are not well investigated. We studied blood pressure, heart rate, and incidence of adverse circulatory events in patients undergoing shoulder surgery in general anaesthesia with or without an interscalene block.

METHODS

Prospective, randomised, blinded study in outpatients (age 18 to 80 years) undergoing shoulder arthroscopy. General anaesthesia was with propofol/opioid, interscalene block with 40 ml 1% mepivacaine. Hypotension requiring treatment was defined as a mean arterial pressure <60 mmHg or a systolic pressure <80% of baseline; relevant bradycardia was a heart rate <50 bpm with a decrease in blood pressure.

RESULTS

Forty-two patients had general anaesthesia alone, 41 had general anaesthesia plus interscalene block. The average systolic blood pressure under anaesthesia in the beach-chair position was 114 ± 7.3 vs. 116 ± 8.3 mmHg (p = 0.09; all comparisons General vs. General-Regional). The incidence of a mean arterial pressure under 60 mmHg or a decrease in systolic pressure of more than 20% from baseline was 64% vs. 76% (p = 0.45). The number of patients with a heart rate lower than 50 and a concomitant blood pressure decrease was 8 vs. 5 (p = 0.30).

CONCLUSION

One can safely combine interscalene block with general anaesthesia for surgery in the beach-chair position in ASA I and II patients.

CLINICAL TRIAL NUMBER

DRKS00005295.

[Localization of peripheral nerves. Success and safety with electrical nerve stimulation]

Peripheral electrical nerve stimulation is one of the standard applications in peripheral regional anesthesia in addition to the ultrasound technique. Among other findings, the visualization of needle and nerve during ultrasound-guided blockade caused a change in clinical practice of peripheral nerve stimulation in the last decade. In the present article old and new aspects of principles and clinical practice of the nerve stimulation technique are presented and summarized in a total clinical concept in order to achieve safe and successful peripheral regional anesthesia using electrical peripheral nerve stimulation.

Ultrasound for regional anesthesia in children

The use of regional anesthesia in children is increasing. Rapid advancement in the use of ultrasound guidance has allowed for a greater ease in performing peripheral regional anesthesia in pediatrics. Successful peripheral nerve blockade provides children with analgesia that will improve their operative experience.

The use of train of four monitoring for clinical evaluation of the axillary brachial plexus block

The axillary approach of brachial plexus anesthesia is the most commonly used technique for forearm and hand surgery. Dynamometer is known as objective test for the clinical assessment of motor block of the nerves in brachial plexus block. However, the use of this device may not always be practical in operating room. The train-of-four (TOF) test is a non-invasive peripheral nerve stimulator that shows the level of motor block of muscle relaxants. The aim of the study is to investigate the use of TOF testing as a peripheral nerve stimulator for objective clinical evaluation of motor block at axillary brachial plexus block. 44 patients were randomized according to the development of partial or complete motor in the axillary brachial plexus block. The nerves were selectively localized by nerve stimulation and ultrasound guidance. After obtaining an appropriate peripheral motor response, predetermined volumes of bupivacaine were selectively injected to the 4 nerves. Sensory, motor block levels and TOF values were measured at 10th, 20th, 30th minutes immediately after the axillary brachial plexus block. TOF values were gradually decreased and significant difference was observed between the development of a complete and partial motor block at 30th minute. TOF values were also significantly less in patients of complete sensory block than the patients of partial sensory block at 30th minute. The use of TOF monitoring may be beneficial to assess the objective clinical effect of motor block in the patients with axillary brachial plexus nerve block.