Anesthetic effect of ultrasound-guided block of the musculocutaneous nerve during endovascular treatment of dysfunctional radiocephalic arteriovenous fistulas

BACKGROUND

Delivering requisite and minimal anesthesia for endovascular treatment (EVT) of dysfunctional arteriovenous fistulas (AVFs) under the target nerve block can achieve reasonable analgesia. We evaluated the anesthetic efficacy of ultrasound (US)-guided selective block of the musculocutaneous nerve (MCN) during the EVT of runoff venous strictures in the forearm through the radiocephalic (RC)-AVF at the wrist or the anatomical snuff box and analyzed the factors inhibiting the analgesia achieved under the MCN block.

METHODS

We enrolled 30 adult patients undergoing hemodialysis who had received 78 EVT sessions in an outpatient clinic mainly for long and/or multiple outflow-venous strictures in the forearm under US-guided blocks of the MCN, which provides sensory innervation to the anterolateral forearm where the cephalic vein courses. We assessed patients' pain during balloon dilations using the Wong-Baker FACES® Pain Rating Scale (WBFRS) and evaluated the factors increasing the pain (WBFRS score ⩾4), including patient characteristics, dilated strictures, additional nerve blocks, and types of balloon catheters.

RESULTS

In 25 EVT sessions (32.1%) out of 78 sessions, patients complained of stronger pain (WBFRS score ⩾4), while in the other 53 sessions (67.9%), presented with no pain and slight pain (WBFRS score = 0 or 2). Univariate analysis clarified that dilation of the AVF anastomosis, presence of dilated stenosis >4 cm, and a single block of the MCN or its sensory terminal significantly triggered more pain (p < 0.05). Consequently, multivariate analysis of all the factors with p < 0.1 in the univariate analysis, including multiple dilated stenosis sites, demonstrated that dilation of the AVF anastomosis significantly caused severe pain despite the anesthesia of the MCN block (p < 0.05).

CONCLUSION

US-guided selective block of the MCN could be a leading anesthetic option for EVT for multiple long stenoses of the cephalic vein draining through the RC-AVF in the wrist or anatomical snuff box.

Comparing Electrical Stimulation With and Without Ultrasound Guidance for Phenol Neurolysis to the Musculocutaneous Nerve

BACKGROUND

Ultrasound guidance is increasingly being used for neurolytic procedures that have traditionally been done with electrical stimulation (e-stim) guidance alone. Ultrasound visualization with e-stim-guided neurolysis can potentially allow adjustments in injection protocols that will reduce the volume of neurolytic agent needed to achieve clinical improvement.

OBJECTIVE

This study compared e-stim only to e-stim with ultrasound guidance in phenol neurolysis of the musculocutaneous nerve (MCN) for elbow flexor spasticity. We also evaluated the ultrasound appearance of the MCN in this population.

DESIGN

Retrospective review.

SETTING

University hospital outpatient clinic.

PARTICIPANTS

Adults (N = 167) receiving phenol neurolysis to the MCN for treatment of elbow flexor spasticity between 1997 and 2014 and adult control subjects.

METHODS

For each phenol injection of the MCN, the method of guidance, volume of phenol injected, technical success, improved range of motion at the elbow postinjection, adverse effects, reason for termination of injections, and details of concomitant botulinum toxin injection were recorded. The ultrasound appearance of the MCN, including nerve cross-sectional area and shape, were recorded and compared between groups.

MAIN OUTCOME MEASURES

The volume of phenol injected and MCN cross-sectional area and shape as demonstrated by ultrasound.

RESULTS

The addition of ultrasound to e-stim-guided phenol neurolysis was associated with lower doses of phenol when compared to e-stim guidance alone (2.31 mL versus 3.69 mL, P < .001). With subsequent injections, the dose of phenol increased with e-stim guidance (P < .001), but not with e-stim and ultrasound guidance (P = .95). Both methods of guidance had high technical success, improved ROM at elbow postinjection, and low rates of adverse events. In comparing the ultrasound appearance of the MCN in patients with spasticity to that of normal controls, there was no difference in the cross-sectional area of the nerve, but there was more variability in shape.

CONCLUSIONS

Combined e-stim and ultrasound guidance during phenol neurolysis to the MCN allows a smaller volume of phenol to be used for equal effect, both at initial and repeat injection. The MCN shape was more variable in individuals with spasticity; this should be recognized so as to successfully locate the nerve to perform neurolysis.

LEVEL OF EVIDENCE

IV.

Evaluation of the relationship between the topographical anatomy in the axillary region of the brachial plexus and the body mass index

To investigate the topographic anatomy of the median, musculocutaneous, radial and ulnar nerves with respect to the axillary artery and to seek whether these configurations are associated with baseline descriptive data including age, gender, and body-mass index. This cross-sectional trial was carried out on 199 patients (85 women, 114 men; average age: 46.78 ± 15.45 years) in the department of anaesthesiology and reanimation of a tertiary care center. Topographic anatomy of the median, musculocutaneous, radial and ulnar nerves was assessed with ultrasonography. Localization of these nerves with respect to the axillary artery was marked on the map demonstrating 16 zones around the axillary artery. Frequencies of localizations of every nerve in these zones were recorded, and the correlation of these locations with descriptive data including age, gender and BMI was investigated. There was no difference between women and men for the distribution of the median (p = 0.74), ulnar (p = 0.35) and radial (p = 0.64) nerves. However, the musculocutaneous nerve was more commonly located in Zone A13 in men compared to women (p = 0.02). The localization of the median (p = 0.85), ulnar (p = 0.27) and radial (p = 0.88) nerves did not differ remarkably between patients with BMI < 25 kg/m² and patients with BMI ≥ 25 kg/m². Notably, the musculocutaneous nerve was more often determined in Zone A10 in cases with BMI ≥ 25 kg/m² (p = 0.001). Our results imply that the alignment of the musculocutaneous nerve may vary in men and overweight people. This fact must be considered by the anaesthetist before planning the axillary block of brachial plexus. All these informations may enlighten the planning stages of the brachial plexus blockade.

Sonography of the lateral antebrachial cutaneous nerve with magnetic resonance imaging and anatomic correlation

OBJECTIVES

Abnormalities of the lateral antebrachial cutaneous nerve (LABCN) are associated with antecubital elbow conditions, such as distal biceps brachii tendon tears and traumatic cephalic vein phlebotomy. These can lead to lateral forearm, elbow, and wrist symptoms that can mimic other disease processes. The purpose of this study was to characterize the sonographic appearance of the LABCN using cadaveric dissection and retrospective analysis of sonographic examinations of symptomatic patients with magnetic resonance imaging correlation.

METHODS

For the first part of this study, a cadaveric elbow specimen was examined, and sonography was performed after dissection to identify the LABCN. Subsequently, 26 elbows in 13 patients with LABCN abnormalities were identified with sonography and retrospectively evaluated to characterize the appearance of the LABCN in both symptomatic and asymptomatic elbows.

RESULTS

The symptomatic LABCNs showed fusiform enlargement, increased echogenicity, and loss of the normal fascicular echo texture. The mean cross-sectional area of the symptomatic nerves was 12.0 mm(2) (range, 6.1-17.2 mm(2)), with a maximum thickness of 3.5 mm (range, 2.3-5.9 mm), compared to 3.3 mm(2) (range, 1.9-5.2 mm(2)), with a maximum thickness of 1.3 mm (range, 0.9-2.2 mm), in the contralateral normal elbows.

CONCLUSIONS

The close proximity of the LABCN to the distal biceps tendon and the cephalic vein makes it vulnerable to compression and injury in the setting of distal biceps tendon tears and traumatic phlebotomy, which may cause nerve enlargement and increased echogenicity. Awareness of the location and appearance of the LABCN on sonography is important for determining potential causes of lateral elbow and forearm pain.

[Ultrasound-guided axillary block: anatomical variations of terminal branches of the brachial plexus in relation to the brachial artery]

OBJECTIVES

To describe the distribution of the terminal branches of the brachial plexus at the axillary level and define distribution patterns after ultrasound evaluation.

MATERIAL AND METHOD

Fifty volunteers underwent ultrasound bilateral axillary brachial plexus scanning exploration. Nerve distribution around the humeral artery was described and the distance between each nerve and the center of the artery was measured. The distance and relationship between the ulnar nerve and the humeral vein were also recorded.

RESULTS

The median nerve was located in the anterolateral quadrant (-29±40°) and at a mean distance of 2.1±0.9mm from the artery (85%). The ulnar nerve was found at 53±26° and at 4.2±2.1mm from the artery in the anteromedial quadrant (90%), anterolateral to the vein in 46% of cases, and deep to it in 54%. The radial nerve was at 122±38° and at 3.3±1.7mm from the artery in the posteromedial quadrant (86%). The musculocutaneous nerve was found at -103±22° and 9.3±5.6mm from the artery in the posterolateral quadrant (90%) and in the anterolateral quadrant (-55±16°) at 4.8±2.7mm (10%). There were no differences regarding laterality, gender or overweight patients.

CONCLUSIONS

Our results allow defining four different anatomical patterns, two based in the position of the musculocutaneous nerve and two based on the disposition of the ulnar nerve with respect to the humeral vein. These patterns were not related to laterality, gender or body weight.

Variant location of the musculocutaneous nerve during axillary nerve block

We present the case of a 56-year-old man who underwent axillary nerve block for a wrist arthroscopy procedure, with real-time ultrasound and peripheral nerve stimulator guidance. The ulnar nerve and radial nerve were located medial and posterior to the brachial artery, respectively. A large complex structure was noted in the position typically occupied by the median nerve. Contact of this structure with the stimulating needle produced strong biceps contraction, and slight adjustment of the needle resulted in forearm pronation. After injection of 10 mL of local anesthetic near this structure, it appeared to consist of two separate components on ultrasound. We believe that these components represented the median and musculocutaneous nerves lying together, lateral to the artery. Radial, median, ulnar, and musculocutaneous nerve block ensued, and wrist arthroscopy was carried out uneventfully. Knowledge of this anatomical variation may improve anesthesiologists' ability to provide effective axillary block.

The musculocutaneous nerve: ultrasound appearance for peripheral nerve block

BACKGROUND AND OBJECTIVES

To gain complete anesthesia of the forearm, block of the musculocutaneous nerve is necessary. Variations in its course and position make localization of the musculocutaneous nerve problematic. The aim of the study is to describe the ultrasound appearance of the musculocutaneous nerve in the axilla and to suggest potential areas to target neural block.

METHODS

We scanned the axillary regions of 19 volunteers and assessed the size and shape of 34 musculocutaneous nerves at entry into, exit from, and in the center of the coracobrachialis muscle. Furthermore, we measured the depth of the musculocutaneous nerve under the skin surface and its distance from the axillary artery at those 3 measurement points.

RESULTS

As it travels through the coracobrachialis muscle, the musculocutaneous nerve changes in shape from oval to flat-oval to triangular. During this course, the musculocutaneous nerve also separates from the axillary artery and becomes more lateral while changing its depth from the surface. The musculocutaneous nerve increases its transverse area along this nerve path. In 2 subjects, the musculocutaneous nerve could not be visualized unilaterally within the course of the coracobrachialis muscle.

CONCLUSIONS

Knowledge of its ultrasound appearance facilitates localization and successful block of the musculocutaneous nerve. Because the distance between the musculocutaneous nerve and brachial plexus varies, different locations of musculocutaneous nerve puncture during ultrasound-guided regional anesthesia can be chosen.

Ultrasound-guided musculocutaneous nerve block: a description of a novel technique

BACKGROUND AND OBJECTIVE

Localizing the musculocutaneous nerve for neural blockade is crucial to providing surgical anesthesia for the distal forearm. We present a novel approach for localizing and anesthetizing the musculocutaneous nerve.

CASE REPORTS

Ten patients underwent successful ultrasound-guided musculocutaneous nerve blocks. In this technique, either a 10-MHz or a 12-MHz linear probe was placed at the junction of the pectoralis major muscle and the biceps muscle such that the axillary artery was visualized in cross section. The probe was moved towards the biceps muscle until the musculocutaneous nerve was visualized lying between the coracobrachialis and biceps muscles. A 22-gauge, 50-mm b-bevel needle was inserted under direct vision until the needle was adjacent to the nerve. Local anesthetic was then injected, which generated surgical anesthetic conditions in all patients.

CONCLUSION

Ultrasound can facilitate the localization and local anesthetic block of the musculocutaneous nerve.