Yumin Jo and Jiho Park are contributed equally to this work.
The corner pocket (CP) approach for supraclavicular block (SCB) prevents ulnar nerve (UN) sparing due to needle proximity to the lower trunk. Improved ultrasound resolution has suggested that the intertruncal (IT) approach is a suitable alternative method. We compared efficiency of these two approaches on the UN blockade.
Sixty patients were randomized to undergo SCB using the ultrasound-guided CP or IT approach. For lower trunk blockade, 10 ml of local anesthetic agents (1 : 1 mixture of 0.75% ropivacaine and 1% lidocaine) were injected in the CP (CP approach) or between the lower and middle trunks (IT approach). Additional 15 ml was injected identically to block the middle and upper trunks in both groups. Sensory and motor blockade was evaluated after intervention.
Complete sensory blockade (75.9% [22/29] vs. 43.3% [13/30], P = 0.023) and complete motor blockade (82.8% [24/29] vs. 50.0% [15/30], P = 0.017) of the UN at 15 min after SCB were significantly more frequent in the IT than in the CP group. Sensory block onset time of the UN was significantly shorter in the IT compared to the CP group (15.0 [10.0, 15.0] min vs. 20.0 [15.0, 20.0] min, P = 0.012).
The IT approach provided a more rapid onset of UN blockade than the CP approach. These results suggest that the IT approach is a suitable alternative to the CP approach and can provide faster surgical readiness.
The supraclavicular block (SCB) is widely used for intraoperative anesthesia and postoperative analgesia. The location of the lower trunk deep within the neural cluster, however, has raised concerns of ulnar nerve (UN) sparing when local anesthetic is not appropriately injected [
Recent improvements in ultrasound resolution have enhanced the ability to accurately identify and selectively block the three trunks of the brachial plexus [
Although both approaches have been found to avoid UN sparing during SCB, no studies to date have directly compared the efficiency of UN blockade by the IT and CP approaches. We hypothesized that the IT approach (injection between lower and middle trunks) would result in a more complete blockade rate of the UN compared to the CP approach (injection below the lower trunk) at 15 min after blockade. The present study therefore compared the ulnar block characteristics of these two approaches.
The protocol of this prospective, parallel-arm, double-blind, randomized controlled superiority study was approved by the Institutional Review Board of Chungnam National University Hospital (CNUH 2020-05-070-001) and the trial was registered at the Clinical Research Information Service, a clinical trial registry in Korea (KCT0005268). This clinical research was done following the ethical principles for medical research involving human subjects in accordance with the Helsinki Declaration 2013. This study enrolled patients aged 20–70 years with American Society of Anesthesiologists physical status classification I and II and scheduled for elective forearm or hand surgery at Chungnam National University Hospital (Daejeon, Korea). All patients provided written informed consent. Patients were excluded if they refused to participate, had a local infection at the nerve block site, were hypersensitive to amide local anesthetic, had ipsilateral arm neuropathy, or had a history of neck surgery.
Study data were collected and managed using Research Electronic Data Capture (REDCap) software, a secure, web-based platform designed to support capturing of data for research studies and hosted at Chungnam National University Hospital (redcap.cnuh.co.kr) [
All blocks were performed by a single anesthesiologist (Y.J.) with experience in ultrasound guided regional anesthesia and under the direct supervision of the principal investigator (B.H.). Patients were randomly assigned at a ratio of 1 : 1 to the IT or CP group. Block randomization at sizes of 2 and 4 was performed using a random sequence generator (
Immediately prior to the block, each patient was administered 1 mg intravenous midazolam for pre-medication. All blocks were performed under ultrasound guidance using an in-plane technique with a high-resolution ultrasound system (X-Porte, FUJIFILM SonoSite, Inc., USA), a high frequency linear probe (HFL50xp: 15–6 MHz, X-Porte), and a nerve stimulator (0.1 ms, 0.5 mA, 2 Hz, sentinel mode, MultiStim SENSOR, PAJUNK, Germany). Each patient was injected with a total of 25 ml of a 1 : 1 mixture of 0.75% ropivacaine and 1% lidocaine using a 22 gauge, 80 mm, echogenic needle (SonoPlex cannulas, PAJUNK, Germany).
Patients were maintained in a supine position with the head turned to the contralateral side and the ipsilateral shoulder slightly elevated with a pillow. The needle was inserted lateral to the brachial plexus through the prevertebral fascia. In the IT group, the hyperechoic outer boundaries (epineurium) of each trunk were distinguished by ultrasound scanning. The optimal image for patients in the IT group was defined as an image with well differentiated middle and lower trunks. Efforts were not required to obtain a perfect CP view. The gap between the lower and middle trunks was confirmed, first by carefully injecting 0.5 ml of local anesthetic agents to open up the adipose tissue layer (hydrodissection), and subsequently by securing a safe route for needle advancement in the IT plane. While confirming that the trunk of the brachial plexus was not swollen, 10 ml of local anesthetic agents was slowly injected between the lower and middle trunks, 7.5 ml was injected between the middle and upper trunks, and the remaining 7.5 ml was injected between the upper trunk and prevertebral fascia (
Sedation was induced using dexmedetomidine (loading dose 1 μg/kg for 10 min and maintenance dose of 0.2–0.5 μg/kg/h) and discontinued at the beginning of skin suture. Supplemental oxygen was administered prior to sedation at a rate of 5 L/min via a simple facial mask. Brachial plexus block (BPB) was considered successful when the surgery was completed without the need to inject additional local anesthetics into the surgical field, without the need to perform a rescue nerve block, and without conversion to general anesthesia. These decisions were completely at the discretion of the attending anesthesiologist. At the time of the BPB procedure, the procedure time, defined as the interval between needle insertion and removal, and the presence of the dorsal scapular artery (DSA) in the ultrasound scan images were recorded.
Immediately after the BPB procedure, the assigned, blinded outcome assessor, who was not present during the BPB procedure, measured patient satisfaction by asking the patients: How would you score your discomfort during the block on a scale of 0 to 10, where 0 indicates no discomfort and 10 indicates the worst discomfort imaginable. The same researcher assessed sensory block (pin-prick test) and motor block in the areas of the ulnar (UN), median (MN), musculocutaneous (MCN), and radial (RN) nerves every 5 min for at least 30 min until the blockade was complete. Sensory blockade was graded on a 10-point scale (normal = 10, absent = 0) relative to a pin-prick sensation in the contralateral arm. Sensory blockade of the UN, MN, MCN, and RN was assessed on the volar aspect of the fifth finger, the volar aspect of the thumb, the lateral aspect of the forearm, and the lateral aspect of the dorsum of the hand, respectively. Motor blockade was graded on a three-point scale (normal = 3, mildly reduced = 2, markedly reduced = 1, unable to move = 0). Motor blockade of the UN, MN, MCN, and RN was assessed by measuring thumb opposition with the little finger, thumb opposition with the index finger, elbow flexion, and wrist extension, respectively.
Sensory recovery in the UN territory was assessed every 30 min by the patients. The patients were instructed to repeatedly pinch the little finger of each hand and check the time of sensory normalization in the anesthetized hand by comparison with the opposite hand. The assessor visited the patient the following morning (within 24 h postoperatively) to ascertain the presence of residual blockade, neurologic deficits, and any other symptoms. Neurologic complications were evaluated again during an outpatient clinic visit 7 days after surgery. Postoperative chest radiography is a routine postoperative pathway of our institution and was used to identify accidental pneumothorax.
The primary outcome was the proportion of participants with complete sensory block of the UN 15 min after BPB. Complete sensory blockade of each nerve was defined as a pin-prick score of 0. Time to readiness for surgery was defined as the time required to achieve complete sensory block of the areas of all four nerves. Secondary outcomes included the proportion of patients with complete motor blockade, duration of the procedure, patient discomfort score during the procedure, incidence of noticing the DSA during the procedure, duration of sensory blockade of the UN, and sensory and motor scores as a function of time.
The sample size was calculated based on the primary outcome according to the superiority hypothesis [
All analyses were per protocol using R software version 4.0.0 (R Project for Statistical Computing, Austria). Normality of distribution of continuous variables was assessed using Shapiro–Wilk tests. Normally distributed continuous variables were reported as mean ± standard deviation (SD) and analyzed by independent sample t-tests, whereas non-normally distributed continuous variables were reported as median (interquartile range) and analyzed by Mann–Whitney
Of 60 patients assessed for eligibility, 59 were enrolled and analyzed; one patient randomized to the IT group was excluded due to uncooperative outcome evaluation (
The rates of complete sensory blockade (75.9% [22/29] vs. 43.3% [13/30], P = 0.023) and complete motor blockade (82.8% [24/29] vs. 50.0% [15/30], P = 0.017) of the UN after 15 min were significantly higher in the IT than in the CP group (
Total procedure duration and patient discomfort scores were not significant in the IT and CP groups. However, the DSA was only seen in ultrasonographic images in the 7 patients of IT group. Unlike the onset time, which was faster in the IT group, the total duration of UN sensory block did not differ in the IT and CP groups (
UN sparing is a frequent limitation in the conventional approach to SCB when relying on blind techniques or nerve stimulated muscle contraction [
Compared with extrafascial injection, subfascial injection was reported to induce a faster onset and prolonged duration of sensory and motor blockade without causing neurological complications [
Early papers of ultrasound guidance described the brachial plexus as a ‘cluster of hypoechoic nodules’ or as a main and other satellite ‘neural clusters’ [
Recent advancements in sonographic resolution have led to the recognition that the original cluster was composed of individual trunks and/or divisions [
During proper injections, we observed the expansion of extraneural tissues and increases in the diameter of the entire complex under the fascia, while each trunk remained at its original size. For successful SCB, the block needle should penetrate the brachial plexus sheath and local anesthetic agents should be injected into the connective tissue matrix between the neural elements [
To obtain the optimal image of the CP and avoid pleural puncture, the probe had to be tilted more caudally until the subclavian artery and brachial plexus were above the first rib, particularly when the brachial plexus was located more medially with respect to the first rib. An important advantage of the IT approach is that caudal tilting of the probe and deep injection were not absolutely required during lower trunk block. Despite these advantages, however, the DSA was observed in about 24% of patients in the IT group. In such cases, it was inevitable to tilt the probe caudally as in the CP approach to avoid arterial puncture. The DSA was identified as a branch of the subclavian artery that passed through the brachial plexus. A study assessing the presence of the DSA at three ultrasound probe positions commonly used in SCB found that the DSA passed most frequently (23/106, 21.7%) through a probe position in which the brachial plexus was on the first rib or was partially on the pleura and lateral to the subclavian artery, which lay directly on the pleura [
Another interesting point of our study is that unlike the previous study reporting UN sparing after the CP approach [
This study had several limitations. First, the success of the block was evaluated at 15 min, suggesting the need for caution when generalizing our results. The time setting in this study was based on the work flow in our institution. Second, all nerve blocks were performed by experienced anesthesiologists. Because the IT approach requires the use of hydrodissection to construct a path between the trunks to avoid neural injury, there is a need for a learning curve. Third, the sensory block duration time was determined based on self-reporting by patients, suggesting that the quality of the data may be relatively low.
In conclusion, the IT approach provides a more rapid onset of UN blockade than the CP approach and can be a good alternative for SCB. However, additional studies are required to ascertain the safety of the IT approach, especially in terms of neural damage.
This research was supported by National Research Foundation of Korea (NRF-2019R1G1A1099660).
No potential conflict of interest relevant to this article was reported.
Yumin Jo (Conceptualization; Data curation; Methodology; Project administration; Writing – original draft)
Jiho Park (Investigation; Resources; Software; Writing – review & editing)
Chahyun Oh (Formal analysis; Software; Validation; Visualization)
Woosuk Chung (Validation; Visualization; Writing – review & editing)
Seunghyun Song (Conceptualization; Methodology; Software)
Jieun Lee (Investigation; Project administration; Resources)
Hansol Kang (Conceptualization; Methodology; Project administration; Validation)
Youngkwon Ko (Investigation; Supervision; Validation)
Yoon-Hee Kim (Investigation; Resources; Supervision)
Boohwi Hong (Conceptualization; Formal analysis; Funding acquisition; Supervision; Writing – review & editing)
Progression of sensory and motor blockade of the UN territory in patients in the IT and CP groups. Sensory score (normal: 10, absent: 0), Motor grade (normal = 3, mildly reduced = 2, markedly reduced = 1, unable to move = 0). IT: intertruncal, CP: corner pocket.
(A) Ultrasonography image during the IT approach. Note the needle (white arrow head) has penetrated the brachial plexus sheath, and its tip is lying in the IT layer. The middle trunk appeared to be floating on the injected local anesthetic drug. (B) Ultrasonography image during the CP approach. Injection of local anesthetic agents in the CP. *CP: corner pocket, FR: first rib, IT: intertruncal, SA: subclavian artery, Pl: pleura.
CONSORT diagram showing the patients at every stage of the randomized controlled trial. IT: intertruncal, CP: corner pocket.
Proportions of patients with complete sensory (A) and motor (B) block according to time in distributions of the ulnar nerve. Proportions of patients with complete sensory (C) and motor (D) block according to time in distributions of the all four nerves (total). IT: intertruncal, CP: corner pocket. *P < 0.05.
Onset times of sensory block of each nerve and all four nerves in the IT and CP groups. IT: intertruncal, CP: corner pocket, ns: not significant. *P < 0.05.
Demographic and Clinical Characteristics
Variable | IT group (n = 29) | CP group (n = 30) |
---|---|---|
Age (yr) | 52.0 (27.0, 59.0) | 48.5 (26.0, 60.0) |
Sex (M/F) | 15/14 | 15/15 |
Height (cm) | 167.0 (157.0, 176.0) | 164.0 (154.0, 175.0) |
Weight (kg) | 65.0 (56.0, 80.0) | 62.5 (55.0, 74.0) |
Surgery time (min) | 60.0 (52.0, 80.0) | 64.0 (48.0, 82.0) |
ASA PS (I/II) | 9/20 | 9/21 |
Type of surgery (a/b/c/d) | 2/17/6/4 | 3/10/4/13 |
Values are presented as median (Q1, Q3) or numbers. IT: intertruncal, CP: corner pocket, ASA PS: American Society Anesthesiologists physical status, Type of surgery; a: arthroscopic surgery, b: fracture or ulnar shortening, c: hardware removal, d: soft tissue, tendon, ligament repair surgery.
Effects of IT and CP Blockade on Patient Outcomes
Variable | IT group (n = 29) | CP group (n = 30) | P value |
---|---|---|---|
Procedure time (s) | 250.0 (232.0, 277.0) | 268.0 (213.0, 299.0) | 0.834 |
Patient discomfort scale (0–10) | 3.0 (2.0, 6.0) | 5.0 (3.0, 6.0) | 0.304 |
Visualization of DSA | 7 (24.1) | 0 (0) | 0.014 |
Sensory block duration of UN (min) | 548.5 (476.0, 698.0) | 502.5 (433.5, 646.0) | 0.313 |
Values are presented as median (Q1, Q3) or number (%). IT: intertruncal, CP: corner pocket, DSA: dorsal scapular artery, UN: ulnar nerve.