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Anesthesia & Analgesia:
doi: 10.1213/ANE.0000000000000224
Regional Anesthesia: Research Report

A Randomized Comparison Between Double-Injection and Targeted Intracluster-Injection Ultrasound-Guided Supraclavicular Brachial Plexus Block

Techasuk, Wallaya MD*; González, Andrea P. MD; Bernucci, Francisca MD*; Cupido, Tracy DO, FRCPC*; Finlayson, Roderick J. MD, FRCPC*; Tran, De QH MD, FRCPC*

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Author Information

From the *Department of Anesthesia, Montreal General Hospital, McGill University, Montreal, Quebec, Canada; and Department of Anesthesia, Hospital de Carabineros, Santiago, Chile.

Accepted for publication February 4, 2014.

Funding: None of the authors received funding for this study.

The authors declare no conflicts of interest.

Reprints will not be available from the authors.

Address correspondence to De QH Tran, MD, FRCPC, Department of Anesthesia, Montreal General Hospital, 1650 Ave., CedarD10-144Montreal, QcCanadaH3G-1A4. Address e-mail to de_tran@hotmail.com.

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Abstract

BACKGROUND: In this prospective, randomized, observer-blinded study, we compared double-injection (DI) ultrasound-guided supraclavicular block to a novel targeted intracluster-injection (TII) technique, whereby local anesthetic is injected inside the main and satellite neural clusters (confluences of trunks and divisions of the brachial plexus).

METHODS: Ninety patients were randomly allocated to receive a DI (n = 45) or TII (n = 45) technique for ultrasound-guided supraclavicular block. The local anesthetic drug (lidocaine 1.5% with epinephrine 5 μg/mL) and total volume (32 mL) were identical in all subjects. In both groups, half the volume (16 mL) was injected inside the main neural cluster. For the DI technique, the second half (16 mL) was deposited at the “corner pocket” (intersection of the first rib and subclavian artery). In contrast, for the TII technique, the remaining half was divided into equal aliquots and injected inside every single satellite cluster. The main outcome variable was the total anesthesia-related time (sum of performance and onset times).

RESULTS: Due to a quicker onset (mean ± standard deviation (SD): 10.1 ± 6.4 vs 18.5 ± 8.3 minutes; P < 0.0001), the total anesthesia-related time was shorter with the TII technique (21.2 ± 7.7 vs 27.7 ± 9.0 minutes; P = 0.001; 95% confidence interval for the difference of the means: 2.90–10.08 minutes). There were 0 (of 45) and 3 (of 45) surgical failures for the TII and DI group, respectively. Thus, the 2 methods achieved comparable rates of surgical anesthesia (93.3%–100.0%; 95% confidence interval for the difference of the success rates: −2.3% to 17.9%). No intergroup differences were observed in block-related pain scores and adverse events. The DI group required fewer needle passes (median ± interquartile range: 4 ± 2 vs 7 ± 3; P < 0.0001) as well as shorter needling (8.4 ± 2.9 vs 10.7 ± 2.7 minutes; P < 0.0001) and performance (9.0 ± 3.2 vs 11.2 ± 3.0 minutes; P = 0.001) times.

CONCLUSION: Although DI and TII ultrasound-guided supraclavicular blocks seem to provide comparable success rates, we cannot exclude the possibility that an intergroup difference of 17.9% might have gone undetected. Due to its quick onset, the TII technique results in a shorter total anesthesia-related time.

Two approaches have been described for ultrasound-guided supraclavicular blocks. The “proximal” approach, pioneered by Kapral et al.1 and performed at the base of the neck, aims to anesthetize the brachial plexus where its 3 trunks can be visualized as a column of hypoechoic nodules.1 Alternately, a “distal” approach, described by Chan et al.2 and performed just above the clavicle, targets the neural cluster (confluence of trunks and divisions), which is situated superolateral to the subclavian artery.

Techniques for distal supraclavicular blocks include injecting the entire volume of local anesthetic at the intersection of the first rib and subclavian artery (i.e., the “corner pocket” technique)3 as well as a 2-injection technique, whereby half the volume is deposited at the corner pocket, and half is injected inside the neural cluster.4–6 In a previous trial, we observed similar success rates and total anesthesia-related times (sums of performance and onset times) for the 2 methods as the shorter onset time associated with the double-injection (DI) technique was counterbalanced by its longer performance time.4 Nonetheless, we continued to use and teach the DI technique5 because, with acquired proficiency, our trainees were able to shorten the performance time while retaining the benefit of a quick onset. We also observed that, in many patients, rather than being a singular entity, the neural cluster is composed of 1 main structure surrounded by smaller satellite clusters, We hypothesized that, with the DI method, the corner pocket injection serves to anesthetize the satellite clusters through indirect local anesthetic diffusion. Therefore, we refined our technique by foregoing local anesthetic deposition at the corner pocket in favor of a novel targeted intracluster-injection (TII) technique, whereby local anesthetic is injected inside the main as well as the satellite clusters.

In this trial, we compared DI and TII ultrasound-guided supraclavicular blocks. Based on our initial experience, we expected a shorter onset time with the new TII method. However, we could not exclude the possibility that it would also require a longer performance time. As a precautionary measure, we hypothesized that the total anesthesia-related time could be comparable for the 2 techniques and designed the study as an equivalence trial.

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METHODS

After obtaining ethics committee approval (McGill University Health Center, Montreal, Canada, and Hospital de Carabineros, Department of Anesthesia, Santiago, Chile) and written informed consent, 90 patients undergoing surgery of the elbow, forearm, wrist, or hand were prospectively enrolled in 2 teaching hospitals (Montreal General Hospital and Hospital de Carabineros). Inclusion criteria were age between 18 and 80 years, ASA physical status I to III, and body mass index between 20 and 35 kg/m2. Exclusion criteria were inability to consent to the study, preexisting neuropathy, coagulopathy, hepatic, or renal failure, allergy to local anesthetic, pregnancy, and previous surgery in the supraclavicular fossa.

After arrival in the induction room, an 18- or 20-gauge IV catheter was placed in the upper limb contralateral to the surgical site and standard IV premedication (0.03 mg/kg of midazolam and 0.6 μg/kg fentanyl) was administered to all patients. Supplemental oxygen (nasal cannulae at 4 L/min) and standard American Society of Anesthesiologists monitors were applied throughout the procedure.

Using a computer-generated sequence of random numbers and a sealed envelope technique, 90 patients were randomly allocated to receive a DI or TII ultrasound-guided supraclavicular block. All blocks were performed by residents, fellows, or staff anesthesiologists. Independently of their status, operators were considered experts for a given technique if, before the start of the study, they had an experience level equal or superior to 60 blocks. Otherwise, they were considered trainees.7 All blocks were supervised by 1 of 3 coauthors (DQHT, WT, and APG), who have experience with both techniques. The 21-gauge, 5-cm block needles (StimuQuick Echo, Arrow International Inc., Reading, PA), portable ultrasound machine (Sonosite M-Turbo, Bothell, WA), and 6 to 13 MHz linear probes were the same in all patients.

For both techniques, the ultrasound probe was applied in a sterile fashion in the supraclavicular fossa to obtain a short-axis view of the subclavian artery and the neural clusters (Fig. 1). A skin wheal was raised with 3 mL lidocaine 1%. For the DI technique, using an in-plane technique and a lateral to medial direction, the block needle was initially advanced until its tip was positioned at the intersection of the first rib and subclavian artery (corner pocket). Half the volume (16 mL) of lidocaine 1.5% with epinephrine 5 μg/mL was injected in this location. Subsequently, the needle was redirected toward the main (largest) neural cluster, where the remaining volume (16 mL) of lidocaine was deposited.5 For the TII technique, the first half of the local anesthetic volume was injected inside the main neural cluster. Subsequently, the remaining local anesthetic volume (16 mL) was divided into equal aliquots and deposited inside each satellite cluster. For instance, if 2, 3, 4, or 5 satellite clusters were identified; aliquots of 8, 5.3, 4, and 3.2 mL were used, respectively. Neural clusters were easily differentiated from sonographic artifacts by their ability to roll away when contacted by the needletip.2 Although hydrodissection was not used for either group, a small volume of normal saline (<1 mL) was initially injected to ensure that the needletip was correctly positioned at the intended targets (corner pocket, main, or satellite cluster). A video clip of TII supraclavicular block can be found on the authors’ free access, educational website: www.regionalworks.ca.

Figure 1
Figure 1
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For both techniques, the imaging time was defined as the time interval between contact of the ultrasound probe with the patient and the acquisition of a satisfactory picture. The needling time (defined as the temporal interval between the start of the skin wheal and the end of local anesthetic injection through the block needle) was also recorded. Thus, performance time was defined as the sum of imaging and needling times. The number of needle passes was also recorded. The initial needle insertion counted as the first pass. Any subsequent needle advancement that was preceded by a retraction of at least 10 mm counted as an additional pass.8 The number of clusters, level of procedural pain as well as the incidence of vascular puncture, and paresthesia were noted. In both groups, recording of imaging/needling/performance times, number of needle passes, number of clusters, vascular puncture, and paresthesia was performed by the coauthor supervising the block (DQHT, WT, or APG). The time required to identify the different clusters was factored into the imaging time as a nonsterile preprocedural scan was not performed in either group.

After local anesthetic injection through the block needle, measurements of brachial plexus blockade were performed every 5 minutes until 30 minutes by a blinded observer. Sensory blockade of the musculocutaneous, median, radial, and ulnar nerves was graded according to a 3-point scale using a cold test: 0 = no block, 1 = analgesia (patient can feel touch, not cold), 2 = anesthesia (patient cannot feel touch).9 Sensory blockade of the musculocutaneous, median, radial, and ulnar nerves was assessed on the lateral aspect of the forearm, the volar aspect of the thumb, the lateral aspect of the dorsum of the hand, and the volar aspect of the fifth finger, respectively.9 Motor blockade was also graded on a 3-point scale: 0 = no block, 1 = paresis, 2 = paralysis.9 Motor blockade of the musculocutaneous, radial, median, and ulnar nerves was evaluated by elbow flexion, thumb abduction, thumb opposition, and thumb adduction, respectively.9 Overall, the maximal composite score was 16 points. We considered the patient ready for surgery when a minimal composite score of 14 points was achieved, provided the sensory block score was equal or superior to 7 of 8 points. The onset time was defined as the time required to obtain 14 points. Therefore, the total anesthesia-related time was equal to the sum of performance and onset times. If, after 30 minutes, the composite score was <14 points, the patient was transferred to the operating room for the start of the surgery. For these patients, we did not record an onset time. Surgical anesthesia was recorded by the same blinded observer and defined as the ability to proceed with surgery without the need for narcotics, general anesthesia, rescue blocks, or local anesthetic infiltration by the surgeon.9–12 However, in case of anxiety (as voiced by patients or determined by the treating anesthesiologists), subjects could receive a propofol infusion (25–80 μg/kg/min) intraoperatively, provided response to verbal stimulus was maintained. In case of pain during surgery, the block was considered a failure, and patients were allowed to receive narcotics, general anesthesia, rescue blocks, or local anesthetic infiltration. This was left to the discretion of the treating anesthesiologist. The blinded observer also recorded the patient’s anthropometric data, the level of procedural pain, as well as the incidence of Horner syndrome.

Postoperatively, for hand surgery, pain control was managed in the recovery room with ultrasound-guided supplemental blocks at the elbow using a long-acting local anesthetic agent (bupivacaine). The choice of supplemental block (median, radial, or ulnar) was left to the discretion of the treating anesthesiologist and was not recorded for the purpose of the study. For surgical procedures involving the elbow, forearm, or wrist, perineural supraclavicular catheters were placed with ultrasongraphy using a 17-gauge Tuohy needle and a standard kit (StimuCath, Teleflex Medical, Research Triangle Park, NC). Placement of perineural catheters, performed by the same operator as the initial block with lidocaine 1.5%, did not impact the recording of data since it was performed during the 5-minute interval between the end of the lidocaine injection through the 21-gauge block needle and the first sensorimotor assessment of the block. During the insertion of the perineural catheter, no additional local anesthetic or normal saline was injected. Furthermore, procedure-related pain was assessed before skin puncture with the 17-gauge Tuohy needle.

One week after the surgery, all patients were contacted by the blinded investigator to inquire about complications such as persistent numbness/paresthesia or motor deficit.

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STATISTICAL ANALYSIS

We expected a shorter onset time with the new TII method. However, the latter could also require a longer performance time. As a precautionary measure, we hypothesized that the total anesthesia-related time could be comparable for the 2 techniques and designed the study as an equivalence trial.

Based on our experience, a DI supraclavicular block, whereby half the volume of local anesthetic drug is injected at the corner pocket and half inside the main neural cluster, provides a total time of 23.3 ± 7.7 minutes.5 We deemed that a difference in total time of 25% (5.8 minutes) or less has minimal clinical relevance. Thus, a calculated sample size of 40 patients per group was required to provide a statistical power of 0.90 and a type-I error of 0.025. Since onset and total times can only be calculated for patients who achieve a minimal composite score of 14 points at 30 minutes and since we expected 90% of subjects to achieve such a score with 32 mL lidocaine 1.5% with epinephrine 5 μg/mL,5 we recruited 45 patients per group to account for those who would not reach 14 points.

Results for the primary outcome were reported as a 95% confidence interval (CI) for the difference of the means, and equivalence was accepted if it was within the tolerated interval (± 5.8 minutes). Statistical analysis was performed using SPSS version 20 statistical software (IBM Armonk, NY). For continuous data, normality was first assessed with the Kolmogorov-Smirnov test and then analyzed with the Student t test with unequal variances. Data that did not have a normal distribution, as well as ordinal data, were analyzed with the Mann-Whitney U test. For categorical data, Fisher exact test was used. The 95% CI for the difference in success rate was calculated using the Newcombe-Wilson test with continuity correction13 according to the website http://vassarstats.net/prop2_ind.html. All P values presented were 2-sided, and values inferior to 0.05 were considered significant.

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RESULTS

Between February 4, 2013 and June 4, 2013, 90 subjects were recruited. There were no patient dropouts. No differences in anthropometric data or surgical procedure were observed between the 2 groups (Table 1).

Table 1
Table 1
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Our primary end point was the total anesthesia-related time. All other variables were considered secondary end points. Due to a quicker onset, the total anesthesia-related time was shorter with the TII technique (P = 0.001) (Table 2). There were 0 and 3 surgical failures for the TII and DI group, respectively. Thus, the 2 methods achieved comparable rates of surgical anesthesia (P = 0.242). The DI group required fewer needle passes as well as shorter needling and performance times. No differences were found in procedural pain, imaging time, and adverse events (Table 2). Despite identical median (3) and range (2–5) values, there was a statistical difference (P = 0.001) in the number of clusters, as 132 and 156 total clusters were recorded in the DI and TII groups, respectively.

Table 2
Table 2
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During the first 25 minutes, the TII group displayed higher proportions of patients with minimal composite scores of 14 points (all P ≤ 0.01). However, no differences were found at 30 minutes (Fig. 2). The rates of complete sensory and motor blockade of the median/radial/ulnar nerves were more elevated with the TII technique during the first 15 to 20 minutes (all P < 0.05). Higher rates of complete sensory and motor blockade of the musculocutaneous nerve were seen in the TII group at all measurement intervals (all P < 0.05) (Figs. 3 and 4).

Figure 2
Figure 2
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Figure 3
Figure 3
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Figure 4
Figure 4
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Patient follow-up at 1 week revealed no motor deficit. Numbness occurred in 1 patient in each of the 2 groups. Only the patient randomized to the TII technique reported a paresthesia during the performance of the block. In both cases, the numbness had spontaneously resolved by the subsequent follow-up (1 month).

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DISCUSSION

In this prospective, randomized trial, we compared the DI technique with a novel TII method for ultrasound-guided supraclavicular block. Our results show that both techniques provide similar rates of surgical anesthesia. Because the longer performance time was compensated by a shorter onset, we observed that the TII method was associated with a shorter total anesthesia-related time. Expectedly, TII supraclavicular block required more needle passes. However, the additional needle redirections did not lead to an increased incidence in vascular puncture, paresthesia, or postoperative neurologic deficits. We recorded a higher number of neural clusters in the TII group: we speculate that this intergroup difference did not stem from a discrepancy in neural architecture but in block technique. Occasionally, puncture of a cluster (followed by the injection of 1 mL saline) resulted in a division of the latter into smaller clusters. Thus, with the DI technique, since we were only allowed to penetrate the main cluster, we may have underestimated the number of satellite clusters and what appeared unitary on screen could have been in fact a grouping of smaller structures.

Compared with our previous dose-finding study for ultrasound-guided supraclavicular block,5 the DI technique required longer onset and total times in the current study (18.5 and 27.7 vs 15.3 and 23.3 minutes, respectively). We attribute these differences to a change in equipment. In the current trial, we used a 21-gauge block needle instead of a 17-gauge Tuohy needle. Since resistance to flow decreases with larger bore needles, we speculate that local anesthetic injected at the corner pocket in the previous study dispersed and reached the satellite clusters more efficiently. In turn, this led to shorter onset and total times. Despite the difference in needle size, the percentage of patients with a 14-point minimal composite score at 30 minutes (88.9%) and performance time (9.0 minutes) echo our previous findings (90.0% and 8.0 minutes, respectively).5

The significance and safety of needletip placement inside the neural clusters deserves special mention. In a 2009 observational study, Bigeleisen et al.14 opined that positioning the needletip inside a cluster equated to intraneural placement (and intraneural local anesthetic injection). In contrast, in a recent editorial, Franco15 argued that “penetrating the prevertebral fascia during an interscalene or supraclavicular block, for example, does not constitute intraneural injection.” Regardless of whether local anesthetic deposition inside the neural cluster amounts to true intraneural injection,16 the current evidence seems to support the safety of this technique. In a large series of ultrasound-guided supraclavicular blocks (n = 510), Perlas et al.17 reported only 2 cases (0.4 %) of transient, spontaneously resolving, postoperative numbness. Nonetheless, we believe that the connective tissue surrounding the neural clusters (epineurium versus prevertebral fascia) requires further elucidation.

Our protocol has some limitations. First, we found a 6.5-minute decrease in total anesthesia-related time with the TII technique. In our practice, where upper limb surgery is performed under regional anesthesia, such a reduction is clinically meaningful, as it amounts to a sparing of 40 minutes over the course of a busy day. However, we concede that such a difference may not be clinically relevant in centers that only perform a few cases per day. Second, we used a total volume of 32 mL. We selected this volume because our previous dose-finding study had demonstrated that, for DI ultrasound-guided supraclavicular block, a 32-mL injectate of adrenalized lidocaine 1.5% corresponded to the volume required to anesthetize the brachial plexus in 90% of patients (MEV90).4 However, we acknowledge that a larger injectate might have decreased the onset time of the DI technique and minimized the difference in total time between the 2 groups. Third, in the context of a teaching hospital, most TII blocks were performed by supervised trainees. Because the TII method required numerous needle redirections, the level of difficulty for novice operators was increased compared to its DI counterpart. Thus, the difference in total times could have been even more pronounced had all the blocks been performed by experienced operators. Finally, although no patient randomized to the new TII technique had neurological deficits exceeding 1 month, our sample size was too small to assess safety.

In conclusion, DI and TII ultrasound-guided supraclavicular blocks provide comparable success rates. However, in light of the 95% CI, we cannot exclude the possibility that an intergroup difference of 17.9% might have gone undetected. Due to its quick onset, the novel TII technique results in a shorter total anesthesia-related time. Further studies are required to validate the safety of TII ultrasound-guided supraclavicular block.

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DISCLOSURES

Name: Wallaya Techasuk, MD.

Contribution: This author helped conduct the study, analyze the data, and write the manuscript.

Attestation: Wallaya Techasuk has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.

Name: Andrea P. González, MD.

Contribution: This author helped conduct the study, analyze the data, and write the manuscript.

Attestation: Andrea P Gonzalez has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.

Name: Francisca Bernucci, MD.

Contribution: This author helped conduct the study, analyze the data, and write the manuscript.

Attestation: Francisca Bernucci has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.

Name: Tracy Cupido, DO, FRCPC.

Contribution: This author helped conduct the study, analyze the data, and write the manuscript.

Attestation: Tracy Cupido has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.

Name: Roderick J. Finlayson, MD, FRCPC.

Contribution: This author helped design and conduct the study, analyze the data, and write the manuscript.

Attestation: Roderick J. Finlayson has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.

Name: De QH Tran, MD, FRCPC.

Contribution: This author helped design and conduct the study, analyze the data, and write the manuscript.

Attestation: De QH Tran has seen the original study data, reviewed the analysis of the data, approved the final manuscript, and is the author responsible for archiving the study files.

This manuscript was handled by: Terese T. Horlocker, MD.

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ACKNOWLEDGMENTS

The authors are grateful to Mr. Derek Mitchell for his assistance with patient recruitment.

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REFERENCES

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