Anesth Analg 2004;99:1225-1230
© 2004 International Anesthesia Research Society
doi: 10.1213/01.ANE.0000131724.73956.8E
REGIONAL ANESTHESIA
A Comparison of Single Versus Multiple Injections on the Extent of Anesthesia with Coracoid Infraclavicular Brachial Plexus Block
Jaime Rodríguez, MD PhD,
M. Bárcena, MD,
M. Taboada-Muñiz, MD,
J. Lagunilla, MD, and
J. Álvarez, MD PhD
Department of Anesthesiology, Complexo Hospitalario Universitario de Santiago, Santiago de Compostela, Spain
Address correspondence to Jaime Rodríguez, MD, PhD, Servicio de Anestesiología y Reanimación, Hospital Clínico Universitario de Santiago, Travesía da Choupana, s.n. 15706, Santiago de Compostela, Spain. Address e-mail to jaimerodriguezgarcia{at}nacom.es
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Abstract
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Single-injection coracoid infraclavicular brachial plexus block produces inconsistent anesthesia of the upper limb. In this study, we sought to determine the number of injections needed to provide a reasonably complete anesthesia of the upper limb with this approach. Seventy-five patients were randomly assigned to receive a coracoid block guided by nerve stimulator with 42 mL of 1.5% mepivacaine with a single-injection (Group 1), dual-injection (Group 2), or triple-injection (Group 3) technique. No search for a specific motor response was performed in any group. Sensory and motor block was assessed 5 and 20 min after the end of the injection of local anesthetic. Significantly less complete anesthesia to pinprick in the distributions of the axillary, musculocutaneous, radial, ulnar, and medial cutaneous forearm nerves was found in Group 1 at 20 min. Significantly less complete paralysis for arm, wrist, and hand movements was found in Group 1 at 20 min. No significant difference was found between Groups 2 and 3. We conclude that dual and triple injection of local anesthetic guided by nerve stimulator increases the efficacy of coracoid block when compared with a single-injection technique.
IMPLICATIONS: Both dual- and triple-injection infraclavicular coracoid block had better efficacy than a single-injection technique in providing anesthesia of the upper limb. Triple injection was not better than dual injection; therefore, the authors recommend dual-injection coracoid block.
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Introduction
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Single-injection coracoid infraclavicular brachial plexus block produces inconsistent anesthesia of the upper limb, with infrequent success in the distributions of the axillary, radial, musculocutaneous, and medial cutaneous nerves of the arm (1). Multiple injections of local anesthetic guided by nerve stimulation have been shown to produce more extensive anesthesia of the upper limb when compared with a similar approach using a single-injection technique in the axillary (2–4) and interscalene (5) approaches for brachial plexus anesthesia. The same finding was observed with both sciatic (6) and femoral (7) nerve blocks. Gaertner et al. (8) found that triple injection of local anesthetic guided by nerve stimulation increased the quality of the motor and sensory block obtained by a coracoid infraclavicular brachial plexus block when compared with a single-injection technique. More recently, dual injection of local anesthetic was shown to produce more extensive anesthesia when compared with single injection in nerve stimulator-guided coracoid block (9). However, multiple-injection techniques are time consuming, may be painful to patients, and could increase the likelihood of producing local complications as a result of multiple punctures (10). The aim of this study was to determine the number of injections needed with infraclavicular coracoid block to provide as complete an anesthesia as possible.
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Methods
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After ethics committee (Comité Ético de Ensayos Clínicos de Galicia) approval and obtaining patients’ written, informed consent, 75 patients undergoing surgery on the upper limb were randomly assigned to receive an infraclavicular block guided by a nerve stimulator (Multistim; Pajunk, Geisingen, Germany) with a single-injection technique (Group 1), a dual-injection technique (Group 2), or a triple-injection technique (Group 3). Assignment was performed by means of a computer-generated randomized list. To perform the block, we asked patients to flex their arm with their forearm and hand lying over the torso. All blocks were performed by two of the authors. Both of them were senior anesthesiologists. Patients were premedicated with midazolam 1, 2, or 3 mg IV, accordingly to clinical judgment. The puncture site was located 1 cm below and 1 cm medial to the coracoid process, and the needle was inserted perpendicularly to the table with the patient in the supine position (1). All blocks were performed with 42 mL of 1.5% mepivacaine. The current output of the nerve stimulator was initially set at an output of 2 mA with a frequency of stimulation of 2 Hz and a pulse duration of 0.1 ms. A 22-gauge, 80-mm-long stimulating needle (Pajunk, Geisingen, Germany) was introduced perpendicularly to the patient’s body and advanced until the elicitation of a motor response of the upper limb. A satisfactory response to nerve stimulation was considered when the motor response could be elicited with a current intensity 
0.5 mA. No specific search to stimulate a specific nerve was made in any group, but the two motor responses in Group 2 and the three responses in Group 3 had to correspond to different nerves for each patient to be accepted as valid. In Group 1, 42 mL of local anesthetic was injected in a single bolus after identification of the brachial plexus. In Group 2, 21 mL of local anesthetic was injected after the first motor response, and the remaining 21 mL was injected after the second response. In Group 3, 14 mL of local anesthetic was injected after the first motor response, another 14 mL after the second, and the remaining 14 mL after the third. In Group 3, 6 min was allowed after the end of the second injection to elicit a third motor response. If a third stimulation was not obtained during this time, the procedure was considered to be finished.
Brachial plexus block was assessed 5 and 20 min after the end of the injection of the total dose of local anesthetic (Time 0) by a blinded investigator. Sensory block was assessed in the distribution of the axillary, musculocutaneous, radial, median, ulnar, and medial cutaneous nerves of the forearm and the medial cutaneous nerves of the arm by the pinprick method with a 18-gauge long-bevel needle by using the following scale: 0 points = pinprick perceived as painful, 1 point = analgesia to pinprick (tactile sensation), and 2 points = anesthesia to pinprick (no perception). Motor block was assessed for flexion and extension of the elbow, flexion and extension of the wrist, flexion and extension of the fingers, and adduction of the thumb by using the following scale: 0 points = no paresis, 1 point = paresis, and 2 points = complete paralysis. Additionally, global scores for both sensory block (minimum, 0 points; maximum, 14 points) and motor block (minimum, 0 points; maximum, 14 points) were calculated on the basis of the sum of the individual scores obtained (see scales above). Side effects and complications such as hoarseness, Horner’s syndrome, dyspnea, vascular puncture, and hematoma formation were noted and recorded. Blocks were supplemented before surgery with additional peripheral nerve blocks when the cutaneous nerve distributions corresponding to the operating area had a score <2. Blocks were supplemented during surgery when the patient complained of pain with infiltration of the operating area with local anesthetic, fentanyl 50–100 µg IV, or general anesthesia, according to clinical judgment.
A higher global quality score for sensory block (9 versus 12.5 points) was found in a similar previous study that compared double-injection with single-injection infraclavicular coracoid block (9). On the basis of those data, we calculated that we would need a sample size of 23 patients per group to be able to find such a difference among any pair of the 3 groups with a statistical power of 0.9 and a Type I error of 0.01. To study differences among the three groups, statistical analysis consisted of a 
2 test for sex, complete anesthesia, and complete paralysis below the shoulder; analysis of variance for quantitative demographic variables; and Kruskal-Wallis nonparametric tests for sensory block and motor block. Wilcoxon’s test followed by Bonferroni’s correction was used to assess differences in motor and sensory block between pairs of groups. A P value 0.01 was considered significant.
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Results
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Demographic variables were similar in the three groups. The male/female ratio was 9:16, 11:13, and 9:16 in Groups 1, 2, and 3, respectively. Age (mean ± SD) was 51 ± 15 yr, 56 ± 13 yr, and 52 ± 16 yr in Groups 1, 2, and 3, respectively. Weight (mean ± SD) was 68 ± 11 kg, 72 ± 11 kg, and 67 ± 13 kg in Groups 1, 2, and 3, respectively. Height (mean ± SD) was 160 ± 8 cm, 162 ± 6 cm, and 162 ± 6 cm in Groups 1, 2, and 3, respectively. No significant difference was found. We did not exclude two patients in Group 3 in whom it was not possible to elicit a third response. Failure to elicit a final response is one of the risks associated with multiple nerve stimulation in clinical practice, and for that reason we included those two patients for further analysis as intent-to-treat. Elicited motor responses, type of surgery, and supplementation are shown in Table 1. No case of Horner’s syndrome, hoarseness, or dyspnea was found. Inadvertent vascular puncture occurred in three patients in Group 3 and in no patients in Groups 1 and 2. Three patients in Group 3 had needle-induced paresthesia during the procedure. In Group 2, one patient experienced a spontaneous shoulder dislocation while preparing for surgery, and another patient presented transient motor aphasia with complete consciousness, probably because of inadvertent vascular injection of the local anesthetic. This patient was excluded from the study.
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Table 1. Type of Surgery, Motor Responses Elicited, and Requirements for Peroperative Supplementation of the Block in the Three Groups (Number of Patients or Mean ± SD, as Appropriate)
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Significantly lower rates of sensory block (analgesia and anesthesia to pinprick) at 5 min were found in the distributions of the axillary, musculocutaneous, and radial nerves in Group 1 when compared with Groups 2 and 3. No difference was found between Groups 2 and 3. Significantly lower rates of sensory block (analgesia and anesthesia to pinprick) at 20 min were also found in the distributions of the axillary, musculocutaneous, radial, ulnar, and medial cutaneous forearm nerves in Group 1 (Table 2). No difference was found between Groups 2 and 3. Significantly less motor block (paresis and paralysis) at the elbow, wrist, and fingers was found in Group 1 at 20 min, whereas differences at 5 min were found only for flexion and extension of the elbow and extension of the wrist in Group 1 (Table 3). No difference was found between Groups 2 and 3. When just complete anesthesia and complete paralysis at 20 min (a more reasonable clinical end-point) were considered, we found significantly lower rates of anesthesia in the distributions of the axillary, musculocutaneous, radial, median, ulnar, and medial cutaneous forearm nerves (Fig. 1) and of paralysis for all joint movements (Fig. 2) in Group 1. Differences between Groups 2 and 3 were not significant. The rate of complete sensory block of the upper limb (including the axillary nerve) was significantly less in Group 1 than in Groups 2 and 3 (Table 1). Complete motor block was significantly less frequent in Group 1 than in Groups 2 and 3 (Table 1).Ten patients in Group 1, 5 patients in Group 2, and 3 patients in Group 3 needed supplementation for pain control. One patient in Group 1 needed general anesthesia.
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Figure 1. Complete anesthesia on the different nerve distributions of the upper limb. Data are shown as percentages. *P < 0.01 for comparison between Groups 1 and 2 and also between Groups 1 and 3. Med. Cut. = medial cutaneous.
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Figure 2. Complete paralysis for joint movements of the upper limb. Data are shown as percentages. *P < 0.01 for comparison between Groups 1 and 2 and also between Groups 1 and 3.
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Discussion
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Anesthesia produced by single-injection coracoid infraclavicular block is usually incomplete (1,8,9), although some authors found that a single-stimulation lateral infraclavicular block, an approach similar to ours, was as effective as a triple-stimulation axillary block (11). They used 40 mL of 0.75% ropivacaine, which is a large dose of local anesthetic, and this might have been responsible for their good results with single-injection coracoid block.
Multiple injections of local anesthetic guided by nerve stimulation were shown to enhance both the extent and the depth of anesthesia after axillary (2–4), interscalene (5), and coracoid (8) blocks. Dual (9) and triple (8) injection of the local anesthetic produced more extensive anesthesia of the upper limb than single-injection lateral infraclavicular block. There is no study that compares the effectiveness of dual-injection infraclavicular block with that of a triple-injection technique.
It was not possible in two patients in Group 3 to elicit a third response six minutes after injection of the second dose of local anesthetic. In a previous study with dual-injection infraclavicular coracoid block, a mean time of four minutes was needed to elicit a second motor response (9). We arbitrarily decided to expand this interval to 1.5 times to limit the search for a third response. Musculocutaneous nerve responses were accepted as valid in our study. The recommendation for rejecting a musculocutaneous response is based on an anecdotal report (12) and on the work by Borgeat et al. (13) with a modified Raj infraclavicular approach. They found that injection of the local anesthetic after elicitation of a proximal response (extension or flexion of the elbow) was followed by lower-quality anesthesia of the upper limb than after elicitation of a distal response. It is conceivable with that oblique approach that, with a proximal response, the tip of the needle might have located the musculocutaneous nerve after it left the neurovascular space. It was found in cadavers that the musculocutaneous and axillary nerves always left the neurovascular space distal to the coracoid process (14). Therefore, it is possible for the local anesthetic solution to reach the musculocutaneous nerve fibers within the neurovascular space with our perpendicular approach, because the puncture is 1 cm below and 1 cm medial to the coracoid process. Another difference with previous studies of the infraclavicular block is that we considered the contractions of triceps brachialis or deltoid muscles as acceptable motor responses. In the latter, special care was taken to distinguish the response from unacceptable shoulder movements, such as protraction of the scapula (application of it to the thorax) or trapezius muscle contraction.
In this study, we showed that dual injection of local anesthetic guided by nerve stimulation increased the efficacy of anesthesia in the same fashion as the triple-injection technique when compared with a single-injection perpendicular coracoid block (Tables 2 and 3). The improvement in sensory block was observed in the distributions of the axillary, radial, musculocutaneous, ulnar, and medial cutaneous forearm nerves. An improvement in motor block (paresis and paralysis) in Groups 2 and 3 when compared with Group 1 was observed in all joint movements studied. When only complete anesthesia and complete paralysis at 20 minutes were considered (Figs. 1 and 2), the same group differences were found. Gaertner et al. (8) found that triple injection of local anesthetic guided by nerve stimulation increased the quality of the motor and sensory block obtained by a coracoid block in comparison with a single-injection technique. They obtained complete sensory and motor block in only 72.5% patients in the triple-injection group. The efficacy of both dual and triple injection in our study was less than the efficacy they had with triple injection, especially with regard to sensory block. This might have been because they used a "cold test" instead of the pinprick method with an 18-gauge needle. Theoretically, the efficacy of triple-injection coracoid block should be superior to that of dual injection coracoid block, but our results show that dual and triple injection had the same efficacy.
A similar phenomenon occurs with axillary block. Sia and Bartoli (15) found that elicitation of three responses corresponding to the musculocutaneous, median, and radial nerves were needed to produce efficient anesthesia with axillary block. They did not need to block the ulnar nerve selectively. In our study, we found that elicitation of two twitches was enough to produce extensive anesthesia of the upper limb. Gaertner et al. (8) also found that triple injection resulted in better patient satisfaction than single-injection infraclavicular block. This was probably due to enhanced anesthesia of the upper limb with the former technique.
A limitation of this study is that patient satisfaction was not assessed. There was also concern about the possibility of an increased risk for postoperative neurological sequelae in patients receiving a multiple-injection peripheral nerve block, although there are no clear data to support this view (16). From this standpoint, dual injection might be safer than triple-injection coracoid block. The study of neurologic complications could not be a realistic objective of this study, because the size of the populations was too small. However, postoperative follow-up at the surgeon’s office was negative for neurologic sequelae. Vascular puncture was more frequent in Group 3. Elicitation of the third twitch was more difficult than elicitation of the second response. This is another reason for not routinely seeking a third response in infraclavicular coracoid block.
In conclusion, dual injection of local anesthetic presents the best balance between efficacy and comfort for patients when compared with single- and triple-injection techniques. Triple injection for coracoid block does not provide a real benefit in comparison with a dual-injection technique.
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Acknowledgments
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We thank Dr. F. Gude for his statistical help in the development of this study.
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References
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Accepted for publication April 23, 2004.
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Abstract
Introduction
