Department of Anesthesiology, New York University School of Medicine, 550 First Avenue, New York, NY 10016, USA*Corresponding author
Accepted for publication: March 6, 2002
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Abstract |
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Methods. Using ultrasound guidance, infraclavicular brachial plexus block was performed in 126 patients. Important aspects of this standardized technique included (i) imaging the axillary artery and the three cords of the brachial plexus posterior to the pectoralis minor muscle, (ii) marking the position of the ultrasound probe before introducing a Tuohy needle, (iii) maintaining the image of the entire length of the needle at all times during its advancement, (iv) depositing local anaesthetic around each of the three cords and (v) placing a catheter anterior to the posterior cord when indicated.
Results. In 114 (90.4%) patients, an excellent block permitted surgery without a need for any supplemental anaesthetic or conversion to general anaesthesia. In nine (7.2%) patients local or perineural administration of local anaesthetic, and in three (2.4%) conversion to general anaesthesia, was required. Mean times to administer the block, onset of block and complete block were 10.0 (SD 4.4), 3.0 (1.3) and 6.7 (3.2) min, respectively. Mean lidocaine dose was 695 (107) mg. In one patient, vascular puncture occurred. In 53 (42.6%) patients, an indwelling catheter was placed, but only three required repeat injections, which successfully prolonged the block.
Conclusion. The use of ultrasound appears to permit accurate deposition of the local anaesthetic perineurally, and has the potential to improve the success and decrease the complications of infraclavicular brachial plexus block.
Br J Anaesth 2002; 89: 2549
Keywords: anaesthesia regional, brachial plexus; anaesthetics local, lidocaine; measurement techniques, ultrasound; surgery, pectoral
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Introduction |
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Methods |
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Technique
With a patient in the supine position, the arm was abducted to 90°. The deltopectoral region was scanned with a 2.5 MHz probe of a Hewlett-Packard 77020A ultrasound monitor (Andover, MA, USA). A transverse image of the second part of the axillary artery and vein, and of the three cords of the brachial plexus, was obtained posterior to the pectoralis minor muscle. The outline of the ultrasound probe was marked on the skin. The area was prepared with betadine and draped. Figure 1 depicts the location of the probe and a diagrammatical representation of the sonographic image. The probe was covered with a sterile sheath (Microtech Medical Inc., Columbus, MS, USA) after applying a liberal amount of gel (Aquasonic, Parker Laboratories, Fairfield, NJ, USA), and placed over the previously marked area which was covered with another layer of sterile gel. Depending on availability, a 17- or 18-gauge Tuohy needle without a stylet was connected to sterile extension tubing attached to a stopcock and two 20-ml syringes, and flushed with local anaesthetic until the air in the system was completely removed. An 18-gauge needle was used to puncture the previously anaesthetized skin. The Tuohy needle was then introduced and advanced until it was imaged. The needle tip was first directed to the medial cord between the axillary artery and vein (Fig. 2). One or 2 ml of 2% lidocaine, with epinephrine 1:200 000, and sodium bicarbonate (0.9 mEq/10 ml), was injected to ensure that the needle tip was within the neurovascular bundle, behind the posterior fascia of the pectoralis minor muscle; local anaesthetic would distribute within the muscle if the needle bevel did not completely penetrate the fascia. After confirming satisfactory spread of lidocaine, an additional 711 ml of local anaesthetic was injected around the medial cord. The needle was partially withdrawn and redirected between the lateral cord and the superior aspect of the axillary artery (Fig. 3). Again, after 12 ml lidocaine injection to ensure satisfactory spread, 711 ml of anaesthetic solution was injected. The needle was then advanced slightly deeper than the posterior aspect of the artery, and its shaft was brought into a more horizontal position to place its tip between the artery and the posterior cord. Then an additional 711 ml of lidocaine was deposited (Fig. 4). The spread of lidocaine around the cords was observed sonographically during each injection. During all manoeuvres the image of the entire needle was kept in view. When the image was lost because of misalignment between the probe and the needle, further manipulation or injection was carried out only after obtaining the image of the entire needle by realignment. Gentle in-and-out jiggling of the needle was also used to help regain the image.
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Results |
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Discussion |
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To our knowledge, only two previous studies used ultrasound imaging as a guide for infraclavicular brachial plexus block. Wu and colleagues5 reported eight successful blocks in nine patients, but three were complicated by subclavian artery puncture. (Based on their landmarks they were probably describing the axillary artery; the subclavian becomes the axillary artery at the lateral border of the first rib.10) These authors did not attempt to identify the echodense cords; instead they deposited the local anaesthetic at the lateral border of the subclavian artery. Furthermore, they used a thin (23-gauge) spinal needle that we find difficult to see sonographically. To reach the target, they calculated the maximum allowable depth of penetration at the angle at which the needle was introduced. The needle then was advanced based on this calculation rather than by following it with real time imaging. In addition to testing the technique in a substantially greater number of patients, we directed our block needle to each of the cords individually. The entire length of the needle was seen at all times. We believe this simple measure was a major factor in obtaining the higher success rate and substantially lowering the rate of vascular puncture (0.8% vs 33%) in our study. Several investigators have already emphasized the importance of depositing local anaesthetic around each nerve in the brachial plexus as a factor in improving success rate.11 12 Using a 17- or 18-gauge Tuohy needle and aligning it with the probe enabled us to follow its image and to direct it to each cord. In addition, the rigidity of a large bore needle provides better control of its tip during manipulations than a thinner needle that bends easily. We believe that use of a Tuohy needle with its blunt tip also helped avoid vascular puncture by pushing away vessels and nerves, although we recognize that vascular puncture with this type of needle may produce greater damage than with a smaller gauge needle. Finally, a large bore Tuohy needle permits easy placement of a catheter for continuous use.
A recent study by Ootaki and colleagues,8 reported 100% success rate with the use of ultrasound guidance in infraclavicular block. Of their 60 patients, in whom blocks were performed by the principal author, 57 did not require any additional local anaesthetic or opioid supplementation. Two patients were given additional infiltration of local anaesthetic and one received analgesia with fentanyl. Although not recorded, the time to perform the block was estimated as 5 min. While they claimed an overall success rate of 100%, the ulnar, radial and median nerves were spared in 10%, 6.7% and 3.3% of patients, respectively, 30 min after injection. Thus we believe their actual success rate is comparable to ours. The onset time in their study appears to be 30 min; it was 6.7 (3.2) min in our series. This delay can be attributed to the fact that no attempt was made to observe the nerve trunks or cords. Consequently, the anaesthetic was deposited on all sides of the subclavian artery to surround it like a doughnut with the expectation that it would spread around the nerves. Incidentally, it appears from their diagram and sonographic image that, like Wu and colleagues,5 they also called the axillary artery the subclavian. More importantly, at their midclavicular needle entry point the divisions of the brachial plexus are all closely apposed posterosuperiorly to the axillary artery.13 Depositing local anaesthetic in a doughnut-like fashion around the artery at this level limits the quantity that diffuses into the nerves, which are located only on one side of the vessel.13 With our technique, the needle entry point is more lateral, at the level of the coracoid process, where the cords of the plexus are not close together, but lie on three sides of the axillary artery. Thus, the anaesthetic can easily be deposited around each cord. We strongly believe that the rapid onset and reliability of the block depends on perineural rather than perivascular spread. Another reason for the slow onset in the study of Ootaki and colleagues8 may be related to the use of a slightly lower concentration of lidocaine (1.5%) without sodium bicarbonate. Sodium bicarbonate is used routinely in our institution to hasten the onset of block irrespective of the technique used for nerve blocks.
The approximately 9.3 mg kg1 dose of lidocaine (average 700 mg) used in our study (similarly to Wu and colleagues5) may appear large as compared with that used by Ootaki and colleagues8 (7.3 mg kg1). Previous studies using 900 mg and up to 18 mg kg1 have demonstrated the safety of larger doses of lidocaine.14 15 Nevertheless, we have recently been able to produce successful infraclavicular blocks with comparable onset time using ultrasound guidance at substantially reduced doses (4.3 mg kg1) and low volume (1315 ml) of 2% lidocaine.16
We used a 2.5 MHz transthoracic echocardiography probe which gives a grainy image. This was the only probe available for this study. At present we use a 3.57 MHz probe that provides substantially better imaging. Ootaki and colleagues8 used a 7 MHz probe, whereas Wu and colleagues5 did not specify the frequency of their probe.
An advantage of ultrasound guidance is that the block may be repeated at the same site when it begins to dissipate; this is not feasible with the nerve stimulator technique. Similarly, a successful block can be administered with this technique in patients with amputated distal upper extremities. Ultrasound guidance also provides an excellent educational tool; more than 90% of the blocks in this study were performed by approximately 20 residents at different levels of training, with no prior experience of peripheral nerve blocks. They were all supervised by an attendant who also held the ultrasound probe in place. It is highly probable that our success rate could have reached 100% if all the blocks had been performed by the authors, as in the study of Ootaki and colleagues.8 Although we did not specifically focus our study to determine the learning curve for this procedure, we feel that approximately 20 procedures under direct supervision of an expert may enable an operator to be proficient.
In conclusion, ultrasound-guided infraclavicular block appears to be associated with a high success rate, short onset time, easy placement of catheter, low complication rate, and excellent analgesia even when a tourniquet is used. It is well tolerated by patients. The cost of the ultrasound device may be considered a limiting factor. However, it represents a one-time capital expense that, if prorated over a large number of patients, may become cost effective, especially when the time saved for each procedure is taken into account.
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Acknowledgements |
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References |
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