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Anesth Analg 2004;98:252-256 © 2004 International Anesthesia Research Society
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Abstract |
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A new infraclavicular brachial plexus block method has the patient supine with an adducted arm. The target is any of the three cords behind the pectoralis minor muscle. The point of needle insertion is the intersection between the clavicle and the coracoid process. The needle is advanced 0°–30° posterior, always strictly in the sagittal plane next to the coracoid process while abutting the antero-inferior edge of the clavicle. We tested the new method using magnetic resonance imaging (MRI) in 20 adult volunteers, without inserting a needle. Combining 2 simulated needle directions by 15° posterior and 0° in the images of the volunteers, at least one cord in 19 of 20 volunteers was contacted. This occurred within a needle depth of 6.5 cm. In the sagittal plane of the method the shortest depth to the pleura among all volunteers was 7.5 cm. The MRI study indicates that the new infraclavicular technique may be efficient in reaching a cord of the brachial plexus, often not demanding more than two needle directions. The risk of pneumothorax should be minimal because the needle is inserted no deeper than 6.5 cm. However, this needs to be confirmed by a clinical study.
IMPLICATIONS: A new infraclavicular brachial plexus block method was investigated using magnetic resonance imaging without inserting needles in the volunteers. The study suggests two needle directions for performance of the block and that the risk of lung injury should be minimal. Expectations need to be confirmed by a clinical study.
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Introduction |
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Infraclavicular brachial block methods may often give complete anesthesia distal to the shoulder by a single injection technique. However, there is no infraclavicular technique satisfying all of the following demands: simple landmarks for defining the needle entry site, clear suggestion for the needle direction, a small angle between the needle and the skin (facilitating the insertion of a perineural catheter), minimal risk of pneumothorax, while the patient maintains the arm comfortably in adducted position (1–10). We have tried to develop such a method. In the present study it has been tested using magnetic resonance imaging (MRI), which allows precise simulation of needle passes in three-dimensional images of volunteers, making needle insertion in the volunteers unnecessary (6,11,12). Our aims were to define appropriate needle angles to the cords and to assess the risk of the needle contacting the pleura, the cephalic vein, the axillary artery, and the axillary vein.
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Methods |
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Using the new approach the patient is supine with relaxed shoulders. The ipsilateral arm is adducted and the hand is on the abdomen. The head rests on a thin pillow and is slightly rotated to the opposite side. The anesthesiologist works from behind the shoulder of the patient. Any of the three brachial plexus cords, posterior to the pectoralis minor muscle, is the target of the method. Sliding a finger laterally below the clavicle, the medial surface of the coracoid process is easily recognized, even in obese or muscular patients, as the first bony prominence. Its most medial palpable point is close to the anterior aspect of the clavicle. All needle directions of the method adhere to the sagittal plane through this coracoid point (Figs. 1, 2A, 2B). The needle is inserted tangentially to the antero-inferior border of the clavicle and directed 0°–30° posterior, to the horizontal (coronal) plane. A nerve stimulator aids in exact positioning of the needle.
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After approval of the protocol by the regional ethical committee and written, informed consent, 20 volunteers were scanned in a 1.5 T unit (Magnetom Vision; Siemens, Erlangen, Germany) using a 3-dimensional spoiled gradient echo pulse sequence (3D FLASH) in the coronal plane (TR/TE = 4.4 ms/1.8 ms, flip angle = 30°, field-of view = 300 x 300 mm, matrix = 256 x 256, number of excitations = 1, partition number = 64, partition thickness = 2.5 mm). Sagittal, axial, or oblique images were obtained from the 3D data set using a multiplanar reconstruction technique. Each volunteer was positioned horizontally, exactly as if to receive our block. The basis for all measurements was the lateral-most sagittal plane allowing a line 30° posterior to the coronal plane to abut the antero-caudad surface of the clavicle without intersecting the coracoid process (the sagittal plane of the method).
Pilot MRI studies suggested testing three needle directions (trajectories), all of them abutting the antero-caudad surface of the clavicle. They were 0°, 15°, and 30° posterior to the coronal plane. From these trajectories the shortest distances to the midaxis of the lateral, posterior, and medial cord, the axillary artery, axillary vein, and cephalic vein were measured (Fig. 3). The depths along the trajectories at which these distances were measured were also recorded. Based on these data, the exact depths and angles to the midaxis of the cords and the vessels were calculated. We defined a trajectory as contacting a cord, the cephalic vein, the axillary artery, or the axillary vein if the distance from the midaxis of these structures were 3, 2, 4, or 5 mm, respectively. The definitions were based on our own MRI estimates of the thickness of these structures at the level of the pectoralis minor muscle. We further assumed that a cord would respond to nerve stimulation if the needle tip was 1 mm from the cord surface, given a current output by 1.5–2.0 mA with 0.1 ms impulse duration (13). If pleura was present in the sagittal plane of the method, the sector limiting the pleura was measured (Fig. 4). Finally, it was recorded whether any needle trajectory on its way to the pleura first contacted the cords of the brachial plexus, the axillary artery, the axillary vein, or a rib.
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Results are presented as mean ± SD or mean (range). Comparisons between groups were made with the Mann-Whitney U-test and correlations computed as Pearson correlation coefficients (r), with a limit for significance of P < 0.05.
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Results |
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The volunteers, 10 women and 10 men, were 42 ± 12 (22–59) yr old with a height of 173 ± 8 cm, weight of 76 ± 15 (55–101) kg, and body mass index (BMI) of 25 ± 4.1 (18.6–32.7) kg/m2. Each volunteer had only one of the infraclavicular sides scanned, but for each gender the right and left side were equally often examined. Table 1 gives the position of all cords, the cephalic vein and the axillary vessels.
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In the sagittal plane of the method the cords were always located behind the pectoralis minor muscle. The 15° trajectory contacted 3 cords in 2 volunteers, 2 cords in 10 cases, and a single cord in 2 cases. The posteriorly located posterior and medial cords were more often reached than the lateral cord (Fig. 5). The 0° trajectory contacted 3 cords in 1 volunteer, 2 cords in 1 case, and a single cord in 8 cases. The anteriorly located lateral cord was more often contacted than the two other cords (Fig. 5). Combining the 0° and 15° trajectories, all volunteers except for one had at least one of the trajectories contacting a cord within a needle depth of 6.5 cm. The 30°trajectory was too posterior to reach any cord or axillary vessels.
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The 15° trajectory contacted the axillary artery in 5 and the axillary vein in 6 cases but never without first reaching a cord. The 0° trajectory contacted the axillary artery in 9 and the axillary vein in 5 cases, without prior contact with a cord in 2 cases for the artery and 2 other cases for the vein. The cephalic vein was reached by the 0° or the 15° trajectories in 2 cases. The depth of all three cords and the axillary vessels decreased significantly with age, and the cephalic vein was located more anteriorly in patients with higher weight and BMI. The depth of the axillary vein was significantly greater in men than in women. Otherwise, no significant relationship was found between the position of the neurovascular structures and the demographic variables. The angles to the cords tended to be more posterior on the right side than on the left, but not statistically significant.
In four subjects the sagittal plane of the method was lateral to the pleura. The remaining 16 volunteers demonstrated pleura within a sector from 16° anterior to 42° posterior. This sector was completely obstructed by the neurovascular bundle in one volunteer and by a rib in another case. In combination the neurovascular bundle and costa(e) obstructed the pleura in 4 further cases, leaving 10 volunteers with still some opening to the pleura. The mean size of this opening corresponded to a sector of 4° (1°–11°). It was located within a wide range from 14° anterior to 36° posterior. Irrespective of pleura-protecting structures the shortest depth to pleura was 103 (75–161) mm by an angle of 15° (10°–27°) posterior. There was no significant correlation between the pleura depth and age, height, weight, or BMI, and no significant difference between men and women. The third costa was the most frequent rib protecting the pleura from needle trajectories, in 13 cases. Trajectories slipping through to the lung would have passed in the third intercostal space in 7 volunteers and in the second intercostal space in three cases.
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Discussion |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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Using our infraclavicular method, this MRI study suggests primarily directing the needle 15° posterior, secondarily to advance it in the coronal plane. Inserting the needle not deeper than 6.5 cm should prevent it from reaching the pleura. In our adult material needle directions to the cords and depths to the pleura could not be predicted by age, gender, height, or weight. To recognize the possible proximity of the needle trajectory to the cephalic vein, we recommend aspirating while anesthetizing the insertion site with a thin needle. Although the cords usually protect the axillary artery and axillary vein from the needle, exceptions suggest not performing the block on patients with coagulopathy. In the MRIs the complete circumference of the neurovascular structures was often not distinctly seen, causing some uncertainty in determining their diameter and therefore representing a limitation of our study.
In conclusion, our MRI study on a new infraclavicular brachial plexus block technique indicates that when using the recommended needle direction(s), the method may prove to be efficient in reaching the brachial plexus. The risk of pneumothorax should be minimal when not inserting the needle deeper than 6.5 cm. Our preliminary clinical experience with the method (82 patients is encouraging. However, the results should be confirmed by clinical studies.
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Acknowledgments |
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We thank Stiftelsen Sophies Minde for grants to funding of the volunteers of the MRI studies and for financing dissections at the Department of Anatomy, University of Oslo.
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References |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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- Raj PP, Montgomery SJ, Nettles D, Jenkins MT. Infraclavicular brachial plexus block: a new approach. Anesth Analg 1973; 52: 897–903.
[Free Full Text] - Sims JK. A modification of landmarks for infraclavicular approach to brachial plexus block. Anesth Analg 1977; 56: 554–5.
[Abstract/Free Full Text] - Whiffler K. Coracoid block: a safe and easy technique. Br J Anaesth 1981; 53: 845–8.
[Abstract/Free Full Text] - Kilka H-G, Geiger P, Mehrkens H-H. Die vertikale infraklavikuläre Blockade des Plexus brachialis. Anaesthesist 1995; 44: 339–44.[Web of Science][Medline]
- Rodríguez J, Bárcena M, Rodríguez V, et al. Infraclavicular brachial plexus block effects on respiratory function and extent of the block. Reg Anesth Pain Med 1998; 23: 564–8.[Web of Science][Medline]
- Wilson JL, Brown DL, Wong GY, et al. Infraclavicular brachial plexus block: parasagittal anatomy important to the coracoid technique. Anesth Analg 1998; 87: 870–3.
[Abstract/Free Full Text] - Salazaar CH, Espinosa W. Infraclavicular brachial plexus block: Variation in approach and results in 360 cases. Reg Anesth Pain Med 1999; 24: 411–6.[Web of Science][Medline]
- Kapral S, Jandrasits O, Schabernig C, et al. Lateral infraclavicular plexus block vs. axillary block for hand and forearm surgery. Acta Anaesthesiol Scand 1999; 43: 1047–52.[Web of Science][Medline]
- Borgeat A, Ekaktodramis G, Dumont C. An evaluation of the infraclavicular block via a modified approach of the Raj technique. Anesth Analg 2001; 93: 436–41.
[Abstract/Free Full Text] - Jandard C, Gentili ME, Girard F, et al. Infraclavicular block with lateral approach and nerve stimulation: extent of anesthesia and adverse effects. Reg Anesth Pain Med 2002; 27: 37–42.[Web of Science][Medline]
- Brown DL, Cahill DR, Bridenbaugh DL. Supraclavciular nerve block: anatomic analysis of a method to prevent pneumothorax. Anesth Analg 1993; 76: 530–4.
[Abstract/Free Full Text] - Klaastad Ø, Lilleås FG, Røtnes JS, et al. Magnetic resonance imaging demonstrates lack of precision in needle placement by the infraclavicular brachial plexus block described by Raj et al. Anesth Analg 1999; 88: 593–8.
[Abstract/Free Full Text] - Ford DJ, Pither C, Raj P. Comparison of insulated and uninsulated needles for locating peripheral nerves with a peripheral nerve stimulator. Anesth Analg 1984; 63: 925–6.
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