Bloqueo Axilar Del Plexo Braquial

Techniques in Regional Anesthesia and Pain Management (2006) 10, 110-114

Axillary brachial plexus block Daniel P. Monkowski, MD,a Camilo S. Gay Larese, MDb From the aDivision of Regional Anesthesia of the Superior Course AAARBA, UBA, Buenos Aires, Argentina; and the b Department of Anesthesiology, “M. Castex” Hospital, Buenos Aires, Argentina. KEYWORDS: Axillary block; Neurovascular sheath; Multiple injections; Nerve-stimulation; Postoperative analgesia; Neuropathy

The axillary brachial plexus block is the peripheral nerve block most used for upper limb surgery, due to its high rate of efficacy and low incidence of complications compared with other brachial plexus approaches. Single and multiple injection techniques were described but, in our opinion, the last one is the best choice for obtaining a complete block of all the terminal nerves at the axilla, because of its particular distribution around the axillary artery within the neurovascular sheath and out of it. Using the nerve-stimulation technique for identifying the nerve structures increases the efficacy and diminishes postoperative neurological complications such as neuropathy. © 2006 Elsevier Inc. All rights reserved.

The axillary blockade of the brachial plexus was first described in 1884 by Halstead1; and in 1911, it was introduced as an anesthetic practice by Hirschel.2 However, only, after Burnham’s3 publication in 1959, did it become popular among anesthesiologists. Since then, despite having suffered several modifications, it has become the most used peripheral nerve block for upper limb surgery, especially due to its low incidence of complications compared with other approaches of the brachial plexus (Kulempkamff supraclavicular).

Anatomy The axilla is a space at the junction of the upper limb, chest, and neck. It is shaped like a truncated pyramid and serves as the passageway for nerves, blood vessels, and lymphatics into or from the limb. Its walls are musculofascial. The base is the concave axilla, the actual floor being the axillary fascia. The anterior wall is composed of the two planes of pectoral muscles and the associated pectoral and clavipectoral fasciae. The lateral border of the pectoralis major muscle forms the anterior axillary fold. The posterior wall of the axilla is made up of the scapula, the scapularis musculature, and the associated fasciae. The lower members of this group, together with the tendon of the latissimus dorsi muscle, form the posterior axillary fold. Address reprint requests and correspondence: Anesthesiologist CCPM, Director of Regional Anesthesia of the Superior Course AAARBA UBA, O’Higgins 3715 3 “A” Buenos Aires, Argentina 1429. E-mail address: [email protected]. 1084-208X/$ -see front matter © 2006 Elsevier Inc. All rights reserved. doi:10.1053/j.trap.2006.07.003

The chest wall, covered by the serratus anterior muscle and its fascia, forms the medial wall. The lateral wall is reduced to a mere chink by the convergence of the tendons of the anterior and posterior axillary fold muscles onto the greater tubercular crest, the intertubercular groove, and the lesser tubercular crest of the humerus. The truncated apex of the axilla is formed by the convergence of the bony members of the three major walls: the clavicle, the scapula, and the first rib. Through the triangular interval so formed pass the neurovascular structures of the limb.4 Before entering in the infraclavicular region, the divisions of the brachial plexus combine again and pass below the clavicular midpoint to form the lateral, medial, and posterior cords of the plexus. They receive their name due to their position around the axillary artery, which is the continuation of the subclavian artery. At the lateral border of the pectoralis minor muscle, the cords divide in the terminal nerves of the brachial plexus: musculocutaneous, median, ulnar, radial, axillary, medial brachial cutaneous, and medial antebrachial cutaneous nerves, which will innervate the whole upper extremity. The cords, the terminal branches, and the vessels are inside the axillary fascia, which is an extension of the prevertebral or scalene fascia, which forms the axillary perivascular space, a tubular extension of the interscalene space.5

The axillary perivascular space The single shot technique described by Eriksson6 and Winnie5 was based on the perivascular arrangement of the

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Axillary Brachial Plexus Block

axillary plexus within the fascial tube. Winnie suggested blocking the brachial plexus at various levels along the neurovascular sheath (NVS) by merely delivering the local anesthetic at a suitable level through a single “firm” needle centrally directed. Thus, the perivascular arrangement of the axillary plexus within a functional single compartment, surrounded by the sheath, was widely accepted. In theory, this construction was very convenient, but sometimes problems arouse when patchy anesthesia was performed especially because the radial or the musculocutaneous nerves block was not always completely achieved.7,8 To explain such incomplete blocks, Thompson and Rorie9 introduced a new concept of the functional anatomy of the brachial plexus sheaths. They stated that the axillary NVS is a multicompartmental structure formed by septa which extend inward from the sheath, and fascial compartments were described for each nerve. The authors concluded that these septa limit the circumferential spread of the local anesthetic, thus making the single shot technique illogical and worthless. Vester-Andersen and coworkers,10 who studied the spread of dyed gelatin injected into the axillary NVS of 20 cadavers, by delivering 15 mL through a catheter directed proximally and inserted just distal to the major pectoralis muscle, with the arm abducted 90o, found that the gelatin spread proximally to at least the coracoid process. The median and ulnar nerves were completely surrounded by or in good contact with the gelatin, whereas only 75% of the radial and 70% of the musculocutaneous nerves were judged to be in sufficient contact with the gelatin injected. No septa were found to separate the nerve and the blood vessels. Partridge and coworkers11 examined the axilla and the neurovascular bundles of 18 cadavers after delivery of 20 to 30 mL of methylene blue or Latex solutions. They found the axillary sheath to be made up of numerous thin layers of velamentous fascia with no free space between layers. The injected solution easily dissected its way within the loose perivascular connective tissue and immediately reached the median, ulnar and radial nerves, although the musculocutaneous nerve is not mentioned. Thus, the septa of Rorie and Thompson do exist, but the injection test proved to be functionally incomplete and easily deranged. The study by Partridge and coworkers shows that perivascular septa of axillary sheath do exist, but seem to be functionally unimportant. More recently, Rodriguez and coworkers12 found that the posterior-to-anterior flow of local anesthetics (LA) occurs more readily after posterior injection than does the anteriorto-posterior flow after anterior injection. The reasoning was that LA (when injected anterior) would accumulate in the anterior aspect of the brachial plexus and lead to an insufficient contact of it with the components of the brachial plexus. At the level of the axilla, the median, radial, and ulnar nerves develop all their itinerary within the neurovascular bundle, whereas the medial brachial cutaneous and the medial antebrachial cutaneous nerves may be either inside or outside the sheath. The musculocutaneous nerve always lies outside (in the thickness of the coracobrachial muscle) because it left the lateral cord before the nerves enter the

111 neurovascular bundle. Therefore, this nerve must be always blocked separately. Within the fascia, according to the axillary artery, the nerves are related as follows: Median: above and anterior; Radial: below and posterior; and Ulnar: below and anterior. These anatomic relationships may sometimes vary (Figure 1). Knowledge of sensory and deep innervations of the upper limb is essential to guarantee success of an efficient block. In conclusion, multiple injection technique is the best choice for obtaining a complete block of all the terminal nerves at the axilla level.13,14

Indications Elbow, forearm, and hand surgeries; Postoperative analgesia; Chronic pain treatment; and Rehabilitation.

Techniques for identifying nerve structures ● ●

Paresthetic: (one or more paresthesiae) Non Paresthetic: 1. Nerve stimulation 2. Transarterial 3. Facial click, Ultrasound, other. They can also be classified in:

Techniques; Single shot injection; Multiple shot injection; and Continuous infusion (catheter).

Equipment Needles. Short bevel (35 to 45o), 50 mm (2 inches) 22- to 24-gauge, or insulated in nerve stimulation technique. Syringes. Two of 20 mL and one of 5 mL (previous infiltration). A 20-cm intermediary to connect the needle and the syringe. LAS. Bicarbonate-Epinephrine. Nerve stimulator. Cutaneous electrode.

Anesthetic techniques The patient’s position is similar to those used for locating the terminal nerves of the brachial plexus at the axilla level in any technique.

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Figure 2

Figure 1 axilla.

Anatomical variations of terminal nerves in the

The patient is placed in the supine position. The arm are abducted 90o from the body at the shoulder and flexed 90o at the elbow (Figure 2). The dorsum of the hand lies on the table and the forearm is parallel to the long axis of the patient’s body. This is the best position for palpating the main anatomic landmark of the axillary block: the artery pulse. Hyperabduction of the arm must be avoided because it obliterates the brachial artery pulse in 80% of normal individuals.15 The axillary pulse is marked on the skin as proximal as possible at the level of the border of the major pectoral muscle. After appropriate skin preparation and draping, the operator feels with the index and medium fingers of the homolateral hand for the axillary pulse. Once identified, it is convenient to press it firmly so as to avoid mobility inside the perivascular sheath during the blockade. If touching the axillary pulse is difficult, it should be found in the space between the major pectoral and coracobrachialis muscles in the proximal region of the arm where it usually remains. It is also possible to locate the axillary pulse by means of a vascular Doppler.

Arm position.

nerves enter the axilla. So, the needle is reoriented upwards to be introduced in the thickness of the coracobrachial muscle, where the nerve is located, and another volume of the LAS is injected.

Nerve-stimulation technique With the patient in the same position as for the previous technique, a 50-mm, 22-gauge insulated needle connected to a nerve stimulator is introduced above the palpating fingers at a 30o angle regarding the skin directed to the apex of the axilla. Then, the needle advances slowly with 1 mA intensity and 2 Hz until a motor response in the hand is obtained. When the needle advances above the pulse of the artery, the most frequent twitch found is either pronation of the hand or flexion of the wrist or fingers, which corresponds to stimulation of the median nerve. Once the motor response is obtained, the intensity is decreased to 0.5 mA or less, and if it persists, part of the LAS is delivered (see below). Then, the needle is reoriented below the artery pulse and introduced in search of another motor response. The latter generally corresponds to the ulnar nerve (adduction of the hand, flexion of the 4- to 5-degree fingers) or radial nerve (extension of the hand or fingers). When any motor response elicited persists at an intensity of 0.5 mA or less,

Paresthetic technique After identification of the axillary pulse, a 50-mm, 22gauge needle (or Doppler) is introduced above the palpating fingers at a 20- to 30-degree angle regarding the skin and directed to the apex of the axilla (Figure 3). Then, it advances slowly until a paresthesia referred to the hand is elicited. At this moment, a part of the LAS is delivered (see volume below). To assure circumferential spread of the LAS within the perivascular sheath, it is advisable to carry out a second injection just below the pulse of the artery. The needle is reoriented in that direction and advances slowly until another paresthesia appears. When it occurs, the other part of the LAS is delivered. Finally, the musculocutaneous nerve should always be blocked separately since it leaves the fascia before the

Figure 3

Needle direction.

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another part of the LAS is delivered. Then, the needle is reoriented to be introduced in the thickness of the coracobrachial muscle. Once a forearm flexion is obtained (musculocutaneous response), the LAS is injected.16 It is advisable to place the cutaneous electrode 20 cm away from the site of the needle insertion opposing the direction of the needle. The precordial region must be not interposed between the electrode and the needle.

Transarterial technique The patient must be placed in the same position as for previous techniques. A needle attached to a syringe with LAS by means of a 20-cm intermediary is slowly introduced at a 30° angle regarding the skin directed toward the pulse of the artery. When blood enters the intermediary, progression continues slowly until aspiration is negative. At this moment, we can deliver the total amount of LAS,17 or inject 50% of the LAS and withdraw slowly until aspiration is negative again. At this point, the remaining 50% of LAS is delivered.18 If venous blood is obtained, the procedure should be repeated.

Figure 4 catheter.

Injection of radiopaque substance through an axillary

Onset time From 20 to 30 minutes depending on the chosen LAS.

Fascial “click” technique The patient’s position and the needle direction are similar to those previously described techniques. It consists in the introduction of the LAS after sensing a “click” after the thick axillary fascia is penetrated. It is a single shot technique not frequently used at present. After intrafascial injection in any of the above described techniques and before withdrawal of the needle, 5 mL of LAS should be delivered subcutaneously anterior to the artery pulse to block the medial brachial cutaneous and the medial antebrachial cutaneous nerves. Then, digital pressure is performed during 5 minutes in the entry site of the needle with the arm in adduction so as to prevent the appearance of hematomas (especially in the transarterial technique) and assure proximal spread of the LAS.

Continuous axillary block The main objectives of the placement of an axillary catheter for continuous infusion of LAS in the perivascular space of the brachial plexus are: (1) to prolong the duration of the anesthetic block, (2) to control the postoperative pain, and (3) to facilitate rehabilitation.19 A kit of an 18-gauge insulated needle and a 20-gauge catheter connected to a nerve stimulator is used. The technique for introducing the needle is similar to the previously described ones. But, only one motor response (usually that of the nerve responsible for the innervation of the surgical area) is required.20 When such response appears, 25% of the LAS is injected. Then, the catheter is placed progressing between 3 and 6 cm in proximal direction. The load dose is completed. The position of the tip of the catheter is confirmed by the injection of 3 mL of radiopaque substance (Figure 4).

Local anesthetic solution Short procedures: Lidocaine 1.5%/epi 1/200.000/Mepivacaine 1.5% with 1/200.000 epinephrine. Long-lasting procedures: Bupivacaine to 0.375% to 0.5% with 1/200.000 epinephrine. Ropivacaine: 0.5% to 0.75%. Postoperative analgesia: Bupivacaine 0.25%. Ropivacaine: 0.2%. Continuous infusion: Bupivacaine to 0.125% 4 to 8 mL/h. Ropivacaine to 0.2% 4 to 8 mL/h.

Volume From 40 to 50 mL, volumes are usually used in the following way: 7 mL for the musculocutaneous nerve, 5 mL for the medial brachial cutaneous and the medial antebrachial cutaneous nerves. Regarding both intrafascial infiltrations, the higher amount of LAS is delivered in the quadrant where the nerve responsible for the surgical area distribution is usually located. For example, in the case of elbow fracture, where the radial nerve is predominant, 20 mL is injected below the artery while 13 mL is injected above the artery.

Adjuvant drugs Epinephrine: 0.10 mg/20 mL of LAS. Bicarbonate 1 mEq/10 mL of LAS (lidocaine). 0.10 mEq/10 mL of LAS (bupivacaine). Clonidine 1 ␮g/kg.

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Complications Vascular and/or neurological complications may occur. The vascular ones include: 1. Accidental intravascular injection (hemodynamic collapse). 2. Arterial occlusion21 (because of compression by hematoma or tourniquet). 3. Hematoma (because of mechanical injury at the level of the axillary vessels). The neurological ones include: 1. Postoperative paresthesias (because of direct needle traumatism).22 They usually wear off ad integrum before 4 weeks’ time.23 2. Seizures (because of accidental intravascular injection). 3. Toxic (conservatives or high concentrations of LA). 4. Ischemic (because of nervous compression by edema, hematoma, or tourniquet).

Contraindications ● ● ● ● ● ●

Local infection. Previous injury of the nerve to be blocked. Lymphangitis. Axillary adenopathies. Lack of patient’s cooperation. Anticoagulant therapy.

Conclusions ● ●

● ●

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Axillary block is a safe and effective regional anesthetic technique. Multiple shot techniques are more effective than single ones. Besides, they do not have a higher rate of postoperative complications. The incidence of postoperative neuropathy diminishes with the use of a nerve stimulator. Perivascular or intrafascial techniques with high volumes of LAS allow successful hand, forearm, and elbow surgeries. If, during a perivascular technique, arterial blood enters the connector, it is advisable to change the technique into a transarterial one.

References 1. Halstead: Peripheral Nerve Blocks: Principles and practice. Hadzic A, Vloka JD (eds). New York, NY, New York School of Regional Anesthesia, 2004

2. Hirschel G: Anesthesia of the brachial plexus for operations on the upper extremity (German). Munchen Med Wochenschr 58:1555-1556, 1911 3. Burnham PJ: Simple regional nerve block for surgery for the hand and forearm. J Am Med Assoc 169:941-943, 1959 4. Netter FH: The Ciba Collection of Medical Illustrations. Musculoskeletal System. Part I: Anatomy, Physiology, and Metabolic Disorders (vol 8), Summit, NJ, Ciba-Geigy Corp., 1991, pp 25-26 5. Winnie AP, Radonjic R, Akkineni S, et al: Factors influencing the distribution of local anesthetic injected into the brachial plexus sheath. Anesth Analg 58:225-234, 1979 6. Eriksson E: Illustrated Handbook in Local Anesthesia(ed 2). Copenhagen, Shultz, 1979, pp 82-83 7. Klaastad O, Smedby O, Thompson GE, et al: Distribution of local anesthetic in axillary brachial plexus block: a clinical and magnetic resonance imaging study. Anesthesiology 96:1315-1324, 2002 8. Lavoie J, Martin R, Tetrault JP, et al: Axillary plexus block using a peripheral nerve stimulator: single or multiple injections. Can J Anesth 39:583-586, 1992 9. Thompson GE, Rorie DK: Functional anatomy of the brachial plexus sheath. Anesthesiology 59:117-122, 1983 10. Vester-Andersen T, Broby-Johanssen U, Bro-Rasmussen F: Perivascular axillary block. VI. The distribution of gelatin solution injected into the axillary neurovascular sheaths of cadavers. Acta Anaesthesiol Scand 30:18-22, 1986 11. Partridge BL, Katz J, Bernische K, et al: Functional anatomy of the brachial plexus sheath: Implications for anesthesia. Anesthesiology 66:743-747, 1987 12. Rodriguez J, Taboada M, Sabela D, et al: A comparison of four stimulation patterns in axillary block. Reg Anesth Pain Med 30:324328, 2005 13. Sia S, Bartoli M, Lepri A, et al: Multiple injection axillary brachial plexus block. A comparison of two methods of nerve stimulation versus paresthesia. Anesth Analg 91:647-651, 2000 14. Fanelli G, Casati A, Garancini P, et al: Nerve stimulator and multiple limb blockade: failure, rate, patient acceptance and neurologic complications. Anesth Analg 88:847-852, 1999 15. Winnie AP: Perivascular techniques of brachial plexus block, in Plexus Anesthesia. Philadelphia, PA, WB Saunders, 1983, pp 4765,114,117-143 16. Inberg P, Annila I, Annila P: Double-injection method using peripheral nerve stimulator is superior to single injection in axillary plexus block. Reg Anesth Pain Med 24:509-513, 1999 17. Cookings E, Moore P, Lewis RC: Transarterial brachial plexus block using 50 ml 05 1.5% mepivacaine. Reg Anesth Pain Med 26:12-16, 2001 18. Stan T: Transarterial brachial plexus block. Reg Anesth Pain Med 20:486-492, 1995 19. Vester-Andersen T, Husum B, Zaric D, et al: Perivascular axillary block V: blockade following 60 ml of mepivacaine 1.5% injected as bolus or as 30 ⫹ 30 ml with a 20 min. interval. Acta Anaesthesiol Scand 28:612-616, 1984 20. Monkowski D, Gay Larese CS, Egidi R, et al: Bloqueo axilar continuo para cirugía de reimplante de 4 dedos de la mano. Congreso Argentino de Anestesiología. Tucumán, September 2-4, 2004 21. Ben David B, Stahl S: Axillary block complicated by hematoma and radial nerve injury. Reg Anesth Pain Med 24:264-266, 1999 22. Selander D, Dhuner K, Lundborg G, et al: Peripheral injury due to injections needles used for regional anesthesia. An experimental study of the acute effects of the needle point trauma. Acta Anaesth Scand 21:182-188, 1977 23. Urban MK, Urquhart B: Evaluation of brachial plexus anesthesia for upper extremity surgery. Reg Anesth Pain Med 19:175-182, 1994