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Brown: Atlas of Regional Anesthesia, 3rd ed., Copyright © 2006 Saunders, An Imprint of Elsevier
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PLACEMENT

Anatomy.

The anatomy of interest for the supraclavicular block is the relation between the brachial plexus and the first rib, the subclavian artery, and the cupola of the lung ( Fig. 5-1 ). My experience suggests that this block is more difficult to teach than many of the other regional blocks, and for that reason two approaches to the supraclavicular block are illustrated: the classic Kulenkampff approach and the vertical (“plumb bob”) approach. The vertical approach has been developed in an attempt to overcome the difficulty and time necessary to become skilled in the classic supraclavicular block approach. Despite that cautionary note, once mastered either technique is clinically useful.

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Figure 5-1  Supraclavicular block: anatomy.


As the subclavian artery and brachial plexus pass over the first rib, they do so between the insertion of the anterior and middle scalene muscles onto the first rib ( Fig. 5-2 ). The nerves lie in cephaloposterior relation to the artery; thus, paresthesia may be elicited before the needle contacts the first rib. At the point where the artery and plexus cross the first rib, the rib is broad and flat, sloping in a caudad direction as it moves from posterior to anterior; although the rib is a curved structure, there is a distance of 1 to 2 cm through which a needle can be walked in a parasagittal anteroposterior direction. Remember that immediately medial to this first rib is the cupola of the lung; and when the needle angle is too medial, pneumothorax may result.

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Figure 5-2  Supraclavicular block: functional anatomy (with detail).


Position: Classic Supraclavicular Block.

The patient lies supine without a pillow, with the head turned to the side opposite the one being blocked. The arms are at the sides, and the anesthesiologist can stand either at the head of the table or at the side of the patient, near the arm to be blocked.

Needle Puncture: Classic.

With the classic approach, the needle insertion site is approximately 1 cm superior to the clavicle at the clavicular midpoint ( Fig. 5-3 ). It is emphasized that this entry site is closer to the middle of the clavicle than to the junction of the middle and medial thirds, as often described in other regional anesthesia texts. Additionally, if the artery is palpable in the supraclavicular fossa, it can be used as a landmark. From this point, the needle and syringe are inserted in a plane approximately parallel to the patient’s neck and head, taking care that the axis of the syringe and needle does not aim medially toward the cupola of the lung. The needle should be a 22-gauge, 5-cm needle that typically contacts the rib at a depth of 3 to 4 cm, although it is sometimes necessary to insert it to a depth of 6 cm in an extremely large patient. The initial needle insertion should not proceed past 3 to 4 cm until a careful search in an anteroposterior plane does not identify the first rib. During insertion of the needle and syringe, the assembly should be controlled with the hand, as illustrated in Figure 5-4 . The operator’s hand can rest lightly against the patient’s supraclavicular fossa because with elicitation of a paresthesia patients often move their shoulder.

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Figure 5-3  Supraclavicular block (classic approach): insertion site.


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Figure 5-4  Supraclavicular block (classic approach): hand and syringe assembly positioning.


Position: Vertical (Plumb Bob) Supraclavicular Block.

Development of the vertical approach to the supraclavicular block resulted from efforts to simplify the anatomic projection necessary for the block. The patient should be positioned in a manner similar to that used for the classic approach: lying supine without a pillow and the head turned slightly away from the side to be blocked. The anesthesiologist should stand lateral to the patient at the level of the patient’s upper arm. This block involves inserting the needle and syringe assembly at an approximately 90-degree angle to the insertion for the classic approach.

Needle Puncture: Vertical (Plumb Bob).

Patients are asked to raise the head slightly off the block table so the lateral border of the sternocleidomastoid muscle can be marked as it inserts onto the clavicle. From that point, a “mental” plane is visualized that runs parasagittally through that site ( Fig. 5-5 ). The name “plumb bob” was chosen for this block concept because if one suspends a plumb bob vertically over the entry site, as shown in Figure 5-6 , needle insertion through that point results in contact with the brachial plexus in most patients. Figure 5-6 also illustrates a parasagittal section obtained by magnetic resonance imaging scanning in the sagittal plane necessary to carry out this block. As illustrated, the brachial plexus at the level of the first ribs lies posterior and cephalad to the subclavian artery. Once this skin mark has been placed immediately superior to the clavicle at the lateral border of the sternocleidomastoid muscle as it inserts into the clavicle, the needle is inserted in the parasagittal plane at a 90-degree angle to the table top. If a paresthesia is not elicited on the first pass, the needle and syringe are redirected cephalad in small steps through an arc of approximately 20 degrees. If a paresthesia still has not been obtained, needle and syringe are reinserted at the starting position and then moved in small steps through an arc of approximately 20 degrees in a caudal direction ( Fig. 5-7 ).

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Figure 5-5  Supraclavicular block (plumb bob): functional anatomy.


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Figure 5-6  Supraclavicular block (plumb bob): parasagittal magnetic resonance image anatomy.


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Figure 5-7  Supraclavicular block (plumb bob): paresthesia-seeking approach.


Because the brachial plexus lies cephaloposterior to the artery as it crosses the first rib, a paresthesia is often elicited before contacting either the artery or the first rib. If that occurs, approximately 30 mL of local anesthetic is inserted at this single site.

If a paresthesia is not elicited with the maneuvers described but the first rib is contacted, the block is carried out just as it is using the classic approach—by walking along the first rib until a paresthesia is elicited. As with the classic approach, care should be taken not to allow the syringe and needle assembly to aim medially toward the cupola of the lung.

Potential Problems.

The most feared complication of the supraclavicular block is pneumothorax. Its principal cause is a needle/syringe angle that “aims” toward the cupola of the lung. Special attention should be directed toward walking the needle in a strictly anteroposterior direction. Pneumothorax incidence ranges from 0.5% to 5% and is at the lower end of that range when an anesthesiologist has become skilled. The cupola of the lung rises proportionally higher in the neck in thin, asthenic individuals, and perhaps the incidence of pneumothorax is higher in these individuals. Development of pneumothorax most often takes a number of hours; thus, it is likely related to impingement of the needle on the lung with subsequent development of pneumothorax rather than to air entering the pleural space as the needle is inserted. Once again, phrenic nerve block occurs in probably 30% to 50% of patients, and the block’s use in patients with significantly impaired pulmonary function must be carefully weighed. The development of hematoma after supraclavicular block, as a result of puncture of the subclavian artery, usually requires only observation.

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