Supraclavicular block





Perspective


Supraclavicular block provides anesthesia of the entire upper extremity in the most consistent, efficient manner of any brachial plexus technique. It is the most effective block for all portions of the upper extremity and is carried out at the division level of the brachial plexus; perhaps this is why there is often little or no sparing of peripheral nerves if an adequate paresthesia is obtained. If this block is to be used for shoulder surgery, it should be supplemented with a superficial cervical plexus block to anesthetize the skin overlying the shoulder.


Patient Selection. Almost all patients are candidates for this block, with the exception of those who are uncooperative. In addition, in less experienced hands it may be inappropriate for outpatients. Although pneumothorax is an infrequent complication of the block, such an event often becomes apparent only after a delay of several hours, when an outpatient may already be at home. Also, because the supraclavicular block relies principally on bony and muscular landmarks, very obese patients are not good candidates because they often have supraclavicular fat pads that interfere with easy application of this technique.


Pharmacologic Choice. As with other brachial plexus blocks, the prime consideration in drug selection should be the length of the procedure and the degree of motor blockade desired. Mepivacaine (1%–1.5%), lidocaine (1%–1.5%), bupivacaine (0.5%), and ropivacaine (0.5%– 0.75%) are all applicable to brachial plexus block. Lidocaine and mepivacaine will produce 2–3 hours of surgical anesthesia without epinephrine and 3–5 hours when epinephrine is added. These drugs can be useful for less involved or outpatient surgical procedures. For extensive surgical procedures requiring hospital admission, a longer-acting agent like bupivacaine can be chosen. Plain bupivacaine produces surgical anesthesia lasting from 4–6 hours, and the addition of epinephrine may prolong this time to 8–12 hours, whereas ropivacaine is slightly shorter acting.


Traditional block technique


Placement


Anatomy. The anatomy of interest for this block is the relationship between the brachial plexus and the first rib, the subclavian artery, and the cupola of the lung ( Fig. 6.1 ). Our 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. Both techniques are clinically useful once mastered. 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. 6.2 ). The nerves lie in a cephaloposterior relationship to the artery; thus a 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 caudad as it moves from posterior to anterior, and although the rib is a curved structure, there is a distance of 1–2 cm on which a needle can be “walked” in a parasagittal anteroposterior direction. Remember that immediately medial to the first rib is the cupola of the lung; when the needle angle is too medial, pneumothorax may result.




Fig. 6.1


Supraclavicular block: anatomy.



Fig. 6.2


Supraclavicular block: functional anatomy (with detail).


Position: Classic Supraclavicular Block. The patient lies supine without a pillow, with the head turned opposite the side to be 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 Supraclavicular Block. In the classic approach, the needle insertion site is approximately 1 cm superior to the clavicle at the clavicular midpoint ( Fig. 6.3 ). 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). In addition, 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. A 22-gauge, 5-cm needle typically will contact the rib at a depth of 3 to 4 cm, although in a very large patient it is sometimes necessary to insert it to a depth of 6 cm. The initial needle insertion should not be carried out past 3–4 cm until a careful search in an anteroposterior plane does not identify the first rib. During the insertion of the needle and syringe, the assembly should be controlled with the hand, as illustrated in Fig. 6.4 . The hand can rest lightly against the patient’s supraclavicular fossa because patients often move the shoulder with elicitation of a paresthesia.




Fig. 6.3


Supraclavicular block (classic approach): insertion site.



Fig. 6.4


Supraclavicular block (classic approach): hand and syringe assembly positioning.


Position: Vertical (Plumb Bob) Supraclavicular Block. The vertical approach to the supraclavicular block was developed 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, with 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 approximately a 90-degree angle to that used in the classic approach.


Needle Puncture: Vertical (Plumb Bob) Supraclavicular Block. Patients are asked to raise the head slightly off the block table so that the lateral border of the sternocleidomastoid muscle can be marked as it inserts onto the clavicle. From that point, a plane is visualized running parasagittally through that site ( Fig. 6.5 ). The name “plumb bob” was chosen for this block concept because if one were to suspend a plumb bob vertically over the entry site ( Fig. 6.6 ), needle insertion through that point, along the continuation of the vertical line defined by the plumb bob, would result in contact with the brachial plexus in most patients. Fig. 6.6 also illustrates a parasagittal section obtained by magnetic resonance imaging in the sagittal plane necessary to carry out this block. As illustrated, the brachial plexus at the level of the first rib 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 tabletop. 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 caudad ( Fig. 6.7 ).


Jun 15, 2021 | Posted by in ANESTHESIA | Comments Off on Supraclavicular block
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