INFRACLAVICULAR BLOCK ANATOMY the Infraclavicular Block Is Performed at the INTRODUCTION Level of the Cords of the Brachial Plexus

$INFRACLAVICULAR BLOCK ANATOMY the Infraclavicular Block Is Performed at the INTRODUCTION Level of the Cords of the Brachial Plexus$

9. INFRACLAVICULAR BLOCK ANATOMY The infraclavicular block is performed at the INTRODUCTION level of the cords of the brachial plexus. The cords The infraclavicular brachial plexus block is ideal are named according to their relation to the axillary for operations distal to the elbow. Adequate time artery: lateral, medial, and posterior. The lateral (approximately 20 minutes) should be allowed after cord is formed from the anterior divisions of the the block placement to achieve a surgical level of an- superior and middle trunks, the medial cord is esthesia. Although there are multiple approaches to formed from the anterior division of the inferior the infraclavicular block, success depends on where trunk, and the posterior cord is formed from the the needle tip stimulates the plexus. Caution must posterior divisions of all three trunks. The plexus, be taken to ensure that the needle tip is maintained which begins to spread around the axillary artery within the infraclavicular fossa at the level of the at this level, is not as compact as the more proximal cords and not directed distally toward the terminal trunks (Figures 9-1 through 9-3). Therefore, this branches located in the axilla. The latter erroneous block typically has a longer latency, and may not be position usually results from excessive angulation as dense, as a supraclavicular nerve block. of the needle toward the axilla and may result in Compared to the supraclavicular block, inadequate blockade of the musculocutaneous and an advantage of the infraclavicular block is axillary nerves. the reduced possibility of pneumothorax and avoidance of cervical vascular structures. This block does not produce a reduction in respiratory function. Additionally, the infraclavicular block Figure 9-1 has been shown to be superior to the axillary nerve block for anesthe- Figure 9-2 tizing the axillary and musculocutaneous nerves, Figure 9-3. Dermatomes anesthetized with the infraclavicular block making a supplemental (dark blue) musculocutaneous nerve block unnecessary. Acceptable muscle stimulation patterns are either extension (radial nerve) or flexion (median nerve) of the digits. A biceps twitch (musculocutaneous nerve), suggests that the needle placement is too lateral. The axillary vessels can be punctured using this approach, and vessel compression in this area is difficult.

33 9 INFRACLAVICULAR BLOCK

PROCEDURE Alternative Approach

Landmarks. Externally rotate and abduct the op- • 18-gauge, 10-cm, insulated Tuohy needle for cath- A simple alternative to the coracoid approach erative arm. Palpate the coracoid process. Make eter placement. Catheters inserted 3 cm. is the deltopectoral groove approach (see Figure a mark 2 cm medial and 2 cm caudad from the 9-5). With the patient’s arm at his or her side, mark coracoid process (Figure 9-4). This is the inser- Stimulation. The nerve stimulator is initially set the base of the clavicle and palpate the deltopec- tion point. Palpate the axillary artery as proximal between 1.0 and 1.2 mA. Finger and/or thumb toral groove from the axilla up to the clavicle. At as possible in the axilla. This is the direction of flexion at 0.5 mA or less indicates adequate needle approximately 1 cm below the clavicle, place the initial insertion. Insert the needle at an approxi- placement for local anesthetic injection. Finger needle in the deltopectoral groove (perpendicular to mately 60° angle from the horizontal (Figure extension with stimulation is also acceptable. the bed), and then redirect it 10° toward the axilla. 9-5). Stimulation of the musculocutaneous nerve indi- Advance the needle until the plexus is encountered. cates that the needle is too lateral. Compared to the coracoid approach, this approach Needles will block the plexus at a more proximal loca- Local Anesthetic. In most adults, 30 to 40 mL of tion, which is desirable because the plexus is more • 21-gauge, 10-cm, insulated needle. local anesthetic will block the plexus at this level. compact and easier to block proximal.

Figure 9-4 Figure 9-5

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BLOCK WITH ULTRASOUND PROBE Teaching Points. Probe. High frequency (5–12 MHz), linear. As with the nerve stimulator Probe Position. The parasagittal plane gives the technique, care best transverse view of the brachial plexus; below must be taken to the level of the clavicle, the nerves appear hyper- avoid vascular echoic. Position the probe beneath the clavicle and puncture because medial to the coracoid process (Figure 9-6). compression for bleeding in Approach. The needle is typically inserted this area can be in-plane at the cephalad (lateral) aspect of the difficult. Always probe, and will be visualized at the lateral border keep the axillary of the axillary artery. The hyperechoic structure artery and vein lateral to the artery is the lateral cord; the needle in view during should pass lateral to this cord and progress needle guidance, farther to the posterior cord. The posterior cord and always ensure is the hyperechoic structure located at the base of that the full length the axillary artery (Figure 9-7). Recent evidence of the needle to the suggests that deposition of local anesthetic tip in the longitudi- around the posterior cord will result in improved 26 nal (in-plane) view block success. is clear. Another approach to the posterior cord is via the inferior aspect of the probe (still in the parasagittal Figure 9-6 plane). With this technique, the needle is visualized at the medial border of the axillary artery, and Figure 9-7 Figure 9-8 between the axillary artery and vein. The needle must travel along the lateral aspect of the medial cord to reach the posterior cord. This approach is technically more difficult because of the close proximity of the axillary artery to the needle path; however, it allows catheters to be threaded with less difficulty.

Injection. It is important to observe the spread of the local anesthetic during the injection, which allows readjustment of the needle position if the spread is not appropriate. Spread should appear around the posterior cord; any spread above the artery in the area of the pectoralis muscles will likely result in block failure (Figure 9-8).