Infraclavicular Brachial Plexus Block

The infraclavicular approach is yet another addition to the multitude of different approaches, techniques, and variations on the brachial plexus block.
Like the interscalene and supraclavicular approaches, the infraclavicular block is designed to deposit anesthetic high in the plexus, achieving anesthesia of the hand, forearm, elbow and arm up to the shoulder. The block targets the musculocutaneous, axillary, and intercostobrachial nerves at the level of the cords before these nerves leave the brachial plexus "sheath". Unlike the supraclavicular and interscalene approaches, however, the infraclavicular block carries no risk of accidental intrathecal, epidural, or intravertebral injection, stellate ganglion block, paralysis of the hemidiaphragm, or pneumothorax. This block can be considered an alternative to the axillary approach in instances where abduction of the arm is uncomfortable or difficult, or when infection is located at the axilla. When an indwelling catheter technique is indicated, the infraclavicular approach allows suture fixation of the catheter to the relatively clean, immobile infraclavicular region (in contrast to the axilla or neck). This may provide patients with greater comfort and freedom of movement with less risk of catheter dislodgement and entry site infection.

The infraclavicular approach carries virtually no risk of pneumothorax¹
The needle is inserted at the midpoint of the clavicle and is directed laterally and posteriorly, under the pectoralis major muscle toward the apex of the axilla. Since the lung lies behind the medial third of the clavicle and its surface falls away from the path of the laterally-directed needle, the risk of pneumothorax theoretically is very low at any depth of needle insertion. This risk has not been quantitated.

The Technique
The patient is placed in the supine position with the head turned away from the arm to be blocked. The block may be easier to perform when the upper extremity is abducted 90 degrees and flexed at the elbow. Although this position makes performing the block easier, the block can be performed with the head and arm in any position (Figure). The anesthesiologist stands on the opposite side from the arm to be blocked.

The entire length of the clavicle is marked. The C6 (Chassaignac's) tubercle, the subclavian artery where it dips under the clavicle, and the axillary artery on the medial surface of the arm is marked. A line is drawn from the C6 tubercle to the axillary artery, going through the midpoint of the clavicle (Figure).

The infraclavicular area is prepped and draped sterilely.

In the awake patient, a skin wheal is raised 2.5 cm below the midpoint of the clavicle where the subclavian artery dips below the clavicle.

A long (4-6 inch) 22 gauge short-bevel teflon-insulated nerve stimulator needle is used for the single-injection technique. When placing an indwelling catheter for a continuous technique, a 5 1/4 inch 16 gauge plastic cannula and standard-bevel needle is attached to a metal hub or alligator clip and control syringe and charged with saline (Figure).

The needle is inserted 2.5 cm below the midpoint of the clavicle at a 45 degree angle to the skin and directed laterally and posteriorly toward the axillary artery (Figure and Figure).

As the needle is advanced, the neurovascular bundle is located using the nerve stimulator with an initial stimulus intensity of 1.5-2.0 mA. When a hand twitch is obtained, the needle position and stimulus intensity is adjusted to maximize the twitch at a stimulus intensity< 0.5 mA (Movie QuickTime, about 2.0 mb). A biceps twitch should be avoided since it may indicate contact with the musculocutaneous nerve outside of the axillary sheath.²

The needle is now held immobile. When a single injection technique is used, after a negative aspiration and negative epinephrine containing test dose, 40-50 cc of local anesthetic (1.5% lidocaine or mepivacaine, or 0.375% bupivacaine) is injected in divided doses.

With the continuous catheter technique, the needle is withdrawn leaving the cannula (Figure).

A 20 gauge (epidural-type) catheter is inserted through the cannula (Figure).

The cannula is withdrawn, leaving the catheter in place (Figure).

The catheter is secured by suture fixation to the skin and dressed with a bioocclusive dressing reinforced with tape (Figure)

Aspiration through the catheter is performed to detect unintentional intravascular placement. An epinephrine-containing test dose is administered, followed by the initial dose of local anesthetic given incrementally (Figure). Typical doses are 30-40 cc of 1.5% lidocaine, 1.5% mepivacaine, or 0.375% bupivacaine. The block is maintained with an infusion of 0.25% bupivacaine at 6-10 cc/hr.

References

1. Prithvi Raj-P, Montgomery-S-J, Nettles-D, Jenkins-M-T. Infraclavicular brachial plexus block: A new approach. Anesth Analg 1973;52(6):897-903.

2. Fitzgibbon DR, Debs AD, Erjavec MK. Selective musculocutaneous nerve block and infraclavicular brachial plexus anesthesia. Case report. Reg Anesth 1995 May;20(3):239-241

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