Infraclavicular Brachial Plexus Block

Fig. 21.1

Patient positioning and surface landmarks for infraclavicular brachial plexus block

Preferably, the patient is positioned supine with a pillow under the shoulder. The arm is adducted and the elbow flexed at 90° with the hand resting on the abdomen. If the patient is awake, the arm may rest at the patient’s side if this will avoid discomfort. Surface landmarks include:

Cephalad
- Clavicle
Medially
- Sternal notch and sternoclavicular joint
- Medial end of the clavicle
Laterally
- Anterior aspect of the acromion: palpate the clavicle and move laterally to the acromioclavicular joint. The acromion can be differentiated from the humerus through passive movement of the arm.
- Coracoid process: medial and inferior to the acromioclavicular joint, which can be palpated just medial to the head of the humerus.

21.3 Nerve Stimulation Technique (Table 14.1)

21.3.1 Needle Insertion (Figs. 21.2 and 21.3)

Fig. 21.2

Flow chart of the procedures and needle insertion site for an infraclavicular block of the brachial plexus

Fig. 21.3

Flowchart of the procedure for employing nerve stimulation techniques for infraclavicular nerve block

Clean the skin with antiseptic solution, and drape the patient to ensure sterility.
Infiltrate the skin with local anesthetic (e.g., 0.5 mL of 1 % lidocaine).
The point of needle insertion depends on the age of the patient, but is approximately 0.5–1 cm inferior to the coracoid process.
Insert a 30–50 mm, 21–24G insulated needle in a vertical direction while applying nerve stimulation.

If the needle encounters a bone (rib), the needle has been placed too deep to the plexus. Withdraw the needle to the subcutaneous tissue and reinsert. See Table 21.1 for responses and recommended needle adjustments when using nerve stimulation for infraclavicular block.

Table 21.1

Responses and recommended needle adjustments for use during nerve stimulation at the infraclavicular location

Correct response from nerve stimulation

Distal responses (hand or wrist flexion or extension) are best for surgery of the elbow and below

Other common responses and needle adjustments

Muscle twitches from electrical stimulation

Pectoralis (adduction of arm)

Explanation: needle tip is too shallow

Needle adjustment: advance needle deeper

Deltoid (axillary nerve stimulation)

Explanation: needle tip is too inferior

Needle adjustment: withdraw needle to subcutaneous tissue and reinsert slightly more superiorly

Biceps (musculocutaneous nerve)

Explanation: needle tip is too superior

Needle adjustment: withdraw needle to subcutaneous tissue and reinsert slightly more inferiorly

Vascular puncture

Cephalic vein (seen as blood withdrawal when needle appears to be placed superficially)

Explanation: cephalic vein is superficial to the plexus and the subclavian artery and vein

Needle adjustment: withdraw needle and redirect carefully while observing the needle tip at all times using in-plane approach

Subclavian or axillary artery/vein puncture (seen as blood aspiration)^a

Explanation: artery and vein are next to the plexus

Needle adjustment: withdraw needle completely for pressure treatment and reinsert carefully while observing the needle tip at all times using in-plane approach; if the blood is venous, the needle tip is likely too caudal

Bone contact

Needle stops at rib

Explanation: needle is inserted too deep and has passed the plexus and subclavian artery. However, it is unlikely with ultrasound-guided technique

Needle adjustment: withdraw needle to subcutaneous tissue and reinsert

Pleural – more risk with medial locations of needle insertion

Needle observed to pass beyond the white line (rib), with a pocket forming

Explanation: needle is inserted too deep, has passed the plexus and subclavian artery, and is entering into the pleural space. However, it is unlikely with US-guided technique

Needle adjustment: withdraw to subcutaneous tissue and reinsert

^aSubclavian vessels when needle insertion is at a more medial location; axillary vessels when block is performed at a more lateral location

Blood aspiration indicates axillary artery/vein puncture. If this occurs, carefully reinsert the needle after complete withdrawal.
An initial current of 0.8 mA (frequency 2 Hz, pulse width 0.1 msec) is sufficient for stimulation of the plexus. The current is then reduced to aim for a threshold current of 0.4 mA while maintaining the appropriate motor response.
A distal motor response of hand or wrist flexion or extension is ideal.
Ultrasound guidance will help reduce the incidence of both bone contact and vessel puncture.

21.3.2 Modifications to Inappropriate Responses

See Fig. 21.4.

Fig. 21.4

Flowchart of modifications to inappropriate responses to nerve stimulation during infraclavicular brachial plexus block

21.4 Ultrasound-Guided Technique (Fig. 21.5)

Fig. 21.5

Flowchart of ultrasound-guided techniques for infraclavicular nerve block

It is common to perform an infraclavicular brachial plexus block with the patient’s elbow flexed and the hand resting on the abdomen or with the arm resting at the patient’s side. However, it may be more advantageous to position the patient with the elbow flexed and the arm abducted and externally rotated when completing the block under ultrasound guidance. This maneuver can render the cords taut and bring them to a more superficial location, thus accentuating their ultrasonographic appearance. Stretching the cords also brings the nerves closer around the axillary artery, which may facilitate local anesthetic spread around the nerves.

The location of the needle puncture will be where the brachial plexus cords, axillary vessels, and pleura are visualized best. It is ideal to make small probe adjustments (i.e., superior-inferior or medial-lateral) with the goal to have a well-defined cross section of the axillary artery. Blocks below the clavicle are associated with complications (Table 21.2); therefore, knowledge of the anatomical details of this region is crucial to perform this block correctly (Fig. 21.6a) and to avoid adverse events. Similar to the nerve stimulation technique, a lateral approach decreases the risk of pleural puncture, although a more medial location will allow higher resolution of the structures (Fig. 21.6b). If using a medial puncture site, ensure to maintain a view of the pleura and needle tip on the ultrasound screen at all times.

Table 21.2

Complications of nerve blocks below the clavicle

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