Pharmacological Sciences

Interscalene Block

The interscalene block targets the brachial plexus at the level of the trunks or roots and is used for surgeries performed on the shoulder and lateral aspect of the upper arm. Innervation of the shoulder and many of the nerves affected by an interscalene nerve blockade are identified in Table 20.6.

Indication

Indications include primary anesthesia and/or postoperative pain management with or without a continuous catheter for shoulder and shoulder joint, lateral two-third of clavicle, and proximal humerus surgeries. Arm and forearm surgeries with an interscalene block do not often provide adequate coverage of the ulnar nerve distribution (C8-T1) and are therefore not completely useful for surgeries of the lower arm, wrist, or hand. Lack of appropriate blockade of the ulnar nerve distribution subsequent to an interscalene block may be circumvented by

Axillary	In fradavicular	Supraclavicular	and	Interscalene
Brandies	Cords	Divisions	Trunks	Roots
				C4
Musculocutaneous	Lateral	Anterior Posterior	Superior	C5
Axillary				C6
Median	Posterior	Anterior Posterior	Middle	C7
Radial			Inferior	C8
Ulnar	Medial	Anterior Posterior		T1

Figure 20.2 (Continued)

Table 20.6 Innervation of the shoulder and interscalene nerve blockade.

Nerve

Brachial plexus

Upper lateral brachial cutaneous (from the axillary n.) Intercostobrachial

Supraclavicular (C3, C4)

Subclavius

Dorsal scapular

Long thoracic Suprascapular

Axillary, suprascapular, subscapular

Motor of the shoulder

Sensory of the shoulder

All except cephalad cutaneous parts innervated by supraclavicular n. (C3-C4) Lateral side of shoulder and skin overlying the deltoid Anterior and medial skin of shoulder and posterior upper arm

Skin over upper deltoid/shoulder

Joint of the shoulder

Subclavius m. Rhomboid and levator scapulae m. Serratus anterior m. Supraspinatus and infraspinatus m. Deltoid and teres minor m.

Acromioclavicular joint Sternoclavicular joint

Shoulder joint

Skin of the shoulder over inferior Shoulder joint deltoid using larger local anesthetic volumes or supplemental blockade of the ulnar nerve at a more distal location of the upper extremity.

Technique Preparation

Arrange sterile towels, sterile gloves, gauze pads, marking pen, antiseptic solution, peripheral nerve stimulator, syringes, and needles for local infiltration and nerve block placement.

Dose

20-40 ml syringes of local anesthetic. Needles

25 g 1.5 in. needle for skin infiltration and 22 g 3 or 5 cm short bevel insulated stimulation needle.

Agents

3% chloroprocaine, 2% lidocaine, 0.5% ropivacaine, 0.5% bupivacaine.

Surface Anatomy and Landmarks Landmarks

Landmarks include posterior and lateral borders of the sternal and clavicular heads of sternocleidomastoid m., C6 tubercle, interscalene groove formed by the middle and anterior scalene m., upper border of cricoid cartilage, and clavicle (Fig. 20.3).

The patient should be positioned supine with their head turned away from the side to be blocked. The arms are to remain relaxed at the patient's side. A line drawn laterally from

Figure 20.3 Surface landmarks for the classical interscalene approach to the brachial plexus. (a) Sternal notch, (b) external jugular vein, and c sternocleidomastoid muscle. Line #1 identifies the clavicle. Dashed line #2 indicates the C6 vertebral process and is the line/path along which to follow in search of the appropriate muscle response. X marks the needle entry site.