Interscalene Block

Indications

• Surgery of the shoulder or upper arm

Set-Up

• Two 30 ml syringes with local anesthetic (1.5% mepivacaine + epinephrine (1:200,000) + HCO3 - (0.1 mEq/cc)
• For longer acting blocks, 10 ml of 0.75% bupivacaine + epinephrine (1:200,000) may be added.
• The syringes are attached to a three-way stopcock that is connected to IV extension tubing fitted to a 23 gauge, 1 inch needle. This provides an immobile needle technique

Essential Anatomy (Fig. 2-1)

• Cricoid cartilage
• Sternocleidomastoid muscle
• Anterior and middle scalene muscules
• Transverse processes of the cervical spine
• Things to avoid: vertebral artery, epidural space, and spinal cord.

Figure 2-1 Illustration by Beth Halasz, Western Reserve Medical Art

 

Technique

• Place the patient supine with the neck in the neutral position and the head turned slightly away from the shoulder to be blocked.
• Clean the neck in an aseptic manner. Palpate the posterior border of the lateral (clavicular) head of the sternocleidomastoid muscle at the level of the cricoid cartilage (C-6). If identifying the sternocleidomastoid is difficult, have the patient elevate their head slightly. Roll your fingers laterally over the anterior scalene muscle and identify a narrow groove just lateral to it. Often the anterior scalene muscle lies behind the posterior border of the sternocleidomastoid. If the scalene muscles cannot be appreciated, have the patient take a slow deep breath through the nose to help accentuate the muscles by giving them increased tone. One should feel both the anterior and middle scalene muscle tense during inspiration.
• Usually a 1 inch needle is used although occasionally a 1.5 inch needle is needed in very large patients. Introduce the needle slowly, focusing the patients attention to their arm, shoulder, or hand. Move slowly, observing the patient for nonverbal indication of a paresthesia, and then inquiring when necessary. Ensure that the needle direction remains in a slightly dorsal, slightly caudad, and medial direction in order to minimize risk of entering the spinal cord.
• After an appropriate paresthesia is illicited, 45 to 55 mls of local anethetic are injected incrementally with frequent aspiration. During the initial injection, the paresthesia may become more intense, which may be an early indication of a successful block. Injection should not be very difficult nor should it be very painful as these may be signs of an injection directly into a nerve root.

Limitations

• Patient cooperation is necessary for any paresthesia technique
• Partial or incomplete blockade of the ulnar nerve.
• Contraindicated in patients with significant pulmonary impairment
• Contraindicated in patients with contralateral vocal cord paralysis or phrenic nerve paralysis

Side effects and complications

• 100% incidence of phrenic nerve paralysis
• Patients develop a hoarse voice from sympathetic blockade and possibly vocal cord paralysis.
• Rare complications include epidual block, subarachnoid block, pneumothorax, seizure, local anesthetic toxicity, phrenic and vocal cord paresis.

Pearls

Figure 3-2

• With larger volumes, a visible swelling will appear in most patients defining the inferior portion of the supraclavicular brachial plexus.
• The interscalene groove becomes wider and easier to palpate at its distal end (toward the clavicula). It is then easy to track it back to the desired level (C6).
• Onset of sufficient blockade takes approximately 15 minutes. Pinprick testing within 2 minutes shows decreased sensation on the superior aspect of the shoulder on the C5 or C6 dermatome, followed within a few minutes by the inability to raise or Figure 2-2 abduct the straightened arm against gravity (the deltoid sign). A perceptible decrease in handgrip strength may be seen and pronation of the hand during maximal grip is usually seen.
• Although the appearance of Horner’s syndrome on the side of the block does not necessarily indicate successful interscalene block because the stellate ganglion can be blocked without blocking the plexus— it can confirm accompanying sympathetic block.
• Interscalene nerve block often does not extend to the T2 nerve root. Often the surgery may extend to the T2 dermatome and the surgeons must be encouraged to infiltrate the skin with local anesthetic. The underlying joint, bones, and muscles of the shoulder are covered by the interscalene block.

References

1. Winnie AP: Interscalene brachial plexus block. Anesth Analg 1970; 49:455.
2. Sharrock NE, Bruce G: an improved technique for locating the interscalene groove. Anesthesiology 1976; 44:431.
3. Loring SH, DeTroyer A: Actions of the respiratory muscles. In Roussos C, Macklem PT (eds): The Thorax, p 341. New York, Marcel Dekkar, Inc, 1985.
4. Urmey WF, Mcdonald M: Hemidiaphragmatic paresis during interscalene brachial plexus block: effects on pulmonary function and chest wall mechanics. Anesth Analg 1992; 74:352.
5. Urmey WF, Talts KH, Sharrock NE: One hundred percent incidence of hemidiaphragmatic paresis associated with interscalene brachial plexus anesthesia as diagnosed by ultrasonography. Anesth Analg 1991;72:498.
6. Urmey WF, Gloeggler PJ: Pulmonary function changes during interscalene block: effects of decreasing local anesthetic injection volume. Reg Anesth 1993;18:244.
7. Roch JJ, Sharrock NE, Neudachin L: Interscalene brachial plexus block for shoulder surgery: a proximal paresthesia is effective. Anesth Analg 1992;75:386.
8. Seltzer JL: Hoarseness and Horner’s syndrome after interscalene brachial plexus block. Anesth Analg 1970; 49:986.
9. Dhumer KG, Mobey E, Orne L: Paresis of the phrenic nerve during brachial plexus block analgesia and its importance. Acta Chir Scand 1955; 109:53.
10. Shaw WM: Paralysis of the phrenic nerve during brachial plexus anesthesia. Anesthesiology 1949;10:627.

These technique descriptions are presented for educational purposes and are not intended to substitute for actual hands-on training.