Chapter 133. Interscalene Block

Indications:

• Surgery of the distal clavicle, the shoulder, and the proximal one third of the humerus
• Unreliable block of C8 and T1: not advisable for surgery below midhumerus (medial aspect of the extremity not covered)

Contraindications:

• Contralateral phrenic nerve palsy or severe respiratory disease
• Contralateral vocal cord/recurrent laryngeal nerve palsy

Technique using NS:

• Landmarks (Figure 133-3):
  • Posterior border of SCM muscle (ask patient to lift head if difficult to palpate), anterior and middle scalene muscles just posterior to the SCM, groove between the two scalene muscles
  • Cricoid cartilage, or better tubercle of Chassaignac (i.e., transverse process of C6), to locate the level of C6
• A 5-cm needle is introduced at an angle of about 45° with the long axis of the neck (too perpendicular to the neck, the needle could pass between transverse processes and lead to an epidural or intrathecal injection; aiming too caudad, it increases the risk of pneumothorax). This angle should not change during the procedure. Only the anterior/posterior angle (and the depth) should be altered
• The index finger of the other hand is held on the groove and the needle is aimed at the plane of that groove
• The stimulator is set at 1.2 mA, 2 Hz (0.1 millisecond)
• Typically, the brachial plexus will be encountered after only 1–2 cm. Do not push the needle all the way!
• Once an acceptable response has been obtained, the current should be decreased while needle position is optimized, until a current of less than 0.4 mA still triggers a motor response. If the response disappears as soon as one decreases the current below 0.5 mA, regardless of needle position changes, this typically means that the needle is outside of the interscalene sheath and needs to be repositioned
• To insert a catheter, the needle insertion point should be about 2 cm more cephalad, with the needle directed more caudad. This will allow the catheter to be more parallel to the plexus