Interscalene Approach

The technique aims at entering the interscalene space at its upper end, near the transverse process of C6.^[225] The patient is placed in the supine position, with the head turned opposite to the side to be blocked. The landmarks are the interscalene groove between the anterior and middle scalene muscles and the anterior ramus of the transverse process of the sixth cervical vertebra (i.e., Chassaignac's tubercle), which projects at the intersection of the interscalene groove with the circular line passing over the cricoid cartilage. This intersection corresponds to the site of puncture. The classic approach consists of inserting the block needle at an 80-degree angle (not perpendicularly) to the skin (i.e., slightly dorsally and caudad) until muscle twitches are elicited in the upper limb ( Fig. 45-9 ). This technique provides a very effective block of the lower branches of the cervical plexus and upper branches of the brachial plexus, whereas the caudal branches of the brachial plexus may be poorly anesthetized. Because shoulder surgery is not usual in children, this block procedure has limited indications in pediatrics, the more so because it can result in severe adverse effects: vascular lesions, especially vertebral artery injury; undesirable nerve blocks (e.g., phrenic nerve, recurrent laryngeal nerve, stellate ganglion) with diaphragmatic paraparesis or paralysis in virtually all patients; and accidental epidural or intrathecal penetration, especially when the needle is inserted at a 90-degree instead of an 80-degree angle to the skin. Using the same site of puncture, a variant of the technique^[226] introduces the block needle almost tangential to the skin and in the direction of the midpoint of the clavicle until twitches are elicited in the upper arm. This technique is easy,

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Figure 45-9 Interscalene approaches to the brachial plexus: classic approach (after Winnie) (A) and modified approach (after Borgeat) (B), indicating the midpoint of the clavicle (1).