Interscalene nerve blocks
Interscalene nerve blocks represent the most cranial approach to the brachial plexus. Various puncture techniques are possible. In the following, we describe two different means of access: the anterior (according to Meier) and the posterior (according to Pippa). Both procedures can be said to be essentially equivalent with respect to their indications, contraindications and side effects. According to our own studies, the anterior approach proves to be somewhat less time consuming and complicated and (as reported in the literature) less risky. The posterior approach, by contrast, offers certain benefits under specific anatomical circumstances, like in no-neck patients, and in terms of adverse side effects, including potential catheter dislocations, particularly when combined with continuous catheter analgesia. Not least, the use of one or the other technique also depends on the personal skills of the individual anaesthesiologist.
Anterior access (according to Meier)
The interscalene nerve block is a modification of the technique described by Winnie in 1970. In the classical technique of Winnie, the interscalene nerve block is performed at the posterior scalene gap. This puncture site is thus at the level of the cricoid. The puncture is made in the medial, dorsal and caudal direction.
Ultrasound-guided interscalene nerve block
Positioning of the patient for purposes of a block corresponds by and large to the conventional Meier technique. The key structures are easiest to identify from a supraclavicular view of the brachial plexus (as shown). After identification of the subclavian artery, which is surrounded dorsolaterally by the various parts of the brachial plexus in a half-moon or cluster formation, the probe is turned in a cranial direction, showing on the screen the reorganization of the supraclavicular trunks and/or fascicles back to the cervical roots of the plexus. In the classical case, at least C5-C7 are clearly seen to line up as a hypodense „string of pearls“ between the anterior and medial scalene muscles.
Posterior access (according to Pippa)
A posterior access can be used as an alternative to the anterior access. The puncture site is located on the back of the neck, at the level of C6/C7 and is directed dorsad towards the scalenus gap. This technique was first described by Kappis in 1912. Then it was forgotten until Pippa started using the posterior interscalene block again in 1990, applying the loss-of-resistance technique for localising the target. Thanks to the use of electrical nerve stimulation, this approach has gained importance over the last few years.
Indications / Contraindications / Side effects
Indications for interscalene nerve blocksSingle-shot technique
All surgical interventions on the shoulder including shoulder total arthroplasty, proximal humerus, lateral clavicle.
For operations known to have high postoperative analgesia requirements, e.g., arthroplasty of the shoulder joint or in supportive physiotherapy following mobilisation of the shoulder joint.
Contraindications for interscalene nerve blocks
- Contralateral recurrent paresis
- KContralateral phrenic paresis
Side effects/complications of interscalene nerve blocks
- Phrenic paresis
- Horner Trias (stellate ganglion)
- Recurrent paresis
- Vessel puncture (external jugular vein, internal jugular vein, common carotid artery)
- Pneumothorax (rare)
Limits of the Method
The application of local anaesthetic into the more cranial area of the plexus will relatively frequently lead to incomplete analgesia of the supply area of the nerves arising from the more caudad region of the plexus (medial cord, ulnar nerve, cutaneous nerve of the arm, medial cutaneous nerve of the forearm). Neither can this be prevented by the administration of high doses of local anaesthetics. Hence, interscalene nerve blocks belong in the realm of shoulder surgery.