Fig. 1
Interscalene block with eletcroneurostimulator (ENS). Superficial positioning points are represented by the posterior edge of sternocleidomastoid muscle and the superior edge of the cricoid cartilage and the left clavicle body
Interscalene groove (between anterior and medium scalene muscle), located back to the posterior edge of sternocleidomastoid muscle
Superior edge of the cricoid cartilage (transversal process of C6)
To better identify these points, it can be useful to flex patient’s head.
The needle, 50 mm long, should be inserted into the interscalene groove at the level of superior edge of cricoid cartilage and should be directed downward, medially, and backward. The needle encounters the nervous fibers at 2.5–3.5 cm deep from cutaneous plain.
Contractions to be evoked:
Bend of forearm towards arm (musculocutaneous nerve)
Shoulder abduction (axillary nerve)
Interscalene Block according to Alemanno with ENS
The patient is positioned supine, with the head extended and slightly rotated contralaterally to the side of the block [23]. Superficial positioning points are represented by:
Median point of the clavicle
Supraclavicular pulse of the subclavian artery
The needle (50 mm long), connected to the ENS, is introduced 0.5 cm laterally to the above-mentioned points and is then moved in posterior-medial direction, toward the spinous process, arch and C7 body, in order to induce a motor stimulation.
Ecoguided Interscalene Block
The patient is positioned supine with the head rotated contralaterally to the side of the block and the arm in neutral position along the body (Fig. 2a, b) [23]. An echographic probe at high frequency regulated at 12–18 MHz and stimulating 50 mm needles (22 G) are used.
Fig. 2
(a, b) Ecoguided interscalene block
The brachial plexus can be easily visualized by ultrasounds in correspondence of the posterior interscalene space (Fig. 3). The search for the brachial plexus starts laterally to the larynx, passing through the thyroid, carotid artery, and internal jugular vein. Then, moving the probe more externally and downward along the lateral edge of the sternocleidomastoid muscle, the nervous structures become visible in transversal vision as oval or circular hypoechogenic areas delimited by the anterior and medium scalene muscles.
Fig. 3
Soundanatomy of interscalene groove: ASM anterior scalene muscle, MSM medium scalene muscle, BP brachial plexus
The roots of brachial plexus (C5, C6 e C7) are located immediately behind the anterior scalene muscle and appear as round hypoechogenic structures, sometimes “traffic light-shaped”. By ultrasonography, both the needle movement through the interscalene space and the diffusion of the local anesthetic can be monitored (Fig. 3).
Most complications associated with the block of brachial plexus, continuous or not, are transient and do not have any consequence; however, extreme caution should be given during the procedure due to the proximity between the exploratory needle and neurovascular structures [17, 18].
Common complications of the interscalene brachial plexus block include the block of homolateral phrenic nervous (consensual hemi-diaphragmatic paralysis), Horner’s syndrome due to the block of stellate ganglion (exophthalmos, palpebral ptosis), recurrent block of laryngeal nerve (dysphonia), and vascular cut (hematomas). Rare complications, but potentially severe, are carotid and intervertebral cuts, pneumothorax, subaracnoidal or intraforaminal cut (cause of spinal anesthesia and cervical epidural, respectively), and direct nervous lesion. In continuous, blocks perineural catheters can infect, kneel, tie, or become imprisoned [19, 20].
Supraclavear Block
The use of ultrasounds allows to easily perform anesthetic procedures which were associated with a high risk up to date. This is the case of supraclavear block that was progressively neglected in clinical practice due to the high incidence of pneumothorax dependent on close relationship between neurovascular structures and lung. The introduction of echography has drastically reduced those risks, making this block feasible also in pediatric patients.
In patients who are not eligible to general anesthesia – even if light – the association of supraclavear and interscalene blocks allows the intervention on shoulder in totally conscious patient.
The patient is positioned supine with the head rotated contralaterally to the side of the block and the arm in neutral position along the body. An echographic probe at high frequency set between 12 and 18 MHz is positioned into the supraclavear groove, in parallel to the third medium of clavicle and with the ultrasound beam in caudal direction.
Then, the probe is laterally and medially slid to search for the subclavian artery that will appear, over the short axis, as a hypoechogenic and pulsatile structure [23]; color Doppler can be used to confirm the vascular nature (especially when the anatomy is abnormal). The subclavian vein is more superficial and medially located with respect to the artery [23]. Behind the artery, the surface of the first rib will appear as a hyperechogenic line with an underlying hypoanechogenic shadow, since the bone surface totally reflects ultrasounds. The first rib and its posterior shadow interrupt the continuity of an underlying hyperechogenic line which represents the parietal pleura that, − unlike the rib – is passed by ultrasounds, thus generating reflection artifacts. These artifacts, defined as “comet tail”, are typical of the tissue-air interface that represents pulmonary parenchyma (Fig. 4) [23].
