The brachial plexus is situated between the anterior and middle scalene muscles (
). The phrenic nerve is anterior to the anterior scalene muscle and lateral to the stellate ganglion. The vertebral artery and vein are situated anterior to the pars intervertebralis or the articular column of the vertebrae. The approach described avoids the extensor muscles of the neck by entering the neck at the level of the “V” formed by the trapezius muscle and the levator scapulae muscle.
The brachial plexus is situated between the anterior and middle scalene muscles ( Fig. 37-2 ). The phrenic nerve is anterior to the anterior scalene muscle and lateral to the stellate ganglion. The vertebral artery and vein are situated anterior to the pars intervertebralis or the articular column of the vertebrae. The approach described avoids the extensor muscles of the neck by entering the neck at the level of the “V” formed by the trapezius muscle and the levator scapulae muscle.
The patient is positioned in either the sitting or the lateral decubitus position (the levator scapulae muscle is usually easier to identify if the patient is in the sitting position). The neck of the patient is slightly flexed forward. The anesthesiologist stands behind the patient.Needle puncture.
Following preparation of the skin with an appropriate disinfectant and placement of sterile drapes, local anesthetic infiltration of the skin and subcutaneous tissue is performed to the level of the pars intervertebralis (articular column) and the intended catheter tunneling site. Next, an insulated 17- or 18-gauge Tuohy needle is inserted at the apex of the “V” formed by the trapezius and levator scapulae muscles at the level of the sixth cervical vertebrae (see Figs. 37-1 and 37–2 ).
The negative lead of the nerve stimulator, set at a current of 1.5 to 3 mA, a frequency of 2 Hz, and a pulse width of 100 to 300 μsec is attached to the needle. The needle is advanced anteromedially and approximately 30 degrees caudad, aiming toward the suprasternal notch or cricoid cartilage until the short transverse process of C6 or the pars intervertebralis (articular column) of C6 is encountered. The stylet of the needle is removed and a loss-of-resistance syringe is attached to the needle. While continuously testing for loss of resistance, the needle is laterally walked off this bony structure and then advanced anteriorly. Usually a distinct loss of resistance to air occurs simultaneously with a motor response in the muscles of the shoulder as the cervical paravertebral space is entered approximately 0.5 to 1 cm beyond the transverse process. At this level, the motor (anterior) and sensory (posterior) fibers have joined to become the roots of the brachial plexus, and more current is typically required to elicit a motor response than with an anterior interscalene technique ( Fig. 37-3 ).
When the tip of the needle nears the roots of the brachial plexus (indicated either by a motor response or a patient report of sensory pulsation at a nerve stimulation output setting of approximately 0.5 mA), the needle is held steady while the loss-of-resistance syringe is removed. If a nonstimulating technique is used, a bolus injection is performed through the needle followed by advancement of a standard epidural catheter.
The nerve stimulator lead is now attached to the proximal end of a 19- or 20-gauge stimulating catheter, and its distal end is inserted into the needle shaft. If a stimulating catheter is used with this method, the nerve stimulator output is kept constant at a current that provides brisk muscle twitches of the shoulder or upper extremity muscles, the catheter tip is advanced 5 cm beyond the tip of the needle, as described in Chapter 2 . Following catheter advancement, the catheter is tunneled approximately 5 cm to a convenient position and covered with a transparent dressing.Potential Problems.
Problems that can arise are the same as those for a continuous interscalene block. Horner’s syndrome occurs frequently with this block, and phrenic nerve paralysis, although not yet studied, should have the same prevalence as during interscalene block. Posterior neck pain probably indicates that some of the extensor muscles of the neck have been penetrated.