Carotid Endarterectomy Using Single Injection Posterior Cervical Paravertebral Block

Abstract

To the Editor: Regional anesthesia for carotid endarterectomy allows continuous clinical assessment of cerebral function intraoperatively (1). However, performance of deep cervical plexus block carries an inherent risk of injury to the vertebral vascular structures, which are all anterior to the nerve roots. An alternative approach for blocking the C2-4 dermatomes is a single injection posterior cervical paravertebral block performed at the C4 level, based on techniques described by Pippa et al. (2) and later modified (3). This posterior approach enjoys a bony “backstop” that eliminates the risk of vascular involvement (Fig. 1). Moreover, by relying on spread along the paravertebral space (Fig. 2), the block can be performed as a single injection at one level.Figure 1.: A view of the cervical spine from posterior, which demonstrates the “bony backstop” formed by the pars intervertebralis, the articular columns, and the short spinous processes of the vertebrae. A 18-gauge insulated Tuohy needle is shown demonstrating anteromedial and caudad placement before lateral advancement towards the cervical nerve roots.Figure 2.: This anteroposterior view of the neck shows the paravertebral spread of C4 injected contrast medium (encircled) from the base of the skull to the area of the fifth cervical vertebra. The wires are electroencephalography leads.With the patient in lateral decubitus position and after skin and subcutaneous tissue infiltration of local anesthetic agent, a 17- or 18-gauge insulated Tuohy needle (StimuCath ™; Arrow International, Reading, PA), attached to a peripheral nerve stimulator set at 1.5 mA and 200 μs pulse width, is introduced at a point at the level of the angle of the jaw, 4 cm caudad to the mastoid process where the anterolateral border of the trapezius muscle and posteromedial border of the levator scapulae muscle form a natural groove overlying the cervical transverse processes. The needle is then advanced in an anteromedial and caudad direction, aiming for the “Adam’s apple,” until it comes in contact with the pars intervertebralis of C4. A loss of resistance syringe is then attached and the needle “walked” off the bone in an anterolateral and caudad direction until loss of resistance to air occurs (representing the paravertebral space), followed immediately by muscle twitches in the lateral neck. After negative aspiration 15 mL ropivacaine (0.75%) is injected slowly. We have obtained excellent results with this technique in a number of patients and further evaluation is ongoing. André P. Boezaart, MBChB, FFA (CMSA), MMed(Anaesth), PhD Mace A. Nosovitch, MD Regional Anesthesia Study Center of Iowa (RASCI) Department of Anesthesiology University of Iowa Hospital and Clinics Iowa City, Iowa [email protected]