The patient lies supine with the neck hyperextended and a thin
pillow under the shoulders. The carotid artery is palpated, the
trachea identified, and using two fingers, the transverse body of
C6 (Chassaignac tubercle) is palpated (block at C7 is associated
with a higher incidence of pheumothorax). This is the most prominent
of the cervical transverse processes and lies at the level of the
cricoid cartilage. A skin wheal is raised and a 22-gauge 1½-inch
needle is advanced between the carotid and cricoid perpendicular
to the skin until it contacts the transverse process. The needle
then is pulled approximately 2 mm back, the syringe is aspirated,
and a 1-ml test dose is given. Assuming there is no untoward reaction,
the remaining solution is injected. This volume will spread along
the fascial plane, typically from the middle cervical ganglion to
T4 or T5 ganglion, thus affecting the sympathetic supply to structures
of the head and neck, upper extremity, and chest.