Cervical Plexus Blockade
The cervical plexus is derived from the C1, C2, C3, and C4 spinal
nerves and supplies branches to the prevertebral muscles, strap muscles of the neck,
and phrenic nerve. The deep cervical plexus supplies the musculature of the neck
segmentally and the cutaneous sensation of the skin between the trigeminally innervated
face and the T2 dermatome of the trunk. Blockade of the superficial cervical plexus
results in anesthesia of only the cutaneous nerves.
Clinical Applications
Blocks of the cervical plexus are easy to perform and provide
anesthesia for surgical procedures in the distribution of C2 to C4, including lymph
node dissections, plastic repairs, and carotid endarterectomy. The ability to monitor
the awake patient's neurologic status continuously is an advantage of this anesthetic
technique for the latter procedure and has resulted in an upsurge in the popularity
of this technique.[55]
[56]
Bilateral blocks can be used for tracheostomy and thyroidectomy.
Technique: Superficial Cervical Plexus
The superficial cervical plexus is blocked at the midpoint of
the posterior border of the sternocleidomastoid muscle. A skin wheal is made at
this point, and a 22-gauge, 4-cm needle is advanced, injecting 5 mL of solution along
the posterior border and medial surface of the sternocleidomastoid muscle ( Fig.
44-22
). It is possible to block the
Figure 44-22
Anatomic landmarks and method of needle placement for
a superficial cervical plexus block.
accessory nerve with this injection, resulting in temporary ipsilateral trapezius
muscle paralysis.
Technique: Deep Cervical Plexus
The deep cervical plexus block is a paravertebral block of the
C2 to C4 spinal nerves as they emerge from their foramina in the cervical vertebrae
( Fig. 44-23
; see Plate
4
in the color atlas of this volume). The traditional approach uses three
separate injections at C2, C3, and C4. The patient lies supine with the neck slightly
extended and the head turned away from the side to be blocked. A line is drawn connecting
the tip of the mastoid process and the Chassaignac tubercle (i.e., transverse process
of C6); a second line is drawn 1 cm posterior to this first line. The C2 transverse
process lies 1 to 2 cm caudad to the mastoid process, where it can usually be palpated.
The C3 and C4 transverse processes lie at 1.5-cm intervals along the second line.
After skin wheals are raised over the transverse processes of C2, C3, and C4, three
22-gauge, 5-cm needles are advanced perpendicular to the skin entry site with a slight
caudad angulation. The transverse process is contacted at a depth of 1.5 to 3 cm.
If a paresthesia is obtained, 3 to 4 mL of solution is injected after careful aspiration
for blood and cerebrospinal fluid. If no paresthesia is elicited initially, the
needle is walked along the transverse process in the anteroposterior plane until
a paresthesia is obtained.
This block can also be performed with a single injection of 10
to 12 mL at the C4 transverse process.[57]
Figure 44-23
Anatomic landmarks and method of needle placement for
deep cervical plexus blocks at C2, C3, and C4 (see Plate
4
in the color atlas of this volume).
Cephalad spread of the local anesthetic usually anesthetizes the C2 and C3 nerves.
Cervical plexus anesthesia can also be observed after injection at the interscalene
level for brachial plexus blockade. Maintenance of distal pressure and a horizontal
or slightly head-down position may facilitate the onset of cervical plexus blockade
using the interscalene technique.
Side Effects and Complications
Although these blocks are technically straightforward, needle
placement for the deep cervical block allows local anesthetic injection in close
proximity to a variety of neural and vascular structures. Reported complications
and side effects include intravascular injection, blockade of the phrenic and superior
laryngeal nerve, and spread of local anesthetic solution into the epidural and subarachnoid
spaces.
