Indications: The most common surgical indication for cervical plexus block is carotid endarterectomy.
The regional approach to anesthesia for carotid endarterectomy offers several advantages over general anesthesia. With the patient awake, it offers an instant monitor of adequate blood flow from the contralateral side when the carotid artery is clamped. Additionally, hemodynamics are better preserved, compared with emergence from general anesthesia and extubation.
Cervical plexus block is an easy block to do in most patients, but there is a learning curve. As with most regional techniques, they are not always perfect, and it is important to have a plan to manage the failed blocks.
There are several points of note when doing regional anesthesia for carotid endarterectomy. First, it is important to choose patients who understand what is expected and explain the procedure well to them. They need to know they will be awake with little sedation, which means they will know they are being worked on and that they will feel touch, pressure, and temperature, but should be free from pain and discomfort for most of the procedure. Do not be afraid to change to a general anesthetic if when you begin the block the patient seems unduly uncomfortable with this approach. Second, it helps if the surgeon can complete the procedure in less than one and a half hours. Most of these patients are elderly and have arthritis, and will get uncomfortable if lying on a hard operating table for extended periods. Third, it is important that the surgeon be prepared to supplement the block with additional local anesthetic. There are two areas where this may be necessary. First, there are areas of overlap of unanesthetized dermatomes coming from the contralateral side, and because the incision comes close to the midline, it may be necessary to add additional local. Also, structures inside the carotid sheath receive innervation from the cranial nerves IX and X. If painful for the patient when the carotid sheath is entered, this can be eliminated by topical administration of local anesthetic to the area. If bradycardia becomes a problem with traction on the carotid sinus, then local anesthetic to that area can help. At the completion of the procedure and in the recovery room, it is important to control the blood pressure, as improved blood supply to the affected side can produce some mild cerebral edema and confusion if the blood pressure is too high.
Contraindications (absolute and relative)
· Patient refusal
· Patients that are confused and cannot cooperate
· Patients with an uncontrollable cough
· Patients that cannot lie flat
· Patients with a high bifurcation of the common carotid requiring excessive retraction for surgical exposure
Anesthesia for carotid endarterectomy can be adequately supplied by blocking cervical nerves 2, 3 and 4. These nerves supply the area from behind the head down to the clavicle. Also, there is some overlap of dermatomes from the contralateral side. In addition, the third division of the trigeminal nerve supplies sensation down to the superior surface of the mandible. Lastly, the structures within the carotid sheath are supplied by cranial nerves IX and X.
The roots of the cervical nerves emerge superior to the transverse process of each cervical vertebra. The superficial plexus emerge form the border of the posterior border of the sternocleidomastoid muscle, the majority arising from the midpoint.
· Mayo stand and sterile cover
· Three sterile towels
· Prep solution
· Cup for local anesthetic
· Package of 4 × 4 sterile sponges
· Three 5-cc syringes
· One 10-cc syringe
· Three 22-gauge × 1.5-in needles
· One 25-gauge or smaller needle
· One short extension tubing
· One 20-cc vial of lidocaine 1.5% with 1/400,000 epi
· One 20-cc vial of lidocaine 1% plain
It is important not to oversedate the patient. The patient must be awake enough to follow commands, indicating adequate cerebral blood flow. A combination of benzodiazepines and narcotics can be titrated to a desired effect. In the elderly benzodiazepines may result in restlessness and confusion.
The patient is placed on the table with the head slightly extended and turned to the contralateral side.
Figure 16-1. Anatomic landmarks.
Figure 16-2. Location of C-2, C-3, and C-4.
A line is drawn from the mastoid process, to a point located two fingerbreadths lateral to the midline of the cricothyroid membrane (a point representing the transverse process of C-6) (Fig. 16-1).
To locate C-2, a point is marked two fingerbreadths caudal to the mastoid process along a line approximately 30° to the previous line. C-3 and C-4 are located one fingerbreadth respectively along that line as shown in Figure 16-2.
The neck is prepped and draped.
A skin wheal is raised at C-2, C-3, and C-4, with lidocaine 1%, (Figs. 16-3 through 16-5) followed by subcutaneous injections at the same levels.
A 22-gauge needle is inserted at C-2, C-3, and C-4, (slightly anterior and cephalad), deep to the transverse process of the respective levels and then pulled back 1 to 2 mm.
Next, C-2, C-3, and C-4 are blocked by attaching a syringe with a short extension and after negative aspiration, injecting 6 cc of lidocaine 1.5% with 1/400,000 of epinephrine at each level (Fig. 16-6).
Next, the superficial portion of the block is carried out by injecting subcutaneously along the incision line (Fig. 16-7). It is also necessary to inject along the inferior border of the mandible to include that sensation supplied by the V-3 portion of the trigeminal nerve.
Figures 16-3 through 16-5. A needle is inserted at C-2, C-3, and C-4 deep to the transverse process of the respective levels and then pulled back 1 to 2 mm.
Figure 16-6. C-2, C-3, and C-4 are blocked by attaching a syringe with a short extension and after negative aspiration, injecting 6 cc of lidocaine 1.5% with 1/400,000 of epinephrine at each level.
Figure 16-7. The superficial portion of the block is carried out by injecting subcutaneously along the incision line.
1. Patient selection is important. Cooperation is mandatory and therefore sedation is kept to a minimum and titrated to effect. Benzodiazepines in the elderly may have the opposite effect.
2. Oxygen by nasal cannula is often better tolerated than by face mask. Monitoring as for any other major procedure is mandatory.
3. Since it is possible to block the phrenic nerve, only one side should be blocked at a time; patients with severe COPD should be watched closely.
4. Complications are rare, but significant should they occur. The vertebral artery and subarachnoid space lie in close proximity. Therefore, an intravascular or subarachnoid injection is possible with CNS toxicity and either seizure activity, cardiac instability, or a total spinal occurring.
5. During clamping of the carotid artery, it is important to communicate closely with the patient for signs of altered or loss of consciousness. If this occurs, it will be necessary to unclamp and place a shunt.
6. Proper control of hemodynamics should occur preoperatively, making intraoperative and postoperative management of blood pressure easier.
7. Postoperatively it is important to control hypertension. Because of improved blood flow to the operative side, excessive hypertension may produce mild cerebral edema and confusion.
A. Cervical Plexus Block: Revisited One-Puncture Technique
Patient positioning: The patient is positioned supine, without pillow, and with the head rotated contralaterally to the operation site.
Indications: Carotid surgery.
Needle Size: 25-gauge 1.5 cm length, insulinlike needle.
Volume: 20 to 30 mL of local anesthetic.
Anatomic Landmarks: The puncture site is located along the posterior border of the sternocleidomastoid (SCM) muscle, midway between the mastoid and clavicle (Fig. 16-8). An injection of local anesthetic, internally to the fascia superficialis, diffuses through the fascia prevertebralis, determining a superficial and deep cervical plexus block.
Approach and Technique: The needle is inserted perpendicular to the skin for all its length (1.5 cm), avoiding muscular (SCM) or vascular (external jugular vein) puncture, without looking for any paresthesia or any bony contact. The volume of 10 to 15 mL of the chosen local anesthetic is injected over 5 min with multiple aspiration tests and maintenance of verbal contact with the patient.
This block is systematically associated with the subcutaneous infiltration (10–15 mL of local anesthetic) of the incision line as previously drawn by the surgeon.
1. A needle longer than 1.5 cm may be necessary for morbidly obese patients.
2. Transitory disturbance of phonation and deglutition, phrenic paralysis, and sensitive or motor brachial block are undesired but usual effects of local anesthetic diffusion.
Figure 16-8. Surface landmarks. (1) mastoid; (2) clavicular insertion of the SCM muscle; (3) sternal insertion of the SCM muscle; cross, site of puncture. In red, the incision line.
3. Despite a relatively long onset time, long-acting local anesthetics offer the advantage of an excellent postoperative analgesia.
4. Additional local anesthetic can be administered topically during the surgery (e.g., before or during the adventitia dissection), as necessary.
5. The single-puncture technique offers the advantage of reduced risk of complications that may result from the successive injections used in multipuncture techniques.
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