1. Anesthetic Methods in the Management of Carotid Endarterectomies
Daniel Park MD
CA-2
Boston Medical Center

2. Positioning Placed in supine position
No head elevation
Head tilted away from surgical site
Shoulder roll may be helpful for exaggerated neck extension

3. Surgical Technique
Incision from the mastoid process extending down the anteromedial border of the sternocleidomastoid muscle
Ends 1-2 fingerbreaths from the sternal notch

4. Surgical Technique
Carotid sheath dissected to expose the carotid artery, internal jugular vein, vagus nerve, and deep cervical lymphatic chain
Prior to shunt placement or clamping of artery, heparin to be administered
Incision made from proximal common carotid artery into internal carotid artery
Vessel cleaned of atheromatous plaque
Closure either primary with vein or prosthetic patch
Townsend: Sabiston Textbook of Surgery, 17th ed., 2004

5. Pathophysiology Type I and Type II baroreceptors present
Opened artery exposes baroreceptors to atmospheric pressure
Causes firing down the myelinated A-type fibers and C-type fibers of the glossopharyngeal nerve to the nucleus tractus solitarius
Triggers central systemic pressure response
Carotid chemoresponse
Rapid drop in oxygen tension
Further cause increasing signals down afferent pathway
Overall, causes onset of tachycardia and severe hypertension and thus increases in afterload and myocardial oxygen demand

6. Complications of CEA Stroke Neck hematoma Cardiac complications (MI)
Nerve injury
Glossopharyngeal nerve
Phrenic nerve injury
Recurrent laryngeal or vagus nerve injury

7. General Anesthesia versus Regional/Local Anesthesia
Remains a controversial topic
Cochrane review 2004
7 randomized trials, 41 non-randomized trials
Insufficient evidence to make a clear decision between GA and regional

8. General Anesthesia Tracheal intubation versus LMA
NMBA often used for immobilizing patient
TIVA compared to inhaled anesthetics with no difference in hemodynamic events or postoperative pain

9. General Anesthesia
GA does not prevent hemodynamic response of manipulation of the carotid sinus (severe vagal response)
Advisable to inject 1-2 ml of 1% lidocaine in the tissue between the internal and external carotid arteries before surgical manipulation
Severe hemodynamic response can lead to spasming of the coronary artery

10. General Anesthesia
Due to comorbidities (ie CAD, MI) important to avoid large BP swings
Especially upon intubation and emergence
Study done comparing hypnotic technique (high dose propofol with remifentanil versus opioid technique (low dose propofol with remifentanil)
Less BP swings and tachycardia with opioid group

11. General Anesthesia Maintenance of normocarbia Quick emergence
Hypercarbia leads to cerebral vasodilation
Steal syndrome could occur
Hypocarbia leads to vasoconstriction
Ischemia to compromised area of brain
Quick emergence
Important to assess neurological function quickly

12. Regional Anesthesia Deep Cervical Plexus Block
Three separate injections
Line drawn connecting the tip of the mastoid proxess and the Chassaignac tubercle (ie transverse process of C6)
Another line drawn 1 cm posterior to the first line; C2 transverse process lies 1 to 2 cm caudad to the mastoid process
22 G needle x3 advanced perpendicular to the skin and slightly caudad until contacting the transverse process (depth about 1.5 to 3 cm)
If paresthesias elicited, inject 3 to 4 ml of solution, if not elicited, walk along transverse process in a caudad or cephalad direction OR
Inject in single injection at C4 transverse process and rely on cephalad spread of the anesthetic to C2 and C3 nerves

13. Regional Anesthesia Deep Cervical Plexus Block Complications
Intravascular injection
Intrathecal injection
Paralysis of the ipsilateral diaphragm
Laryngeal block causing hoarseness, coughing and dysphagia

14. Regional Anesthesia Superficial Cervical Plexus block
Anesthetize C2 to C4 branches
Midpoint of the posterior border of the sternocleidomastoid muscle
Injection of solution along the posterior border and medial surface of the muscle
May block accessory nerve causing trapezius muscle paralysis

15. Regional Anesthesia Bupivicaine Levobupivicaine Ropivicaine
Longest duration of block
Greatest cardiac toxicity
Levobupivicaine
Similar duration
Less potential toxicity
Expensive
Ropivicaine
Similar quality of block
Shorter duration of postoperative pain relief
Sardanelli et al demostrated 8 ml dose of 0.75% was adequate for a good quality block

16. Cerebral Monitoring Why is it important?
Once compromise is discovered (or predicted) carotid shunt can improve cerebral oxygen delivery
Carotid shunt can be placed in both external or internal carotid artery; however internal carotid is much more effective

17. Cerebral Monitoring Why not shunt everyone?
Potential displacement of atheromatous debris, introduction of air embolism or thrombosis of shunt
Increases surgical time
Presence of shunt makes surgical field less than optimal

18. Cerebral Monitoring Awake patient the gold standard
Assessment of grip strength of the contralateral hand
Responsive to verbal commands
Same anesthesiologist for assessment in comparison of before and after crossclamping

19. Cerebral Monitoring Backpressure measurement
Gives an estimate of reasonable collateral circulation above the crossclamp
Carotid stump pressure to predict need for temporary shunt placement
Traditionally the cutoff has been 50 mmHg

20. Cerebral Monitoring EEG current best measurement for GA patients
Gives ability to assess both focal and global changes
General anesthetic may change EEG patterns
Difficult to interpret, needing special expertise
BIS has been used to identify severe ischemia
Unable to differentiate global versus focal changes

21. Cerebral Monitoring SSEP usefulness inconclusive
Retrospective review concluded could be useful
Prospective study of 50 patients concluded that although there is a 2% false negative rate, in general there is a limited value of SSEP in the detection of cerebral ischemia

22. Cerebral Monitoring
TCD ultrasonography noninvasive monitoring of the velocity of blood flow in the middle cerebral artery
Belardi suggests that U/S may not be effective in the prediction for shunt placement
Could be useful in the detection of cerebral emboli

23. Cerebral Monitoring
Carotid angiography may be a useful predictor of assessment of collateral circulation
Shunt more common when failure of collateral flow from contralateral hemisphere or when the contralateral internal collateral flow was occluded
Reported sensitivity 91% and specificity 35%