1. Anesthetic considerations
Carotid Surgery
Anesthetic considerations
Sam Hemans MD DDS
Charles Smith MD
3 August 2004

2. Objectives Pathophysiology of carotid dz
Strategy for anesthetic evaluation
Perioperative management
Complications
New therapies in the field

3. Epidemiology 1.2m strokes or tia’s each yr in the US
>150,000 deaths each yr
3rd leading cause of death
CEA introduced in 1954 as a preventive measure for occlusive dz.

4. Indications >70% in symptomatic patients
50- 69% in symptomatic patients with low risk
>60% in asymptomatic patients with favourable surgical risks

5. Physiologic considerations
Carotid dz is due to atheroslerosis
Most common site is the bifurcation of vessels
Ischemia is often due embolic phenomenon
During ischemia collateral flow critical
Principal pathways : Circle of Willis,extracranial anastomotic channels,leptomeningeal communications

6. Preoperative evaluation
CEA has an inherent risk of perioperative stroke and cvs events
25% strokes associated with CEA occur intra-op
33% mostly embolic; some hemodynamic in origin
Recent data from the NASCET reports a 6.5% rate of stroke and death
1.1% rate of death, 0.9% disabling stroke,4.5% disabling stroke
Increased risk for stroke is most strongly associated with an active neurologic process prior to surgical intervention

7. Preoperative evaluation
Other risk factors for poor neurologic outcome
Hemispheric vrs retinal tia’s
Left sided procedure
Ipsilateral ischemic lesion on ct
Contralateral carotid occlusion
Impaired consciousness
Poor collaterals
An irregular or ulcerated plaque
Cea with CABG

8. Pre-op Medical complications occur 10% of time
Hypertension: incidence of neurologic deficit related pre-op uncontrolled HTN
Multicenter study , diastolic>110 predictor of adverse events
Reasonable recc is delay elective surgery for diastolics>110
A less firm recc is to delay elective sx for sys >180
Carotid dz is a manifestaton of systemic dz: Good cardiac hx, previuos mi,angina,exs tolerance,chf,arrhythmias,ekg,cxr routine.Echo and stress test may be indicated as well.
Diabetes, may have increased cardiac related death but data seems to indicate that CEA can be performed safely in these patients
Renal Insufficiency, have a overall increased risk for stroke, death and cardiac morbidity

9. Monitoring
Awake patient
Likely the gold standard for neurologic monitoring.However, there is absence of prospective data that will compel one to choose this method of neurologic monitoring
EEG
Neurologic changes may correlate with EEG. However, there is a fairly high rate of false positives for discriminating ischemia with the EEG
SSEP
Probably not any better than the EEG, but more complex. May be a better indicator of subcortical ischemia
Stump Press
Poor sensitivity/specificity
TCD
TCD may be beneficial for assessing hemodynamic ischemia,shunt function,embolic phenomenon,hyperperfusion syndrome
Oximetry
High false positive rate
JvO2
Sensitivity,specificity and intervention thresholds not determined

10. Monitoring Std ASA monitors Continuous lead II , V5
Arterial line routine
PA cath and TEE may be considered in patients with symptomatic dz or recent mi

11. Anesthetic Management
No compelling advantage has been demonstrated with either regional or general anesthesia
Technique should optimize perfusion to the brain,minimize myocardial stress and allow rapid recovery
Choice is often strongly influenced by the surgeon’s preference and the anesthesiologist familiarity with a specific technique
Recent study, sevo and des provided quicker extubation times and recovery profiles after CEA c/w iso with no significant peri-op differnces in CI and ST segment analysis
Propofol and narcotics may be associated with hypotension

12. Regional technique
A regional technique for CEA necessitates the correct combination of patient, surgeon and anesthesiologist
CEA requires block of C2- C4.
Superficial cervical block, deep cervical, epidural and straight local or a combination of these have been utilized successfully

13. Regional technique
Tangkanakul et al performed a meta – analysis of studies evaluating the efficacy and safety of regional anesthesia
The non-randomized study suggested that the use of regional was associated with approx 50% reductions in the odds of stroke, death, mi, pulmonary complications and length of hosp stay.
There was far too little data to either confirm or refute the study.

14. Modalities of Cerebral Protection
Surgical- placement of a shunt during x-clamp
Physiologic: Mild hypothermia 33-34C
Rx hyperglycemia
Hypertension
Hemodilution
Maintenance of normocarbia
Anesthetic:Barbiturates, no evidence for permanent focal deficits
volatile anesthetics, iso and sevo associated with lower critical bf
c/w halothane and enflurane
Etomidate shown to worsen outcome in animal models,thio
shown to improve ischemic injury
Propofol , animal studies have produced mixed results

15. Post- op
The objective is a smooth and prompt emergence with optimal systemic and cerebral hemodynamics, additional problems as follows:
Hypertension
Hypotension
Myocardial Infarction
Stroke, usually embolic
Bleeding
Cranial Nerve injury, occurs in 10% of patients
The most commonly injured nerves are,hypoglossal nerve,vagus, recurrent laryngeal,accessory nerve.
Unilateral damage usually no immediate sx or intervention
Bilateral damage could result in upper airway obstruction
Beware of patients with pre-existing neck surgery

16. CEA and CABG One of the more difficult decision matrices
regards the patient who presents with simultaneous dz of the carotid and the coronary vessels
Best available evidence – doubling of risk of death or stroke if performed as a single
anesthetic as opposed to a staged procedure
In a staged procedure risk is related to which procedure is performed first: If CEA is performed first the risk of mi increases; if CABG is performed first the risk of stroke increases

17. Timing of CEA after Stroke
Presently there is insufficient data to establish any guidelines
In the 1980’s CEA patients typically stayed in the ICU for1-2days then floor 3-5days
Recent data has shown that 24hr ICU IS sufficient since most perioperative strokes following CEA occurred within 24hrs after the surgery

18. Summary Post op concerns, usually due to htn
Indications, symptomatic patients if stenosis>70% and for selected patients if the lesion is %
Pre-op concerns, uncotrolled htn
Anesthetic technique no demonstrated advantage of regional vrs general
Cerebral Monitoring, neurologic status in the awake patient, and the EEG may be considered close to the gold standard
Post op concerns, usually due to htn
Whichever anesthetic method is chosen, it is imperative that CBF be optimized, with min cardiac stress especially during x-clamping.
The risk of ischemia may be decreased by maintaining normal to high perfusion pressure

19. New Therapies
Carotid stenting and Angioplasty, the procedure involves the placement of a saline filled balloon,pre-loaded with a stent under angiographic guidance and applying 15atm for 3mins, anesthetic technique is sedation
Drawbacks, profound bradycardia, high incidence of strokes from the angiography alone.
SAPPHIRE (Stenting and Angioplasty with Protection at High-Risk for Endarterectomy)
First randomized trial to evaluate the safety and efficacy of carotid artery stenting with emboli prevention in high surgical risk patients.
High risk criteria included, prior cea, neck surgery, radiation to the neck, occlusion of the contralateral carotids, chf and other confounding medical problems

20. conclusion
Study actually a randomized trial which compared cea with stenting and angioplasty
Enrollment terminated after 723 patients were enrolled, 416 registry and 307 randomized, as interim analysis showed a marked benefit in favour of stenting. Success defined as <30% residual stenosis
30 day periprocedural combined stroke/mi/death rate which was the study endpoint was 5.8% in the stent group but 12.6% in the surgical group
SAPPHIRE study
Showed that in high risk patients CAS was a superior to CEA and that emboli prevention was also improved in the CAS group of patients.