By Dr. Mohamed Dorgham , MD Lecturer of Anesthesia, Critical Care medicine and Pain Therapy

1. Carotid End Arterectomy By Dr. Mohamed Dorgham, MD Lecturer of Anesthesia, Critical Care medicine and Pain Therapy

2. Anatomy

3. Pathophysiology Atheroscelerosis Embolization Hypoperfusion Carotid Artery Occlusive Disease Asymptomatic Bruit Stroke TIA Amaurosis Fugax

4. Stroke is the 3rd leading cause of Death and long term disability in USA Stroke Carotid Stenosis > 50% 3.6% Asymptomatic Carotid Bruit Perioperative Stroke 1.0%

5. Indications 1992 North American Symptomatic CEA Trial European Carotid Surgery Trial 70-99% 9% # 26% 2.8% # 16.8% Definitive results for symptomatic patients with high grade stenosis > 70%

6. 5 Randomized trials evaluated CEA in Asymptomatic Pts Mayo Asymptomatic CEA Study CA Surgery Asymptomatic Narrowing Operation Versus ASA Increased no. of MI & TIA In Surgical Group CEA is not indicated 50-90% stenosis Asymptomatic CA (60%) Atherosclerosis Study Depatment of veterans CEA + Aspirin Versus Asprin alone >or= 50% No difference in the incidence Of Stroke & Death 5 yrs risk of Ipsilateral Stroke CEA+ASA: 5.1% ASA alone: 11.0% Largest Trial European Asymptomatic CA Surgery Trial CAS ~70% CEA+ASA: 6.4% ASA alone: 11.8%

7. Perioperative Morbidity and Mortality rates Systematic review of 51 studies ( from 1980- 1995) reported the results below 5.6% 3.8% 1.6% 1.3%

8. Preoperative Evaluataion Systemic Atherosclerosis Correctable CAD 28% CAD Leading cause of Early & Late Mortalities Recent MI Unstable Angina Evaluation of Myocardial Function Severe Valvular Disease Decompensated CHF

9. It would be unlikely that further specialized tests would cancel the procedure Trials established that CEA prevents Stroke in selected patients 1 2 Perioperative medical TTT is standard for all CEAs Further tests would have little potential to alter TTT 3 Percutaneous angioplasty + Stenting may be an alternative in high risk pts CEA Remains the Gold Standard No reduction in short term mortality with prophylactic revascularization Low overall rates of cardiac M & M 4

10. Severe CAD (Unstable) + Severe Carotid Artery Occlusive disease (Symptomatic) Combined CEA + Coronary revascularization Role of Carotid Angioplasty + Stenting Before Staged CABG Still unproven

11. Anesthetic management Ablation of Surgical pain Awake patient during or at the end of surgery For neurological examination Ablation of Stress responses HR & BP control Heart Protection Brain Protection Goals

12. Regional Versus General Anesthesia No large scale prospective randomized trials evaluated the difference in Neurologic & Cardiac outcomes with Regional versus General Anesthesia Most reports indicate no difference in perioperative mortality rates on basis of anesthetic technique • Rate of conversion from RA to GA 2-6% • Decision to use one technique is based on: • Surgeon’s & Anesthetist’s experience • Patient pereference

13. General Versus Regional Anesthesia Advantages Advantages • Difficult vascular anatomy • Short neck • High carotid bifurcation • Control of respiration • Brain protective measures • Avoids excessive neck palpitations • Continuous neurological assessment • Greater stability of BP. • Reduced need for shunting • Avoidance of expensive monitoring • & Reduced hospital costs • High patients preference (92%) Disadvantages Inability to use pharmacological cerebral protection Inadequate access to airway Near toxic level of LA Phrenic nerve paresis Claustrophobia Increased catechoaminelevel Disadvantages No clinical neurological assessment Less BP stability

14. General Anaesthesia Commonly used Induction agents Commonly used maintenance anesthetics Short to Intermediate acting NDMR Stable hemodynamics Awake patient at the end of procedure Sufentanil: 0.5-1.0 mcg/kg for sedation slow speech or delayed response to questions Thiopental /Etomidate / Propofol O2 50% + Low dose (< 0.5 MAC) inhaled Anesthetic Vecuronium Combined Remifentanil + Propofol infusion Sevoflurane Same Critical rCBF Rapid Emergence Isoflurane Low Critical rCBF Less EEG changes during CA clamping

15. Anesthetic Problems Baroreceptors activation Hypotention & Bradycardia Stress of Laryngoscopy & Intubation Hemodynamic Fluctuation Esmolol Used liberally during induction Esmolol Nitroglycerine Nitroprusside Phenylephrine 50-100 mcg IV volume depletion High normal BP Induced HTN Surgical manipulations of carotid sinus Light anesthesia Phenylephrine Ephedrine Vasopressors IV fluids 5ml/Kg Titration of Anesthetics Immediate TTT Infiltration of Carotid Biforcation Intra & Postopertive Hypertension

16. Anesthetic Problems Normocapnia Or Mild Hypocapnia Hypercarbia CO2 management Steel Phenomenon Poor Collaterals Chronic Hypo perfusion Vasomotor Paralysis Inverse steel Phenomenon Relation between hypercarbia & cerebral ischemia is unproven Hypocarbia Little clinical evidence of Inverse steel PaCO2 23 mmHg increases risk of ischemia Vasoplegia significantly improve after CEA

17. Anesthetic Problems Hyperglycemia increases ischemic injury Blood Sugar management Blood glucose > 200mg% Increase incidence of Stroke / TIA / MI / Death Maintain blood sugar < 200 mg% Avoid dangerous Hypoglycemia

18. Anesthetic Problems Emergence • Neurological • Deficits • Hypertension • & • Tachycardia • Myocardial • Ischemia Discuss with Surgeon Angioplasty Reoperation Propofol # Isoflurane Control BP Aggressive pharmacological TTT Propofol > Isoflurane Decreased incidence of Myocardial ischemia during emergence All patients with myocardial ischemia on emergence had SBP>200mmHg Propofol # Isoflurane Decreased pharmacological intervention during emergence

19. Regional Anesthesia Blocking C2 to C4 dermatomes Superficial & Deep Cervical Plexus block Requires Patient cooperation Constant communication Gentle handling of tissues Supplemental infiltration of LA by surgeon especially at the lower border and ramus of mandible Sedation must be kept to minimum Assess conscious / speech / contralateral hand grip Clamp test 2-3 mins in awake pt indicates the need of shunt placement BP augmentation with phenylephrine if neurologic deficit During Clamp Test After shunt placement

20. Monitoring Stump Pressure Goals It’s the back pressure from the contralateral CA & vertebrobasilar system Easy Inexpensive Continously available Critical Stump pressure is Unknown <50mmHg is associated with hypoperfusion Prevent IO Strokes Identify need of shunting Identify benefit from BP augmentation

21. Monitoring Regional cerebral Blood Flow Goals Iv or CA injection of Radioactive Xenon Detectors placed over the ipsilateral cortex supplied by MCA Before – During – After CA clamping Provided the relationship between Critical rCBF (ml/100gm/min) & EEG Isoflurane: 10 Enflurane:15 Sevofluran: 10 Halothane: 20 Limitations: Expenses & Expertise Prevent IO Strokes Identify need of shunting Identify benefit from BP augmentation

22. Monitoring Electroencephalogram Goals Incidence of ischemic changes: 7.5-20% Contralateral CA stenosis: 50% Ischemic changes: CA clamping Hypotension Shunt malfunction Cerebral emboli Limitations: Subcortical & small cortical infarcts False negative results Affected by: BP Temperature Anesthetic depth False +ve results perioperative strokes occur PO Prevent IO Strokes Identify need of shunting Identify benefit from BP augmentation

23. Monitoring SSEP Goals Based on the response of sensory cortex “supplied by MCA” to peripheral sensory nerve stimulation Decreased CBF: Decrease amplitude Increase latency or both CBF<12ml/100gm/min: Abolished response Limitations: Affected by: BP Hypothermia Anesthetics False –ve results Validity not definitively established Prevent IO Strokes Identify need of shunting Identify benefit from BP augmentation

24. Monitoring Transcranial Doppler Goals Continuous measurement of mean blood flow velocity: Detects microemblic events in MCA Shunt function Need of early CA clamping Detects early asymptomatic CA occlusion Hyperperfusion syndrome Limitations: High rate of technical failure Improved outcome not yet reported Prevent IO Strokes Identify need of shunting Identify benefit from BP augmentation

25. Monitoring Cerebral Oxygenation Goals Cerebral Oximeter Jugular Bulb Venous monitoring Prevent IO Strokes Global cerebral O2 Metabolism: Arterial – Jugular venous O2 content SjvO2 Continuous regional cerebral SO2 Through Scalp Limitations: Wide Pt to Pt variability Lack of clinical threshold Identify need of shunting Identify benefit from BP augmentation

26. Postoperative Considerations Neurological Complications Thromboembolic Major mechanism Hemodynamic 21% Hypoperfusion Hyperperfusion Syndrome of abrupt increased blood flow + Loss of autoregulation in surigicallyreperfused brain • Risk Factors • Post operative HTN • Preop. severe CA stenosis • Recent contralateral CEA Headache Seizures Focal neurological signs Brain edema Intracerebralhage1-5 days PO(0.4-2.0%)

27. Postoperative Considerations Post operative Hypotension Occurs as frequent as HTN Carotid sinus hypersensitivity and reactivation More common after regional anesthesia Myocardial ischemia & Cerebral ischemia COP: Normal or elevated SVR: reduced Judicious fluids + Vasopressors Resolves within 12-24 hrs

28. Postoperative Considerations Cranial & Cervical nerve dysfunction Recurrent Laryngeal Nerve Superior Laryngeal Nerve Hypoglossal Nerve Marginal Mandibular Nerve

29. Postoperative Considerations Carotid Body Denervation Due to Surgical manipulation Bilateral Unilateral Loss of normal ventilatory responses Impaired ventilatory response to mild hypoxemia Loss of normal arterial pressure Responses to acute hypoxia Increased resting PaCO2 Central chemoreceptors are the primary sensors for maintaining ventilation Serious respiratory depression in response to opioid administration

30. Postoperative Considerations Wound Hematoma North American Symptomatic CEA Trial: 5.5% Most of cases due to venous oozing Immediate evacuation External Compression Aggressive BP control

31. Endovascular Intervention Management of carotid artery stenosis By percutaneous intervention Femoral or CCA Angioplasty Stenting GA with short acting drugs Sedation With MAC Considerations Contraindications Anticholinergics Intolerance to antiplatelets Protective devices against embolization Aortic arch disease Heparin ........> ACT= 250-300 sec CA torsiousity Calcification / Heavy thrombus burden / Unstable plaque

32. Manifestations: of CAD (Asymptomatic bruit ...> Stroke) Indications: Symptomatic Pt. +/- High grade stenosis Further evaluation of myocardial function Combined versus Staged operation Goals of anesthetic management Regional versus GA Anesthetic problems Postoperative considerations Endovascular intervention Summary

33. ANY QUESTIONS ?