Lesson 14 Carotid Artery Disease and Strokes PDF

- Anterior circulation provides the majority of circulation and the internal carotid artery serves as the primary vessel - Anterior circulation pathway = aorta carotid internal carotid Circle of Willis cerebral hemispheres - Internal carotid arteries enter the skull throu...

- Anterior circulation provides the majority of circulation and the internal carotid artery serves as the primary vessel - Anterior circulation pathway = aorta carotid internal carotid Circle of Willis cerebral hemispheres - Internal carotid arteries enter the skull through the foramen lacerum - Bifurcate near optic chiasm into the anterior and middle cerebral arteries - Each carotid supplies the ipsilateral cerebral hemisphere - ACA supplies medial surface - MCA supplies lateral surface - Striate arteries are common sites for CVAs - Common carotid - Left common carotid arises from aorta - Right carotid arises from brachiocephalic artery - External carotid - Internal carotid branches - Posterior circulation primarily supplied by the vertebral arteries - Posterior circulation pathways = aorta subclavian basilar posterior fossa structures and cervical spinal cord - Vertebral arteries arise from the subclavian artery - Enter skull through the foramen magnum - Branches of the basilar and vertebral arteries supply cervical spinal cord, brainstem, cerebellum, vestibular apparatus, cochlea, diencephalon, occipital lobes, temporal lobes - Circle of Willis - Anterior and posterior circulations converge at the circle of Willis - Anterior circulation: - Common carotid -\> Internal carotid -\>ACA and MCA -\>Ant. communicating artery - Posterior circulation: - Vertebral arteries -\>Basilar artery -\>PCA (Posterior Cerebral Arteries) -\>Posterior Communication Arteries - Atherosclerosis = most common cause of carotid disease that is characterized by accumulation of fatty deposits along the subintimal layer of the arteries - Plaques can rupture and cause thrombus, embolization, and stroke - Can also lead to narrowing of the vessel and decreased blood flow - 2 types of stroke = ischemic and hemorrhage - Ischemic (80%) is most common and caused by embolism or thrombus or severe vasospasm - Most common cause of ischemic stroke is thrombi or emboli - Hemorrhage (20%) is caused by a break or tear in a vessel in the brain - Ischemic stroke can follow severe vasospasm following SAH - Carotid artery disease risk factors = older age, male, family hx, genetics, HTN, smoking, diabetes, obesity, sedentary living, HLD - Carotid artery disease typical pt = 55-80 YO, male, co-existing CAD - Carotid artery disease sx - Asymptomatic = plaques present but adequate blood flow is maintained - Symptomatic disease will show symptoms of ischemia and may result in TIA or stroke - Cerebral injury depends on plaque morphology, duration of hypoperfusion, cerebrovascular vasoreactivity, integrity of the circle of Willis, cerebral collateral circulation - TIA = transient ischemic attack - Sudden temporary loss of blood flow to an area of the brain - Usually lasts \>5 mins but no longer than 24 hours to complete recovery - Symptoms = - Sudden weakness, clumsiness, paralysis of an arm and/or leg on one side of the body - Loss of coordination or movement - Confusion, dizziness, fainting, and/or headache - Numbness or loss of sensation - Temporary vision loss or blurred vision - Inability to speak clearly or slurred speech - TIAs are warning signs of a future stroke -- 30% of stroke after TIA within 2 years. Risk increases to 55% after 12 years - CVA = neurological deficits that last \>24 hours - Bifurcation of common carotid is the most common site - Stroke in evolution = stroke with progressively worsening sx - Complete stroke = entire area affected - Incomplete stroke = additional brain remains at risk for ischemia - Sx depend on location and adequacy of collateral circulation - Stroke sx = are same as TIA but last longer than 24 hours - Medical treatment for carotid disease - Education on modifiable risk factors = be healthier, stop smoking - Medications = antiplatelets, anticoagulants, statin therapy, antihypertensives - Surgical options for carotid disease - Carotid endarterectomy (CAE) = surgical procedure - Carotid artery angioplasty stenting (CAS) = endovascular procedure - Check apex cardiovascular pathophysiology - Carotid endarterectomy (CAE) - 2^nd^ most common vascular procedure done in US - Better option for pts with high-grade stenosis compared to medical management - Can be performed under GA or regional with LA and light sedation - Higher risk of perioperative MI - Want to avoid hypotension so maintain hypertension or normotension - Carotid artery angioplasty stenting - Usually LA with light or no sedation in endovascular suite - Steps - Femoral access typically used but can do brachial or high radial - Aortic arch angiogram - Selective cannulation of common carotid artery and angiogram - Advance guidewire into external carotid - Carotid sheath placement and advancement into common carotid - Placement of embolic protection device - Stent placement - Increased risk of stroke in pts \>70 YO - Lower risk of MI - Pt selection for carotid endarterectomy vs CAS - CAS better - Opposite side RLN injury - Tracheostomy - Radical neck procedure - Severe obesity - Limited neck mobility - High lesions - Contralateral carotid occlusion - COPD - CHF with EF\ 200 on day of surgery associated with perioperative stroke - Preop meds to optimize = beta blockers, statins, antiplatelet agents - Baseline vitals and neuro assessment - Id coexisting disease - Carotid bruit present? Thrill? - Amaurosis fugax = a temporary loss of vision in one eye that occurs when blood flow to the retina is disrupted - Microthrombi from internal carotid to ophthalmic artery - Impaired perfusion of the optic nerve and causes retinal dysfunction - Occurs in 25% if patients with high-grade carotid stenosis - Cranial nerve assessment -- assess for abnormal responses - Facial nerve - Glossopharyngeal -- abnormal is difficulty swallowing with ipsilateral Horner syndrome - Vagus -- abnormal laryngeal muscle movement secondary to SLN and RLN injury - Spinal accessory - Hypoglossal - Technique selection -- regional vs general - No evidence to support better outcomes - GA technique advantages = pt tolerance, motionless surgical field, inhalation agents decrease cerebral and cardiac metabolism, ischemic preconditioning - Regional technique advantages = continuous neuro assessment, avoid postop cognitive dysfunction, cerebral circulation better maintained, less hemodynamic fluctuations - Horner syndrome = oculosympathetic paresis - Causes = stroke, tumor, trauma, demyelinating diseases, dissections or aneurysm of the internal carotid artery, idiopathic - Symptoms = miosis, ptosis, anhidrosis - Maintain CPP - CPP = MAP -- ICP or CVP - Autoregulation for CBF 50-150 - CO2 effect on CBF = directly proportional when PaCO2 is 20-80 - CBF response to changes in PaCO2 during carotid cross-clamping is impaired - Not worried about ICP in carotid stenosis, worried about MAP to maintain CPP - MAP plays most important role in maintaining CPP during CEA - Carotid enterectomy GA - During CEA, the surgeon clamps the carotid artery so that they can open the vessel, remove the plaque, and apply a graft - After carotid artery is clamped, ipsilateral cerebral perfusion relies on collateral flow from the circle of Willis - Periop goals = close BP monitoring with art line, avoid tachycardia to decrease myocardial oxygen demand, maintain normocarbia - Induction = avoid preop sedatives, propofol and etomidate are good options for induction, small doses of opioid or beta blockers to blunt hypertensive response to intubation - Maintenance - Hemodynamic fluctuations are common - HTN? treat with NTG or nitroprusside - Hypotension? Treat with neo. Avoid hypotension at all costs due to dependence of CPP on MAP - Manipulation of carotid baroreceptor can cause bradycardia and hypotension - Treat with atropine if LA at site by surgeon isn't effective - LA infiltration can cause bradycardia - Goal BP 10-20% above baseline during carotid clamping - Volatile gas selection - Isoflurane provides best protection against cerebral ischemia - Sevo and desflurane allow for quicker emergence - Avoid hypercapnia, hypocapnia, hyperglycemia - Heparin prior to occlusion of the carotid artery (50-100 units/kg) - Monitor ACT (activated clotting time) - Goal is \>250 seconds - High ACT = increased bleeding risk - Activated clotting time (ACT) is used to monitor bleeding risk during surgery instead of partial thromboplastin time (PTT) or PT they are not clinically useful at high levels of heparin, which are often used during surgery - Maintain CBF - Measure cerebral oximetry, EEGs, SSEPs, carotid stump pressure, transcranial doppler - Carotid stump pressure assesses perfusion pressure in operative carotid artery - Transcranial doppler assesses blood flow velocity in the middle cerebral artery - Shunt or not shunt - The purpose of a shunt is to reduce the amount of time blood flow to the brain is interrupted - Risk of shunting = embolization - Risk of not shunting = cerebral hypoxemia - Emergence - Smooth and rapid emergence with no bucking on tube - No sedatives to interfere with neuro assessment - Protamine used to reverse heparin - Protamine can cause hypotension and anaphylaxis - Want to assess neuro status ASAP - Carotid endarterectomy regional technique - Block superficial cervical plexus (C2-C4) - Advantages = awake pt, more stable hemodynamics - Disadvantages = - Surgeon may need to supplement LA at carotid sheath - Conversion to GA 2-6% - Potential for inadvertent phrenic nerve dysfunction - Use caution in patients with severe COPD or untreated contralateral pneumothorax - Requires cooperative patient and surgeon - CAE complications - Postop HTN is common and associated with strokes. Postop goal is SBP\220, DBP\>120, MAP\>130 - Avoid succs if \>24 hours due to upregulation of AChR - If pt is at risk for stroke due to atherosclerosis, they are also at risk for MI - What anesthesia does the cervical plexus block? - Targets sensory branches of C2-C4 so skin of the anterolateral neck, skin over clavicle and shoulder, lower part of the ear, angle of mandible, lateral occiput - Used for carotid endarterectomy - What is the arterial blood supply to the brain? Anterior via carotids and posterior via vertebral arteries circulation - How should the paco2 be during CAE? Normocapnia - Local or general outcomes for carotid endarterectomy? They are the same - Complications of a deep cervical plexus block include subarachnoid or epidural injection, intravascular injection and local haematoma. Phrenic nerve palsy affecting diaphragmatic movement has been shown ipsilaterally in 60% of cases but is usually well tolerated. Transient recurrent laryngeal nerve palsy, Horner\'s syndrome and stellate ganglion block may all occur but are expected and not considered a complication.