PERIPHERAL VASCULAR DISEASE/CAROTID ENDARTERECTOMY – Flashcards
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Which organs are most vulnerable in patients with peripheral vascular disease? (2)
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1) MI (Incidence 4-5%) 2) CVA (Incidence 2-3%)
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What are the patient factors for coexisting disease and risk factors for patients with PVD?
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-Age >60 yrs-68% -History of cigarette smoking-88% -Coexisting Disease: Hypertension-40-68% - BP labile d/t vascular volume depletion and antihypertensives Previous MI-40-60% CAD-40-60% Angina-10-20% Dysrhythmia-36% Diabetes mellitus-8-44% COPD-25-50% CHF-5-20% Renal insufficiency-5-15%
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What are the surgical factors for coexisting disease and risk factors for patients with PVD?
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-Expertise of surgeon -Emergency/semi-emergent state -Major fluid shifts -Clamping and unclamping major vessels -Intraoperative hypertension/hypotension
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Preoperative optimization is key to ...
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decreasing perioperative mortality
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What are keys to preoperative cardiovascular assessment for patients with PVD?
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-10% of patients with coronary artery disease (myocardial dysfunction) have carotid disease. -Valvular dz?
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What are keys to preoperative neurological assessment for patients with PVD?
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-cerebral function. Stoke? Deficiencies due to stroke? TIA? Known specific dz of carotids or coronary arteries. Turn their head and see if they get dizzy
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What are keys to preoperative respiratory assessment for patients with PVD?
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-smokers usually. COPD? ABG? PFTs? CXR? Prolonged post op intubation?
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What are keys to preoperative renal assessment for patients with PVD?
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-renal function preoperatively is the indicator for post operative function. Dialysis (hypovolemic/hypotensive)? Most current Electrolytes?
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What are keys to preoperative hematologic assessment for patients with PVD?
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-anemic. Blood & blood products avail. Anticoags? INR? Receive heparin intraop
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What factors increase supply?
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-coronary blood flow (autoregulation) -decreased HR -increased DBP -increased oxygenated hgb
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What factors increase demand?
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-increase HR -increase afterload (map) -increase wall tension -increase contractility
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T or F: Patients with peripheral vascular disease and a history of hypertension should stop taking their B blockers 24 hours before surgery?
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FALSE
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Describe the negative effects associated with Beta blockers.
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-Asthma attacks/bronchoconstriction -VASO CONSTRICTION
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What are some intraoperative considerations for patients with PVD?
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-Avoid hypertension and hypotension -Avoid hypothermia -Avoid anemia -Maintenance of NSR with controlled rate
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Is regional or general better?
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None per scientists. -Very tight hemodynamic control is required with both.
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What are six postoperative concerns with patients with PVD?
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1) Blood pressure and HR control 2) Pain control 3) Volume status 4) normothermia 5) graft occlusion (vasodilating effect of GA helps) 6) long term survivability decreases as age increases, preoperative risk is greater, if they have an intraoperative cardiac event, and PROLONGED HYPOTENSION
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Patients with significant CAD may not exhibit symptoms due to...
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adequate collateral flow.
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What are the 4 ACC/AHA Guidelines for Acute Coronary Syndrome (ACS)?
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1) Oxygen 2) Aspirin 3) IV Nitroglycerin 4) Morphine
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How long should O2 be given after an acute coronary event?
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For minimum of 6 hours after acute coronary event
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Whats the dose for ASA?
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126-325 mg QD
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What should you consider when giving nitro for ACS?
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-Titrate to effect -Keep SBP>90 mm/Hg -Hx hypertension, titrate SBP no lower than 30 mm/Hg below baseline -Consider avoiding nitrates if phosphodiesterase inhibitors taken within 48 hours (Viagra/Cialis/Levitra)
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What should you ultimately do if your patient has an MI?
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get a cardiology consult
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What are the two types of stroke?
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1) Ischemia 2) Hemmorhage
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What are two types of hemmorhagic stroke?
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1) Subarachnoid 2) Intracerebral
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Risk factors associated with hemorrhagic stroke include:
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-HTN -Coagulopathy -Trauma -Medications (stimulants)
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What are causes of ischemic stroke?
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-15-20% of ischemic strokes are caused by carotid artery disease -Systemic hypoperfusion (hypotension) -Thrombosis -Embolism
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Risk factors associated with ischemic stroke include:
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-Prolonged hypotension -Carotid disease -Heart disease
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Symptoms and severity of stroke depend on:
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-Adequacy of collateral circulation -Size and location of ischemia -Presence of increased ICP
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TIA's/ CVAs related to CAS are usually caused by ...
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thrombosis/embolism or hypoperfusion
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What are 5 indications for CEA?
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-Asymptomatic carotid bruit - DOES NOT ALWAYS OCCUR WITH CAROTID ARTERY DISEASE and vice versa -Transient ischemic attacks -Reversible ischemic neurological deficits with;70% stenosis of the vessel wall or an ulcerated plaque, with or without stenosis -TIA's lasting longer than one hour with angiographic evidence of carotid artery stenosis -Unstable neurologic status, evidence of carotid artery stenosis that persists despite anticoagulation
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What are some s/s of carotid disease?
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1) syncope. can be caused by metabolic prob, decreased perfusion to brain, and Heart problems 2) Amaurosis fugax 3) Altered LOC 4) Motor dysfunction - Takes up to one year post CVA function will be. Deficits may be severe but may resolve themselves
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What is •Amaurosis fugax?
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Monocular blindness - "shade going over one eye". -Occurs with 25% of patients with high grade carotid artery stenosis. Transient sign. -Lasts <10 minutes. -Embolus floats down central circulation into circle of willis and lodges into one of the ophthalmic arteries. -Left eye = left carotid artery and vice versa
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what are two tests used for diagnosis of carotid stenosis?
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1) Carotid Duplex Scan (Doppler ultrasonography) 2) Arteriography/CT or MRI without with or without contras
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What is • Carotid Duplex Scan (Doppler ultrasonography)
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-Uses Bernoulli's Law to determine blood flow velocity BF faster when lumen is smaller -Poiseuille's Law F=pressure gradient x 4th power of radius/viscosity x length -Decrease radius by ½ you decrease flow 16 times
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What is the difference between Transitional and Turbulent Flow?
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BF greater in the center because of no friction like on the outside
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Arteriography/CT or MRI without with or without contrast is...
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more invasive and CVA risk
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the velocity of flow in turbulent flow is..
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increased
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T or F-All patients with high grade carotid artery stenosis (CAS) have a carotid bruit.
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FALSE
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Look at PREVALENCE OF CARDIAC DISEASE AND ASSOCIATED RISK FACTORS IN 614 PATIENTS UNDERGOING CAROTID ENDARTERECTOMY chart
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top two are: cigarette smoking and HTN
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What are keys to cardiovascular assessment for CAS?
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-Unstable or severe coronary artery disease with carotid artery stenosis -Uncontrolled Hypertension - make sure that you look at their medications and that they've been taking them
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What are keys to neurological assessment for CAS?
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-a complete preoperative assessment versus PACU
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What are keys to endocrine assessment for CAS?
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- diabetes. Prefer 180 or 200 morbidity and mortality increased 4X after CEA. Glucose sits around in blood, brain develops hypoxia, glucose is converted to lactic acid.
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What are keys to airway assessment for CAS?
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-vertebrobasilar disease - careful with neck extension because we can decrease BF. Check LOC before induction
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What are typical medications for patients with CAS?
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AntiHTN
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External carotid artery perfuses: (6)
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1) superior thyroid artery 2) maxillary artery 3) lingual artery 4) facial artery 5) occipital artery 6) superficial temporal artery
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Internal carotid artery perfuses: (3)
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1) Anterior 2) middle cerebral artery 3) ophthalmic artery
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each carotid artery provides __% blood flow to the brain other __% from basilar artery
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40;20
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Normal cerebral blood flow is...
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50ml/100g/min
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CBF =
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CPP/CVR
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CPP=
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MAP - ICP
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Greatest determinant of CPP IS...
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MAP
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Normal CPP is
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60-100 mm/Hg
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CPP is mainly dependent on
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MAP
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Slowing of the EEG occurs with CPP of approximately
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50mmhg
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Flat EEG occurs with CPP of approximately
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25mmhg
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What is Cerebral Vascular Autoregulation?
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-The cerebral vascular dilates in the presence of systemic hypotension and constricts in the presence of systemic hypertension to maintain a consistent blood flow to the brain. This phenomena is called Cerebral Vascular Autoregulation.
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Cerebral autoregulation occurs between mean arterial pressures of ...
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60-160 mm/Hg.
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Patients with cerebrovascular disease have cerebral autoregulation curves that are shifted to the ...
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__right____. Therefore, they will need a higher MAP to maintain an adequate CPP.
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Where should we keep patients MAP intraoperatively?
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MAP ;20% higher than preoperative value
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Increases in PaCO2 above normal physiologic parameters causes cerebral vascular
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dilation
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Decreases in PaCO2 below normal physiological parameters causes cerebral vascular...
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constriction
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Cerebral blood flow changes _-_% per degree C
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5-7
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Hypothermia decreases both ....
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cerebral metabolic rate and cerebral blood flow.
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What is cerebral steal?
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-The cerebral steal refers to stealing of blood from one area of the brain to another. -The stealing is possible only if there is a pressure gradient between the circulatory beds of two areas. -In clinical practice the steal refers to no increase in CBF of an ischemic area as compared to the normal area when hypercapnia is instituted (causing cerebral vasodilation) or other vasodilators, e.g. volatile anaesthetics, sodium nitropruside and nitroglycerine etc are administered. -As the blood vessels of the ischemic area are maximally dilated with an exhausted "cerebrovascular reserve", they do not respond by any further vasodilation receiving the same or even lesser blood flow, whereas, the normal adjacent brain regions get vasodilated and receive an increased flow. -INCREASED FLOW TO AREAS THAT ARE HEALTHY
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What is cerebral inverse steal?
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-a vasoconstriction caused by hypocapnia or a suitable anaesthetic agent such as thiopentone will cause a reduced blood flow to the normal responsive regions of the brain resulting into redistribution.
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Anesthesia protects the brain d/t ...
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decrease CMRO2.
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Operative mortality rate for CEA is
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1-4%
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Perioperative stroke rate for CEA is
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0.5-2%
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Perioperative myocardial infarction rate
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1-4%
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The most common cause of perioperative and late postoperative mortality after CEA is:
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MI
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Describe the process of CEA
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-Oblique neck incision along the anterior border of the sternocleidomastoid muscle. -The common, internal and external carotid artery is exposed. -The internal carotid artery is isolated. -Ties or clamps are positioned along the distal and proximal carotid artery. -Heparin 5,000-10,000 Units IV 3-5 minutes prior to cross clamp. -Cross clamp-write down time -BLOOD PRESSURE DURING CROSS CLAMPING??? Map 20% ; baseline -The internal carotid artery is incised -Possible shunt application -Ties or clamps are applied and a shunt may or may not be used. -The ulcerated or plaque containing area is dissected and removed. -Prior to complete closure, the carotid artery is flushed. -The internal carotid artery is closed. -Blood flow is reestablished-write down time
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What is the dose for heparin for this procedure?
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50-100units/kg
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What the the intraoperative monitors for CEA?
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-Standard monitors/arterial line necessary/vasodilator/vasopressor (phenylehphrine and nitro) -CBF monitoring during carotid artery cross clamp -AWAKE PATIENT! -Electroencephalographic monitoring (EEG) - -SSEP monitoring -superficial and deep. Affected by our anesthetics -Transcranial doppler ultrasonography - middle cerebral artery BF, emboli. Operator dependent. Hard to find acoustic window -Cerebral oximetry (NIRS) -Stump pressures
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What is cerebral oximetry?
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looks at spo2 in frontal lobes of brain. Decrease by 20%=significant but not positive for stroke
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What are stump pressures?
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reflective of pressures in circle of willis. Put shunt in distal part of internal carotid artery. Back flow comes up with a number. -Normal: 25-70 mmhg or ;50-60
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What is the most sensitive monitor used to assess adequate CBF during CEA ?
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AWAKE PATIENT!
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What is the gold standard for ischemia in superficial layers of the brain?
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Electroencephalographic monitoring (EEG) - Affected by anesthesia
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What are two anesthetic goals for CEA?
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hemodynamic stability, rapid wake up
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What are advantages of GA for CEA?
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-use of mild hypothermia -brain protection afforded by inhalational agent -immobility -maintenance of a patent airway control -patient comfort -hemodynamic control -monitoring and control of carbon dioxide
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What are disadvantages of GA for CEA?
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-hypertensive/hypotensive episodes -loss of consciousness with general anesthesia -general anesthesia with coexisting disease
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What are regional anesthesia advantages for CEA?
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-neurological monitoring -cardiovascular safety? -decreases incidence of shunting
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What are the regional anesthesia disadvantages for CEA?
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-increased levels of catecholamines -patient cooperation -airway management
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What are some considerations to doing GA for this procedure?
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-Avoid of cervical hyperextension -Intravascular volume repletion -Controlled induction -Consider balanced technique -Mild hypothermia, active rewarming after reperfusion occurs -Burst suppression prior to surgical cross clamping -Maintenance of MAP 10-20% above preoperative baseline for contralateral carotid stenosis prior to cross clamping. -Surgical manipulation of the carotid sinus causing baroreceptor stimulation - LA ; anticholinergic -Protamine administration (allergic rxn) 1mg/100units of heparin give -Concerns regarding nitrous oxide don't use pneumocephalus or pnx -Establish neurological integrity -Control hemodynamic response during perioperative phase
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What are some considerations for doing regional anesthesia for this procedure?
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-4% conversion rate -Patient acceptance and education -Deep and superficial cervical plexus block of C2-C4 and wound infiltration. Phrenic nerve block -Light sedation as needed - not too much LOC and hypoventilate
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What are some postoperative considerations for CEA?
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-Postoperative respiratory insufficiency -Carotid body dysfunction -Recurrent/superior nerve damage -Cranial nerve injury -Cardiovascular instability -Hypertension (common) 60% develop HTN. 3 times more likely with uncontrolled HTN for stroke -Hypotension - volume pressors -Myocardial infarction -Hyperperfusion syndrome -Postoperative stroke
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What happens with postoperative stroke?
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-hemorrhage, emboli, ischemic -Immediate re-exploration of wound -Cerebral angiogram micro emboil....yes = dextran and heparin -Anticoagulation
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What is the cause of Hyperperfusion syndrome?
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-uncontrolled HTN. Or if a second one is performed <3 months from the last one. Increased pressure to the brain, cerebral edema ensues -Signs and symptoms include: increased ICP, vision changes ALOC, seizures
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What is carotid body dysfunction?
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-body is a chemoreceptor and is destroyed during this. Wont respond to hypoxia decreasing ph and increase co2. 2nd carotid patients need 02
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How often does cranial nerve damage occur?
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10% of patients post CEA
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What is the role of inflammation during CEA?
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during sx mediators increase CRP leukotrients and neutrophils. -Increase CV event likelihood. -May be advantageous is giving them statins to decrease inflammation
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What are patient populations for carotid artery angioplasty and stenting?
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-Asymptomatic lesions of 80-99% stenosis -Symptomatic and 70% or greater stenosis
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What are indications for carotid artery angioplasty and stenting?
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-Severe cardiac disease -Severe COPD -Severe renal insufficiency -Prior carotid endarterectomy (restenosis) -Contralateral vocal cord paralysis -Surgically inaccessible lesion (at or above C2) -Prior ipsilateral radical neck dissection
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Preoperative vascular testing/preparation for carotid artery angioplasty and stenting?
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-Aortic arch, carotid and cerebral angiogram -Preoperative anticoagulation
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What is the process of carotid artery angioplasty and stenting?
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-Femoral artery access -Retrograde threading 70-90 cm guide wire under fluroscopy -Stent deployment
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What are the anesthetic considerations for carotid artery angioplasty and stenting?
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-Done while patients are awake -Light sedation appropriate -Heparinization pre-procedure (100mg/kg) -ACT >250 seconds prior to stent deployment -Distal embolic protection device -Pre-deployment anticholinergic -Potential for hemodynamic instability after stent deployment -Potential for bleeding -Potential for CVA -Potential for myocardial ischemia/infarction
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What are the postoperatice considerations for carotid artery angioplasty and stenting?
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-Hemodynamic stability -Monitored floor-most ambulate in 2-3 hours postop -Discharged next day -Serial outpatient carotid duplex studies
