Anesthesia for vascular surgery 2 Flashcards
The principal cause of carotid artery disease is
atherosclerosis****
Atherosclerosis commonly occurs at the bifurcation of the
common carotid artery and the internal & external carotid arteries
Signs & symptoms of atherosclerosis in the carotid artery include
fatal or debilitating stroke TIA asymptomatic bruit transient attack of monocular blindness- amaurosis fugax ******
The risk of having a first stroke is nearly ______as high for Blacks as it is for Whites
twice
The leading risk factors for strokes include
HTN, smoking, obesity, & DM
87% of strokes are
ischemic
extracranial atherosclerotic disease accounts for up to 20% of all ischemic strokes
For symptomatic patients with high-grade carotid stenosis, the definitive treatment is
carotid endarterectomy*****
For patients who are asymptomatic and have
medical therapy (ASA) percutaneous angioplasty/stenting
Preop assessment for carotid endarterectomy includes
recent symptoms- surgical intervention timing
optimize medical management
CAD is common- which to treat first
Optimizing medical management for carotid endarterectomy includes
beta-blockers, statins, antiplatelet therapy
HTN control, restore intravascular volume, reset cerebral autoregulation
diabetes control
Bad signs of CAD when performing a preop assessment for CEA includes
unstable angina, decompensated HF, significant valve disease
Carotid revascularization is recommended before _________ in patients with
CABG in patients with symptomatic carotid disease & bilateral severe asymptomatic carotid stenosis
Anesthesia for carotid endarterectomy includes
awake (best monitor of function) vs. GA/ETT continue ASA throughout preop period continue cardiac medications aline (rarely CVC) PIV x2, large bore, arms tucked
When monitoring EKG for carotid endarterectomy, leads _______ & _________ should be monitored
II & V5 for detection of rhythm disturbances & ST segment changes
Inferior MIs can be seen in leads
II, III, AvF
Septal MIs can be seen in leads
V1, V2
Anterior MIs can be seen in
V3 & V4
Lateral MIs can be seen in
I, AVL, V5 & V6
Case setup for CEA includes
T&S
aline, ACT machine, fluid warmer, lower body forced air warming blanket
phenylephrine & remifentanil infusions inline
clevidipine & NTG infusions available
beta blockers & ephedrine available
heparin & protamine
Monitoring for CEAs includes
routine with V5 lead & ST segment analysis plus A-line
consider cerebral oximeter especially if the surgeons are not placing a shunt during cross-clamp
occasionally surgeons want to measure “stump” pressures (have extra pressure tubing and blue male to male adapter) to connect to a-line transducer
Arterial blood pressure should be maintained in the
high-normal range throughout the procedure and particularly during the period of carotid clamping to increase collateral flow & prevent cerebral ischemia
In patients with contralateral internal carotid artery occlusion or severe stenosis, induced
hypertension to approximately 10-20% above baseline is advocated during the period of carotid clamping
Surgical manipulation of carotid sinus leads to
baroreceptor reflexes
HR will- decrease
blood pressure will decrease
cessation of surgical manipulation propmtly restores the hemodynamics
_________ on emergence requires immediate discussion with the surgeon about the need for angiography, reoperation, or both
Neurologic deficits
The period of emergence and extubation may be associated with________ which may require aggressive pharmacologic intervention
marked hypertension & tachycardia
-systolic blood pressures as high as 200 mmHg- risk for MI
Regional anesthesia for CEA includes blocking the
c2 to C4 dermatomes by use of a superficial, intermediate, deep, or combined cervical plexus block
Regional & local anesthesia allows ________ of the awake patient
continuous neurologic assessment
Regional anesthesia provides for
greater hemodynamic stability
reduced costs
reduces the need for shunts
requires patient cooperation
The superficial cervical plexus block is performed using the
midpoint of the posterior border of the sternocleidomastoid muscle
injection along the posterior border of the medial surface of the muscle
-can block accessory nerve causing trapezius muscle paralysis
The GALA trial identified that the anesthetic technique was
not associated with a significant difference in the composite end point
Describe the effects of hypocapnia & hypercapnia on cerebral autoregulation.
hypocapnia- decreased cerebral blood flow (i.e. vasoconstriction)
hypercapnia- increased cerebral blood flow (i.e. vasodilation)
In the setting of poor collateralization and resultant cerebral hypoperfusion, cerebral resistance vessels in the
hypo-perfused territories will dilate to maintain cerebral blood flow
Impaired cerebrovascular reactivity to hypercapnia may play a role in the development of
stroke ipsilateral to carotid stenosis or occlusion
-impaired CO2 reactivity would increase the risk for cerebral ischemia after carotid artery clamping
Carotid stump pressures should be
> 50*** (45 at the very minimum)
The internal carotid artery stump pressure represents the back-pressure resulting from
collateral flow through the circle of Willis via the contralateral carotid artery & the vertebrobasilar system
Cerebral oximeters measure the
O2 saturation of hemoglobin in the entire tissue bed which is predominantly venous blood and therefore approximates venous blood O2 saturation**
Postoperative CEA complications include
thromboembolic & hemorrhage intracerebral events hypertension hypotension cerebral hyper-perfusion syndrome cranial & cervical nerve dysfunction carotid body denervation wound hematoma
The CEA postop complication of hypertension results from
surgical denervation of the carotid sinus baroreceptors
The CEA postop complication of hypotension results from
baroreceptor hypersensitivity or reactivation
Cerebral hyper-perfusion syndrome is the
abrupt increase in blood flow with loss of autoregulation
manifested as HA, seizure, focal neurologic signs, brain edema, & possibly intracerebral hemorrhage
Carotid body denervation is the result of
impaired ventilatory response to mild hypoxemia, central chemoreceptors impaired, worsened with opioid administration
Cranial & cervical nerve dysfunction post CEA includes
RLN, SLN, hypoglossal, mandibular
-bilateral recurrent laryngeal nerve injury can result in life-threatening upper airway obstruction
Endovascular carotid artery stenting may include
percutaneous transluminal angioplasty & stenting
dual antiplatelet therapy
self-expanding stents
emboli protection devices
Diseases of the aorta include
peripheral arteries- occlusive disease
aorta & major branches- aneurysms, dissections
Aneurysms are often
medically managed
-dilation of all 3 layers of an artery
occasionally produce symptoms of compression on surrounding areas
Dissections require
emergent surgery (high mortality)
- occurs when blood enters the medial layer
- initiation occurs with a tear in the intima
- can occur over minutes to hours
Describe the key symptom differences between aneurysms & dissections
aneurysms- asymptomatic or pain due to compression of adjacent structures or vessels
dissections- severe sharp pain in the posterior chest or back pain
Risk factors for abdominal aortic aneurysm include
elderly, male, smoking, family history of AAA, atherosclerotic disease & HTN***
Rare causes of AAA disease include
trauma, mycotic infection, syphilis, and Marfan syndrome
Advential elastin degradation results in AAA and may be due to
genetic, biochemical, metabolic, infectious, mechanical, and hemodynamic factors
AAA is typically electively repaired for
6cm or larger*******
controversial 5.5-5.9 cm
surgical repair is often considered if small aneurysms become symptomatic or expand more than 0.5 cm in a 6 month period
Aneurysms less than _____ in diameter are thought to be relatively benign in terms of rupture & expansion
4.0 cm
The frequent incidence of associated ______ enhances aneurysm enlargement
systemic hypertension
Increasing diameter is associated with increased ______ even when arterial pressure is constant
wall tension
Law of Laplace
The classic triad for ruptured AAA is
hypotension, back pain, and pulsatile abdominal mass
-ruptured AAA who die before reaching the hospital may exceed >90%
