Vascular Flashcards
What Is the Primary Objective of CEA
Surgery?
○ Carotid artery stenosis from atheromatous plaque is responsible for 10–20% of ischemic strokes.
○ Rupture of the atheromatous plaque initiates thrombus formation that can lead to embolization and ischemic infarction.
○ Carotid endarterectomy (CEA) is performed to remove atheromatous
plaque from within the carotid artery to reduce the incidence of further embolic strokes in symptomatic patients.
What Are the Indications for Carotid Endarterectomy?
• For patients experiencing a TIA or ischemic stroke within the past 6 months with ipsilateral severe (70–99%) carotid artery stenosis identified on noninvasive imaging, i.e., carotid duplex ultrasound, computed tomography angiography (CTA), or magnetic resonance angiography (MRA), CEA is recommended if the perioperative morbidity and mortality rate is estimated to be less than 6%.
• Secondly, CEA is recommended for patients with a recent TIA or ischemic stroke in the presence of ipsilateral moderate (50–69%) carotid stenosis identified on conventional catheter-based angiography or noninvasive imaging with corroboration (e.g., on MR or CT angiogram) in the presence of certain patient-specific factors, e.g., age, sex, and comorbidities.
○ Again, CEA is recommended for this class of patient when the perioperative morbidity and mortality rate is estimated to be less than 6%.
• CEA is not recommended when degree of stenosis is less than 50%.
Should the Patient with Acute Ischemic
Stroke Have Invasive or Noninvasive
Neurovascular Imaging?
○ Brain imaging and noninvasive vascular imaging from the aorta to the vertex should be undertaken for patients present-
ing with an acute or recent stroke or TIA. As CT angiography is now widely available, vascular imaging can be
performed at the same time as the initial head CT.
○ MR with angiography or carotid ultrasound are suitable alternatives.
○ Due to the risk of stroke with conventional catheter-based
angiography, it is rarely performed in the acute setting despite providing superior images.
○ Moreover, noninvasive imaging, i.e., carotid duplex ultrasound, CTA, and MRA, provides immediate images that are adequate for visualization of intra- and extracranial vascular disease.
When Is the Optimum Time for Surgery Relative to the Onset of Neurological Symptoms? Stroke
○ Analysis of data pooled from the European Carotid Surgery Trial and North American Symptomatic Carotid Endarterectomy Trial showed improved neurological outcomes in
patients undergoing CEA within 2 weeks of the onset of neurological deficits .
○ Subsequently, the American Heart Association and American Stroke Association guidelines recommend revascularization within 2 weeks of the TIA or non-disabling stroke.
○ The Canadian Stroke Best Practice guidelines reiterate this and recommend that those with a 70–99% symptomatic stenosis have an endarterectomy performed within the first days following the initial event and within the first 14 days if the patient’s clinical condition precludes it occurring within first few days.
○ A recent meta-analysis, however, showed that CEA within 48 hours was associated with a significantly increased risk of stroke compared to CEA undertaken after 48 hours (OR 2.35; 95% CI 1.61e3.45, p < .001) [5].
○ Patient optimization before surgery may be limited by time constraints.
○ By understanding the benefits of expedited surgery, anesthesiologists have to be pragmatic in their approach to patient optimization preoperatively.
When Is Carotid Angioplasty and Stenting Favored Over CEA?
○ Carotid stenting should be considered for patients who are
not suitable for CEA due to medical, technical, or anatomical reasons.
○ The peri-procedural morbidity and mortality rates (for stenting) for the interventionist and/or center should be less than 5% for symptomatic stenosis and 3% for asymptomatic stenosis.
○ Carotid stenting is associated with
an increased risk of peri-procedural stroke and death in older patients when compared to endarterectomy.
○ Endarterectomy is, therefore, more appropriate for patients over 70 years
What Complications Is the CEA Patient Subject to in the Perioperative Period?
○ The North American Symptomatic Carotid Endarterectomy Trial (NASCET) Surgical Results of 1415 patients found an overall rate of 6.5% for perioperative events including death, disabling stroke, and non-disabling stroke.
○ At 30 days, the rates were 1.8% for disabling stroke, 3.7% for non-disabling stroke, and 1.1% for death.
○ Following neurological recovery
of patients deemed to be disabled at 30 days, by 90 days, the rates of disabling and non-disabling stroke had changed to 0.9% and 4.5%, respectively.
○ Death rate at 90 days remained
the same at 1.1%.
○ Thromboembolism was the cause of most strokes.
○ One-third of events occurred intraoperatively.
○ Increased surgical risk was predicted by the following variables: symptomatic hemispheric versus retinal TIA, contralateral carotid occlusion, ipsilateral ischemic lesion on CT scan, and irregular or ulcerated ipsilateral plaque.
○ Cranial nerve injuries occurred in 8.6%.
○ The majority (7.9%) were mild, resulting in no delay in discharge and had resolved on follow-up.
○ The incidence of vagus nerve injury was 2.5%.
○ Airway edema requiring reintubation was a rare event,
occurring in only 0.4%.
○ Wound hematomas occurred in
7.1% of patients.
○ Wound hematoma was demonstrated to be a statistically significant risk factor for perioperative stroke and death (14.9% risk versus 5.9% without a wound hematoma)
How Should This Patient Be Evaluated Preoperatively? Acute stroke
○ Most stroke patients will have been thoroughly evaluated by the stroke team by the time they come to the attention of the anesthesiologist.
○ The timing of initial evaluation by stroke expert will depend on the duration between symptom onset
and presentation to a healthcare facility.
○ As the time elapsed between the initial TIA or non-disabling stroke and
presentation to a healthcare facility increases, the risk of recurrent stroke decreases.
○ The highest risk of recurrent TIA
or stroke is within 48 hours of the initial symptoms.
○ Ultimately, investigations undertaken as part of the assessment include brain imaging and noninvasive vascular imaging, the latter to identify any thrombus or carotid stenosis amenable to thrombectomy or surgery.
○ Head CT and CTA from aortic arch
to vertex are most commonly performed.
○ If CTA is not available, carotid ultrasound or MRA with angiography can be performed.
○ MRA has an increased diagnostic sensitivity when compared to CT for detecting small strokes.
○ Invaluable information for the anesthesiologist can be gleaned from
angiography or ultrasound regarding patency of the non-operative internal carotid artery and vertebral arteries. Of particular interest is the degree of blood flow through the contralateral internal carotid artery and both vertebral arteries.
○ Global cerebral perfusion intraoperatively is dependent on
this contralateral flow, while the operative internal carotid
artery is clamped.
○ This will impact the surgeon’s decision to use intraoperative carotid shunting.
○ Standard laboratory investigations include complete blood count, electrolyte, creatinine, coagulation screen, troponin, and random glucose. Lipid profiles and hemoglobin A1C level are routine to identify modifiable stroke risk factors.
○ A 12-lead ECG is essential in all patients to detect cardiac arrhythmias and/or ECG changes indicative of structural heart disease that may be present following acute stroke.
ECG changes have been reported following ischemic strokes
as well as those from a hemorrhagic origin. The incidence of
arrhythmias following acute ischemic stroke has been
reported to be up to 25% in the first 72 hours [9].
○ Atrial fibrillation is the most common arrhythmia and is identified
more frequently following cardioembolic stroke.
○ The stroke assessment may also have included an echocardiogram. This is generally considered in cases where the mechanism of stroke has not been identified
How Should Hypertension Be Managed Perioperatively in This Patient Population?
○ Poorly controlled hypertension is an indicator for labile intraoperative blood pressure.
○ Significant postoperative
hypertension is a risk factor for cerebral hyperperfusion syndrome.
○ Hypertension in the setting of acute ischemic stroke (in those not eligible for thrombolytic therapy) or TIA
is not routinely treated.
○ Extreme blood pressures with a
systolic pressure greater than 220 mmHg or diastolic greater than 120 mmHg are treated carefully to ensure a gradual reduction of 15% but no more than 25% within the first
24 hours.
○ In addition to being the most important risk factor for stroke, hypertension is also a significant risk factor for further stroke.
○ Secondary prevention guidelines therefore recommend a blood pressure target below 140/90 mmHg . ○ In the presence of small subcortical strokes, the target systolic pressure is 130 mm Hg. Frequently, due to the short time period between occurrence of the stroke and surgery, it is difficult to achieve optimal blood pressure control preoperatively in patients with previously undiagnosed or poorly controlled hypertension.
○ For those on antihypertensive
medications, the current practice in our center is to hold angiotensin-converting enzyme inhibitors and angiotensin II receptor antagonists on the day of surgery because of their potential to cause intraoperative hypotension.
How Are Arrhythmias Managed?
○ Patients with an identified arrhythmia, most commonly atrial
fibrillation, should have the ventricular response rate controlled to a preoperative target of 100 beats per minute.
○ Any rate-controlling medications such as beta-blockers and rate-limiting calcium channel blockers should be taken on the day
of surgery.
Describe an Approach to Anticoagulant Medications in the Perioperative Period acute ischemic stroke
○ Antiplatelet therapy with aspirin is recommended for all patients with acute ischemic strokes and TIAs.
○ Those not already on an antiplatelet are usually commenced with a loading dose of 160–320 mg.
○ This is commenced as soon as
any intracranial hemorrhage has been excluded on imaging.
○ The daily dose thereafter ranges from 80 to 325 mg.
○ If alteplase is given, then an antiplatelet agent is not given until 24 hours after this has been administered.
○ Dual-antiplatelet therapy with aspirin and clopidogrel may be considered for patients with a minor stroke (National Institute of Health Stroke Score (NIHSS) of 3 or less), or a high-risk TIA (ABCD2 (age, blood pressure, clinical features, diabetes)) score of 4 or greater.
○ This is not continued for longer than 21–30 days due to the increased risk of bleeding.
○ In very high-risk TIA or minor ischemic stroke patients caused by a high-grade carotid stenosis in whom endarterectomy may be indicated, consultation with the surgical team should be sought to determine the time of commencement of dual-antiplatelet therapy.
○ In a large retrospective review, dual-antiplatelet therapy was associated with a significant increased risk of major bleeding requiring reoperation, although there was a significant reduction in neurological events.
○ The risk of bleeding has subsequently been contested in a smaller prospective study.
○ The surgical team may opt to continue single therapy with aspirin until following surgery or continue dual therapy, depending on the individual patient case.
○ Anticoagulation for patients with atrial fibrillation or paroxysmal atrial fibrillation is recommended.
○ Direct oral anticoagulants (DOACs) such as apixaban and rivaroxaban are now used in preference over warfarin.
○ As was the case with our patient who was on apixaban for paroxysmal atrial fibrillation, DOACs should be discontinued 2 days prior to surgery. Warfarin should be held for 5 days.
○ In the face of acute ischemic stroke and atrial fibrillation alone, there is no requirement to bridge with heparin; therefore our patient did not receive any bridging therapy
Should This Patient Continue Statin Therapy in the Perioperative Period?
○ Dyslipidemia is a well-known cause of atherosclerosis and a risk factor for ischemic stroke.
○ The use of statins in primary and secondary prevention of stroke is irrefutable.
○ Statin therapy is recommended following an ischemic stroke or TIA.
○ Lifestyle modifications should also be made.
○ A reasonable target to strive for is a low-density lipoprotein (LDL) cholesterol level less than 2.0 mmol/L or a greater than 50% reduction from baseline .
○ Observational studies have shown benefits of statin therapy in the perioperative period in patients undergoing CEA.
○ Benefits include reduced in-hospital mortality and stroke and long-term protection against myocardial infarction (MI) and stroke.
○ These beneficial effects have been contested in a smaller prospec-
tive study.
○ On balance, given that discontinuation of statin therapy increases risk of MI following major vascular surgery, it seems prudent to continue statin therapy through-out the perioperative period
Is Glucose Control in the Perioperative
Period in This Cohort of Patients Important? Stroke
○ Diabetes mellitus is a risk factor for stroke and an independent risk factor for stroke recurrence.
○ Hyperglycemia at the time of CEA is associated with significant morbidity and mortality.
○ With blood glucose levels greater than 11.1 mmol/l, patients are 2.8-fold, 4.3-fold, and 3.3-fold more likely to experience a stroke or TIA, MI, or death, respectively.
○ The exception to this may be with lacunar infarcts where moderate hyperglycemia (8–12 mmol/l) has been associated with better outcomes.
○ However, outcomes were worse in the cohort with more severe hyperglycemia (>12 mmol/l) [19].
○ Given the importance of glucose control in the perioperative period, consultation with a diabetologist may be beneficial for those with previously undiagnosed diabetes or poorly
controlled diabetes.
○ At our institution, we use a variable rate insulin infusion with a concurrent low volume infusion of 10% dextrose.
The Patient Has Read on the Internet That He Can Be Awake for His Carotid Endarterectomy. How Do You Advise Him?
○ The type of anesthetic, general anesthesia versus regional anesthesia, for CEA, has long been debated.
○ There are many perceived benefits to both techniques.
○ Local anesthesia allows the patient to act as their own neurological monitor, reduces the rate of arterial shunt intervention, avoids the need for intubation and stress response associated with it (unless there is need to convert to general anesthesia), and may result in less hemodynamic instability.
○ General anesthesia provides immobility not requiring patient cooperation, potential neurological protection from general anesthetic agents, and control of ventilation and arterial carbon dioxide.
○ Despite these perceived benefits, a large randomized controlled trial published in 2008 demonstrated no difference in 30-day outcomes for stroke, including retinal infarction, MI, or death.
○ The primary outcome, stroke, occurred in 4.8% of patients who had undergone general anesthesia and 4.5% who had their procedure under regional anesthesia.
○ Note though that his study was not powered for mortality.
○ As the debate continued, an updated Cochrane review published in 2013 that included 14 randomized controlled trials (although 3526 of the 4596 surgeries were from the GALA trial) found no difference in 30-day stroke rates between the two anesthetic groups.
○ There was also no statistically significant difference between the two groups for the following: MI or death within 30 days of surgery, local hemorrhage, and cranial nerve injury.
○ The length of hospital stay and patient satisfaction were also not different between the groups.
○ More recently a non-randomized comparison of general and regional anesthesia from the Carotid Revascularization Endarterectomy versus Stenting Trial (CREST) showed that general anesthesia presented twice the risk of MI compared to regional anesthesia. The sample size, however, was small and at risk of confounding.
○ Careful patient selection for each type of anesthesia and the manner in which the anesthetic of choice are conducted may well be more important than the actual choice of anesthetic.
What Approaches Are Available for a Regional Anesthetic Technique CEA?
○ Awake CEA may be undertaken using local anesthetic infiltration, superficial cervical plexus block, and/or deep cervical plexus block. ○ The author’s regional anesthesia experience for this procedure is with superficial cervical plexus blocks performed under ultrasound guidance.
○ No matter which regional approach is used, it is important that the patient be fully briefed on what to expect and has an established rapport with the operating room team.
○ Communication with the patient needs to be maintained throughout the procedure, not only to monitor cerebral function but to help alleviate any anxiety the patient may be experiencing.
Is Assessment of Neurocognitive Function During Cross-Clamping Important During Awake Carotid Endarterectomy?
○ Neurocognitive function assessment determines the adequacy of collateral circulation from the circle of Willis.
○ Adequate collateral circulation mitigates the need for shunting.
○ Although the purpose of placing a shunt is to maintain cerebral blood flow, therefore protecting against ischemia, it has associated complications, including arterial dissection, acute occlusion, and distal embolization.
○ It can also make surgical exposure difficult at the distal ends of the incision.
○ Shunt rates during CEA are substantially reduced in regional techniques compared to during general anesthesia (14% versus 43%).
○ Neurocognitive monitoring in awake patients undergoing CEA has been shown to be more sensitive and specific for identifying the need for shunt placement compared to electroencephalography and stump pressure in this cohort.
○ Prior to, immediately after, and throughout cross-clamping of the carotid artery, neurocognitive assessment should be made by assessing level of consciousness, presence of confusion, alterations in speech, and contralateral motor function.
○ A new deficit indicates the need for shunt placement.
○ In the event of new deficits that do not revert quickly with shunt placement and manipulation of cerebral perfusion, general anesthesia will be required
What Are the Risk Factors, Screening Recommendations, Time Course of Enlargement, and Point of Consideration of Surgical Intervention for AAA?
○ The main risk factors for AAA are male sex, age >65 years, smoking, a coronary artery disease and/or peripheral vascular disease history, first-degree relative with AAA, or presence of aneurysms elsewhere.
○ The US Preventive Services Taskforce recommends one-time ultrasonographic screening for AAA in all males between the ages of 65–75 years with an ever-smoking history.
○ The prevalence of AAA in this population is 1.2–3.3% in men over 60 years of age .
○ The average annual expansion rate for aneurysms between 3.0 to 3.9 cm, 4.0 cm to 6.0 cm, and >6.0 cm is 1 tjo 4 mm, 3 to 5 mm, and 7 to 8 mm, respectively.
○ The greater the dimension of the aneurysm, the higher the risk of rupture.
○ Referral for a surgical opinion should be considered when an AAA reaches 5 cm in diameter, particularly in females, and definitive repair is indicated when AAA is > 5.4 cm in diameter if the patient is a suitable surgical candidate
True-False Questions
1. In the case of an AAA
Annual expansion rate increases in line with enlarging dimensions of the aorta.
T
