Anesthesia for Vascular Surgery Flashcards
What is the strongest predictor of postoperative renal dysfunction after vascular surgery?
The degree of preoperative renal insufficiency
What is the leading cause of perioperative mortality at the time of vascular surgery?
Coronary artery disease
Less than …% of patients who undergo vascular surgery have normal coronary arteries, and more than …% have advanced or severe CAD
10
50
Unrecognized myocardial infarction (MI) (determined by …) and silent myocardial ischemia (determined by …) often occur in vascular surgery patients (…% and …%, respectively) and are associated with increased long-term mortality and adverse cardiac events.
wall motion abnormalities at rest in the absence of a history of MI
stress-induced wall motion abnormalities in the absence of angina
23
28
When multiple recent studies about patients undergoing vascular surgery are pooled, the overall prevalence of perioperative MI and death is …, respectively. When outcomes are assessed over the long term (2 to 5 years), the prevalence of MI and death is …, respectively
4.9% and 2.4%
8.9% and 11.2%
Describe the CARP trial
Coronary-artery revascularization before elective major vascular surgery. N Engl J Med. 2004
Patients were eligible for the study if they were scheduled for an elective vascular operation for either an expanding abdominal aortic aneurysm or severe symptoms of arterial occlusive disease involving the legs. The exclusion criteria were a need for urgent or emergency surgery, a severe coexisting illness, or prior revascularization without evidence of recurrent ischemia.
Of the 5859 patients screened in the CARP trial, 1190 underwent coronary angiography based on a combination of clinical risk factors and noninvasive stress imaging data. The incidence and severity of CAD on these angiograms were 43% of patients had one or more major coronary arteries with at least a 70% stenosis suitable for revascularization (and were randomized to either revascularization or no revascularization before vascular surgery).
Of the 510 patients who underwent randomization, 258 were assigned to a strategy of preoperative coronary-artery revascularization, and 252 to no revascularization.
The CARP trial showed that prophylactic revascularization (by CABG or PCI) was generally safe but did not improve long-term outcome after vascular surgery. Longterm mortality (2.7 years) was 22% in the revascularization group and 23% in the group whithout revascularization.
The CARP trial results can be applied to most of the vascular surgery patients; however, they cannot be extrapolated to patients with … because these conditions excluded patients from study participation
unstable cardiac symptoms, left main coronary artery disease, aortic stenosis, or severe left ventricular dysfunction
The lack of benefit of prophylactic coronary revascularization in the CARP and DECREASE-V trials is difficult to reconcile with the more favorable data from Hertzer and co-workers and other studies (Coronary Artery Surgery Study [CASS] and Bypass Angioplasty Revascularization Investigation [BARI]). What factors could explain this inconsistency?
Issues are involved that go beyond critical coronary lesions; perhaps the current understanding of the pathophysiology of perioperative MI is incomplete. For example, perioperative MI may be caused by culprit lesions (i.e., vulnerable plaques with high likelihood of thrombotic complications) often located in coronary vessels without critical stenosis. For this type of MI (atherothrombotic), perioperative strategies aimed at reducing potential triggers of coronary plaque destabilization and rupture may be more appropriate than those leading to coronary revascularization. Demand ischemia is likely the predominant cause of perioperative MI, which has been confirmed by a recent angiographic study
Perioperative administration of … decrease risk for death in vascular surgery patients with renal impairment
β-adrenergic blocker and statin
If a decision is made to initiate beta-blocker treatment in the perioperative period to reduce cardiac risk, the safest approach may be …
to initiate therapy with a small dose and titrate to effect over a 7- to 10-day period before the planned surgery
Abdominal aortic aneurysms (AAAs) occur frequently in elderly men, with an incidence approaching …%.
… are established risk factors
8
Increasing age, smoking, family history of AAA, and atherosclerotic disease
Current guidelines emphasize that it is not possible to recommend a single threshold diameter for operative intervention that can be generalized to all patients. Yet, elective repair should be undertaken in all patients with AAA … cm or larger in diameter.
Although some controversy exists regarding elective AAA repair when its diameter is in the …-cm range, the risk for rupture of a … cm aneurysm (per year) is equal to or greater than the risk for perioperative mortality, and thus surgical repair is indicated.
6
5.5-to 5.9
5.5-
Surgical repair of AAA is often considered if small aneurysms become … or …
symptomatic
expand more than 0.5 cm in a 6-month period
Unlike patients with aortic aneurysmal disease, patients undergo surgery for aortoiliac occlusive disease only if …
they are symptomatic
… is the most common cause of renal artery stenosis. Occlusive lesions are located almost exclusively in the … of the renal artery and are usually an extension of …
… is an important, but less common, cause of renal artery stenosis and most frequently involves the … of the renal arteries
Atherosclerosis
proximal segment and orifice
aortic atherosclerosis
Fibromuscular dysplasia
distal two-thirds
Stenosis at the origin of the celiac and mesenteric arteries occurs as a result of extension of aortic atherosclerosis. The … is by far the most commonly involved, followed by the …
inferior mesenteric artery
superior mesenteric artery and the celiac artery
Describe the Hemodynamic Changes with Aortic Cross-Clamping
↑ Arterial blood pressure above the clamp
↓ Arterial blood pressure below the clamp
↑ Segmental wall motion abnormalities
↑ Left ventricular wall tension
↓ Ejection fraction
↓ Cardiac output†,‡
↓ Renal blood flow
↑ Pulmonary occlusion pressure
↑ Central venous pressure
↑ Coronary blood flow
†Cardiac output may increase with thoracic cross-clamping.
‡When ventilatory settings are unchanged from pre-clamp levels.
Metabolic Changes with Aortic Cross-Clamping
↓ Total body oxygen consumption
↓ Total body carbon dioxide production
↑ Mixed venous oxygen saturation
↓ Total body oxygen extraction
↑ Epinephrine and norepinephrine
Respiratory alkalosis
Metabolic acidosis
Describe Therapeutic Interventions for Afterload reduction, Preload reduction and Renal protection during Aortic Cross-Clamping
1) Afterload reduction
- Sodium nitroprusside
- Inhalational anesthetics
- Amrinone
- Shunts and aorta-to-femoral bypass
2) Preload reduction
- Nitroglycerin
- Controlled phlebotomy
- Atrial-to-femoral bypass
3) Renal protection
- Fluid administration
- Distal aortic perfusion techniques
- Selective renal artery perfusion
- Mannitol
- Drugs to augment renal perfusion
*** Other
Hypothermia
↓ Minute ventilation
Sodium bicarbonate
Cross-clamping of the proximal descending thoracic aorta increases mean arterial, central venous, mean pulmonary arterial, pulmonary capillary wedge pressure and cardiac index by 35%, 56%, 43%, 90% and 29% respectively. Heart rate and left ventricular stroke work are not significantly changed
T or F
F
Cross-clamping of the proximal descending thoracic aorta increases mean arterial, central venous, mean pulmonary arterial, and pulmonary capillary wedge pressure by 35%, 56%, 43%, and 90%, respectively, and decreases the cardiac index by 29%. Heart rate and left ventricular stroke work are not significantly changed
The marked increases in ventricular filling pressure (preload) reported with high aortic cross-clamping have been attributed to …
increased afterload and redistribution of blood volume, which is of prime importance during thoracic aortic cross-clamping. The splanchnic circulation, an important source of functional blood volume reserve, is central to this hypothesis. The splanchnic organs contain nearly 25% of the total blood volume, nearly two-thirds (>800 mL) of which can be autotransfused from the highly compliant venous vasculature into the systemic circulation within seconds. Primarily because of smaller splanchnic venous capacitance, blood volume is redistributed from vascular beds distal to the clamp to the relatively noncompliant vascular beds proximal to the clamp.
Thoracic aortic cross-clamping also results in significant increases in plasma epinephrine and norepinephrine, which may enhance venomotor tone both above and below the clamp. The splanchnic veins are highly sensitive to adrenergic stimulation. The major effect of catecholamines on the splanchnic capacitance vessels is venoconstriction, which actively forces out splanchnic blood, reduces splanchnic venous capacitance, and
increases venous return to the heart
Describe the Anrep Effect
A sudden increase in afterload on the heart causes an increase in ventricular inotropy.
A sudden increase in aortic pressure, for example, causes a rapid increase in left ventricular end-diastolic volume. This leads to an initial increase in the contractile force of the ventricle through the Frank-Starling mechanism. If the increased afterload is maintained for 10–15 minutes, the force of contraction increases further, and in the intact heart, the end diastolic volume decreases. This delayed increase in ventricular contractile force represents an increase in inotropy. The functional significance of the Anrep effect is that the increased inotropy partially compensates for the increased end-systolic volume and decreased stroke volume caused by the increase in afterload. Without this mechanism, increases in afterload would cause greater reductions in stroke volume than what is normally observed.
The mechanisms responsible for the initial response and the delayed response appear to be different. The initial increase in contractile force (Frank-Starling mechanism) is due to increased troponin C sensitivity to calcium. The delayed response likely involves several mechanisms that promote increased release of calcium by the sarcoplasmic reticulum. Suggested mediators include the release of endothelin-1 and angiotensin II by cardiac cells in response to stretch.
Cross-clamping of the thoracic aorta decreases total body O2 consumption by approximately …%. For reasons that are unclear, O2 consumption decreases in tissues above the clamp
50
The cardiovascular response to infrarenal aortic cross-clamping is less significant than with high aortic cross-clamping. Although several clinical reports have noted no significant hemodynamic response to infrarenal cross-clamping, the hemodynamic response generally consists of … . Cardiac output is most consistently …
increases in arterial pressure (7% to 10%) and systemic vascular resistance (20% to 32%), with no significant change in heart rate
decreased by 9% to 33%.
The preload changes with infrarenal aortic crossclamping may depend on the status of the coronary circulation. Patients with severe ischemic heart disease responded to infrarenal aortic cross-clamping with … central venous (35%) and pulmonary capillary (50%) pressure, whereas patients without CAD had … filling pressure
significantly increased
decreased
Urine output is closely monitored and often augmented during aortic surgery. In this cases, intraoperative urine output predict postoperative renal function.
T or F
F
The adequacy of renal perfusion “cannot” be assumed by urine output. Although urine output is closely monitored and often augmented during aortic surgery, intraoperative urine output does not predict postoperative renal function.
Procedures requiring aortic cross-clamping above the renal arteries dramatically reduce renal blood flow. Experimental studies report an 83% to 90% reduction in renal blood flow during thoracic aortic cross-clamping.
Infrarenal aortic cross-clamping in humans is associated with a 75% increase in renal vascular resistance, a 38% decrease in renal blood flow, and a redistribution of intrarenal blood flow toward the renal cortex. These rather profound alterations in renal hemodynamics occurred despite no significant change in systemic hemodynamics, and they persisted after unclamping.
The sustained deterioration in renal perfusion and function during and after infrarenal aortic cross-clamping has been attributed to renal vasoconstriction, but the specific pathophysiologic process remains unknown. Renal sympathetic blockade with epidural anesthesia to a T6 level prevent the severe impairment in renal perfusion and function that occurs during and after infrarenal aortic cross-clamping
T or F
F
The sustained deterioration in renal perfusion and function during and after infrarenal aortic cross-clamping has been attributed to renal vasoconstriction, but the specific pathophysiologic process remains unknown. Renal sympathetic blockade with epidural anesthesia to a T6 level DOES NOT prevent or modify the severe impairment in renal perfusion and function that occurs during and after infrarenal aortic cross-clamping
… accounts for nearly all the renal dysfunction and failure after aortic reconstruction
In addition to aortic cross-clamping-induced reductions in renal blood flow, … all contribute to renal dysfunction
Acute tubular necrosis
ischemic reperfusion injury, intravascular volume depletion, embolization of atherosclerotic debris to the kidneys, and surgical trauma to the renal arteries
Although not proved, pharmacologic “protection” before aortic cross-clamping is believed to be beneficial and is therefore given. The use of … to induce … before aortic cross-clamping is ubiquitous in clinical practice.
… improves renal cortical blood flow during infrarenal aortic cross-clamping and reduces ischemia-induced renal vascular endothelial cell edema and vascular congestion. Other mechanisms by which it may be beneficial include acting as a scavenger of free radicals, decreasing renin secretion, and increasing renal prostaglandin synthesis
mannitol 12.5 g/70 kg
osmotic diuresis
Mannitol
Besides mannitol, what other medications are used to protect the kidneys from aortic cross-clamp-induced injury?
Loop diuretics and low-dose dopamine (1 to 3 mcg/kg/min)
Patients with impaired ventricular function requiring supraceliac aortic cross-clamping are the most challenging.
… is important to avoid abrupt and extreme stress on ‘the heart.
Afterload reduction, most commonly accomplished with the use of … (predominantly … dilators), is necessary to unload the heart and reduce ventricular wall tension.
A normal preload is equally important and involves …
… can be used because it increases venous capacity more than does sodium nitroprusside.
Controlled (i.e., slow clamp application) supraceliac aortic cross-clamping
sodium nitroprusside or clevidipine
arteriolar
careful IV fluid titration and vasodilator administration
Nitroglycerin
In patients without evidence of left ventricular decompensation or myocardial ischemia during supraceliac aortic cross-clamping, a proximal aortic mean arterial pressure of up to … is acceptable
120 mm Hg
The 1-year incidence of probable aorta aneurysm rupture in patients refusing or unfit for elective repair is … for aneurysms 5.5 to 5.9 cm, 6.0 to 6.9 cm, and 7.0 cm or greater, respectively
9.4%, 10.2%, and 32.5%
Factors that increase the Physiologic Changes with Aortic Unclamping
longer duration of cross-clamping and more proximal cross-clamping
Hemodynamic Changes with Aortic Unclamping
↓ Myocardial contractility
↓ Arterial blood pressure
↑ Pulmonary artery pressure
↓ Central venous pressure
↓ Venous return
↓ Cardiac output
Metabolic Changes with Aortic Unclamping
↑ Total body oxygen consumption
↑ Lactate
↓ Mixed venous oxygen saturation
↑ Prostaglandins
↑ Activated complement
↑ Myocardial-depressant factor(s)
↓ Temperature
Metabolic acidosis
Possible Therapeutic Interventions to control Physiologic Changes with Aortic Unclamping
↓ Inhaled anesthetics
↓ Vasodilators
↑ Fluid administration
↑ Vasoconstrictor drugs
Reapply cross-clamp for severe hypotension
Consider mannitol
Consider sodium bicarbonate
What is the most consistent hemodynamic response to aortic unclamping?
Hypotension
What is the dominant mechanisms of the hypotension after aortic unclamping?
Reactive hyperemia in tissues and organs distal to the clamp and the resultant relative central hypovolemia
During open aortic surgery, is the used of a combined anesthetic technique (epidural + general anesthesia) the best option? Explain
No it isn’t.
The duration and intensity of postoperative care after aortic surgery are critically dependent on the physiologic derangements incurred during the perioperative period (i.e., depression of consciousness, hypothermia, excessive intravascular fluids, incisional pain, ileus, and respiratory depression), as well as on the development of certain less common, but more severe postoperative complications (i.e., MI, pneumonia, sepsis, renal failure, and decreased tissue perfusion). Length of hospital stay may therefore be considered the outcome variable most directly proportional to an integrated final negative effect of all significant perioperative
morbidity (excluding in-hospital death) and the variable most likely
to be altered by the anesthetic or analgesic technique.
Randomized trials have not demonstrated any reduction in length of hospital stay after aortic surgery with the use of regional techniques.
Norris and colleagues14 reported the results of a randomized clinical trial
comparing alternative combinations of intraoperative anesthesia (i.e., general or combined epidural and general) and postoperative analgesia (i.e., IV patient-controlled analgesia [PCA] or epidural PCA) with respect to length of stay after abdominal aortic surgery. Although the overall length of stay was much shorter (median, 7.0 days) than that reported in other studies, they were not able to demonstrate a reduction in length of stay or direct medical costs based on anesthetic or analgesic technique. The overall incidence of postoperative complications in the trial was low and not different based on anesthetic or analgesic technique. Postoperative
pain was well controlled overall, with similar pain scores in both analgesic treatment groups. Thus, if perioperative care and pain relief are optimized, epidural anesthetic and analgesic techniques for aortic surgery offer no major advantage or disadvantage over general anesthesia and IV PCA.
The lower part of the body should be warmed during the aorta crossclamp period to reduce the lower extremities vasoconstriction and hypoperfusion.
T or F
F
The lower part of the body should not be warmed during the crossclamp
period because doing so can increase injury to ischemic tissue distal to the cross-clamp by increasing metabolic demand
Aneurysms of the thoracoabdominal aorta occur primarily because of …
The remainder are caused by …
atherosclerotic degenerative disease (80%) and chronic aortic dissection (17%)
either trauma or connective tissue diseases involving the aortic wall from conditions such as Marfan syndrome, cystic medial degeneration, Takayasu arteritis, or syphilitic aortitis
Describe The Crawford classification of thoracoabdominal aortic aneurysms
- Type I: involve all or most of the descending thoracic aorta and the upper abdominal aorta;
- Type II: involve all or most of the descending thoracic aorta and all or most of the abdominal aorta;
- Type III aneurysms involve the lower portion of the descending thoracic aorta and most of the abdominal aorta;
- Type IV aneurysms involve all or most of the abdominal aorta, including the visceral segment.
Patients with Crawford type … aneurysms are at greatest risk for paraplegia and renal failure from spinal cord and kidney ischemia during cross-clamping
II
Describe The DeBakey classification of dissecting aneurysms of the aorta
- Type I: intimal tear in the ascending aorta with dissection extending down the entire aorta.
- Type II: intimal tear in the ascending aorta with dissection limited to the ascending aorta.
Type III: intimal tear in the proximal descending thoracic aorta (just distal to the left subclavian artery) with dissection either limited to the thoracic aorta (type IIIA) or extending distally to the abdominal aorta or aortoiliac bifurcation (type IIIB).
Aortic dissection can be classified by duration, with those less than … classified as acute and those greater than … classified as chronic
2 weeks
2 weeks
Acute aortic dissection involving … is a surgical emergency that requires immediate cardiac surgical repair.
Acute dissections involving … are most often treated conservatively (i.e., arterial blood pressure, heart rate, and pain control) because surgical repair has no proved benefit over medical or interventional treatment in
stable patients
the ascending aorta (DeBakey types I and II, Stanford type A)
the descending aorta (DeBakey type III, Stanford type B)
Patients who undergo replacement of the entire thoracoabdominal aorta (Crawford extent type II) have the most frequent perioperative risk. Contemporary mortality rates reported from large institutions range from …%. Statewide and nationwide mortality rates may be considerably more frequent (∼…%). The perioperative mortality rate may significantly
underestimate the risk associated with TAA repair. In a large statewide series, the mortality with elective TAA repair was …% at 30 days and …% at 365 days
5% to 14
20
19
31
Which system is the most common cause of complications after open thoracoabdominal aorta repair?
Pulmonary system
The incidence of postoperative pulmonary insufficiency approaches 50%,
with 8% to 14% of patients requiring tracheostomy
Where should an arterial line be placed during and open thoracoabdominal aorta repair?
A right radial arterial catheter is used for aneurysms involving the proximal descending thoracic aorta because occasionally the cross-clamp is placed proximal to the left subclavian artery, thus occluding flow to the left upper extremity.
When distal aortic perfusion techniques are used,
arterial blood pressure distal to the cross-clamps can be monitored.
This can be accomplished with the placement of a right femoral
arterial catheter, or the surgical team can place a catheter directly
into the femoral artery or distal aorta
Three general problems exist with SSEP monitoring when used during open thoracoabdominal aorta repair. Describe then.
1) Sensory monitoring is more likely to detect lateral and posterior sensory column ischemia and is a poor monitor for the anterior motor column. As a result, paraplegia can occur despite normal SSEP signals;
2) Inhaled anesthetics and hypothermia can significantly interfere with SSEP signals;
3) Ischemia affects peripheral nerves, and ischemia in the lower extremities delays conduction from the usual stimulation sites (e.g., posterior tibial nerve). To eliminate the peripheral nerves as a confounding factor, spinal stimulation via a lumbar epidural electrode can be used, which may be more specific for ischemic injury than peripheral monitoring alone
During aortic cross-clamping, MEPs are monitored every minute. A
reduction in MEP amplitude to less than … of baseline is considered an indication of spinal chord injury (SCI) and requires corrective measures
25%
What is the single most important determinant of paraplegia and renal failure with the clamp-and-sew technique?
The duration of the cross-clamping
The typical heparin dose for partial bypass is …
100 units/kg
When hypothermia (30°C) is combined with atrial cannulation, approximately 15% of patients experience …
new atrial fibrillation
Complex aneurysms involving the aortic arch often require elective cardiopulmonary bypass with an interval of deep hypothermic (…°C) circulatory arrest (DHCA) because cerebral blood flow is transiently interrupted during surgery. Bypass can be accomplished by cannulation of the …
During the interval of DHCA, some centers also use anterograde (i.e., …) or retrograde (i.e., …) selective cerebral perfusion with cold oxygenated blood to extend the safe maximum duration of circulatory arrest. Without this technique, … is thought to be the safe limit of DHCA, but … has been reported with selective cerebral perfusion
15
femoral artery and the femoral vein (i.e., femoral–femoral bypass)
innominate artery
internal jugular vein
45 to 60 minutes
90 minutes
The spinal cord receives its blood supply from …
two posterior arteries (≈25%) and one anterior spinal artery (≈75%)
The posterior spinal arteries, which supply the sensory tracts in the spinal cord, receive flow from …
the posterior and inferior cerebellar arteries, the vertebral arteries, and the posterior radicular arteries
Describe the vascularization of the anterior portion of the spinal cord
The anterior spinal artery, which supplies the motor tracts in the spinal cord, is formed by two branches of the intracranial portion of the vertebral arteries. The upper cervical segment of the spinal cord receives most of its blood flow from the vertebral arteries. The thoracic portion of the anterior spinal artery is supplied by the anterior radicular arteries (one or two cervical, two or three thoracic, and one or two lumbar). The largest of the radicular arteries is called
the great radicular artery (GRA) or the artery of Adamkiewicz (AKA). The AKA is the major blood supply to the lower two-thirds of the spinal cord. The segmental supplier of the AKA is variable (T5–L5) but is located between T9 and T12 in approximately 75% of cases. The variation in origin of the AKA explains why even infrarenal aortic aneurysm repair is associated with a 0.25% incidence of paraplegia.
Spinal cord perfusion pressure is defined as …
distal mean aortic pressure minus CSF pressure or central venous pressure, whichever is greatest
Autoregulation of spinal cord blood flow is similar to cerebral autoregulation, and blood flow is relatively
constant over the range of …
50 to 125 mm Hg
Describe pros and cons of CSF drainage during thoracoabdominal aorta repair
Pros:
CSF pressure often increases (by 10 to 15 mm Hg) with cross-clamping of the descending thoracic aorta. The increase in CSF pressure reduces spinal cord perfusion pressure and increases the likelihood of ischemic spinal cord injury.
Coselli and colleagues offered the strongest evidence supporting the efficacy of CSF drainage. They conducted a prospective, randomized clinical trial to evaluate the impact of CSF drainage on the incidence of spinal cord injury after Crawford type I and II TAA repair. CSF drainage resulted in an 80% reduction in the relative risk for a postoperative deficit. Nine patients in the control group (13%) had paraplegia or paraparesis versus only two patients in the CSF
drainage group (2.6%). Left heart bypass, moderate heparinization, permissive mild hypothermia, and reimplantation of patent intercostal and lumbar arteries were performed in both treatment groups. The target CSF pressure was 10 mm Hg.
Cons:
Potential complications include headache, meningitis, chronic CSF leakage, spinal or epidural hematoma, and subdural hematoma. The possibility of intraspinal pathologic processes should be considered in any patient with a postoperative lower extremity neurologic deficit.
A retrospective review of 230 patients who underwent TAA repair with CSF drainage reported eight subdural hematomas (3.5%).81 High-volume CSF drainage was identified as a risk factor for its occurrence. Six patients had subdural hematomas detected during hospitalization, with an associated mortality of 67%.
Hypothermia is probably the most reliable method of neuroprotection from ischemic injury. By reducing O2 requirements by approximately …% for each degree centigrade, a two-fold prolongation of tolerated cross-clamp time is achieved by cooling even to mild hypothermia (34°C)
5
Describe significant predictors of delayed neurologic deficit after thoracoabdominal aorta repair
Preoperative renal dysfunction, acute dissection, and extent type II TAA
At the present time, optimal renal protection during TAA surgery should rely on …
hypothermia, mannitol, and prevention of hypotension and hypoperfusion of the kidneys.
Describe the dilutional coagulopathy
Platelets deficient after approximately one blood volume of replacement develops during massive transfusion.
At between one and two blood volumes of replacement, coagulation factors are diluted to levels low enough to increase bleeding.
With the early use of fresh frozen plasma and platelets, severe coagulopathy often can be avoided
Contrast-induced nephropathy (CIN) is defined as …
renal function impairment associated with a baseline increase in serum creatinine concentration of 25% or more or an absolute increase of 0.3 to 0.5 mg/dL within 2 to 3 days of administration of IV contrast
Describe the types and management of endoleaks after EVAR
1) Type 1 endoleak:
The stent graft fails to accomplish a circumferential seal at the distal (IB) or the proximal (IA) positions, thereby demanding immediate treatment due to aneurysm sac systemic pressurization. If not treated promptly, it can result in either expansion of the aneurysm or even rupture.
Endoleaks are normally treated by balloon angioplasty of the proximal attachment site so that the desired seal is obtained through remodeling of the stent graft. The endoleak can also be bridged by covered extension of the native endograft. Embolization is another treatment option specifically when the space between the renal arteries and the endograft is not adequate. Fenestrated or branch graft extensions are also an alternative for more complex proximal endoleaks.
2) Type II endoleak:
The aneurysm sac undergoes reverse filling from the branch vessels through either lumbar or inferior mesenteric arteries. This can result in various anomalies such as aneurysm rupture, sac enlargement, and enhanced intrasac pressures. Type II endoleaks can be treated by transarterial embolization through the iliac arteries or retrograde embolization through the superior mesenteric or inferior mesenteric arteries. They can also be treated by translumbar computed tomography angiogram (CTA)-guided embolization
3) Type III endoleak
The stent graft undergoes a structural failure, thereby causing the blood flow to move into the aneurysm sac. These endoleaks occur either due to device failure such as detachment of modular graft components, a junctional leak, or due to erosion of fabric. They also require immediate intervention and treatment to avoid the risk of rapid expansion and rupture of aneurysm. These endoleaks are treated by inserting a new fabricated stent graft over the faulty position with angioplasty so that the desired seal is accomplished.
4) Type IV endoleak:
Graft porosity. It’s a rare problem, usually self-liited
5) Type V endoleak:
Aneurysm sac enlargement which is devoid of any demonstrable trace in the imaging procedures. No therapy indicated (AAA sac fluid drainage is contraindicated because it tends to reaccumulate
Explain the Postimplantation Syndrome after EVAR
PIS is a poorly understood phenomenon that could occur after endovascular aortic procedures and varies widely in incidence and clinical presentation. Possible explanations could be a sort of systemic inflammatory response syndrome (SIRS) in response to the instrumentation of the vascular endothelium or to the stent-graft
material. Clinical presentation could include a combination of fever, leukocytosis, thrombocytopenia, and coagulopathy. Treatment should be supportive, especially with antipyretics, platelets, or fresh frozen plasma transfusions to treat the coagulopathy
Anesthetic management of thoracic EVAR must facilitate precise deployment of stents at short proximal landing zones near the arch vessels. Deployment is complicated by the hydrodynamics of aortic blood flow that force the stent distally (windsock effect).
Depending on the proximity of the planned stent graft to the left ventricular outflow tract, transient … may be highly beneficial during deployment to limit stent migration. Various drugs have been used for this purpose, but … is usually the preferred technique
hypotension (systolic blood pressure of 60 mm Hg)
rapid ventricular pacing (RVP)
Why rapid ventricular pacing is usually the preferred technique to facilitate precise deployment of stents at short proximal landing zones near the arch vessels in a TEVAR procedure?
RVP is reported to produce more profound hypotension more quickly, and with shorter duration as compared to sodium nitroprusside. While adenosine has been used for transient asystole in the setting of TEVAR and intracranial procedures, an unpredictable duration of asystole and wide individual variation in dose requirement (0.3 to 41 mg/kg) have been reported. Unexpected return of left ventricular contractions can complicate stent deployment at a critical moment. Unlike pharmacologic techniques, the onset and duration of RVP can be controlled precisely
OBS.: The bulk of published data on RVP arises from the transcatheter aortic valve replacement (TAVR) literature, in which RVP is utilized during balloon valvuloplasty and valve deployment. Small studies have shown efficacy and safety of RVP for TEVAR, but deaths have been reported
The incidence of perioperative stroke in unselected patients, patients with asymptomatic carotid bruit, and patients with at least 50% carotid stenosis undergoing general anesthesia and surgery is approximately … respectively
0.1%, 1.0%, and 3.6%,
Patients with combined carotid stenosis and CAD requiring coronary revascularization represent somewhat of a management dilemma because it is often unclear which disease should be treated first.
Carotid revascularization is recommended before CABG (staged procedure) in patients with …
The optimal management of … carotid stenosis in patients undergoing CABG is unclear.
symptomatic carotid disease and bilateral severe asymptomatic carotid stenosis.
severe unilateral asymptomatic
The optimal preoperative assessment for patients undergoing carotid endarterectomy continues to be debated. Patients with recently symptomatic carotid disease present a particular challenge because …
strong evidence exists to support surgical intervention within 2 weeks after manifestation of symptoms, thus limiting the time available for evaluation and optimization of relevant comorbidities as well as the initiation of new medications
Management of arterial blood pressure during carotid endarterectomy
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 and prevent cerebral ischemia. In patients with contralateral internal carotid artery occlusion or severe stenosis, induced hypertension to approximately
10% to 20% above baseline is advocated during the period of carotid clamping when neurophysiologic monitoring is not used
Describe a distinct casue of bradycardia and hypotension during carotid endarterectomy and how it can be managed
Surgical manipulation of the carotid sinus with activation of the baroreceptor reflexes
OBS.: Cessation of surgical manipulation promptly restores the hemodynamics, and infiltration of the carotid bifurcation with 1% lidocaine usually prevents further episodes. Infiltration may, however, increase the incidence of both intraoperative and
postoperative hypertension
Regional and local anesthetic techniques for carotid endarterectomy have been in use for more than 50 years, and many centers consider them to be the techniques of choice. Regional anesthesia is accomplished by … .
Adequate anesthesia can be obtained with an …
blocking the C2 to C4 dermatomes by use of a superficial, intermediate, deep, or combined cervical plexus block
isolated superficial or intermediate cervical plexus block, likely as a result of spread of local anesthetic to the cervical nerve roots
A recent systematic review including over 10,000 cervical plexus blocks for carotid
endarterectomy found that the … block was associated with a higher serious complication rate related to the injecting needle compared with a … block (0.25% vs. 0%).
The conversion rate to general anesthesia was higher with the … (2.1% vs. 0.4%). No difference was found in the incidence of serious systemic complications between the blocks.
Although the incidence of serious complications from a cervical plexus block is infrequent, near-toxic levels of local anesthetic occurs in almost half of patients after superficial and deep cervical plexus block
deep (or combined)
superficial (or intermediate)
deep block
Advantages of Regional and local anesthesia for carotid endarterectomy
Allow continuous neurologic assessment of the awake patient, which is widely considered to be the most sensitive method for detecting inadequate cerebral perfusion and function. Awake monitoring reduces the need for shunting and
avoids the expense associated with indirect monitors of cerebral perfusion. Other advantages that have been reported include greater stability of blood pressure and decreased vasopressor requirements, reduced operative site bleeding, and reduced hospital costs
Potential disadvantages of local or regional anesthesia for carotid endarterectomy
Inability to use pharmacologic cerebral protection with anesthetics, patient panic or loss of cooperation, seizure or loss of consciousness with carotid clamping, and inadequate access to the airway should conversion to general anesthesia be necessary.
OBS.: Phrenic nerve paresis is common after cervical plexus block and is of little clinical consequence except in patients with severe COPD or contralateral diaphragmatic dysfunction
General anaesthesia versus local anaesthesia for carotid surgery (GALA): a multicentre, randomised controlled trial was a multicenter, randomized
controlled trial included 3526 patients with symptomatic or asymptomatic internal carotid stenosis from 95 medical centers in 24 countries. Patients were randomly assigned to carotid endarterectomy under general anesthesia (1753 patients) or local
anesthesia (1773 patients) between 1999 and 2007. The primary outcome was a composite of perioperative death, MI, and stroke (including retinal infarction). The main finding was that …
Anesthetic technique was not associated with a significant difference in secondary outcomes, including duration of surgery, duration of ICU stay, length of hospital stay, or quality of life at 1 month after surgery. Other outcomes, including cranial nerve injury (10.5% vs. 12.0%), wound hematoma (8.3% vs. 8.5%), wound hematoma
requiring reoperation (2.6% vs. 2.3%), and chest infection (2.0% vs. 1.9%) were similar between patients receiving general anesthesia and local anesthesia, respectively. O
anesthetic technique was not associated with a significant difference in the composite end point (4.8% for general vs. 4.5% for local)
The internal carotid artery stump pressure represents the …
back pressure resulting from collateral flow through the circle of Willis via the contralateral carotid artery and the vertebrobasilar system
Characteristic SSEP tracings (i.e., decrease in amplitude, increase in latency, or both) occur with decreased rCBF and are abolished in primates when flow decreases to less than … of brain tissue per minute
12 mL/100 g
The validity of SSEPs as an intraoperative monitor of cerebral ischemia during carotid endarterectomy has not been definitively established
T or F
T
With TCD, intraoperative embolization has been detected in more than …% of patients undergoing carotid endarterectomy. Most intraoperative emboli are characteristic of … and are not associated with adverse neurologic outcomes
90
air
Transcranial Doppler Ultrasonography (TCD) may provide useful information regarding shunt function, malfunction, and the incidence of emboli during shunt insertion. Embolization during carotid artery dissection may indicate … and the need for …
Embolization during dissection and wound closure is associated with …
plaque instability
early carotid artery clamping
operative stroke
Although the use of Transcranial Doppler Ultrasonography monitoring during carotid endarterectomy holds some promise, conclusive evidence demonstrating improved outcome has not been reported. Additionally, the high rate of technical failures significantly limits the clinical utility of this monitoring modality.
T or F
T
During carotid endarterectomy, … factors appear to be the major mechanism of perioperative neurologic complications and most occur in the … period.
It is generally accepted that most neurologic complications are related to…
thromboembolic (rather than hemodynamic)
postoperative
surgical technique
Hypertension is common in the postoperative period after carotid endarterectomy. Not surprisingly, patients with poorly controlled preoperative hypertension often have severe hypertension postoperatively. The causes are not well understood, but … is probably contributory.
…anesthesia is associated with less hypertension
surgical denervation of the carotid sinus baroreceptors
Regional
Describe the Postoperative cerebral hyperperfusion syndrome associated with carotid endarterectomy
It is an abrupt increase in blood flow with loss of autoregulation in the surgically reperfused brain and is manifested as headache, seizure, focal neurologic signs, brain edema, and possibly intracerebral hemorrhage. Unfortunately, little is actually known about the cause and management of this syndrome. Typically, this syndrome does not occur until several days after carotid endarterectomy. Patients with severe postoperative hypertension and severe preoperative internal carotid artery stenosis are believed to be at increased risk for this syndrome. However, more recent data do not corroborate this common belief and suggest that recent contralateral carotid endarterectomy may be predictive of cerebral hyperperfusion
Cranial and cervical nerve dysfunction after carotid endarterectomy is well documented in the literature. Although most injuries are transient, permanent injuries can lead to significant disability. Patients should be examined for injury to the … nerves shortly after …
recurrent laryngeal, superior laryngeal, hypoglossal, and marginal mandibular
extubation
A recent systematic review (Percutaneous transluminal balloon angioplasty and stenting for carotid artery stenosis - Cochrane Database Syst Rev. 2012) of randomized trials (16 trials involving 7572 patients) found that endovascular treatment (including balloon angioplasty or stenting) was associated with … compared with endarterectomy
Endovascular treatment was associated with lower risks for
an increased risk for periprocedural stroke or death (OBS.: Of note, the
increase in risk appeared to be limited to patients 70 years of age and
older)
MI, cranial nerve palsy, and access site hematomas
A recent, large retrospective study reported asystole in 4.9% of patients after carotid stenting. Asystole was more likely to occur in patients …
The administration of … before balloon inflation decreases the incidence of intraoperative bradycardia and cardiac morbidity in primary carotid stenting patients.
undergoing a right-sided procedure, in those with significant contralateral stenosis, and in those with a reduced left ventricular ejection fraction
prophylactic atropine
Describe the Transcarotid artery revascularization (TCAR) techqnique
It involves cannulating the carotid artery via a small supraclavicular incision with a flow-reversal circuit. After heparinization, one end of the circuit will be placed in the carotid artery proximal to the lesion, and the other will be placed in the femoral vein. The circuit incorporates a filter to capture any debris before reaching the venous system.
The proximal carotid artery is then clamped, and blood flows in reverse from the head, through the carotid artery and into the flowreversal circuit before passing into the femoral vein. This flow reversal prevents the migration of micro- and macro-emboli into the cerebral circulation. Instead, emboli are filtered by the flow-reversal circuit before returning the blood flow to the venous circulation. The carotid artery is then stented and the arteriotomy is closed
ROADSTER 1, a prospective, single-arm, multicenter clinical trial, evaluating TCAR and the use of the transcarotid neuroprotective system showed a 30-day stroke rate of …%.
The CREST trial previously demonstrated a stroke rate of …% for transfemoral carotid artery stenting and 2.3% for carotid endarterectomy.
ROADSTER 2 looked to examine the technical success rate in new operators of TCAR and had 1.9% stroke rate in the intent-to-treat population and 0.6% stroke rate in the perprotocol population.
Thus TCAR has the advantages of lower stroke risk than TF-CAS and lower major adverse cardiac events (MACE) than carotid endarterectomy (CEA).
1.4
4.1
The recommended procedural systemic blood pressure during transcarotid artery revascularization is … mm Hg, keeping in mind that blood pressure goals are also dependent on the patient’s baseline
140–160
The Rivaroxaban for the Prevention of Major Cardiovascular Events in Coronary or Peripheral Artery Disease (COMPASS) trial randomly assigned 27,395 participants with stable atherosclerotic vascular disease to receive rivaroxaban (a direct factor Xa inhibitor) (2.5 mg twice a day) plus aspirin (100 mg daily), rivaroxaban alone (5 mg twice a day), or aspirin alone (100 mg daily).200 The primary outcome was a composite of cardiovascular death, stroke, or myocardial infarction. The trial was stopped because of …
Total mortality, CAD mortality, and cardiovascular mortality were …
an overwhelming efficacy
lowered by 20%.
The COMPASS trial provided strong evidence for an alternative to clopidogrel when it comes to patients who are pharmacogenetically resistant to it (slow responders) due to genetic variations in the … enzyme responsible for its activation in the liver. It is assumed that …% of
patients may be pharmacogenetically resistant to clopidogrel.
CYP2C19
30
