Cardiac, Thoracic, and Vascular: Vascular Surgery Flashcards

Question

Carotid Artery Disease: Anatomy (Part 1)

Answer 1

* The common carotid artery on the right arises from the brachiocephalic artery, and on the left, from the aorta. The common carotid then bifurcates into internal and external branches. The internal carotid gives off the ophthalmic artery before continuing to the circle of Willis to supply the brain. The area around the bifurcation is clearly “high-rent” terri- tory, which contains a number of vital structures which can be injured during surgery. The marginal mandibular branch of the facial nerve lies deep and inferior to the horizontal ramus of the mandible. Injury to this nerve during dissection results in lower lip paralysis. Branches of the cervical plexus, including the greater auricular nerve, may be at the cranial aspect of the incision and should be avoided to pre- serve sensation to the ear and the angle of the mandible.

Answer 2

* Posterolateral to the carotid artery in the carotid sheath lies the vagus nerve. Injury results in vocal cord paralysis. One or two centimeters above the carotid bifurcation is the hypoglossal nerve; injury results in dysphagia and tongue deviation. In contrast, the ansa cervicalis, which courses inferiorly from the hypoglossal to innervate the strap muscles, can be sacrificed as needed for exposure. Laterally and deep to the carotid artery lies the jugular vein, a branch of which, the facial vein, is generally divided to facilitate exposure of the carotid.

Answer 3

* Symptoms are the result of atherosclerosis. Mechanisms of morbidity include plaque rupture, ulceration, hem- orrhage, thrombosis, and low flow states. Because of the rich collateralization of the cerebral circulation through the circle of Willis, thrombosis and low flow states may be asymptomatic.

Answer 4

* Atherosclerotic occlusive disease of the carotid artery is a major cause of stroke. In the United States, 400,000 people are hospitalized for stroke each year, and cerebrovascular events are the third most common cause of death. The incidence of stroke increases with age. Other risk factors include hypertension, diabetes, smoking, and hypercholes- terolemia. Markers for carotid disease include evi- dence of other atherosclerotic disease and prior neu- rologic events.

Answer 5

* Patients often relate previous neurologic events, including focal motor deficits, weakness, clumsiness, and expressive or cognitive aphasia. These could occur as a transient ischemic attack, which resolves in 24 hours; a reversible ischemic neurologic deficit, which resolves in greater than 24 hours; or a fixed neurologic deficit. One characteristic presentation for carotid disease is amaurosis fugax, or transient monocular blindness, usually described as a shade being pulled down in front of the patient’s eye. This is due to occlusion of a branch of the ophthalmic artery.

Answer 6

* Patients may exhibit a fixed neurologic deficit. Hollen- horst plaques on retinal examination are evidence of previous emboli. A carotid bruit is evidence of turbu- lence in carotid blood flow, but the presence of a bruit does not unequivocally translate into a hemodynam- ically significant lesion, and the absence of a bruit does not unequivocally indicate the absence of signif- icant disease.

Answer 7

* Carotid duplex scanning is both sensitive and specific for carotid disease. Conventional or magnetic reso- nance angiography is more accurate for assessing the degree of stenosis.

Answer 8

* Treatment depends on the history, degree of stenosis, and characteristics of the plaque. Antiplatelet therapy with aspirin is effective in preventing neurologic events. When dealing with an acute event, heparin should be considered after head CT determines that the event is not hemorrhagic. Indications for carotid endarterectomy are controversial. Results of two large randomized controlled trials—the Asymptomatic Carotid Atherosclerosis Study (ACAS) and the North American Symptomatic Carotid Endarterectomy Trial (NASCET)—suggest surgery is best reserved for the following patients: those with 75% stenosis, those with 70% stenosis and symptoms, those with bilateral disease and symptoms, or those with 50% stenosis and recurring transient ischemic attacks despite aspirin therapy. The role of stenting is controversial. Despite the Systolic and Pulse Pressure Hemodynamic Impro- vement by Restoring Elasticity (SAPPHIRE) trial, which suggested stenting is not inferior to endarterectomy in high-risk patients, there were problems with the study design, and the procedure is still being evaluated as an alternative to open surgery, which has low morbidity and mortality in large centers.

Answer 9

* Perioperative monitoring is surgeon-dependent. Techniques include keeping the patient awake through the procedure, using local or regional anesthesia, using continuous electroencephalogram monitoring, or using no monitoring at all. Administration of intravenous antibiotics, usually a first-generation cephalosporin, precedes the incision. After site verification, the neck is extended, and an incision is made over the anterior border of the sternocleidomastoid muscle. Dissection continues through the platysma and along the stern- ocleidomastoid. Ligation of the facial vein allows com- plete exposure of the carotid, which lies just medial to the jugular vein. Care is taken not to injure the hypoglossal nerve at the superior aspect of the dissec- tion or the spinal accessory nerve (Fig. 16-3). Proximal and distal control of the carotid is obtained, the patient is heparinized, and the artery is opened after clamps are applied. Use of a stent may provide cerebral pro- tection. Plaque is carefully dissected out of the artery, and the artery is usually closed with a patch.

Answer 10

* Acute and chronic mesenteric vascular disease includes disease of the celiac axis, which is the arterial supply to the liver, spleen, pancreas, and stomach; the superior mesenteric artery, which supplies the pancreas, small bowel, and proximal colon; and inferior mesenteric artery, which supplies the distal colon and rectum. In addition, thrombosis of the superior mesenteric vein can cause visceral ischemia. * The celiac axis arises from the aorta below the crus of the diaphragm. It travels ventrally and is surrounded by a dense network of nerves and connective tissue. After a short distance, it gives rise to the splenic artery, which travels to the left behind the pancreas to the spleen; the common hepatic artery, which trav- els to the right toward the hepatic hilum; and the smaller left gastric artery, which travels cranial and toward the left. The superior mesenteric artery courses below the pancreas and slightly to the right toward the mesentery of the bowel. The inferior mesenteric artery arises below the renal arteries and above the aortic bifurcation and travels to the left toward the bowel. The superior mesenteric vein runs above and to the right of the superior mesenteric artery. Its location can be determined by palpating the artery at the root of the mesentery in thin patients. The vein then joins the splenic and inferior mesenteric veins to form the portal vein.

Answer 11

* Acute ischemia is caused by embolization, thrombo- sis, nonocclusive ischemia, and mesenteric vein throm- bosis. Embolization is associated with atherosclerotic disease or mural cardiac thrombus. Acute thrombosis is associated with atherosclerosis and hypercoagulable states. Vasopressor agents can produce acute ischemia. Chronic ischemia usually requires severe atheroscle- rotic disease in at least two major arterial trunks among the superior and inferior mesenteric arteries and the celiac axis, because of the extensive collateralization.

Answer 12

* he incidence of acute mesenteric ischemia is estimated at one in 1,000 hospital admissions, and mortality is greater than 50%. Prevalence of chronic ischemia increases with age, and risk factors include hypertension, smoking, hypercholesterolemia, and diabetes.

Answer 13

* Patients with acute ischemia may have a history of previous embolic events, atrial fibrillation, or conges- tive failure. Abdominal pain is usually sudden in onset and is severe, with diarrhea or vomiting. History in chronic mesenteric ischemia usually reveals crampy abdominal pain after eating. This results in decreased oral intake and weight loss. Nausea, vomiting, consti- pation, or diarrhea may occur. The disease can be mis- taken for malignant disease or cholelithiasis.

Answer 14

* In episodes of acute ischemia, the classic finding is “pain out of proportion to physical examination.” The abdomen may be distended. Rectal examination often reveals guaiac-positive stool. Atrial fibrillation may be present. Physical findings in chronic ischemia include abdominal bruits, guaiac-positive stool, and evidence of peripheral vascular disease or coronary artery disease.

Answer 15

* In acute ischemia, there could be an elevated white blood cell count, metabolic acidosis, or an elevated hematocrit as fluid is sequestered in the infarcting bowel. Abdominal radiographs are often normal in the early phase of the disease, but as the intestine becomes edematous, “thumbprinting” of the bowel wall occurs. Evaluation in chronic ischemia includes selective visceral angiography to identify the site of the lesion.

Answer 16

* Once the diagnosis of acute ischemia is made, laparot- omy with examination and resection of any infarcted bowel should be considered. In selected cases, angiog- raphy can be therapeutic, as well as diagnostic, with catheter-based therapies. Aggressive surgical interven- tion should not be delayed if there is evidence sugges- tive of dead bowel. Despite aggressive intervention, mortality is extremely high. For chronic ischemia, angiography can define the lesion and allow considera- tion of surgical options. Acute mesenteric vein throm- bosis is treated with anticoagulation and laparotomy if necrotic bowel is suspected.

Answer 17

* Lesions may occur in the iliac, common and superficial femoral, popliteal, peroneal, anterior tibial, and poste- rior tibial arteries. The common iliac arteries arise at approximately the level of the umbilicus. They course in the retroperitoneal space and give rise to the inter- nal iliac artery, which runs to the pelvis, and the exter- nal, which becomes the femoral artery in the femoral canal as it passes under the inguinal ligament. It enters the adductor canal, below the Sartorius, and continues through the adductor hiatus, where is becomes the popliteal artery. Below the knee, the popliteal artery branches into the anterior tibial, the posterior tibial, and dorsalis pedis arteries, which supply the distal leg. In general, of the three vessels that supply the distal ankle and foot, a single direct arterial supply is ade- quate to prevent limb loss and rest pain.

Answer 18

* In acute disease, the most common cause is an embolus that causes a sudden decrease in blood flow. The most common sources are the aorta and the heart. Rarer causes include acute arterial thrombosis, acute venous thrombosis, and arterial spasm. In chronic disease, pro- gressive atherosclerotic disease causes narrowing of the arterial lumen and decreased blood flow. Pain occurs as decreased blood flow is unable to meet the metabolic and waste-removal demand of the tissue.

Answer 19

* Acute disease occurs in patients with cardiac throm- bus, atrial fibrillation, or atherosclerosis. Risk factors for chronic disease include atherosclerosis, smoking, diabetes, hypertension, and advanced age.

Answer 20

* Acute ischemia causes sudden and severe lower- extremity pain and paresthesias. Patients with chronic ischemia typically present with claudication, defined as reproducible pain on exercise relieved by rest. The site of claudication provides a clue to the level of dis- ease. Buttock claudication usually indicates aortoiliac disease, whereas calf claudication suggests femoral atherosclerosis. Pain at rest is indicative of severe dis- ease and a threatened limb. Slow or nonhealing ulcers may be present.

Answer 21

* In acute disease, the patient may exhibit pulselessness, pallor, and poikilothermia (coolness). Taken together with pain and paresthesia, these form the five P’s of acute vascular compromise (Fig. 16-4). In chronic disease, the lower extremity may reveal loss of hair, pallor on elevation, rubor on placing the extremity in a dependent position, wasting of musculature, thick nails, and thin skin. The extremity may be cool to the touch, and pulses may be diminished or absent. Ulcers or frank necrosis may be present.

Answer 22

* Angiography is necessary in cases of acute ischemia to identify the lesion. Evaluation for chronic ischemia includes Doppler flow measurement of distal pulses. The normal signal is triphasic; as disease progresses, the signal becomes biphasic, monophasic, and then absent. Ankle-brachial indices are calculated as the systolic blood pressure at the ankle divided by the systolic pressure in the brachial artery. A value of less than 0.5 is indicative of significant disease (Table 16-1). Arteriography is the gold standard for defining the level and extent of disease and for planning surgery.

Answer 23

* Acute ischemic embolus can be treated with heparin, thrombolysis, or embolectomy. For chronic ischemia, patients with claudication have a low rate of limb loss, and initial therapy is based on smoking cessation and a graded exercise program. Success rates with non- operative therapy are good. In patients with disabling claudication, threatened limbs, nonhealing ulcers, or gangrene, angioplasty or revascularization should be considered (Table 16-2). It is always prudent to con- sider amputation in selected patients with long-standing acute ischemia or chronic ischemia, though this decision is often a difficult one and requires experience and care- ful discussions with the patient.

Answer 24

* Patients usually have concurrent coronary artery dis- ease, and preoperative evaluation and intraoperative beta blockade should be considered. The entire leg is usually prepped. Intravenous antibiotics are often a first-generation cephalosporin, and central monitor- ing should be considered. The most common tech- niques for anesthesia include general and regional. If the proximal vessels are open, inflow is usually from the femoral artery, which is dissected via an infrain- guinal incision directly over the artery. If the target is the popliteal, it is isolated via an incision over the medial aspect of the knee, at the level where the out- flow will be targeted. If the target is the dorsalis pedis, tibialis anterior, or peroneal, the incision is made directly over the target. Above-knee popliteal recon- struction can be accomplished with synthetic grafts, but infrapopliteal reconstructions should use either in situ or reversed saphenous vein.

Answer 25

* First-line therapy for patients with deep venous thrombosis or pulmonary embolism is systemic anti- coagulation. In patients for whom this therapy is con- traindicated (e.g., patients requiring a planned major surgery, those with active bleeding, or those facing significant complication of anticoagulation), filter placement in the inferior vena cava may decrease the short-term risk of pulmonary embolism. The use of filters, though common, is generally not well sup- ported by randomized controlled trials. They have not been shown to decrease mortality and are associ- ated with significant complications, including inferior vena cava thrombosis, recurrent deep venous throm- bosis, and postphlebitic syndrome. Recently, removable filters increasingly are being used to try to decrease the risk of long-term complications, but their use is still being studied.

Answer 26

* This is an extremely common lesion, affecting up to 15% of men and 25% of women. Over time, the pressure of gravity in the lower extremity may cause enlargement of the veins in the leg as valves fail. In most cases, the lesions are of cosmetic concern only, though they can become large and painful and cause ulcers. In deep veins this can lead to venous thrombosis. Treatment options include scle- rotherapy, laser or catheter-based ablation, and vein stripping.

Answer 27

* Aneurysms and dissections can be rapidly fatal. * Repair via open operation or stent graft should be considered for asymptomatic aneurysms with diameter \>4 or 5 cm. * Symptomatic aneurysms or dissections require emergency diagnosis and treatment. * Dissections that involve the ascending aorta usually require surgery, whereas dissections that involve the descending aorta are best managed medically. * Carotid artery disease is a major cause of stroke in the United States. * Indications for operation include 75% stenosis, 70% stenosis and symptoms, bilateral disease and symp- toms, or \>50% stenosis and recurring transient ischemic attacks despite aspirin therapy. * Stenting is an option for selected patients. * Patients with acute mesenteric ischemia present with “pain out of proportion to examination,” and amechanism for embolic disease is usually present. * Chronic mesenteric ischemia results in weight loss and abdominal pain and is frequently mistaken for malignant disease. * Acute peripheral embolus is marked by the five P’s: pulselessness, pallor, poikilothermia, pain, and paresthesia. * Symptoms of chronic peripheral vascular disease usually follow a well-defined progression. * Operation should be considered only in patients with severe chronic peripheral vascular disease.