PERIPHERAL ARTERIALOCCLUSIVE DISEASE
Arterial insufficiency of the extremities is usually found in indi-viduals older than 50 years of age, most often in men. The legs are most frequently affected; however, the upper extremities may be involved. The age of onset and the severity are influenced by the type and number of atherosclerotic risk factors (Chart 31-4). In peripheral arterial disease, obstructive lesions are predomi-nantly confined to segments of the arterial system extending from the aorta below the renal arteries to the popliteal artery (Fig. 31-9). However, distal occlusive disease is frequently seen in patients with diabetes mellitus and in elderly patients.
The hallmark is intermittent claudication. This pain may be de-scribed as aching, cramping, fatigue, or weakness that is consis-tently reproduced with the same degree of exercise or activity and relieved with rest. The pain commonly occurs in muscle groups one joint level below the stenosis or occlusion. As the disease progresses, the patient may have a decreased ability to walk the same distance or may notice increased pain with am-bulation. When the arterial insufficiency becomes severe, the patient begins to have rest pain. This pain is associated with critical ischemia of the distal extremity and is persistent, aching, or boring; it may be so excruciating that it is unrelieved by opi-oids. Ischemic rest pain is usually worse at night and often wakes the patient. Elevating the extremity or placing it in a hor-izontal position increases the pain, whereas placing the extrem-ity in a dependent position reduces the pain. In bed, some patients sleep with the affected leg hanging over the side of the bed. Some patients sleep in a reclining chair in an attempt to re-lieve the pain.
A sensation of coldness or numbness in the extremities may ac-company intermittent claudication and is a result of the reduced arterial flow. When the extremity is examined, it may feel cool to the touch and look pale when elevated or ruddy and cyanotic when placed in a dependent position. Skin and nail changes, ulcerations, gangrene, and muscle atrophy may be evident. Bruits may be auscultated with a stethoscope; a bruit is the sound produced by turbulent blood flow through an irregular, tortuous, stenotic vessel or through a dilated segment of the vessel (aneurysm). Peripheral pulses may be diminished or absent.
Examining the peripheral pulses is an important part of assess-ing arterial occlusive disease. Unequal pulses between extremities or the absence of a normally palpable pulse is a sign of peripheral arterial disease. The femoral pulse in the groin and the posterior tibial pulse beside the medial malleolus are most easily palpated. The popliteal pulse is sometimes difficult to palpate; the location of the dorsalis pedis artery on the dorsum of the foot varies and is normally absent in about 7% of the population.
The presence, location, and extent of arterial occlusive disease are determined by a careful history of the symptoms and by phys-ical examination. The color and temperature of the extremity are noted and the pulses palpated. The nails may be thickened and opaque, and the skin may be shiny, atrophic, and dry, with sparse hair growth. The assessment includes comparison of the right and left extremities.
The diagnosis of peripheral arterial occlusive disease may be made using CW Doppler and ankle-brachial indices (ABIs), tread-mill testing for claudication, duplex ultrasonography, or other imaging studies previously described.
Generally, patients feel better with some type of exercise pro-gram. If this program is combined with weight reduction and ces-sation of tobacco use, patients often can improve their activity tolerance. Patients should not be promised that their symptoms will be relieved if they stop tobacco use, because claudication may persist, and they may lose their motivation to stop using tobacco.
Various medications are prescribed to treat the symptoms of pe-ripheral arterial disease. Pentoxifylline (Trental) increases ery-throcyte flexibility and reduces blood viscosity, and it is therefore thought to improve the supply of oxygenated blood to the mus-cle. Cilostazol (Pletal) works by inhibiting platelet aggregation, inhibiting smooth muscle cell proliferation, and increasing vaso-dilation. Antiplatelet aggregating agents such as aspirin, ticlopi-dine (Ticlid), and clopidogrel (Plavix) are thought to improve circulation throughout diseased arteries or prevent intimal hyper-plasia leading to stenosis.
In most patients, when intermittent claudication becomes severe and disabling or when the limb is at risk for amputation because of tissue loss, vascular grafting or endarterectomy is the treatment of choice. The choice of the surgical procedure depends on the degree and location of the stenosis or occlusion. Other important considerations are the overall health of the patient and the length of the procedure that can be tolerated. It is sometimes necessary to provide the palliative therapy of primary amputation rather than an arterial bypass. If endarterectomy is performed, an inci-sion is made into the artery, and the atheromatous obstruction is removed. The artery is then sutured closed to restore vascular in-tegrity (Fig. 31-10).
Bypass grafts are performed to reroute the blood flow around the stenosis or occlusion. Before bypass grafting, the surgeon de-termines where the distal anastomosis (site where the vessels are surgically joined) will be placed. The distal outflow vessel must be at least 50% patent for the graft to remain patent. A higher by-pass graft patency rate is associated with keeping the length of the bypass as short as possible.
If the atherosclerotic occlusion is below the inguinal ligament in the superficial femoral artery, the surgical procedure of choice is the femoral-to-popliteal graft. This procedure is further classified as above-knee and below-knee grafts, referring to the location of the distal anastomosis.
Lower leg or ankle vessels with occlusions may also require grafts. Occasionally, the entire popliteal artery is occluded, and there is only collateral circulation. The distal anastomosis may be made onto any of the tibial arteries (posterior tibial, anterior tib-ial, or peroneal arteries) or the dorsalis pedis or plantar artery.
The distal anastomosis site is determined by the ease of exposure of the vessel in surgery and by which vessel provides the best flow to the distal limb. These grafts require the use of native vein to en-sure patency. Native vein is autologous vein (the patient’s own vein). The greater or lesser saphenous vein or a combination of one of the saphenous veins and an upper extremity vein such as the cephalic vein are used to meet the required length.
How long the graft remains patent is determined by several fac-tors, including the size of the graft, graft location, and develop-ment of intimal hyperplasia at anastomosis sites. Bypass grafts may be synthetic or autologous vein. Several synthetic materials are available for use as a peripheral bypass graft: woven or knitted Dacron, expanded polytetrafluoroethylene (ePTFE, such as Gore-Tex or Impra), collagen-impregnated, and umbilical vein. Infec-tion is a problem that threatens survival of the graft and almost always requires removal of the graft.
If a vein graft is the surgical choice, care must be taken in the operating room not to damage the vein after harvesting (removing the vein from the patient’s body). The vein is occluded at one end and inflated with a heparinized solution to check for leakage and competency. When this is done, the graft is placed in a heparinized solution to keep it from becoming dry and brittle.
The primary objective in the postoperative management of patients who have undergone vascular procedures is to maintain adequate circulation through the arterial repair. Pulses, Doppler assessment, color and temperature of the extremity, capillary refill, and sensory and motor function of the affected extremities are checked, com-pared with those of the other extremity, and recorded every hour for the first 8 hours and then every 2 hours for 24 hours. Doppler eval-uation of the vessels distal to the bypass graft should be performed for all postoperative vascular patients, because it is more sensitive than palpation for pulses. The ABI is monitored at least once every 8 hours for the first 24 hours and then once each day until discharge (not usually assessed for pedal artery bypasses). An adequate circu-lating blood volume should be established and maintained. Disap-pearance of a pulse that was present may indicate thrombotic occlusion of the graft; the surgeon is immediately notified.
Continuous monitoring of urine output (more than 30 mL/hour), central venous pressure, mental status, and pulse rate and volume permit early recognition and treatment of fluid imbalances. Bleed-ing can result from the heparin administered during surgery or from an anastomotic leak. A hematoma may form as well.
Leg crossing and prolonged extremity dependency are avoided to prevent thrombosis. Edema is a normal postoperative finding; however, elevating the extremities and encouraging the patient to exercise the extremities while in bed reduces edema. Elastic com-pression stockings may be prescribed for some patients, but care must be taken to avoid compressing distal vessel bypass grafts. Se-vere edema of the extremity, pain, and decreased sensation of toes or fingers can be an indication of compartment syndrome.
Discharge planning includes assessing the patient’s ability to manage independently. The nurse determines if the patient has a network of family and friends to assist with activities of daily liv-ing. The patient may need to be encouraged to make the lifestyle changes necessary with a chronic disease, including pain man-agement and modifications in diet, activity, and hygiene (skin care). The nurse ensures that the patient has the knowledge and ability to assess for any postoperative complications such as in-fection, occlusion of the artery or graft, and decreased blood flow. The nurse assists the patient in developing a plan to stop using tobacco. The Plan of Nursing Care describes nursing care for patients with peripheral vascular disease.
Arterial occlusions occur less frequently in the upper extremities (arms) than in the legs and cause less severe symptoms because the collateral circulation is significantly better in the arms. The arms also have less muscle mass and are not subjected to the work-load of the legs.
Stenosis and occlusions in the upper extremity result from ather-osclerosis or trauma. The stenosis usually occurs at the origin of the vessel proximal to the vertebral artery, setting up the vertebral artery as the major contributor of flow. The patient may develop a “subclavian steal” syndrome characterized by reverse flow in the vertebral and basilar artery to provide blood flow to the arm. This syndrome may cause vertebrobasilar (cerebral) symptoms. Most patients are asymptomatic; however, some report vertigo, ataxia, syncope, or bilateral visual changes.
The patient typically complains of arm fatigue and pain with exercise (forearm claudication) and inability to hold or grasp ob-jects (eg, painting, combing hair, placing objects on shelves above the head). Some even notice difficulties driving.
Assessment findings include coolness and pallor of the affected ex-tremity, decreased capillary refill, and a difference in arm blood pressures of more than 20 mm Hg. Noninvasive studies performed to evaluate for upper extremity arterial occlusions include upper and forearm blood pressure determinations and duplex ultrasonography to identify the anatomic location of the lesion and to evaluate the hemodynamics of the blood flow. Transcranial Doppler evaluation is performed to evaluate the intracranial circulation and to detect any siphoning of blood flow from the posterior circulation to pro-vide blood flow to the affected arm. If a surgical or interventional procedure is planned, an arteriogram may be necessary.
If a short, focal lesion is identified in an upper extremity artery, a PTA may be performed. If the lesion involves the subclavian artery with documented siphoning of blood flow from the intracranial cir-culation, several surgical procedures are available: carotid–to–sub-clavian artery bypass, axillary–to–axillary artery bypass, and autogenous reimplantation of the subclavian to the carotid artery.
Nursing assessment involves bilateral comparison of upper arm blood pressures (obtained by stethoscope and Doppler); radial, ulnar, and brachial pulses; motor and sensory function; tempera-ture; color changes; and capillary refill every 2 hours. Disappear-ance of a pulse or Doppler flow that had been present may indicate an acute occlusion of the vessel, and the physician is notified immediately.
After surgery, the arm is kept at heart level or elevated, with the fingers at the highest level. Pulses are monitored with Doppler assessment of the arterial flow every hour for 8 hours and then every 2 hours for 24 hours. Blood pressure (obtained by stetho-scope and Doppler) is also assessed every hour for 8 hours and then every 2 hours for 24 hours. Motor and sensory function, warmth, color, and capillary refill are monitored with each arte-rial flow (pulse) assessment.
Discharge planning includes assessing the patient’s ability to manage independently. The nurse determines whether the pa-tient has a network of family and friends to assist with activities of daily living. The patient may need to be encouraged to make the lifestyle changes necessary for a chronic disease, including pain management and modifications in diet, activity, and hygiene(skin care). The nurse ensures that the patient has the knowledge and ability to assess for any postoperative complications such as infection, reocclusion of the artery or occlusion of the graft, and decreased blood flow. The patient is assisted in developing a plan to stop using tobacco. The Plan of Nursing Care describes nursing care for patients with peripheral vascular disease.
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