Primary-Care Interventions for the Population at Risk for Amputation

Abstract

The care of patients at risk for amputation includes the identification of at-risk patients, appropriate follow-up and treatment, and the anticipation of possible complications. Education and long-term follow-up are vital for management of the patient at risk for amputation.

Very little information is available on risk factors for and potential causes of amputation.[1] Certain risk factors have been identified in a number of case series.[2] This information is limited because the patients have been referred for various indications and procedures, and control groups have not been assembled. The identification and treatment of such risk factors for amputation are very important.[1]

Peripheral arterial vascular disease affects 5% of people in their sixth decade and 20% of people older than 70 years of age.[3] The most frequent presentation of arterial occlusive disease is intermittent claudication. Limb-threatening ischemia will develop in 2% to 5% of patients with intermittent claudication monitored for 10 years.[4] Diabetes is associated with more than 50% of the 120,000 lower-limb amputations performed annually in the United States for indications other than trauma.[1] In addition, there is an overall reduction of 10 years in life expectancy among patients with peripheral vascular disease. Mortality is due predominantly to coronary artery disease and complications of diabetes mellitus. The mortality rate in patients with peripheral vascular disease is 20% to 30% at 5 years after diagnosis, 40% to 72% at 10 years, and 74% at 15 years. About 75% of the deaths are caused by cardiovascular events.[5]

There are several causes of arterial occlusive disease. The most common is atherosclerosis obliterans. Other disease processes include thromboangiitis obliterans (Buerger’s disease), Mönckeberg’s medial calcific sclerosis, vasospastic disorders (Raynaud’s phenomenon, livido reticularis, and acrocyanosis), thrombosis, embolism, dissection, vasculitis, and fibromuscular dysplasia.

Risk factors for atherosclerotic disease include smoking, diabetes mellitus, hypertension, hyperlipidemia, abnormalities of hemostatic function and blood flow, abnormalities of homocysteine metabolism, aging, and genetic predisposition. Inactivity and obesity have also been associated with cardiovascular disease.

Who Is at Risk?

Chronic arterial occlusive disease is usually diagnosed from the history and physical examination. Symptoms develop slowly and are progressive. The most common symptom is intermittent claudication. Lower-extremity claudication has two diagnostic clinical features: 1) it is reproduced with a consistent level of exercise from one occasion to the next; and 2) it completely resolves within minutes after the exercise has been discontinued.[6] Patients may adapt their behavior and decrease their level of physical activity so that they do not experience claudication pain. The site of claudication is a rough indicator of the level of occlusion.[7] Patients with occlusion at or above the ankle can present with claudication in the arch of the foot. Calf claudication suggests occlusion at or above the calf. Patients with isolated aortoiliac disease generally present with buttock pain or sexual dysfunction.

The most commonly identified pathway to amputation includes minor trauma, cutaneous ulceration, and wound-healing failure. This sequence of events may be associated with infection and gangrene. In a series of 80 amputations, 69 were preceded by minor cutaneous injury. The definition of causal pathways that predispose to diabetic limb or ischemic peripheral vascular limb amputation suggests practical interventions that may be helpful in avoiding limb loss.[1]

How to Identify At-Risk Patients

Patients at risk for amputation can be identified by history, physical examination, and vascular testing. The most common causal pathways to amputation have been identified; however, supportive clinical findings and laboratory evidence will confirm the increased risk for amputation.

Evaluation includes palpation of lower-extremity (femoral, popliteal, dorsalis pedis, and posterior tibial) pulses and auscultation for bruits. Doppler devices may be necessary to detect circulation in limbs with advanced disease. Clinical findings of ischemia can include trophic changes, dependent rubor, paresthesia (which may be partially or completely relieved with dependency), cutaneous ulceration, and gangrene.

Noninvasive and invasive laboratory testing may be performed to support the clinical suspicion of peripheral vascular disease. Noninvasive testing may be used to determine the level of ischemia and the potential for healing and to provide a baseline for future testing. Measurement of resting ankle pressure is the most common noninvasive study performed on patients with suspected vascular disease. The ankle-brachial blood pressures are analyzed, with values greater than 0.9 considered normal, 0.8 to 0.9 mild, 0.5 to 0.8 moderate, and less than 0.5 severe.[8]

Exercise-induced symptoms may require an exercise assessment. In patients with mild symptoms of claudication, the ankle-brachial index may be normal at rest but reduced after exercise. At rest, the vascular resistance of the leg is relatively high, and the flow through a stenotic lesion can be sufficient to maintain normal distal pressures. After exercise, the vascular resistance is lower, and the blood flow through the stenosis may not be sufficient to keep the distal pressure from decreasing.[9] Postexercise ankle-brachial indices are determined by having the patient walk on a treadmill for 5 minutes at 2 mph at a 10% to 12% grade.[10]

Magnetic resonance imaging—another noninvasive procedure—may yield images of second- and third-generation vessels of sufficient quality to allow the diagnosis of peripheral vascular disease.[11]

Invasive studies remain the most accurate way to evaluate infrainguinal arterial occlusive disease. If surgery is anticipated, arteriography is usually needed to determine the length of the arterial occlusion, level of distal reconstruction, and patency of the plantar arch.

Functional status measures are important to assess the effects of the treatment program. Questionnaires have been developed to evaluate the effects of a community-based walking program and quality of life.[12] These questionnaires are limited in that they are self-assessment measures and subject to bias. Given their cost and complexity, they are used predominantly in research rather than clinical settings.

The complex nature of peripheral vascular disease and the multisystem involvement that often accompanies it necessitate testing for associated diseases. Cardiovascular, renal, and pulmonary conditions must be identified, especially when surgery is contemplated. The prevalence of serious coronary artery disease ranges from 37% to 78% in patients undergoing an operation for peripheral vascular disease.[13] Because of the prevalence of occult coronary artery disease, exercise testing is recommended before patients with diabetes mellitus begin an exercise-conditioning program. Pharmacologic infusions of agents such as dopamine, dipyridamole, or adenosine in combination with cardiac imaging can be performed for cardiac evaluation of peripheral vascular disease patients at rest.

Interventions That May Be Performed

Therapeutic success is most likely to occur with an educated patient and family.[14,15] The strong impact of education on patients at risk for amputation should not be ignored. A prospective randomized study evaluating the influence of a simple education program on the incidence of lower-extremity amputation in diabetic patients showed a significantly reduced rate of amputation and ulceration in the educated, as compared with the uneducated, group. This study demonstrated the effectiveness of a simple education program on the medical course of a group of diabetic patients at risk for amputation.[14] Vascular medicine and wound-care centers have been shown to be highly effective in educating and managing patients with peripheral vascular disease at risk for amputation.[15] The education sessions should explain the diffuse and progressive nature of atherosclerosis, the importance of controlling risk factors, and methods of protecting the ischemic limb. The goal is to develop an effective therapy program that prevents progression of the disease process and possibly promotes regression of the existing lesions. The correct diagnosis and cause of the underlying disease process must be identified prior to proceeding with treatment. Controllable risk factors such as smoking, diabetes, hyperlipidemia, hypertension, and gross obesity should be approached with appropriate pharmacologic measures, dietary measures, or behavior modifications. The medical treatment of patients with arterial occlusive disease is directed at intensive risk-factor modification to decrease cardiovascular morbidity and mortality. A second treatment goal is to improve exercise performance and functional capacity.[16] Candidates for a structured vascular rehabilitation program include individuals with documented peripheral arterial insufficiency and 1) intermittent claudication, 2) decreased ability to perform desired activities (secondary to diminished arterial perfusion), or 3) recent surgical revascularization or peripheral angioplasty.

Exercise programs for patients with peripheral vascular disease are similar to established cardiac programs. Unlike cardiac programs, in which some degree of spontaneous recovery occurs and the overall functional capacity can be quite high (greater than 9 metabolic equivalents), most of the improvement in the patient with arterial occlusive disease is related to the exercise-conditioning program and usually occurs at a lower level of initial exercise capacity (5 metabolic equivalents).[17] Exercise-training programs may have a clinically significant impact on functional capacity in people who have limited treatment options and who do not experience spontaneous recovery.[16]

Exercise protocols vary considerably in the type, frequency, and duration of exercise. Walking programs must be individualized; however, the usual prescription has a goal of 30 to 60 minutes, 3 to 5 days a week at a pace of 2 mph as allowed by cardiac status.[18] Risk stratification will determine the exercise prescription and the level of supervision for each patient. The program, including exercise periods, rest periods, and walking speed, can be tailored to each patient’s requirements.

Protective footwear should be used to avoid mechanical trauma. Most amputations in people with occlusive arterial disease result from some type of trauma (thermal, chemical, or mechanical) superimposed on the limb with chronic occlusive disease.[19] Rocker-sole shoes lessen the work of the gastrocnemius and soleus muscle groups during ambulation and increase walking distance.[20] Double-metal upright ankle-foot orthoses to eliminate ankle motion have also been studied. Despite the added weight, fixed ankle, appearance, and change of gait pattern, most patients noted an increase in their walking distance and were pleased with the results they obtained with this orthotic device.[21]

Risk-factor modification is also a cornerstone in the therapy of any patient with peripheral vascular disease. Peripheral artery disease and coronary artery disease are both manifestations of atherosclerotic disease and have similar risk factors: age, sex (estrogen status), family history, tobacco abuse, hypercholesterolemia, hypertension, diabetes mellitus, and physical inactivity. Patients should be counseled to modify these risk factors to decrease their risk for further progression of atherosclerotic disease and its complications. In addition, if premature atherosclerosis is detected, the patient’s first-degree relatives should be screened for heritable risk factors such as homocystinemia and possible familial lipoproteinemia.

Medical therapy plays an important role in the treatment of patients with peripheral vascular disease. Groups of medications that may be of benefit in patient management include vasodilators, anticoagulants, antiplatelet agents, blood flow–enhancing agents, and antioxidants. Although vasodilator drugs have been shown to increase blood flow to the limbs and various organs in animal experiments and in humans with vasospastic disorders, their use in peripheral arterial occlusive disease remains questionable.[22] β-Blockers should be used with caution in patients with peripheral vascular disease. Anticoagulant and antiplatelet agents are widely used for patients with peripheral vascular disease. Their effect on intermittent claudication is questionable; however, both aspirin and clopidogrel have been shown to decrease cardiovascular complications in this group of patients.[23] Blood flow–enhancing agents have received variable reports of success.[24] Antioxidant agents (vitamins E and C and β-carotene) may have a role in the treatment of patients with peripheral arterial occlusive disease; however, final recommendations await a large-scale study of the effects of antioxidants in patients with peripheral arterial disease.

Various interventions may be used as adjunctive therapy to risk-factor modification and medical therapy. Indications for these procedures are ischemic rest pain, ulceration, gangrene, or the presence of incapacitating intermittent claudication that is refractory to medical therapy.[5] Procedures that may be helpful in patient management include revascularization (angioplasty and surgery), sympathectomy, and pneumatic compression.

Angioplasty is indicated for focal stenosis or short segmental occlusions in which the adjacent vessels are relatively free of disease.[18] Surgery is indicated in complex revascularization procedures that cannot be performed by a percutaneous route. Sympathectomy has been performed with less frequency as revascularization has become more successful. The primary effect of sympathetic denervation appears to be enhancing pain relief rather than augmenting blood flow to an ischemic limb. Intermittent pneumatic compression has also shown promise as a measure to augment limb perfusion and decrease dependent edema. Research to develop this technology is currently under way.

Despite the best medical and invasive management, it may be necessary to consider amputation. A prior knowledge of the patient’s medical problems and an educated patient are important in aiding the decision-making process. When the data collected on a patient suggest that amputation is the desirable method of management, it is critical to involve the patient in this decision. It is also important to view amputation not as a failure of medical management but as a means of improving the patient’s performance and functional status with a limb that has essentially become a liability. Appropriate consultation and resources should be sought prior to proceeding with amputation.