The Role of Open Bypass Surgery for Limb Salvage in Patients With Diabetes
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Index: WOUNDS 2011;23(12):364–368
Abstract: The pathogenesis of foot ulceration in patients with diabetes involves the interplay of neuropathy, vasculopathy, and immune dysfunction. Autonomic neuropathy results in loss of pain sensation, decreased sweating, and the development of brittle skin, which predisposes these patients to foot trauma. As a result, the traumatized tissue progresses to necrosis and subsequent ulceration. Once an ulcer is present, the vascular supply to the foot plays an integral role in healing. Foot ischemia in patients with diabetes may be attributed to atherosclerotic macrovascular disease and additional microcirculatory dysfunction. The following report will review the role of open bypass surgery addressing macrovascular problems for limb salvage.
Patients with limb-threatening critical limb ischemia (CLI) present with nonhealing ulcers and associated tissue necrosis, gangrene, or infection. Evaluation of the extent of tissue loss and relationship with pressure bearing surfaces should be performed. Lower extremity segmental Doppler studies are helpful in determining severity of ischemia. Moderate ischemia is associated with ankle brachial indices (ABI) 0.5–0.9 and severe ischemia with ABI < 0.5. Doppler studies can be inaccurate in patients with diabetes because of noncompressible vessels due to calcified arterial walls, and as a result ABIs can be falsely elevated. Alternatively, pulse volume recording, toe pressures, and transcutaneous oxygen measurements may be utilized. Diagnostic contrast arteriography is typically performed for more accurate evaluation of occlusive disease pattern and for operative planning. While aortoiliac and femoropopliteal levels can have evidence of occlusive disease, patients with diabetes often exhibit tibioperoneal arterial occlusive disease with sparing of the pedal level. Particular attention is paid to both the inflow and outflow target arteries, both of which should be free of occlusive disease above and below intended bypass with continuous patent distal flow to the foot. Ultrasound mapping of potential venous conduits in bilateral lower extremities (great and small saphenous vein) and upper extremities (cephalic and basilic veins) provides information about conduit availability and suitability of operative bypass.
Generally, surgical intervention is recommended for patients with diabetes and CLI from occlusive disease. While endovascular options for treating occlusive disease have expanded in recent years and are best for patients of advanced age, higher medical risk profile, and less severe occlusive disease, operative bypass is preferred, if risk permissible, and for more extensive occlusive disease patterns. The advantages of operative bypass over endovascular approaches is that it is not limited by the extent of occlusion or length of diseased segment, and in the long run has more extended durability, especially for distal tibial occlusive disease patterns more often seen in patients with diabetes.
Revascularization procedures must be tailored to the individual patient based on anatomy, particularly the inflow and outflow, as defined by the preoperative angiography. For patients with multilevel disease, multilevel reconstruction at the aortoiliac and infrainguinal levels may be needed. Infrainguinal bypass procedures need to arise from a patent and uncompromised inflow artery. The quality of the outflow artery is an equally important determinant of patency and a distal vessel of the best quality should be used for distal target. Conduit is also critical with the vein having better long-term patency than prosthetic for infrainguinal revascularization.