Insights On Testing And Treatment Of Ischemic Wounds

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Here is a close-up view of an ischemic foot with necrotic ulcerations.
Here is a stable, non-infected ischemic ulcer with toe pressures of 25 mmHg. Dr. Karlock notes than an absolute toe pressure of less than 30 mmHg is not conducive for healing.
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Author(s): 
Clinical Editor: Lawrence Karlock, DPM

Other tests can be misleading according to Dr. Stillman. He says this is particularly the case when trying to use ankle-brachial pressure indices to assess patients with diabetes. Dr. Stillman points out these patients may have poorly compressible calcified arteries that tend to give normal or high pressures despite poor flow. While ultrasonic visualization of arterial anatomy does help identify aneurysmal disease or ulcerated plaque, Dr. Stillman says it generally correlates poorly with hemodynamic data.
When one employs noninvasive arterial blood flow testing (such as pulse volume recording and plethysmography), pneumatic cuffs encircle the thighs, calves, ankles, feet and, sometimes, individual toes, according to Dr. Stillman. He says a transducer measures the subtle pressure changes that occur with each pulse wave and a computer chip translates the information into easily readable tracings.
“This printout provides useful information about the hemodynamic significance of atherosclerotic disease,” emphasizes Dr. Stillman. “Extremely blunted distal tracings suggest likely wound healing problems unless revascularization can be accomplished.”

Q: How has the role of the “long leg distal bypass” changed your prognosis of these wounds?
A:
In situ bypass is a sophisticated technique for arterializing the greater saphenous vein, notes Dr. Stillman. He says the vein remains in its anatomical position but is anastomosed proximally to the common femoral artery and distally to a runoff vessel such as the posterior tibial, anterior tibial or peroneal artery.
Since leg veins have valves to prevent flow in the caudad direction, Dr. Stillman notes the vascular surgeon would destroy the valves with a valvulotome and then ligate the vein branches in order to avoid arteriovenous fistulas.
While he calls it “an arduous and technically challenging operation,” Dr. Stillman says a successful in situ bypass has a respectable long-term patency rate and a well-deserved reputation for limb salvage, often despite extensive arterial disease.

Q: What role does angioplasty/ stenting play in the infrapopliteal occlusive lesion in the diabetic foot?
A:
Dr. Stillman says short segment stenotic and occlusive disease responds well to endovascular managememt such as angioplasty or stenting. Stenting is particularly effective in larger vessels such as the iliac arteries, notes Dr. Stillman. He adds that the infrainguinal segment and particularly the infrapopliteal segment carry a higher restenosis rate after endovascular reconstruction.
As the technology advances, Dr. Stillman says one can look for improving patency rates. He also emphasizes that even a short-term boost in arterial flow can be “a limb- and life-saver for a surgically high-risk patient with a non-healing, ischemic foot wound.”

Q: What is your approach in managing ischemic wounds?
A:
Dr. Karlock says you should avoid aggressive debridement in a potentially ischemic wound. “This just adds insult to injury,” notes Dr. Karlock. When it comes to noninfected, stable ischemic wounds, he suggests keeping them dry until appropriate revascularization techniques are carried out. Dr. Karlock says he would avoid using any enzymatic debriding agents in this situation. Dr. Beylin notes that he does employ enzymatic-type agents such as Panafil and Accuzyme on necrotic wounds.

Q: What are your thoughts on the timing of a foot amputation after bypass surgery?
A:
Amputation for infected gangrene should precede bypass surgery by about 10 days, notes Dr. Stillman, who adds that doing so allows the clearing of bacterial seeding from the lymphatic channels that one would encounter during the bypass. On the other hand, he says one may treat dry gangrenous toes or clean, non-healing ulcers before or after vascular reconstruction.
Within five to seven days, it becomes more or less clear whether a vascular bypass has been successful, according to Dr. Beylin.
Dr. Stillman says waiting until the bypass has been accomplished facilitates a more accurate assessment of local perfusion and the amputation level. Occasionally, he notes vascular surgeons will excise a clean foot ulcer or amputate a dry gangrenous toe concurrently with the bypass, but they would always use an isolated operative field and separate instruments to do so.

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