Critical Limb Ischemia

What is Critical Limb Ischemia? Critical Limb Ischemia (is keem' ee uh) (CLI) occurs when the arteries carrying blood to the limbs are so badly blocked that there is not enough blood flow to maintain healthy skin or heal open sores. Most often, it affects the feet or legs and is always associated with a severe and characteristic pain. CLI, the most serious stage of peripheral arterial disease (PAD) having progressed to the point of severe pain and even skin ulcers or gangrene, needs intense treatment by a vascular specialist. This condition will not improve on its own! Besides increasing the risk for an amputation, CLI also greatly increases the likelihood for heart attack and stroke.

Symptoms and Signs. Patients usually experience severe pain in the forefoot or toes. Sores, or actually non-healing skin ulcers, or even areas of gangrene may be present, although early on, one may have the pain without the sores. The pain can serve as a warning that the sores are surely to follow. Patients often have a history of not being able to walk far without pain in the calf, called claudication (see Keeping In Circulation Spring 2004 issue). Claudication pain is associated with an earlier stage of PAD, whereas CLI causes pain at rest. Typically it is related to the leg's position. This "rest pain," is worse when the leg is elevated (as when lying down flat) and can usually be relieved temporarily by hanging the leg over the bed or getting up to walk around. This dependent position helps get more blood into the leg, relieving the pain. The pain can be so severe it can interrupt sleep at night, or can occur whenever lying down, such as when taking a nap. The pain caused by CLI does not respond to most strong pain medicines. Often the foot looks dusky purple or red when the leg is hung down and becomes pale when the leg is elevated. Other signs may include the thinning of the skin of the foot and its muscles and decreased or absent hair growth on the foot and toes. Additionally, the toenails may become thick and brittle and the leg may feel cool to the touch.

Diagnosis. The health care provider will perform a physical examination, followed by one or more blood flow studies. One of the most valuable blood flow studies is the Ankle Brachial Index (ABI), because it is quick and easy to perform. The blood pressure is measured at the ankle and compared to the blood pressure of the arm. An ABI of 1.0 or more is normal (except in diabetic patients, where a false high reading is not unusual). An ABI of .3 or below indicates critical limb ischemia. Occasionally, the patient may be asked to walk on a treadmill to see if this causes a further fall in the ankle pressure. Segmental limb pressures (blood pressures taken at different levels up the leg) can sometimes help locate the blockage.

Medical Treatment. Certain medications are prescribed to help prevent further progression of the underlying arteriosclerosis which is responsible for the blockages causing CLI, and can cause the blockages in arteries throughout the body, including the coronary or carotid arteries, which could result in heart attacks or strokes. Therefore, it is important to take appropriate medications to control associated medical conditions like high blood pressure, high cholesterol, and diabetes. Other medications, called "vasodilators", designed to improve the circulation in the legs may be helpful. However, these rarely improve circulation enough to control rest pain and heal up foot sores. At this stage of PAD, a major increase in blood flow is needed and some procedure will usually be required. For good reason these have been called "limb salvage" procedures.

Limb Salvage Procedures. Open surgical or endovascular procedures can be highly successful in restoring the flow of oxygenated blood to the legs and healing areas of skin breakdown or ulcers. An endovascular procedure consists of a small incision through which a catheter is inserted to where the blockages occur. Interventions might include an angioplasty, inserting a stent to hold the artery open, or having a clot broken up (thrombolysis).

A bypass graft is the most common open surgical procedure, and may be performed in more serious cases. An artificial tube or one of the patient's veins is used as a new artery to bypass the blocked segment and bring improved blood flow to the needy areas. Less often, the surgeon may cut open the artery and remove the plaque, restoring the flow channel through the diseased artery. One of the above procedures will be successful in restoring flow and saving the leg in the majority of cases where only the forefoot or toes are involved. Only if gangrene or secondary infection has already progressed up to the ankle or higher would amputation of the leg be needed. Amputation occurs in about 25% of CLI patients, but earlier diagnosis can reduce this significantly.

General Care. If there is only rest pain or the foot lesions have not progressed to gangrene, and particularly if the patient is a poor risk for surgery, then non-operative measures can be tried and may prove successful. Keep the leg dependent (down) to allow more blood flow. Don't apply external heat, but keep the legs warm and free from pressure or injury. Patients who have low blood pressure or low hemoglobin (anemia) or whose heart function is weak should have these vigorously corrected. A strong heartbeat, pumping well oxygenated blood at normal pressures, can often overcome blocked blood vessels and help save the leg. By the same token, improving lung function can also help significantly. For example, stop smoking, or inhale oxygen as needed.

Smoking Cessation. Smoking tobacco, the greatest risk factor, must be stopped as well. If you smoke, stop! It may save your leg and your life! (For more information on smoking and PAD, visit the VDF web site at www.vdf.org.)

Ulcer Care. Treatment for ulcers will likely include topical medications and dressings. Foot ulcers can be soaked periodically in mild antiseptic solutions, but soaking gangrenous areas invites infection. At other times the foot should be kept clean and dry, although clean lubricating lotions are helpful to prevent cracks and fissures. These treatments should be prescribed by a physician or nurse, but can be applied by the patient or home caregivers.

Since treatment depends on the severity of the disease and many individual parameters, it is essential that someone with ulcers or rest pain in the legs or feet see a vascular specialist as soon as possible. The earlier a diagnosis can be made, the earlier treatment can be started, and the more likely the outcome will avoid serious consequences.