Definition of Critical Limb Ischemia & Limb Salvage
Peripheral vascular disease (PVD) of the legs is a problem that may not have any symptoms at all, or may cause symptoms so severe that patients complain of constant leg pain and ultimately have to have an amputation. Patients with severe leg pain due to poor blood flow are said to have critical limb ischemia (CLI). Ischemia means “insufficient blood flow.” Critical limb ischemia can severely affect a patient’s quality of life. Also, patients with CLI are more likely to die of heart attacks and other problems related to vascular disease like stroke.
There are a lot of definitions for CLI, but a well-accepted one is the presence of ischemic “rest pain” (pain that requires a patient to hang their leg over the side of the bed or sleep in a chair) requiring pain medication for more than two weeks; having a non- wound (“leg ulcer”) or gangrene of the lower extremity, or having poor circulation as measured by certain types of tests (an ankle systolic blood pressure ≤ 50 mmHg and/or toe systolic pressure ≤ 30 mmHg).
Patients with CLI are at risk of losing a leg due to amputation. In these patients, we talk about needing “limb salvage.” This means doing something to ensure that the leg is not lost (although sometimes it is not possible to save all the toes). Limb salvage can be defined as procedure aimed at improving the blood flow to the leg with the purpose of preventing limb loss. Hopefully, these procedures will also get a wound to heal and get rid of the pain of poor circulation. We call these procedures “revascularization” procedures, and they may be done with surgery or by going into the artery and cleaning it out (“endovascular”).
How does Limb Ischemia Happen?
In most patients, chronic critical limb ischemia is related to “hardening of the arteries,” also called “atherosclerosis.” When there is no longer enough blood getting to tissues to keep them alive, the tissues begin to die, and that is when patients develop ulcers and gangrene. Patients with diabetes may have “neuropathy” which is a type of nerve damage that prevents them from feeling injury to the feet. This may make them more likely to develop sores on the feet since they can’t tell when they have injured themselves. Also, diabetics have a harder time fighting off infection so they are more likely to get a deep wound infection or a bone infection (osteomyelitis).
Clinical Signs of CLI
CLI can be an emergency. It is sort of like having a “heart attack in your feet.” Patients may need to come into the hospital right away to get revascularized. Physicians are taught to remember the 5-“P’s”: Absence of Pulse, presence of resting Pain, Pallor (whitish color to the skin), Paresthesia (lack of sensation) and Paralysis (not being able to move the foot).
Chronic CLI more likely to be found in patients with a history of intermittent claudication (this is cramping in the calves that occurs when walking but stops when you rest), smokers, diabetics, or people with a history of stroke. When someone with one of those problems develops one or more of the following, they may have chronic CLI: resting pain, non-healing foot or legulcers (wounds), dry gangrene, and absence of palpable pulses.
- Resting Pain: Patients with CLI usually describe their pain as a throbbing pain, dull ache, or numbness that usually worsens when the patient elevates the leg. It is usually worse at night. It is made better by keeping the legs down so patients often have to sleep in a chair.
- Non Healing Ulcers: Ulcers (wounds) usually appear in the tips of the toes, or over bony areas. They can be on the leg. These sores are associated with severe pain (except in diabetic patients with neuropathy). The ulcers are generally dry (they do not drain much fluid) and the bottom of the ulcer is often pale, gray or covered with black tissue or dead tissue.
- Dry Gangrene: The presence of dead tissue is one of the last stages of CLI. It is usually very painful. It can smell bad.
- Absence Of Palpable Pulses: A doctor should examine the pulses of the feet to determine if it is possible to feel the pulses in the top of the foot and the back of the ankle. If these pulses cannot be felt, it may be possible to hear them with an instrument called a “Doppler.” The physician may also measure the blood pressure in the arm and in the foot and compare these measurements. The ankle brachial index (ABI) is the ratio between the ankle systolic blood pressure and the brachial (arm) systolic blood pressure. In patients with CLI the ABI is almost universally below 0.5. However, in diabetics this test may not be reliable because of hardening of the arteries.