Critical limb ischaemia

What it is

Chronic limb ischemia is the inability of the arterial supply to meet the cellular metabolic demand. Critical limb ischemia is its end, not a separate disease: on the La Fontaine classification the grades run asymptomatic, intermittent claudication, rest pain, then ulcer or gangrene, and grades III and IV are critical limb ischemia.

Causes and risk

The causes are atherosclerosis, vasculitis and artery entrapment. The risk factors divide into two ranks:

• Major: smoking and DM
• Minor: HTN, dyslipidemia, obesity, sedentary lifestyle, and a PMH or F Hx of CAD or CVD

Because the cause is atherosclerosis, its other manifestations sit alongside: CVD, CAD, impotence and splanchnic or mesenteric ischemia.

How it presents

Intermittent claudication is cramping muscular pain on exertion, distal to the site of obstruction, relieved by a short rest of 2-5 min sitting or standing. It is reproducible: the same distance elicits the pain, in the same location, relieved by the same amount of rest. The claudication distance is the distance in which the patient starts to walk until symptoms develop.

Critical limb ischemia changes the story. The pain is continuous and severe, worse at night, waking the person from sleep, often relieved by hanging the foot off the bed, increased by movement or pressure. It is felt in the forefoot, and tissue loss appears as ulceration or gangrene of the foot.

In critical limb ischemia the foot has thin shiny cold skin, loss of subcutaneous fat and muscle wasting, a CRT over 15s, and pallor on elevation to 20; a cold foot and leg with an absent or weak pulse and bruits are set down on the intermittent claudication side. The signs of poor perfusion in chronic limb ischemia are absent pulses and present bruits, hair loss, hypertrophic nails, atrophic muscles, skin ulceration, slow capillary refill, prolonged pallor on elevation with rubor on dependency, and venous troughing. Where the pain sits names the level of obstruction: aorto-iliac gives claudication in both buttocks, thighs and calf with absent femoral, popliteal and DP pulses and impotence, which is Leriche's syndrome of chronic aortoiliac occlusive disease; iliac or common femoral gives unilateral thigh and calf claudication with unilateral absence of femoral and distal pulses; superficial femoral or popliteal gives unilateral calf claudication with absent distal pulses; the tibial and peroneal vessels give absent ankle pulses with claudication in calf and foot.