Fig. 6.5 (a) The foot has developed spreading necrosis, (b) Close-up view of foot, (c) The patient had fever whilst the necrosis was spreading and this resolved when ceftazidime as antipseudomonal treatment was started.
• After an episode of acute ischaemia patients may develop areas of necrosis even following successful revascularization
• Such necrosis is related to the markedly reduced perfusion during the acute ischaemic episode
• These areas of necrosis are usually dry but may become wet if they become infected
• Such necrosis can be treated conservatively
• If necrosis develops after an arterial bypass, it is important to check perfusion of the foot immediately to ensure that the graft is still patent.
Another cause of necrosis, particularly to the toe, is the passage of emboli to the digital circulation often originating from atherosclerotic plaques in the aorta and leg arteries.
'Showers of emboli' may originate from plaques in the aortoiliac and the superficial femoral arteries. The plaques are usually irregular or ulcerated and covered with debris particularly in the aorta. The emboli lead to cool painful cyanotic toes and the development of areas of necrosis at the tips of the toes, which generally heal without the need for amputation (Fig. 6.7). These patients may present with palpable pedal pulses.
Emboli may also occur as a complication of invasive angiographic procedures. Emboli may also originate from the heart. Cholesterol emboli may also be related to warfarin therapy.
The initial sign of emboli may be bluish or purple discolouration which is quite well demarcated but which quickly proceeds to necrosis. If it escapes infection it will dry out and mummify.
If patients with emboli have minimal or no neuropathy the foot is extremely painful.
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