Microvascular changes in arterial occlusive disease: target for pharmacotherapy

The main techniques which have been used to study skin microcirculation in patients with peripheral arterial occlusive disease include intravital microscopy with and without the use of fluorescent dyes, laser Doppler fluxmetry and transcutaneous oximetry. In patients with severe ischaemia (rest pain or incipient gangrene) the number of perfused skin capillaries is reduced. Parallel to the decreased number of microvessels containing blood, transcutaneous oxygen tension is low or even approaches the zero level. The tendency to oedema formation is documented by increased leakage of intravenously injected sodium fluorescein at the capillary apex of foot skin ('candlelight phenomenon'). Laser Doppler flux at rest may still be within the normal range even in advanced disease, since the sample volume of these instruments also contains non-nutritive shunt vessels. However, reactive hyperaemia after arterial occlusion is decreased and delayed in peripheral ischaemia. Whereas rhythmic low-frequency vasomotion is significantly enhanced in patients with intermittent claudication, vasoparalysis with no flux fluctuations prevails in patients with critical ischaemia.