Why critical limb ischemia criteria are not applicable to diabetic foot and why you should care

Jörneskog G.
Scand J Surg. 2012;101(2):114-8.

Karolinska Institutet, Department of Clinical Sciences, Danderyd Hospital, Stockholm, Sweden.

Neuropathy, peripheral arterial occlusive disease and microvascular disturbances are important factors contributing to foot problems in diabetic patients. In the diabetic foot with ischemia, the alterations in skin microvascular function are pronounced including severely reduced capillary circulation and abolished hyperaemic responses. These microvascular disturbances, which are superimposed on the already existing structural diabetic microangiopathy, are compatible with a state of “chronic capillary ischemia” and an increased shunting of blood through arteriovenous channels. This maldistribution of blood in skin microcirculation is not detected by measurement of peripheral blood pressure (systolic ankle blood pressure, systolic toe blood pressure). As indicated in several studies toe blood pressure is a poor predictor of local tissue perfusion, tissue survival and healing of chronic foot ulcers. Consequently, the disturbances in peripheral tissue perfusion of the diabetic foot may be underestimated leading to delayed vascular interventions and/or medical treatment. Thus, measurements of peripheral blood pressure, e.g. toe blood pressure, should be combined with investigations of local tissue perfusion in order to get an adequate estimation of peripheral tissue perfusion in diabetic patients. For this purpose local skin microcirculation can be investigated by transcutaneous oxygen tension of the forefoot. Also, due to these reasons, the threshold for revascularization should be lower in diabetic patients with foot ulcer.

One thought on “Why critical limb ischemia criteria are not applicable to diabetic foot and why you should care

  1. It is clear that tissue perfusion is important for wound healing and that patients with diabetes often exhibit a complex nexus of neuropathy, ulceration (even gangrene) and abnormal tissue perfusion. Some of these patients require improvement in tissue perfusion to expedite wound healing, and in other patients, wound healing is impossible without revascularization. Unfortunately, we don't yet have an appropriate classification system that allows us to analyze all these factors, we don't have sensitive indicators of perfusion (although toe pressures and TcPO2 work pretty well for forefoot wounds), and we don't have appropriate outcome measures. Our SALSA group will soon be reporting more information regarding the use of Indocyanine Angiography (ICG) to assess tissue perfusion, and we are also working on a new classification system for patients with diabetes. A key concept is that there is no such thing as Critical Limb Ischemia in patients with DFU and infection. Ischemia does not have a sharp cutoff, but is rather best represented by a sigmoid curve. Stay tuned!

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