Study to Explore the Effect of Lowering Blood Viscosity in Patients With Treatment-resistant Critical Limb Ischemia

Overview

PAD is caused by an increased flow resistance in atherosclerotic ischemic limbs. The investigators hypothesize that reducing blood viscosity (through controlled phlebotomy), thereby increasing the deformability of red blood cells, should reduce the flow resistance and improve tissue perfusion leading to improved clinical function and a reduction in symptoms. Preliminary data demonstrates that phlebotomy causes a measurable change in blood viscosity as measured by the home-made rheologic method. To evaluate the effectiveness of changes in blood viscosity, obtained through controlled phlebotomy, as a therapy to improve functional status associated with atherosclerotic ischemic limbs in pre-amputation patients.

The first study is a pilot study and will act as proof of principle. This first study will include 20 patients divided into 2 groups on the basis of a randomized controlled trial: 10 patients in the control group receiving conventional treatment and 10 patients receiving therapeutic phlebotomy to lower blood viscosity. The objective is to evaluate the effect of controlled phlebotomy in patients with Grade 3, Category 5 or 6 chronic critical limb ischemia having tissue loss on Rutherford classification (Fontaine stage IV), end-stage peripheral vascular disease resistant to maximal medical therapy and where revascularization therapy (both percutaneous and surgical) has either proved insufficient or is contra-indicated or declined by the patient, usually resulting in amputation. The primary outcome parameters will be: the salvage rate of the limb as compared with the salvage rate of the limb with conventional therapy. Objective classification of improvement in perfusion of the distal extremities using ankle-brachial index (ABI), visual analogue pain scale, and photos. Subjective classification of improvement in pain scale on critical limbs. The relationship between alteration in outcome parameters (i.e., the end point is a reduced amputation rate) and blood viscosity will be evaluated as measured by the home-made rheologic methods.