The current state of extracorporeal haemorheotherapy: from haemodilution via cascadefiltration to rheohaemapheresis

Rheological therapy aims at an improvement of organ perfusion however, it has to be stressed that the tonus of the blood vessels also plays an important role for both the blood distribution and the rheology in the micro- and the macrocirculation. Conventional rheotherapy consists of attempts to influence nutrition and life style, to apply drugs such as purin derivatives, vasodilatating or defibrinising substances and hypervolaemic (using infusion therapy), hypovolaemic, e.g., blood letting, erythrocytapheresis and--the most widely distributed- -isovolaemic haemodilution. With the introduction of centrifugal devices, and approximately 10 years later with the introduction of hollow fibre and flat sheet membrane techniques, a considerable increase of therapeutical efficacy was achieved. These technologies were successfully applied for the treatment of cellular and plasmatic hyperviscosity syndromes. The treatment of less severe diseases of the micro- and macrocirculation, vessel stenosis, vessel wall sclerosis, malformation of the blood vessel architecture, pathological clinical-chemical blood parameters and maldistribution have hardly been taken into consideration. Our group at Köln investigated different plasma differential separation techniques and demonstrated, that adsorption as well as filtration could be applied. These different techniques being 6-10 times more effective as conventional haemodilution techniques have in common high molecular weight proteins determining the viscosity of plasma and thus whole blood viscosity is removed, however differences among the different elimination techniques do exist. The rheological and clinical importance of such differences has to be determined. Applying filtration techniques for both primary and secondary separations, the concept of Rheohaemapheresis was developed. A corresponding quality program was also introduced into our clinical routine. Rheohaemapheresis is supported from the currently introduced concept of the synergetic consideration of the microcirculation. Age related macular degeneration, so far without generally accepted therapy, is a most advanced indication based on several pilot studies and a prospective, randomised controlled trial. Other diseases of the microcirculation have also successfully been treated.