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ABSTRACf Two patients with Waldenstrom's macroglobulinemia presented with visual impainnent in both eyes. The funduscopic examination showed venous engorgement, retinal hemorrhages, microaneurysms, macular and disc edema. Video fluorescein angiography showed marked disturbances of retinal microcirculation. Due to high intravascular concentration of IgM, plasma viscosity was dramatically increased to values higher than 5 mPas. After plasma exchange procedures plasma viscosity dropped to about 2.5 mPas resulting in improvement of retinal microcirculation. Subsequently the funduscopic appearance of the retina improved. When the maculae flattened in the eyes, visual recovery occurred. These cases demonstrate the significance of blood fluidity and especially plasma viscosity on retinal microcirculation in patients with Waldenstrom's macroglobulinemia. The improved funduscopic appearance of the retina after the reduction of plasma viscosity proves the pathophysiological correlation between blood fluidity, retinal circulation, and visual function.

For the first time, a weak clinical efficacy of a 12-week therapy with garlic powder (daily dose, 800 mg) is demonstrated in patients with peripheral arterial occlusive disease stage II. The increase in walking distance in the verum group by 46 m (from 161.0 +/- 65.1 to 207.1 +/- 85.0 m) was significantly higher (P0.05) than in the placebo group (by 31 m, from 172.0 +/- 60.9 to 203.1 +/- 72.8). Both groups received physical therapy twice a week. The diastolic blood pressure, spontaneous thrombocyte aggregation, plasma viscosity, and cholesterol concentration also decreased significantly. Body weight was maintained. It is quite interesting that the garlic-specific increase in walking distance did not appear to occur until the 5th week of treatment, connected with a simultaneous decrease in spontaneous thrombocyte aggregation. Therefore, garlic may be an appropriate agent especially for the long-term treatment of an incipient intermittent claudication.

The efficacy of three weekly interventions with hypervolumetric hemodilution of a new preparation of hydroxyethyl starch (HES 100/0.5, 10%, C2/C6 substitution ratio of 6.5) on pain-free walking distance of patients with peripheral arterial occlusive disease (PAOD) stage IIb on the Fontaine classification was investigated. In addition quantitative data on the pharmacokinetic properties of this HES preparation, and it's impact on hemorheology, hemostasis and homeostasis were shown. Ten patients were included according to a predefined protocol, and treated openly with 500 ml HES 100/0.5 10% on nine occasions over 18 days. Pain-free walking distance, the main outcome measure, showed a mean increase of 82 m (+60%). Hematocrit decreased 4 percentage points on average (5.5 percentage points one hour after interventions). Plasma viscosity dropped 5% on average with significant changes immediately after interventions only in patients whose baseline values had been equal to or above the 2 s reference area. Erythrocyte aggregation decreased by 16% in the course of treatment (8% immediately after interventions), systolic blood pressure by 13%, and total protein by 7%. Complement showed a trend towards lower values (-20%), and creatinine, pH and urine viscosity remained unchanged. Apart from complement changes, all reductions mirrored the dilution effects. As to pharmacokinetics, serum mean molecular weight distribution was very similar to that of the infusion. A minor adverse drug reaction (light, spontaneously disappearing pruritus) was observed in one case.

In this perspective we address a fundamental and unresolved issue in biomaterials science: What are the molecular mechanisms which make a material blood compatible - or not? Despite the widespread use and the billion-dollar industry producing medical devices and implants, there is still a lack of fundamental understanding of the –admittedly– complicated and interlinked reactions that occur when an artificial material is exposed to blood. The increasing number of clinical reports about in vivo dysfunctional cardiovascular devices underlines the importance to understand –and be able to predict– the pathophysiological events occurring upon contact of blood with “hemocompatible” materials. The missing knowledge about the pathophysiological processes in the material/blood interphase and the lack of reliable correlations between in vitro-in vivo experiments, hinders us to develop scientific design principles to avoid complications in a clinical situation and achieve the optimal and lasting treatment. One may ask why this is the case, despite the huge research efforts taking place in laboratories worldwide to improve existing biomaterials and to develop new and better ones. One reason is certainly the analytical, intellectual and financial efforts it takes to unravel the interlinked biochemical reactions taking place in the interphase between the material and the body. But what actually slows the scientific community from developing models and theories on hemocompatibility is the fact that hardly any publication targeted at developing hemocompatible biomaterials conducts and describes the experiments and results in enough detail to allow a direct comparison to data in the literature or results of other laboratories. The lack of defined and certified positive or negative standards and experimental protocols even prevents us from concluding if a material is relatively better than another material, which may or may not be in use in medical