Abstract

DO.11.02

Update isovolaemic haemodilution

Hansen L. L. 
Universitäts-Augenklinik Freiburg

Objective: Whole blood viscosity increases logarithmically when the flow velocity decreases. This is caused by blood cells, mainly erythrocytes. A decrease of the haematocrit leads to an improvement of microcirculation, and hence, to better supply of oxygen in the low perfused retina.
Methods: Haemodilution is best-performed isovolaemically (blood letting + simultaneous Infusion of hydroxyethylstarch [HAES 200000/0,5-10%]). While hypervolaemic infusion leads to a maximal decrease of 2-4%, the isovolaemic can be customized according to the patient’s compatibility. We favour to lower the haematocrit to 35-37% and hold this level over a time of 6 weeks.
Results: The natural course of central retinal vein occlusion leads to an improvement of more than two lines in only 10-25% of eyes, while about 40-45% of eyes show a better visual outcome with haemodilution. The number of eyes reaching reading acuity (=0,5) is nearly doubled. A comparable improvement applies for retinal branch vein occlusion. However, the larger percentage of patients still does not benefit from isovolaemic haemodilution. Furthermore one has to be aware of the neovascular complications, as haemodilution fails to solve this problem.
Conclusions: Many new treatment modalities, some very promising, have been tried during the last ten years. Nevertheless, evidence-based data still lack. Therefore haemodilution remains the only evidence-based standard treatment for visual improvement and should still be applied, in particular, as it does not interfere with newer experimental treatments but may be supportive.

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