ACTION OF HYDROXYETHYL STARCH (HES) ON THE ACTIVITY OF PLASMATIC CLOTTING FACTORS

Studies were carried out on the effects of different doses of hydroxye thyl starch 200/0.5 (HES) on plasma clotting factors in dogs, as an an imal model for the human clotting system. In 8 German shepherd dogs 15 % of the total blood was isovolemically substituted either by Ringer's solution with lactate alone (controls) or with 0.6, 1.3, 1.9, 2.5 g H ES/kg b.w. Immediately after the infusion, the HES concentration in th e recipients' plasma amounted to 8 mg/ml up to 38 mg/ml. In the follow ing 6 h, the HES decreased to 25% in each case. It was found that the higher the plasma HES content was, the lower the haematocrit. Neither the thrombin- nor the batroxobin-time showed any significant change, i rrespective of the plasma HES concentration. The prothrombin-time was decreased directly after the infusion in parallel to the haematocrit. The single clotting factors FI, FII, FV, FVII, FVIII, FX, and FXII beh aved approximately in the same way: their activities directly after in fusion, but also 6 h later, were lowered in proportion to the amount o f HES infused. The loss of factor activity correlated with the volume- expanding effect of HES shortly after the infusion, but not 6 h later It is concluded that there are two different modes of HES action on cl otting factors: the dilution by plasma volume expansion and a non-dilu tional action. Cautious handling might be required in patients with cl otting disturbances as well as in long-term treatment.