HEMOSTASIS IN PATIENTS WITH SEVERE VON-WILLEBRAND-DISEASE IMPROVES AFTER NORMAL PLATELET TRANSFUSION AND NORMALIZES WITH FURTHER CORRECTIONOF THE PLASMA DEFECT

BACKGROUND: A defective hemostatic effect of plasma concentrate infusi on in patients with severe von Willebrand disease (vWD) has been ascri bed to the absence of platelet von Willebrand factor (vWF) STUDY DESIG N AND METHODS: The role of platelet vWF in hemostasis of severe vWD wa s investigated plateletpheresis unit (4-5 x 10(11) platelets) from a n ormal compatible donor was transfused before any cryoprecipitate infus ion to three type 3 vWD patients and to one patient with severe type 1 vWD with low levels of platelet VWF who required replacement therapy for breeding episodes. Autologous platelets were transfused to one of the patients with type 3 vWD. RESULTS: Partial corrections of bleeding times (14-17 min vs. baseline >30 min) were observed in all patients after the transfusion of normal platelets. During cryoprecipitate infu sion, bleeding times were normalized (<6 min), and bleeding episodes s topped when plasma levels of vWF activity ranged from 14 to 18 U per d L. Platelet interactions with the subendothelium increased in parallel with the correction of bleeding times. These results indicate that if approximately 20 percent of the total number of platelets have normal vWF antigen and if plasma vWF levels are at least 14 U per dL, then b leeding times will normalize and mucosa[ hemorrhages will stop. Transf usion of autologous platelets in one patient with type 3 vWD did not m odify bleeding times or platelet adhesion on the subendothelium. CONCL USION: The hemostatic effect of normal platelets in type 3 vWD seems t o be related to the platelet vWF in the transfused platelets.