Hematological parameters influencing the Thrombostat 4000.

The effects of platelet counts, hematocrit, and leukocyte counts were studied on the closure times of the Thrombostat 4000 (in-vitro bleeding time, IVBT). Closure times became longer with platelet counts < 50 x 10(9)/L; an inverse linear correlation could be established. Hematocrit was also inversely correlated with the closure time. At constant platelet counts a hematocrit of 55% yielded an immediate closure of the filter, while with a hematocrit < 15% no closure times could be measured. At constant platelet counts and hematocrits, nomonuclear and polymorphonuclear leukocytes also influenced closure times; increased counts resulted in shorter closure times. Leukocytes from a patient with chronic myelocytic leukemia had the same effects.

[Ex-vivo bleeding time as a control for platelet transfusion]. / Ex-vivo-Blutungszeit zur Kontrolle der Thrombozytentransfusion.

Thrombocytopenia is the most common cause of bleeding tendency and, if due to impaired platelet production, is best treated by platelet transfusion. For patients with acute leukemia prophylactic platelet transfusion should be considered if platelet count is below 20 x 10(9)/l. This will be underlined by a retrospective analysis at our clinic of 231 patients suffering from acute myelocytic leukemia (AML FAB M1-7) and showing an early-death rate of 7.7% by bleeding complications. To estimate the effectiveness of platelet transfusions, not only stopping of bleeding symptoms and corrected count increment (CCI) should be taken into account but also whether the patient has fever, sepsis, hepato-splenomegaly or has taken special drugs. Measuring the in vivo bleeding time is of little use for low reproduction and is stressing for patients. In 1985 Kratzer described a new and sensitive method for the evaluation of platelet function. After modifying this method it is now possible to test platelet function even with platelet counts below 50 x 10(9)/l.