HEMATOCRIT AND BLEEDING-TIME - AN UPDATE

The bleeding time is prolonged in anemic patients independent of their platelet count and is shortened by elevating the hematocrit. It is th eorized that an increase in circulating red blood cells increases plat elet radial movement and interaction with endothelium. Platelet dysfun ction in uremia is well known but poorly understood. Anemia is one con tributory factor; others may involve storage pool deficiency, increase d vessel wall prostaglandin production, and abnormal platelet arachido nic acid metabolism. Ameliorating anemia with red blood cell transfusi ons has been shown to shorten the bleeding time without affecting othe r platelet function values. Recently, recombinant human erythropoietin has been shown to shorten the bleeding time, with a parallel rise in hematocrit level to 30%. Clinicians should be aware that a diminished hematocrit may contribute to the bleeding tendency already present in patients with thrombocytopenia.