title: Anemia-induced increase in the bleeding time: implications for treatment of nonsurgical blood loss.
abstract: BACKGROUND
  Preoperative bleeding time (BT) does not correlate with postoperative bleeding in patients subjected to surgical procedures. A significant positive correlation has been reported between the BT 2 hours after cardiopulmonary bypass surgery and the nonsurgical blood loss during the first 4 hours after bypass surgery. This study was done to investigate the effect of Hct and platelet count on the BT measurement in normal, healthy men and women.
  
  
  METHODS
  To assess the relative effect of RBCs and platelets on the BT, 22 healthy male and 7 healthy female volunteers were subjected to the removal of 2 units of RBCs (360 mL), followed by the return of the platelet-rich plasma (PRP) from both units and the infusion of 1000 mL of 0.9-percent NaCl. Four of the men and all seven women received their RBCs 1 hour after their removal. Shed blood levels of thromboxane B(2) (TXB(2)), 6-keto prostaglandin F(1 alpha), and peripheral venous Hct were measured. BTs were measured in 15 men and 13 women before and after a plateletpheresis procedure to collect 3.6 x 10(11) platelets per unit.
  
  
  RESULTS
  The 2-unit RBC apheresis procedure produced a 60-percent increase in the BT associated with a 15-percent reduction in the peripheral venous Hct and a 9-percent reduction in the platelet count. The plateletpheresis procedure produced a 32-percent decrease in the platelet count, no change in peripheral venous Hct, and no change in the BT. After the removal of 2 units of RBCs, the shed blood TXB(2) level decreased significantly. Reinfusion of 2 units of RBCs restored the BT and restored the TXB(2) level to the baseline levels.
  
  
  CONCLUSIONS
  The acute reduction in Hct produced a reversible platelet dysfunction manifested by an increase in BT and a decrease in the shed blood TXB(2) level at the template BT site. Return of the RBCs restored both the BT and the shed blood TXB(2) level to normal. The platelet dysfunction observed with the reduction in Hct was due in part to a reduction in shed blood TXB(2) and other, unknown mechanisms.
authors.affiliation: Naval Blood Research Laboratory, Boston University School of Medicine, Massachusetts 02118, USA. navblood@BU.edu
authors.forename: C R
authors.initials: CR
authors.lastname: Valeri
authors.forename: G
authors.initials: G
authors.lastname: Cassidy
authors.forename: L E
authors.initials: LE
authors.lastname: Pivacek
authors.forename: G
authors.initials: G
authors.lastname: Ragno
authors.forename: W
authors.initials: W
authors.lastname: Lieberthal
authors.forename: J P
authors.initials: JP
authors.lastname: Crowley
authors.forename: S F
authors.initials: SF
authors.lastname: Khuri
authors.forename: J
authors.initials: J
authors.lastname: Loscalzo
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D000740:Anemia / Q000097:blood* / Q000150:complications; D001760:Bleeding Time; D001781:Blood Component Removal; D017707:Erythrocyte Transfusion; D005260:Female; D006400:Hematocrit; D006470:Hemorrhage / Q000209:etiology / Q000628:therapy*; D006801:Humans; D008297:Male; D010976:Platelet Count; D010983:Plateletpheresis; D013929:Thromboxane B2 / Q000097:blood
chemical_list: D013929:Thromboxane B2