High-dose tranexamic acid significantly reduces intraoperative blood loss and perioperative donor exposure in patients with end-stage parenchymal liver disease who are undergoing orthotopic liver transplantation, with marked reductions in platelet and cryoprecipitate requirements.

No abstract

The addition of latex particles to native (no anticoagulant) or citratcd human platclctrich plasma (PRP), or to a once-washed platelct suspension causes platelet aggregation. This aggregation is associated with phagocytosis of t'ae latex particles by the platelets and appcars to be due to release of adenosine diphosphate (ADP) from the platclets. Adenosinc and adenosine monophosphate, which are known to inhibit platelet aggregation induced by ADP, also block that induced by latex. These compounds do not prevent the phagocytosis of latex particles by the platelet. The addition of iodoacctate and 2,4-dinitrophcnol in appropriate concentrations to the PRP, prior to the addition of the latex, blocks platelet aggregation and phagocytosis. This is also true for the chelating agent ethylenediaminetetraacetate (EDTA). Platclets left in contact with latex for a sufficient period of time show loss of their granules. Leucocytcs phagocytose both latex and platelets that had themselves phagocytosed latex. It is concluded that phagocytosis of latex particlcs by platelcts rcscmblcs that by white cells, and that in both processes metabolic changes appear to bc involved.

A B S T R A C T The adherence to collagen of rabbit platelets labeled in vivo with 35SO4= has been studied both in vitro and in vivo. The young platelets are labeled with 35SO4= 2-3 days after administration of the isotope to the animals. We exposed platelet-rich plasma (ethylenediaminetetraacetate, EDTA, as anticoagulant), prepared from blood taken from rabbits 54 hr after giving the 85SO4=, to collagen in vitro. There was a fall in the specific radioactivity of the nonadherent platelets which indicated a selective adhesion of young platelets to the collagen. In experiments designed to have most of the 35S label in the oldest platelets it was found that exposure of plasma containing these platelets to collagen resulted in an increase in the specific radioactivity of the nonadherent platelets. Similar observations were obtained when glycine-14C was used as a platelet label. However, when DF32P (di-isopropyl phosphorofluoridate-32P), which is thought to label platelets of all ages equally, was used, the adherence of platelets to collagen did not result in any changes in the specific activity of the nonadherent platelets. In in vivo studies in which we infused a collagen suspension into rabbits 54 hr after giving 35SO4= we found that the specific radioactivity of the platelets remaining in the circulation fell.

This prospective, double-blind, randomized trial assessed the effectiveness of high-dose tranexamic acid given in the preoperative period on blood loss in patients undergoing cardiopulmonary bypass. One hundred fifty patients scheduled to undergo cardiac operations with cardiopulmonary bypass were randomized into three groups of equal size. The first group received 10 gm of tranexamic acid intravenously over 20 minutes before sternotomy and a placebo infusion over 5 hours. The second group received 10 gm of tranexamic acid over 20 minutes and then another 10 gm infused intravenously over 5 hours. The control group received a placebo bolus and a placebo infusion over 5 hours (0.9% normal saline solution). The blood loss after the operation was measured at 6 hours and 24 hours. The homologous blood and blood products given during and up to 48 hours after operation were recorded. Eighteen percent of the control group patients shed more than 750 ml blood in 6 hours compared with only 2% in both tranexamic acid groups. Patients who shed more than 750 ml blood required 93% more red blood cell transfusions than patients without excessive bleeding. Tranexamic acid (10 gm) given intravenously in the period before cardiopulmonary bypass reduced blood loss over 6 hours by 50% and over 24 hours by 35%. Continued tranexamic acid infusion (10 gm over 5 hours) did not reduce bleeding further. There was no difference in the coagulation profile before operation between patients with and without excessive bleeding. However, coagulation tests done in the postoperative period indicated ongoing fibrinolysis and platelet dysfunction in patients with excessive bleeding.