title: Infusible platelet membranes improve hemostasis in thrombocytopenic blood: experimental studies under flow conditions.
abstract: BACKGROUND
  The potential hemostatic effect of infusible platelet membranes (IPM; Cyplex, Cypress Bioscience) prepared from outdated human platelets is investigated.
  
  
  METHODS
  Increasing concentrations of IPM were added to blood samples anticoagulated with low-molecular-weight heparin, in which platelets and WBC counts had been experimentally reduced by a filtration procedure. Thrombocytopenic blood with IPM was circulated in a perfusion chamber at various shear rates (300, 600, and 1200/sec(-1)), and platelet and fibrin deposition on the surface of a damaged vessel was measured. Prothrombin fragments 1 and 2 (F1+2) levels were also monitored.
  
  
  RESULTS
  Under conditions of severe thrombocytopenia (<6000 platelets/microL) IPM did not increase platelet deposition. However, a dose-dependent increase in fibrin deposition was observed with concentrations of IPM ranging from 0.5 to 2 mg per kg in perfusions at 300 and 600 per sec(-1) (p<0.05 vs. thrombocytopenic blood). Experimental studies performed under conditions of moderate thrombocytopenia and higher shear rates (25, 000-30,000 platelets/microL; at 600 and 1200/sec(-1)) showed that IPM concentrations equivalent to 0.5 or 1 mg per kg improved fibrin deposition (33.5 +/- 9.5% and 37.7 +/- 12.8%, respectively, vs. 22.7 +/- 5.2% in controls) and also promoted a moderate increase in platelet deposition, with a concomitant significant increase in the size of platelet aggregates (p<0.05). Exposure of thrombocytopenic blood to a damaged vessel resulted in an increase of F1+2 levels from 0.8 +/- 0.15 to 1.7 +/- 0.22 nM at 300 per sec(-1) and 1.94 +/- 0.46 nM at 600 per sec(-1). Postperfusion levels of F1+2 after the addition of IPM were always similar to levels in untreated controls.
  
  
  CONCLUSIONS
  IPM promotes local procoagulant activity at sites of vascular damage under conditions of severe and moderate thrombocytopenia. IPM also appears to facilitate platelet cohesive functions under conditions of moderate thrombocytopenia.
authors.affiliation: Hemotherapy and Hemostasis Service, Hospital Clínic, Barcelona, Spain. agalan@clinic.ub.es
authors.forename: A M
authors.initials: AM
authors.lastname: Galán
authors.forename: J
authors.initials: J
authors.lastname: Bozzo
authors.forename: M R
authors.initials: MR
authors.lastname: Hernández
authors.forename: M
authors.initials: M
authors.lastname: Pino
authors.forename: J C
authors.initials: JC
authors.lastname: Reverter
authors.forename: R
authors.initials: R
authors.lastname: Mazzara
authors.forename: G
authors.initials: G
authors.lastname: Escolar
authors.forename: A
authors.initials: A
authors.lastname: Ordinas
mesh_terms: D001792:Blood Platelets / Q000166:cytology*; D002462:Cell Membrane / Q000502:physiology; D004730:Endothelium, Vascular / Q000378:metabolism; D005337:Fibrin / Q000378:metabolism; D006487:Hemostasis / Q000502:physiology*; D006801:Humans; D017713:Platelet Transfusion; D013921:Thrombocytopenia / Q000097:blood*
chemical_list: D005337:Fibrin