title: Low level of procoagulant platelet microparticles is associated with impaired coagulation and transfusion requirements in trauma patients.
abstract: BACKGROUND
  Following activation, platelets release small vesicles called platelet-derived microparticles (PMPs). PMPs accelerate thrombin generation and thus clot formation at sites of injury by exposing the procoagulant membrane phospholipid phosphatidylserine (PS). The role of PMPs in coagulopathy and hemorrhage following trauma remains elusive. We hypothesized that low levels of PS-positive PMPs (PS + PMPs) would be associated with impaired clot formation.
  
  
  METHODS
  This is a prospective observational study of 210 trauma patients admitted directly to a Level 1 trauma center. Plasma levels of PS + PMPs were determined by flow cytometry. Coagulation status was assessed by rotational thrombelastometry, and impaired clot formation was defined by an α angle less than 63 degrees using the tissue factor-based EXTEM reagent. Transfusion requirement was assessed by number of units of red blood cells (RBCs) transfused within 24 hours of admission; platelet aggregation capacity was evaluated by the Multiplate assay; and injury severity was determined by the Injury Severity Score (ISS).
  
  
  RESULTS
  The median ISS was 17, and blood samples were obtained after a median of 65 minutes following injury. Significantly lower levels of PS + PMPs were found in patients with impaired clot formation (p < 0.001). A low level of PS + PMPs was associated with a higher number of RBCs transfused during the initial 24 hours after admission (p < 0.03) when corrected for risk factors, for example, platelet count, hemoglobin level, and ISS. Platelet aggregation and PS + PMPs did not correlate significantly.
  
  
  CONCLUSIONS
  Low levels of PMPs were associated with impaired clot formation in trauma patients at admission and also with the number of RBC transfusions. This suggests that PMPs may play an important and not previously investigated role in trauma-induced coagulopathy.
  
  
  METHODS
  Prognostic study, level III.
authors.affiliation: From the Department of Anesthesia (N.A.W., A.M.S., L.S.R.), Center of Head and Orthopedics; Section for Transfusion Medicine (P.I.J., S.R.O.), Capital Region Blood Bank; Trauma Center (A.M.S., C.F.L.), Center of Head and Orthopedics; Department of Intensive Care (A.P.), Abdominal Center; and Department of Cardiothoracic Anesthesia and Intensive Care (M.W.), The Heart Center, Copenhagen University Hospital, Rigshospitalet, Denmark; and Department of Surgery (P.I.J.), Center for Translational Injury Research, University of Texas Medical School at Houston, Houston, Texas.
authors.forename: Nis Agerlin
authors.initials: NA
authors.lastname: Windeløv
authors.forename: Pär Ingemar
authors.initials: PI
authors.lastname: Johansson
authors.forename: Anne Marie
authors.initials: AM
authors.lastname: Sørensen
authors.forename: Anders
authors.initials: A
authors.lastname: Perner
authors.forename: Michael
authors.initials: M
authors.lastname: Wanscher
authors.forename: Claus Falck
authors.initials: CF
authors.lastname: Larsen
authors.forename: Sisse Rye
authors.initials: SR
authors.lastname: Ostrowski
authors.forename: Lars Simon
authors.initials: LS
authors.lastname: Rasmussen