title: Levels of procoagulant microvesicles are elevated after traumatic injury and platelet microvesicles are negatively correlated with mortality.
abstract: BACKGROUND
  Microvesicles (MV) have been implicated in the development of thrombotic disease, such as acute respiratory distress syndrome (ARDS) and multiple organ failure (MOF). Trauma patients are at increased risk of late thrombotic events, particularly those who receive a major transfusion. The aims of this study were: (a) to determine whether there were increased numbers of pro-coagulant MV following injury; (b) to determine their cellular origin; and (c) to explore the effects of MV with clinical outcomes; in particular red cell transfusion requirements and death.
  
  
  METHODS
  Trauma patients were recruited at a Level 1 trauma centre. The presence of MV procoagulant phospholipid (PPL) was assessed using 2 activity assays (PPL and thrombin generation). Enumeration and MV cellular origin was assessed using 2 colour flow cytometry.
  
  
  RESULTS
  Fifty consecutive patients were recruited; median age 38 (IQR: 24-55), median ISS 18 (IQR: 9-27). Circulating procoagulant MV, rich in phospholipid, were significantly elevated following traumatic injury relative to controls and remained elevated at 72 h post-injury. Red cell/AnnV+ and platelet/AnnV+ MV numbers were 6-fold and 2-fold higher than controls, respectively. Patients who died (n=9, 18%) had significantly fewer CD41/AnnV+ MV and lower endogenous thrombin potential relative to patients who survived.
  
  
  CONCLUSIONS
  MV are elevated following traumatic injury and may be implicated in the increased risk of trauma patients to pro-thrombotic states such as MOF and ARDS. Lower levels of procoagulant MV are associated with mortality and further investigation of this association is warranted.
authors.affiliation: Oxford Haemophilia & Thrombosis Centre, Oxford University Hospitals Trust, Churchill Hospital, Oxford, UK.
authors.forename: Nicola
authors.initials: N
authors.lastname: Curry
authors.affiliation: National Blood & Transplant, John Radcliffe Hospital, Oxford, UK.
authors.forename: Amber
authors.initials: A
authors.lastname: Raja
authors.affiliation: Oxford Haemophilia & Thrombosis Centre, Oxford University Hospitals Trust, Churchill Hospital, Oxford, UK.
authors.forename: James
authors.initials: J
authors.lastname: Beavis
authors.affiliation: National Blood & Transplant, John Radcliffe Hospital, Oxford, UK.
authors.forename: Simon
authors.initials: S
authors.lastname: Stanworth
authors.affiliation: School of Immunity and Infection, University of Birmingham Medical School, Birmingham, UK; p.harrison.1@bham.ac.uk.
authors.forename: Paul
authors.initials: P
authors.lastname: Harrison
keywords: flow cytometry; microvesicles; thrombin generation; trauma