Equis ISSN 2398-2977

Blood: hemostasis

Contributor(s): Annalisa Barrelet, Robert Shull

Introduction

  • Normal hemostasis depends on a complex interaction between vascular endothelial cells, platelets, plasma proteins, and the fibrinolytic system.
  • Diagnosis of hemostatic dysfunction is based on a battery of assays, some of which may not be readily available to the equine practitioner.
  • The more readily available and hence most commonly measured parameters are:
  • Platelet count   Blood: platelet evaluation  .
  • Activated coagulation time (ACT): measures intrisic and common coagulation pathways, (Becton Dickinson VACUTAINER Systems.
  • Simple bleeding time: sensitive to coagulation and platelet deficiencies.
  • Commercial laboratories or human medical facilities may offer more specialized coagulation testing.
  • Prothrombin time (PT): a measure of the extrinsic and common coagulation pathways.
  • Activated partial thromboplastin time (APTT): assesses intrinsic and common coagulation pathways.
  • Fibrinogen degradation products (FDP) concentration.: assess rate of fibrinolysis.
  • Initial screening is performed on blood collected by standard venipuncture   Blood: collection  into sodium citrate tubes (one part 3.8% citrate to 9 parts blood) for platelet count, prothrombin time and APTT, and into a tube containing trypsininhibitior and a procoagulant venom for FDP. (Thrombo-Wellco test, Murex Diagnostics) .
    Note that EDTA and heparin coagulations may produce spuriously low platelet counts by stimulating in vitroagglutination of platelets
    This can be differentiated from true thrombocytopenia by microscopic identification of platelet clumps and repeating the platelet count on a sample collected into sodium citrate anticoagulant. Careful sample handling is essential to avoid spurious results
  • Control samples from a normal horse should be collected where possible and analyzed concurrently.
  • See also:

Normal ranges - adult

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