title: Use of viscoelastic coagulation testing to monitor low molecular weight heparin administration to healthy horses.
abstract: OBJECTIVE
  To evaluate the utility of thromboelastography (TEG) and Sonoclot analyses to monitor the effects of low molecular weight heparin (LMWH) administration to healthy horses.
  
  
  METHODS
  Randomized crossover study.
  
  
  METHODS
  Large animal veterinary teaching hospital.
  
  
  METHODS
  Six adult mixed breed healthy mares.
  
  
  METHODS
  LMWH (dalteparin) was administered (50 U/kg subcutaneously) either every 12 or 24 h for 3 consecutive days. Blood samples were collected before LMWH administration and then at selected time points for analysis. Thromboelastography derived R-time (R), K-time (K), angle (ANG), and maximum amplitude (MA), and Sonoclot activated clot time (ACT), clot rate (CR), and platelet function (PF) were measured in whole blood 30 min after sample collection. Change (Δ) and percentage change (%Δ) from baseline of each TEG and Sonoclot variable were subsequently calculated. Anti-factor Xa activity and activated partial thromboplastin time (aPTT) were assayed in harvested plasma. The association between anti-factor Xa activity and TEG and Sonoclot (measured and calculated) variables was assessed by calculating correlation coefficients and multiple regression analysis. The ability of measured and calculated TEG and Sonoclot variables to predict when anti-factor Xa activity fell below suggested thromboprophylactic levels was assessed using receiver operating characteristic curve analysis.
  
  
  RESULTS
  The correlation between aPTT and anti-factor Xa activity was weak (r = 0.343). Changes in TEG and Sonoclot variables following LMWH administration were consistent with hypocoagulation. All measured and calculated TEG variables were significantly correlated with anti-factor Xa activity. Sonoclot ACT, ΔACT, CR, ΔCR, and %ΔCR were also significantly correlated with anti-factor Xa activity. TEG ΔR and %ΔR best predicted anti-factor Xa activity below the suggested thromboprophylactic level.
  
  
  CONCLUSIONS
  Although correlations were modest, serial measurement of TEG variables may be used to monitor LMWH therapy in horses; however, further research is required in sick horses.
authors: Department of Large Animal Medicine, University of Georgia College of Veterinary Medicine, Athens, GA, USA. bretttbrown@gmail.com
authors: Brett S
authors: BS
authors: Tennent-Brown
authors: Kira L
authors: KL
authors: Epstein
authors: Dorothy D
authors: DD
authors: Whelchel
authors: Steeve
authors: S
authors: Giguère
mesh_terms: D000818:Animals; D000925:Anticoagulants / Q000494:pharmacology*; D019540:Area Under Curve; D018592:Cross-Over Studies; D017985:Dalteparin / Q000494:pharmacology*; D005260:Female; D006736:Horses / Q000097:blood*; D010314:Partial Thromboplastin Time / Q000662:veterinary; D012212:Rheology / Q000379:methods; D012680:Sensitivity and Specificity
chemical_list: D000925:Anticoagulants; D017985:Dalteparin