Coagulation effects of low molecular weight heparin compared with heparin in dogs considered to be at risk for clinically significant venous thrombosis

J Vet Emerg Crit Care (San Antonio). 2009 Feb;19(1):74-80. doi: 10.1111/j.1476-4431.2008.00339.x.


Objective: Compare the effects of 3 anticoagulation protocols on anti-factor Xa activity (AXa).

Design: Prospective, randomized, double-blind study.

Setting: University veterinary teaching hospital.

Animals: Eighteen dogs considered to be at risk for venous thrombosis.

Interventions: Each dog was randomly assigned to 1 of the following 3 groups (n=6/group) and was treated for 24 hours: low-dose heparin (LDH), high-dose heparin (HDH), and dalteparin (DP). Dogs in the LDH group received a constant rate infusion (CRI) of unfractionated heparin (UFH) at 300 U/kg/d, the HDH group received a bolus of 100 U/kg of UFH IV, then a CRI of 900 U/kg/day, and the DP group received 100 U/kg DP SC at 0, 12, and 24 hours.

Measurements and main results: A total of 54 samples for activated partial thromboplastin time (aPTT) and AXa assays were collected at 0, 4, and 28 hours. Six samples had an AXa >0.1 U/mL, 5 of those were from the HDH group at hour 4. Two samples from the HDH group at hour 4 had a prolonged aPTT (93 and 200 seconds) and the highest AXa (0.6 and 1.0 U/mL, respectively). Four additional dogs in the HDH group did not complete the study due to hemorrhage; none of the dogs completing the study showed signs of hemorrhage.

Conclusions: Neither DP nor LDH increased AXa to values considered therapeutic in humans (0.5-1 and 0.35-0.75 U/mL, respectively), and both protocols appear to be inadequate to increase AXa in dogs with clinical illness. HDH increased AXa to this range in 2 of 6 dogs, but had unpredictable effects on aPTT and resulted in hemorrhage in some dogs.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Animals
  • Anticoagulants / therapeutic use*
  • Dalteparin / administration & dosage
  • Dalteparin / therapeutic use*
  • Dog Diseases / drug therapy*
  • Dogs
  • Risk Factors
  • Venous Thrombosis / drug therapy
  • Venous Thrombosis / veterinary*


  • Anticoagulants
  • Dalteparin