Coagulation effects of low molecular weight heparin compared with heparin in dogs considered to be at risk for clinically significant venous thrombosis.
OBJECTIVE
Compare the effects of 3 anticoagulation protocols on anti-factor Xa activity (AXa).


METHODS
Prospective, randomized, double-blind study.


METHODS
University veterinary teaching hospital.


METHODS
Eighteen dogs considered to be at risk for venous thrombosis.


METHODS
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.


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.
Scott
Kielyn C
KC
Department of Clinical Sciences, Veterinary Teaching Hospital, North Carolina State University, Raleigh, NC 27606, USA. kielyns@yahoo.com
Hansen
Bernie D
BD
DeFrancesco
Teresa C
TC
D000818:Animals; D000925:Anticoagulants / Q000627:therapeutic use*; D017985:Dalteparin / Q000008:administration & dosage / Q000627:therapeutic use*; D004283:Dog Diseases / Q000188:drug therapy*; D004285:Dogs; D012307:Risk Factors; D020246:Venous Thrombosis / Q000188:drug therapy / Q000662:veterinary*
D000925:Anticoagulants; D017985:Dalteparin