Thromboelastography in healthy dogs and in dogs with immune-mediated hemolytic anemia
This thesis is an investigation of the use of thromboelastography (TEG) to characterize changes in hemostasis associated with prednisone and/or acetylsalicylic acid therapy in normal dogs and dogs with immune-mediated hemolytic anemia (IMHA). Canine IMHA is frequently associated with thromboembolic disease (TED). There are few hemostastic tests available to predict TED, and TEG holds promise in this regard. The objective of this thesis consisted of three parts: 1) Development of reference intervals for TEG in clinically healthy dogs; 2) Determine the independent and combined effects of prednisone and acetylsalicylic acid (ASA) on TEG in clinically healthy dogs; and 3) Describe the appearance of TEG in cases of canine IMHA before and after treatment. Reference intervals were developed for TEG using citrated whole blood from 40 healthy dogs, using both activated (kaolin) and non-activated TEG. It was determined that the addition of kaolin caused the TEG to appear relatively more hypercoagulable compared to non-activated samples, but would probably not provide a diagnostic advantage over non-activated samples. In the second study of the thesis, 16 purpose-bred hounds were randomized to 4 treatment groups (4 dogs/group). Group 1 received prednisone 2mg/kg PO, q24h from days 0-6. Group 2 received ASA 0.5mg/kg PO, q24h from days 0-6. Group 3 received prednisone and ASA at the aforementioned doses. Group 4 received no treatment. TEG was performed pre-treatment and then every 48 hours until day 6. The TEG tracings appeared hypercoagulable in dogs treated with prednisone, both with and without ASA. In addition, decreased fibrinolysis was demonstrated in prednisone-treated dogs. In the third study of the thesis, TEG was performed on 20 cases of naturally-occurring canine IMHA. TEG was performed on the day of admission and then every 48 hours until discharge from hospital or death/euthanasia. Eighty percent of dogs were considered to be hypercoagulable based on a coagulation index (CI) above the reference interval. However, a CI or Maximum Amplitude within the reference interval were found to be poor prognostic indicators. In addition, prolongation of the activated clotting time was also associated with a poor outcome, and this parameter was correlated with the TEG parameters.