Effects of oral prednisone administration with or without ultralow-dose acetylsalicylic acid on coagulation parameters in healthy dogs

Objective: To determine the effects of oral prednisone administration with or without ultralow-dose acetylsalicylic acid on coagulation parameters in healthy dogs and to assess intraindividual variation in thromboelastography results. Animals: 14 healthy research dogs and 10 healthy client-owned dogs. Procedures: In a randomized controlled trial, research dogs underwent thromboelastography twice (3 days apart), and intraindividual variation in test results was calculated. Dogs were given prednisone (2 mg/kg/d, PO) plus acetylsalicylic acid (0.5 mg/kg/d, PO) or prednisone (2 mg/kg/d, PO) plus a placebo for 14 days, after which thromboelastography and other tests were repeated. Differences from preadministration (baseline) test results between and within groups were compared. In a separate trial, client-owned dogs also underwent thromboelastography twice 2 days apart to assess intraindividual variation in untreated dogs. Results: Intraindividual variation in thromboelastography results for research dogs was ≤ 10% for maximum amplitude (MA) and α angle. In the research dogs, MA and fibrinogen values significantly increased from baseline, whereas percentage lysis 30 minutes after attainment of the MA as well as antithrombin activity significantly decreased within each group. In the dogs that received prednisone plus a placebo, percentage lysis 60 minutes after attainment of the MA was significantly lower than at baseline. For all parameters for research dogs, there was no difference between groups for change from baseline. Intraindividual variation in findings for client-owned dogs was similar to the variation for research dogs. Conclusions and Clinical Relevance: Prednisone administration resulted in hypercoagulability in healthy dogs as indicated by an increase in MA and plasma fibrinogen concentration and a decrease in antithrombin activity. Concurrent ultralow-dose acetylsalicylic acid use had no effect on measured thromboelastography values. The high intraindividual variation in some thromboelastography parameters may preclude routine use of this technique in clinical practice.