Sonoclot® Evaluation of Single‐ and Multiple‐Dose Subcutaneous Unfractionated Heparin Therapy in Healthy Adult Dogs

Background Heparin therapy is difficult to monitor due to variation in animal response. While laboratory measurements of activated partial thromboplasin time (aPTT) and Anti‐Xa activity (AXA) accurately describe heparin effect, their availability is limited. Hypothesis Sonoclot analysis would be as sensitive as AXA and aPTT to monitor effects of unfractionated heparin (UFH) in healthy adult dogs. Animals Six adult mixed‐breed dogs. Methods A prospective study design was employed. On day 1, baseline samples were collected (CBC, PT, aPTT, and Sonoclot), and UFH (300 U/kg SC) was administered to 6 dogs following an IV loading dose of 50 U/kg. Sonoclot and aPTT were performed hourly for 12 hours. AXA was assayed at hours 3, 6, 9, and 12. UFH (300 U/kg q8 h SC) was administered at 12 hours, and subsequently (q8 h) for 2 additional days. On day 4, a final dose of UFH was administered, and a sampling protocol identical to day 1 was performed. Results Sonoclot activated clotting time (ACT) and clot rate (CR) correlated with AXA (R = 0.69, R = 0.65, respectively, P