Prolonged holding time and sampling protocol affects viscoelastic coagulation parameters as measured by the VCM-Vet™ using fresh equine native whole blood

OBJECTIVES Determine the effect of sample holding time and single sample reuse on viscoelastic coagulation parameters when using fresh equine native whole blood. ANIMALS 8 healthy adult horses from a university teaching herd. PROCEDURES Blood collected by direct jugular venipuncture (18 ga needle, 3 mL syringe) was held at 37 °C for 2, 4, 6, or 8 minutes according to 1 of 2 protocols. Syringes were gently inverted twice, a small amount of blood was expressed, testing cartridges were filled, and placed within the VCM-Vet™ device (Entegrion Inc). Protocol A: samples were processed from a single syringe. Protocol B: 4 syringes were drawn through a single needle. VCM-Vet™ measures assessed included clot time (CT), clot formation time (CFT), alpha angle (AA), amplitude at 10/20 minutes (A10/A20), maxi-mal clot firmness (MCF), and lysis index at 30/45 minutes (LI30/LI45). Differences over time were examined using the Friedman test and post hoc Wilcoxon Rank Sum Test with Bonferroni correction, P ≤ .05. RESULTS Following Protocol A, there was a significant effect of holding time for CT (P = .02), CFT (P = .04), and AA (P = .05). CT and AA decreased over time, while CFT increased. Samples handled by Protocol B showed no significant differ-ence over time for any of the VCM-Vet™ parameters. CLINICAL RELEVANCE Sample holding time and handling protocol impact VCM-Vet™ testing results of fresh equine native whole blood. Viscoelastic coagulation samples tested using the VCM-Vet™ may be held unagitated for up to 8 minutes after collection while warm, but should not be reused.