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

This study investigates how the length of time a sample of fresh equine blood is held, and the protocol used to handle it, can influence clotting factors when tested using the VCM-Vet™ device.

Research Context and Methodology

• The study was conducted on 8 healthy adult horses from a university teaching herd.
• The researchers collected blood from each horse using a direct jugular venipuncture method, then held the samples at a temperature of 37 degrees Celsius for 2, 4, 6, or 8 minutes.
• They used two different protocols for processing the samples: Protocol A, in which samples were processed from a single syringe, and Protocol B, where 4 syringes were drawn through a single needle.

Procedure and Testing

• Blood samples were gently inverted twice, a small amount was expressed, testing cartridges were filled and then placed within the VCM-Vet™ device (by Entegrion Inc), which was used to measure different coagulation parameters.
• The VCM-Vet™ device was used to assess clot time (CT), clot formation time (CFT), alpha angle (AA), amplitude at 10/20 minutes (A10/A20), maximal clot firmness (MCF), and lysis index at 30/45 minutes (LI30/LI45).
• The researchers compared differences over time with a statistical analysis called the Friedman test, followed by a post hoc Wilcoxon Rank Sum Test, with P ≤ .05 indicating statistical significance.

Findings

• When using Protocol A, there was a significant effect on CT, CFT, and AA, depending on how long the blood sample was held. The CT and AA decreased over time, while CFT increased.
• On the other hand, samples processed using Protocol B did not show significant differences over time for any of the parameters measured by the VCM-Vet™ device.

Conclusion

• The holding time of a sample and the protocol used for handling it significantly impact the results of VCM-Vet™ testing of fresh equine whole blood. Therefore, the handling method is crucial when gathering information about the blood’s viscoelasticity and ability to form clots.
• The researchers recommend that samples tested using the VCM-Vet™ be held at rest for up to 8 minutes after collection while warm, but they caution against reusing any samples.