Resumen de The effects of protamine sulfate on clot formation time and clot strength thromboelastography variables for canine blood samples

• Objective�To determine the effects of protamine sulfate on clot formation time and clot strength thromboelastography variables for canine whole blood samples.

  Animals�Blood samples obtained from 11 healthy dogs.

  Procedures�Blood samples were collected from jugular veins of dogs into syringes with 3.2% sodium citrate (blood to citrate ratio, 9:1). Blood samples were divided into aliquots, and protamine sulfate was added to various concentrations (0 [control], 22, 44, and 66 µg/mL). Prepared samples were activated with kaolin (n = 8) or not activated (8), CaCl2 was added, and thromboelastography was performed. Reaction time (R), clot formation time (K), rate of clot formation (a angle), and maximum amplitude (MA) were measured.

  Results�For kaolin-activated and nonactivated blood samples, protamine (66 µg/mL) significantly increased R and K and decreased a angle and MA, compared with values for control samples. Also, protamine (44 µg/mL) decreased MA in nonactivated blood samples and increased K and decreased a angle in kaolin-activated samples, compared with values for control samples.

  Conclusions and Clinical Relevance�Results indicated protamine prolonged clot formation time and decreased overall clot strength in a dose-dependent manner; such effects may contribute to a hypocoagulable state in dogs. Kaolin-activated and nonactivated blood samples were appropriate for measurement of the effects of protamine on coagulation. Administration of protamine to reverse the effects of heparin should be performed with caution.