Comparison of the effects of open-tube and evacuated tube-assisted sampling methods on thromboelastography variables for blood samples from healthy dogs.

Objective: To compare the effects of open-tube blood sampling with previously investigated blood sampling methods via evacuated tube on thromboelastography variables for blood samples from dogs.

Animals: 10 healthy Beagles from the research colony owned by the Clinic of Small Animal Internal Medicine, University Veterinary of Medicine, Vienna, were used.

Procedures: In this prospective study, blood was sampled from each dog serially into citrate solution-containing tubes via 20-gauge needle. One evacuated tube was filled from a jugular vein via the evacuated tube port, and the second tube was opened and filled by catching blood flowing through the needle from a lateral saphenous vein. Venipuncture quality was scored with a previously described method. Thromboelastography was performed for each sample.

Results: Inferential statistics used with the Wilcoxon signed rank test showed significant differences in reaction time (R) of 3.43 ± 0.84 minutes versus 4.53 ± 0.62 minutes (mean ± SD) between evacuated tube assisted and open-tube sampling, respectively. No other significant differences were identified.

Clinical Relevance: The sampling methods compared have a small but significant effect on R in thromboelastographic analysis for blood samples from healthy dogs. Shear stress by vacuum sampling seems to accelerate coagulation in jugular blood samples harvested by evacuated tube, resulting in a shortened R. Results suggested that the open-tube method avoids shear stress induced activation of coagulation and is an appropriate sampling method for thromboelastography when used within a standardized protocol.