Effect of venipuncture quality on thromboelastography

Objective - To determine if the quality of venipuncture impacts thromboelastography (TEG) results and if an initial discard tube mitigates any effects of traumatic venipuncture. Design - Prospective, observational study. Setting - Veterinary teaching hospital. Animals - Fifteen privately owned and research colony adult dogs. Measurements - Samples were collected from each jugular vein using 1 of 2 venipuncture techniques per vein. The venipuncture technique was randomized to the vein as follows: (1) clean venipuncture (CV) from 1 jugular vein, and (2) suboptimal venipuncture (SOV) from the opposite jugular vein. CV was defined as a direct entry into the vein on the first attempt. SOV was defined as needle insertion adjacent to the vein with redirection at least once to enter the vein. Two consecutive samples were collected from each venipuncture without removal of the needle, yielding 4 samples: CV1, CV2, SOV1, and SOV2. TEG was performed on each blood sample and the TEG parameters R, K, alpha, and MA were recorded. Results-Mean +/- SD of R for the SOV1 group (4.1 +/- 1.3 s) was significantly shorter than that of the CV1 group (5.7 +/- 1.4 s) and the SOV2 group (5.5 +/- 1.9 s), P < 0.05. There was no difference in R between CV1 and CV2 groups, or between SOV2 and either CV1 or CV2. There was no significant difference in alpha, K, or MA among groups. Conclusions - Mild-to-moderate venipuncture trauma had little effect on TEG overall, but R was significantly affected. Poorer quality collection resulted in a more rapid initiation of clot formation. However, the effect was mild and mitigated by testing samples in a second collection tube after discard of an initial sample.