In veterinary medicine, TEM/TEG has been used to investigate different conditions of hypocoagulabilty [25, 30], and hypercoagulabilty [21, 23, 31] in dogs and, to a lesser extent, in other species [20, 24]. In bovine medicine, only one preliminary study on thromboelastometry  has been published to date. In this study the analytical performance of the instrument in the bovine species has been evaluated and coefficients of variation have been calculated. In general, in cattle, as in dogs , the use of strong clotting activators (as the in-TEM® and ex-TEM® reagents), instead of recalcification only (as in na-TEM®) reduce the impact of pre-analytical phactors on TEM tracings and allow more reproducible results. Furthermore it is not known at this moment if also in cattle, as in human beings, the TEM results are influenced by age and gender (Sucker et al. 2011). For this reason further studies are necessary to investigate the impact of age, gender and also breed category (e.g. dairy vs. beef breed) on TEM results.
The results of the present study indicate a hypercoagulable condition in the dexamethasone-treated group (increase in alpha angle and MCF with a reduction in CFT on all profiles; decrease in CT on the in-TEM® profile), with the involvement of both plasma and cellular components of hemostasis. Interestingly, the CT was shortened on the in-TEM® profile of the treated calves but prolonged on the ex-TEM® and fib-TEM® profiles. This difference could be explained by an increase in the activity of factor VIII and XI, as observed in humans after corticosteroid administration . Both factors are involved in the intrinsic pathway (in-TEM®), whereas the profiles triggered by tissue factor (ex-TEM® and fib-TEM®) are less influenced by these changes. The reason for CT prolongation in the ex-TEM® and fib-TEM® profiles is not clear. Further qualitative assessments of the hemostatic process (e.g., plasma factor levels) are needed to elucidate these changes.
In human studies, hypercoagulability after corticosteroid administration has been related also to an increase in fibrinogen levels . This condition could be the cause for the increase in the MCF observed in this study. A significant increase in MCF was observed not only on the in-TEM® and ex-TEM® profiles but also on the fib-TEM® profile, where platelet contribution to clot stability is annulled by the addition of cytochalasin D. Here, again, further studies are needed to quantify the contribution of factor XIII. A limitation of this study is the lack of fibrinogen concentration measurement.
Certain preanalytical factors are known to influence the thromboelastometric results in different species (e.g., sampling technique and storage condition) [24, 33]. Also, because TEG tracings can be altered in some pathologic conditions due to an increase or a decrease hemostasis [21, 23, 34, 35], it is essential to standardize sampling technique and storage conditions and to evaluate the patient’s clinical status when performing TEM analysis, as was done in the present study.
The results of the ROC curves show that parameters such as in-TEM MCE and fib-TEM MCE are able to identify cattle treated with dexamethasone for long periods at low doses. These preliminary results could be useful in field identification of illicitly treated cattle, even in a fairly small (n = 11) sample of heads simultaneously treated in each herd.
All the calves in both groups were affected by anemia due to the particular zootechnic. This variation in hematocrit is known to affect the TEM tracing, also in bovine species, since it increases the blood coagulability measured by the instrument . It is not known whether this phenomenon reflects an in vivo effect of red blood cell mass on hemostasis or whether it is simply an artifact of the viscoelastic technology . In our study, anemia was not considered as a confounding factor, because both groups showed the same severity of anemia. It is not known, at this moment, if the anemia observed in our study population, could have enhanced the hemostatic changes secondary to dexamethasone treatment. For this reason, further studies are necessary to investigate the effects of dexamethasone in bovines not affected by anemia.
To the best of authors’ knowledge this is the first study to assess the effect of steroids on blood coagulation in bovines.