Viscoelastic Tests (VET) Versus Conventional Coagulation Tests (CCT) for Management of Trauma-Induced Coagulopathy

Traumatic coagulopathy is a complex, multifactorial event that occurs in 20-30% of patients on admission. It increases mortality, and its treatment is one of the main priorities in the early management of severely injured patients. Diagnosis of coagulopathy has traditionally been based on conventional coagulation tests (CCTs), which provide an assessment of patients' coagulation in over 60 minutes. Over the past fifteen years, viscoelastic tests (VETs) have been proposed, providing a more rapid result (≤ 10 min) and can guide the administration of labile blood products (LBP). Various studies, mainly retrospective, have shown that the use of VETs is associated with a significant reduction in the use of LBP and the incidence of massive transfusions (MT).

For example, it has been showed that the use of VETs was accompanied by a reduction in the administration of LBP and more particularly of RBC (Red blood cell concentrate) (4.8 units vs. 1.9 units). The investigators obtained the same result on a larger number of patients, with a further reduction in the administration of other LBP and in the incidence of MT (33% vs. 8%, p<0.01).

However, the main limitation of these 2 studies is that the results may not have been due solely to the use of ROTEM, but rather to a care package combining the use of ROTEM with the administration of tranexamic acid and the implementation of Damage Control Surgery techniques.

To avoid this methodological criticism, we recently compared 2 contemporary French cohorts (2012-2019), in which patients had similar management of traumatic injuries, with the exception of the type of coagulation tests: CCT vs. VET. The use of VET s was associated with an increase in the number of patients alive at 24h without MT (76% vs. 55%, p<0.001), but also with a sharp reduction in the administration of all LBPs.

This composite criterion associating the occurrence of a MT with survival at 24 hours after hospital admission was the primary endpoint of the randomized iTACTIC study. iTACTICS was published in 2021, and aimed to compare in severely injured patients 2 strategies for the diagnosis and treatment of coagulopathies, based on CCT in one arm and VET in the other. In this work, the use of VET was not associated with an improvement in the proportion of patients alive at 24 hours without MT (64% vs. 67%, OR 1.15, CI95%: 0.8-1.7), nor with any of the other criteria studied. The main limitation of this study is that less than a third of the patients included had a coagulopathy on admission. The probability of receiving LBP was therefore low. In the subgroup of the most severe patients, an improvement in the primary endpoint was observed for patients randomized to the VET group. The small sample size and subgroup analysis, however, limited the significance of this result.

All these elements suggest that it is necessary :

* to use a composite endpoint rather than a single endpoint (mortality) for the evaluation of VET-based strategies, combining early mortality with the occurrence of a transfusion event. * conduct a randomized trial comparing the use of VETs with that of CCTs in trauma patients with a high probability of coagulopathy on admission to hospital.