Noncitrated whole blood is optimal for evaluation of postinjury coagulopathy with point-of-care rapid thrombelastography.

INTRODUCTION: Progressive postinjury coagulopathy has become the fundamental rationale for damage control surgery, and the decision to abort operative intervention must occur prior to overt laboratory confirmation of coagulopathy. Current coagulation testing is most commonly performed for monitoring anticoagulation therapy, the results are delayed, and the applicability of these tests in the trauma setting is questionable. Point-of-care (POC) rapid thrombelastography (r-TEG) provides real time analysis of thrombostatic function, which may allow for accurate, goal directed therapy. The test differs from standard thrombelastography (TEG) because the clotting process and subsequent analysis is accelerated by the addition of tissue factor to the whole blood sample, but is limited by the requirement that the analysis be performed within 4 min of blood draw to prevent clot formation. Consequently, citrated specimens have been proposed to obviate this time limitation. We hypothesized that the speed of r-TEG analysis following tissue factor addition to citrated blood might compromise accurate determinations compared with noncitrated whole blood. Additionally, we sought to compare the use of r-TEG with conventional coagulation tests in analysis of postinjury coagulopathy.
METHODS: We conducted a retrospective study of severely injured patients entered into our trauma database between January and June 2008 who were at risk for postinjury coagulopathy. Patients needed simultaneous conventional coagulation (INR, fibrinogen, platelet count) and r-TEG specimens with either fresh or citrated whole blood for inclusion in the study. kappa-Statistics were used to determine the agreement between the tests in predicting hypocoagulability. McNemar's chi(2) tests were used to compare theoretical blood product administration between r-TEG and conventional coagulation tests for noncitrated specimens. Therapeutic transfusion triggers were: INR (>1.5) and r-TEG ACT (>125 s) for FFP administration; fibrinogen (<133 mg/dL) and alpha-angle (<63 degrees ) for cryoprecipitate; and platelet count (<100K) and maximum amplitude (MA) (<52 mm) for aphaeresis platelets. Statistical significance was established as P<0.05 using two-sided tests.
RESULTS: Forty-four patients met the inclusion criteria. kappa-Values (correlation) were higher in noncitrated versus citrated specimens for all comparisons between conventional and r-TEG tests, indicating better performance of r-TEG with the noncitrated specimens. FFP would have been administered to significantly more patients based on conventional transfusion triggers (61.5% by INR transfusion triggers versus 26.9% by r-TEG-ACT triggers, P=0.003). There was no statistically significant difference in potential cryoprecipitate or aphaeresis platelet administration.
CONCLUSION: POC r-TEG is superior when performed with uncitrated versus citrated whole blood for evaluation of postinjury coagulation status. As a real time measure of total thrombostatic function, our preliminary data suggest that r-TEG may effectively guide transfusion therapy and result in reduced FFP administration compared with conventional coagulation tests.