Functional definition and characterization of acute traumatic coagulopathy

Abstract

Objective: To identify an appropriate diagnostic tool for the early diagnosis of acute traumatic coagulopathy and validate this modality through prediction of transfusion requirements in trauma hemorrhage.

Design: Prospective observational cohort study.

Setting: Level 1 trauma center.

Patients: Adult trauma patients who met the local criteria for full trauma team activation. Exclusion criteria included emergency department arrival >2 hrs after injury, >2000 mL of intravenous fluid before emergency department arrival, or transfer from another hospital.

Interventions: None.

Measurements: Blood was collected on arrival in the emergency department and analyzed with laboratory prothrombin time, point-of-care prothrombin time, and rotational thromboelastometry. Prothrombin time ratio was calculated and acute traumatic coagulopathy defined as laboratory prothrombin time ratio >1.2. Transfusion requirements were recorded for the first 12 hrs following admission.

Main results: Three hundred patients were included in the study. Laboratory prothrombin time results were available at a median of 78 (62-103) mins. Point-of-care prothrombin time ratio had reduced agreement with laboratory prothrombin time ratio in patients with acute traumatic coagulopathy, with 29% false-negative results. In acute traumatic coagulopathy, the rotational thromboelastometry clot amplitude at 5 mins was diminished by 42%, and this persisted throughout clot maturation. Rotational thromboelastometry clotting time was not significantly prolonged. Clot amplitude at a 5-min threshold of ≤35 mm had a detection rate of 77% for acute traumatic coagulopathy with a false-positive rate of 13%. Patients with clot amplitude at 5 mins ≤35 mm were more likely to receive red cell (46% vs. 17%, p < .001) and plasma (37% vs. 11%, p < .001) transfusions. The clot amplitude at 5 mins could identify patients who would require massive transfusion (detection rate of 71%, vs. 43% for prothrombin time ratio >1.2, p < .001).

Conclusions: In trauma hemorrhage, prothrombin time ratio is not rapidly available from the laboratory and point-of-care devices can be inaccurate. Acute traumatic coagulopathy is functionally characterized by a reduction in clot strength. With a threshold of clot amplitude at 5 mins of ≤35 mm, rotational thromboelastometry can identify acute traumatic coagulopathy at 5 mins and predict the need for massive transfusion.

Figure 1. Comparison and limitations of central laboratory PTr (Prothrombin Time ratio) and Point of Care (PoC) PTr measurements

A: Histogram representation of the time delays incurred from individual blood draw (PTr sample acquisition) to availability of result on electronic patient record. B: Comparison according to Bland and Altman of laboratory PTr assay with point of care (PoC) PTr assay. Solid line = mean bias (−0.015). Dotted line = 95% limits of agreement (−0.197 - 0.168). C: Association of lower hematocrit levels in trauma hemorrhage with higher discrepancies between laboratory and PoC PTr assays. Median, inter-quartile and minimum/maximum ranges (Hematocrit: 0.2-0.29 vs 0.3-0.39, p =0.05; vs 0.4-0.49, p =0.04)

Figure 2. Comparison of ROTEM traces and clot amplitudes from non-coagulopathic (PTr ≤1.2) vs coagulopathic (PTr >1.2) and the effect of shock and injury on thromboelastometry profiles

A: Computer simulated EXTEM trace from averaged ROTEM data of all non-coagulopathic vs all coagulopathic patients. B: Comparison of EXTEM clot amplitude over time from non-coagulopathic vs coagulopathic patients. Mean values ± SEM. 2-way ANOVA (p<0.001). C: Combined effects of trauma (injury severity score >15) and shock (base deficit >6) on the ROTEM trace. Comparison of clot amplitudes over time: “normal” trauma patients (uninjured and no shock) vs patients with severe injury and shock. Mean values ± SEM. 2-way ANOVA (p<0.001). D: Histogram demonstrating spread of clot amplitude at 5 minutes (CA5) amongst normal and ATC patients. Dotted line represents new threshold for ATC (CA5 ≤35mm).

Figure 3. Average transfusion requirements based on ROTEM clot strength at 5 minutes

A: Mean PRBC transfusion requirement. p<0.001 comparing CA5≤35 with CA5 36-44, CA5 45-50 and CA5>50. Mean ± 95% confidence intervals. Clot Amplitude at 5 minutes (CA5). B: Mean FFP transfusion requirement. p<0.001 comparing CA5≤35 with CA5 36-44, CA5 45-50 and CA5>50. Mean ± 95% confidence intervals. C: Histogram of proportional distribution in PTr for patients receiving massive transfusion (MT) vs those not receiving MT. Dotted line represents threshold for ATC (PTr >1.2). D: Histogram of proportional distribution of CA5 for patients receiving MT vs those not receiving MT. Dotted line represents new ROTEM threshold for ATC based on clot strength (CA5 ≤35mm).