Thrombin generation profiles as predictors of symptomatic venous thromboembolism after trauma: A prospective cohort study.

BACKGROUND: Reliable biomarkers predictive of venous thromboembolism (VTE) after acute trauma are uncertain. The objective of the study was to identify risk factors for symptomatic VTE after trauma, including individual plasma coagulome characteristics as reflected by thrombin generation. METHODS: In a prospective, case-cohort study, trauma patients were enrolled over the 4.5-year period, 2011 to 2015. Blood was collected by venipuncture into 3.2% trisodium citrate at 0, 6, 12, 24, and 72 hours after injury and at hospital discharge. Platelet poor plasma was stored at -80 °C until analysis. Thrombin generation, as determined by the calibrated automated thrombogram (CAT) using 5 pM tissue factor (TF)/4 µM phospholipid (PS), was reported as peak height (nM thrombin) and time to peak height (ttPeak [minutes]). Data are presented as median [IQR] or hazard ratio with 95% CI. RESULTS: Among 453 trauma patients (injury severity score = 13.0 [6.0, 22.0], hospital length of stay = 4.0 [2.0, 10.0] days, age = 49 [28, 64] years, 71% male, 96% with blunt mechanism, mortality 3.2%), 83 developed symptomatic VTE within 92 days after injury (35 [42%] after hospital discharge). In a weighted, multivariate Cox model that included clinical and CAT characteristics available within 24 hours of admission, increased patient age (1.35 [1.19,1.52] per 10 years, p < 0.0001), body mass index ≥30 kg/m (4.45 [2.13,9.31], p < 0.0001), any surgery requiring general anesthesia (2.53 [1.53,4.19], p = 0.0003) and first available ttPeak (1.67 [1.29, 2.15], p < 0.00001) were independent predictors of incident symptomatic VTE within 92 days after trauma (C-statistic = 0.799). CONCLUSION: The individual's plasma coagulome (as reflected by thrombin generation) is an independent predictor of VTE after trauma. Clinical characteristics and ttPeak can be used to stratify acute trauma patients into high and low risk for VTE. LEVEL OF EVIDENCE: Prognostic, level III.

Thrombin generation and procoagulant microparticle profiles after acute trauma: A prospective cohort study.

OBJECTIVE: The two sides of trauma-induced coagulopathy, the hypocoagulable and the hypercoagulable states, are poorly understood. To identify potential mechanisms for venous thromboembolism and bleeding after acute trauma, we estimated changes in circulating procoagulant microparticles (MPs) and thrombin activity during hospitalization for trauma. METHODS: Whole blood was collected by venipuncture into 3.2% trisodium citrate at 0, 6, 12, 24, and 72 hours after injury and discharge. Platelet-poor plasma was harvested and stored at -80°C until analysis. Thrombin generation was determined using the calibrated automated thrombogram (CAT), reported as lag time (minutes), peak height (nM thrombin), and time to reach peak height (ttPeak, minutes). The concentration of total procoagulant MPs (number/µL) was measured by flow cytometry. Data are presented as median (interquartile range [IQR]). RESULTS: Among 443 trauma patients (1,734 samples; Injury Severity Score [ISS], 13.0 [IQR, 6.0-22.0]; hospital length of stay, 4.0 days [IQR, 2.0-10.0]; age, 48 years [IQR, 28-65]; 70.7% male; 95% with blunt mechanism; mortality, 3.2%), no discernable patterns in thrombin generation or MP concentration were observed over time. The peak height and MPs were significantly different from healthy volunteers and were 337 nM (IQR, 285-395) and 400/µL plasma (IQR, 211-772), respectively. Extreme (defined as highest or lowest 5%) values reflecting a possible "hypercoagulable state" (lag time ≤ 1.98, peak height ≥ 486.2, ttPeak ≤ 3.61, and total procoagulant MP ≥ 2,278) were reached within 12 hours after acute trauma, while extreme values representing a possible "hypocoagulable state" (lag time ≥ 18.6, peak height ≤ 17.8, and ttPeak ≥ 29.45) were not reached until 1 day to 3 days. CONCLUSION: Although there was no predictable pattern of coagulopathy observed in each patient after trauma, those who reached extreme values did so relatively early after injury. These findings should be taken into account when designing risk model tools involving coagulation laboratory parameters. LEVEL OF EVIDENCE: Epidemiologic study, level III.