Clot dynamics and mortality: The MA-R ratio

Viscoelastic Hemostatic Assays are Associated With Mortality and Blood Transfusion in a Multicenter Cohort

Objectives

Trauma-induced coagulopathy (TIC) carries significant risks, including increased mortality. Traditional TIC definitions rely on laboratories that result slowly and do not highlight therapeutic targets. We hypothesized that a TIC score, based on thromboelastography (TEG) and rotational thromboelastometry (ROTEM), collectively termed viscoelastic hemostatic assays, is associated with in-hospital mortality and packed red blood cell (pRBC) transfusion.

Methods

This retrospective cohort study used a database of adult patients undergoing institutional massive transfusion at seven level 1 trauma centers (2013-2018). A "TIC score" was developed, with 1 point assigned for abnormal TEG R-time (≥ 9 min) or ROTEM clot time (≥ 80 sec), ɑ-angle (< 65o), or maximum amplitude (< 55 mm). TIC+ patients (TIC score 1-3) were compared with TIC- patients (TIC score 0). TIC Score composition and abnormal cutoff values were adjusted to investigate optimal weighting and thresholds. Multiple logistic and negative binomial regression was used to control confounders while evaluating the association between abnormal TIC values, in-hospital mortality, and 24-hour pRBC transfusion.

Results

Of 1499 patients in the final analysis, 591 (39.4%) were TIC+. Each 1-point increase in TIC score was associated with a 53% increase in the odds of mortality (odds ratio [OR], 1.53, 95% CI, 1.33-1.76, P < .001) and a 25% increase in pRBC transfusion volumes (incidence rate ratio, 1.25, 95% CI, 1.16-1.34, P < .001). Abnormal maximum amplitude was associated with both mortality (OR 1.50, 95% CI, 1.03-2.19, P = .034) and pRBC transfusion volumes (P < .001), whereas abnormal ɑ-angle was associated with mortality (OR, 1.59, 95% CI, 1.09-2.32, P = .015). The unequal weighting of TIC score components and adjustments to normal/abnormal cutoff thresholds were maintained but did not improve the model's predictive power.

Conclusion

A viscoelastic hemostatic assay-based TIC score is independently associated with mortality and pRBC transfusion volumes. This association persists with unequal weighting and adjustment of normal/abnormal cutoff thresholds of TEG components.

O blood type is not associated with worse coagulopathy or outcome in exsanguinating trauma

BACKGROUND

Despite improving understanding of trauma-induced coagulopathy (TIC), mortality and morbidity due to exsanguinating trauma remain high. Increased complications due to hemorrhage have been reported in blood group O, possibly due to reduced levels of von Willebrand factor (vWF).

METHODS

An urban level 1 adult trauma center registry was retrospectively queried. Patients receiving ≥6 units of pRBC within 4 ​h of presentation were included. Patient demographics, admission labs and outcomes were obtained. Univariate and multiple logistic regression analyses were performed.

RESULTS

562 patients were identified. There were no significant differences in demographics, admission labs, or outcome between different ABO groups. After adjustment, Type A patients were more likely to be hypocoagulable compared to Type O patients (p ​= ​0.014). No mortality differences were seen between ABO types in multiple regression analysis.

CONCLUSIONS

No outcome or mortality differences were seen between ABO types, therefore factors other than vWF expression should be considered to explain coagulopathy in trauma patients.

Evaluating Factor VIII Concentrates Using Clot Waveform Analysis

Background/Objectives: FVIII reagent activity varies across different assays, as well as activated partial thromboplastin time (APTT) reagents. The hemostatic ability of various FVIII reagents was examined via clot waveform analysis (CWA). Methods: APTT was measured using 12 APTT reagents, a small amount of tissue factor-induced FIX activation (sTF/FIXa) and a small amount of thrombin time (sTT) in order to examine 10 FVIII reagents and reference plasma (RP) using CWA. FVIII activity was measured using CWA-APTT, a chromogenic assay, or CWA-sTT. Results: Although the peak time (PT) and peak height (PH) of the CWA-APTT were markedly different in different FVIII reagents using several APTT reagents, the PTs of CWA-APTT were generally normal or shortened and the PHs of CWA-APTT were generally lower than those of RP. The FVIII activity varied, as evaluated using APTT, and was higher when using the CWA-sTT method than the APTT or chromogenic methods. CWA-sTT showed an elevated second peak of first DPH in all FVIII reagents, and both CWA-sTF/FIXa and CWA-sTT were enhanced using APTT reagents. Conclusions: Our evaluation of the hemostatic ability of FVIII reagents varied among APTT reagents. CWA-sTT can be used to further evaluate the hemostatic ability of an FVIII concentrate based on thrombin burst.

Admission maximum amplitude-reaction time ratio: Association between thromboelastography values predicts poor outcome in injured children

INTRODUCTION

Thromboelastography (TEG)-derived maximum amplitude-reaction time (MA-R) ratio that accounts for both hypocoagulable and hypercoagulable changes in coagulation is associated with poor outcomes in adults. The relationship between these TEG values and outcomes has not been studied in children.

METHODS

In a retrospective cohort study, a level I pediatric trauma center database was queried for children younger than 18 years who had a TEG assay on admission between 2016 and 2020. Demographics, injury characteristics, and admission TEG values were recorded. The MA-R ratio was calculated and divided into quartiles. Main outcomes included mortality, transfusion within 24 hours of admission, and thromboembolism. A logistic regression model was generated adjusting for age, Injury Severity Score, injury mechanism, admission shock, and Glasgow Coma Scale.

RESULTS

In total, 657 children were included, of which 70% were male and 75% had blunt mechanism injury. The median (interquartile range) age was 11 (4-14) years, the median (interquartile range) Injury Severity Score was10 (5-22), and in-hospital mortality was 7% (n = 45). Of these patients, 17% (n = 112) required transfusion. Most R and MA values were within normal limits. On unadjusted analysis, the lowest MA-R ratio quartile was associated with increased mortality (15% vs. 4%, 5%, and 4%, respectively; p < 0.001) and increased transfusion need (26% vs. 12%, 16%, and 13%, respectively; p = 0.002) compared with higher quartiles. In the logistic regression models, a low MA-R ratio was independently associated with increased in-hospital mortality (odds ratio [95% confidence interval], 4.4 [1.9-10.2]) and increased need for transfusion within 24 hours of admission (odds ratio [95% confidence interval], 2.0 [1.2-3.4]) compared with higher MA-R ratio. There was no association between MA-R ratio and venous thromboembolic events (venous thromboembolic event rate by quartile: 4%, 2%, 1%, and 3%).

CONCLUSION

Although individual admission TEG values are not commonly substantially deranged in injured children, the MA-R ratio is an independent predictor of poor outcome. Maximum amplitude-reaction time ratio may be a useful prognostic tool in pediatric trauma; validation is necessary.

LEVEL OF EVIDENCE

Therapeutic/Care Management; Level III.

Association of Thromboelastography with Progression of Hemorrhagic Injury in Children with Traumatic Brain Injury

INTRODUCTION

Progression of hemorrhagic injury (PHI) in children with traumatic brain injury portends poor outcomes. The association between thromboelastography (TEG), functional coagulation assays, and PHI is not well characterized in children.

METHODS

This was a retrospective cohort study of children presenting with PHI at a pediatric level I academic trauma center from 2015 to 2020. Inclusion criteria were as follows: age less than 18 years, intracranial hemorrhage on admission head computed tomography scan, and admission rapid TEG assay and conventional coagulation tests. PHI was defined by the following radiographic criteria: any expansion of or new intracranial hemorrhage on subsequent head computed tomography scan. Rapid TEG values included Activated Clotting Time (ACT), alpha angle, maximum amplitude, and lysis at 30 min. Wilcoxon rank-sum test was used to assess baseline differences between groups with PHI and without PHI, including laboratory assays. Univariate analysis was performed to examine the association between variables of interest and PHI. Patients were dichotomized on the basis of this cut point to generate a "low ACT" group and a "high ACT" group. These variables were included in a multivariable logistic regression model to determine independent association with traumatic brain injury progression.

RESULTS

In total, 219 patients met criteria for analysis. In this cohort, the median (interquartile range [IQR]) age = 6 (2-12) years, median (IQR) Injury Severity Score = 21 (11-27), 68% were boys, and 69% sustained blunt injury. The rate of PHI was 25% (54). Median (IQR) time to PHI was 1 (0-4) days. Children with PHI had a higher Injury Severity Score (p < 0.001), lower Glasgow Coma Scale (p < 0.001), greater incidence of shock (p = 0.04), and lower admission hemoglobin (p = 0.02) compared with those without PHI. Children with PHI had a higher International Normalized Ratio (INR) and longer TEG-ACT; other TEG values (alpha angle, maximum amplitude, and lysis at 30 min) were not associated with PHI. In the logistic regression model accounting for other covariates associated with PHI, elevated ACT remained an independent predictor of progression (odds ratio = 2.25, 95% confidence interval 1.09-4.66; p = 0.03; area under the receiver operating characteristic curve = 0.76). After adjusting for confounders, INR fell out of the model and was not an independent predictor of progression (odds ratio = 1.32, 95% confidence interval 0.60-2.93; p = 0.49).

CONCLUSIONS

Although INR was elevated in children with PHI and has been associated with poor clinical outcomes, only admission TEG-ACT was independently associated with PHI. Further study is warranted to determine whether TEG-ACT reflects an actionable therapeutic target.

Variations in clot phenotype following injury: The MA-R ratio and fragile clots

INTRODUCTION

Trauma-induced coagulopathy is a continuum ranging from hypercoagulable to hypercoagulable phenotypes. In single-center studies, the maximum amplitude (MA) to r-time (R) (MA-R) ratio has identified a phenotype of injured patients with high mortality risk. The purpose of this study was to determine the relationship between MA-R and mortality using multicenter data and to investigate fibrinogen consumption in the development of this specific coagulopathy phenotype.

METHODS

Using the Pragmatic Randomized Optimal Platelet and Plasma Ratios data set, patients were divided into blunt and penetrating injury cohorts. MA was divided by R time from admission thromboelastogram to calculate MA-R. MA-R was used to assess odds of early and late mortality using multivariable models. Multivariable models were used to assess thrombogram values in both cohorts. Refinement of the MA-R cut point was performed with Youden index. Repeat multivariable analysis was performed with a binary CRITICAL and NORMAL MA-R.

RESULTS

In initial analysis, MA-R quartiles were not associated with mortality in the penetrating cohort. In the blunt cohort, there was an association between low MA-R and early and late mortality. A refined cut point of 11 was identified (CRITICAL: MA-R, ≤11; NORMAL: MA-R, >11). CRITICAL MA-R was associated with mortality in both penetrating and blunt subgroups. In further injury subgroup analysis, CRITICAL patients had significantly decreased fibrinogen levels in the blunt subgroup only. In both blunt and penetrating injury, there was no difference in time to initiation of thrombin burst (lagtime). However, both endogenous thrombin potential and peak thrombin levels were significantly lower in CRITICAL patients.

CONCLUSIONS

MA-R identifies a trauma-induced coagulopathy phenotype characterized in blunt injury by impaired thrombin generation that is associated with early and late mortality. The endotheliopathy and tissue factor release likely plays a role in the cascade of impaired thrombin burst, possible early fibrinogen consumption and the weaker clot identified by MA-R.

LEVEL OF EVIDENCE

Therapeutic/care management, level II.

Insights into the association between coagulopathy and inflammation: abnormal clot mechanics are a warning of immunologic dysregulation following major injury

Background

Severe injury initiates a complex physiologic response encompassing multiple systems and varies phenotypically between patients. Trauma-induced coagulopathy may be an early warning of a poorly coordinated response at the molecular level, including a deleterious immunologic response and worsening of shock states. The onset of trauma-induced coagulopathy (TIC) may be subtle however. In previous work, we identified an early warning sign of coagulopathy from the admission thromboelastogram, called the MAR ratio. We hypothesized that a low MAR ratio would be associated with specific derangements in the inflammatory response.

Methods

In this prospective, observational study, 88 blunt trauma patients admitted to the intensive care unit (ICU) were identified. Concentrations of inflammatory mediators were recorded serially over the course of a week and the MAR ratio was calculated from the admission thromboelastogram. Correlation analysis was used to assess the relationship between MAR and inflammatory mediators. Dynamic network analysis was used to assess coordination of immunologic response.

Results

Seventy-nine percent of patients were male and mean age was 37 years (SD 12). The mean ISS was 30.2 (SD 12) and mortality was 7.2%. CRITICAL patients (MAR ratio ≤14.2) had statistically higher shock volumes at three time points in the first day compared to NORMAL patients (MAR ratio >14.2). CRITICAL patients had significant differences in IL-6 (P=0.0065), IL-8 (P=0.0115), IL-10 (P=0.0316) and MCP-1 (P=0.0039) concentrations compared to NORMAL. Differences in degree of expression and discoordination of immune response continued in CRITICAL patients throughout the first day.

Conclusions

The admission MAR ratio may be the earliest warning signal of a pathologic inflammatory response associated with hypoperfusion and TIC. A low MAR ratio is an early indication of complicated dysfunction of multiple molecular processes following trauma.

Admission thrombelastography does not guide dose adjustment of enoxaparin in trauma patients

Background

Enoxaparin is used as chemoprophylaxis to reduce incidence of venous thromboembolism and its complications following trauma. Serum anti-Xa monitoring is used to assess efficacy but requires several doses to be administered. Thrombelastography assesses hypercoagulability and may have utility identifying high-risk patients for venous thromboembolism. The objective was to evaluate whether thrombelastography parameters could identify trauma patients requiring enoxaparin dose adjustment earlier than serum anti-Xa concentrations.

Methods

A single-center, retrospective medical record review evaluated patients admitted to a regional level I trauma center that received an admission thrombelastography and a dose of enoxaparin with a serum trough anti-Xa concentration drawn. Patients were divided into standard-dose or dose-adjusted enoxaparin. Venous thromboembolism incidence between groups and risk factors for enoxaparin dose adjustment and venous thromboembolism development were evaluated.

Results

A total of 204 patients were included. Differences observed between groups included age (standard-dose enoxaparin, 48.5 [29.3–72] vs dose-adjusted enoxaparin, 38.5 [25–55.7] years; P = .005), admission creatinine clearance (standard-dose enoxaparin, 92.9 [67.4–113.4] vs dose-adjusted enoxaparin, 102.1 [83.8–129.2] mL/min; P = .017), and time to venous thromboembolism prophylaxis initiation (standard-dose enoxaparin, 23.8 [11.2–36.4] vs dose-adjusted enoxaparin, 34.5 [18.3–52.7] hours; P = .004). No differences in thrombelastography parameters or venous thromboembolism incidence were observed. No independent risk factors for enoxaparin dose adjustment were identified; however, risk assessment profile score > 10 was an independent risk factor for venous thromboembolism development.

Conclusion

No relationship between admission thrombelastography and need for enoxaparin dose adjustment in trauma patients was observed. As thrombelastography continues growing in clinical use, it is prudent to investigate other potential applications. Currently, thrombelastography should not be used to guide enoxaparin dosing.

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Admission thrombelastography does not predict need for enoxaparin dose adjustment.

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No thrombelastography parameter predicted need for dose adjustment.

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Physiologic criteria are better predictors of chemoprophylaxis pharmacodynamics.

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Risk assessment profile score > 10 continues to correlate with VTE risk in trauma patients.