Sex discrimination after injury: is inequity in tranexamic acid administration just the tip of the iceberg?

Transfusion in trauma: empiric or guided therapy?

A state of the art lecture titled "Transfusion therapy in trauma-what to give? Empiric vs guided" was presented at the International Society on Thrombosis and Haemostasis Congress in 2024. Uncontrolled bleeding is the commonest preventable cause of death after traumatic injury. Hemostatic resuscitation is the foundation of contemporary transfusion practice for traumatic bleeding and has 2 main aims: to immediately support the circulating blood volume and to treat/prevent the associated trauma-induced coagulopathy. There are 2 broad types of hemostatic resuscitation strategy: empiric ratio-based therapy, often using red blood cells and fresh frozen plasma in a 1:1 ratio, and targeted therapy where the use of platelets, plasma, or fibrinogen is guided by laboratory or viscoelastic hemostatic tests. There are benefits, and limitations, to each strategy and neither approach has yet been shown to improve outcomes across all patient groups. Questions remain, and future directions for improving transfusion therapy are likely to require novel approaches that have greater flexibility to evaluate and treat heterogeneous trauma cohorts. Such approaches may include the integration of machine learning technologies in clinical systems, with real-time linkage of clinical and laboratory data, to aid early recognition of patients at the greatest risk of bleeding and to direct and individualize transfusion therapies. Greater mechanistic understanding of the underlying pathobiology of trauma-induced coagulopathy and the direct effects of common treatments on this process will be of equal importance to the development of new treatments. Finally, we summarize relevant new data on this topic presented at the 2024 ISTH Congress.

Predicting blood transfusion following traumatic injury using machine learning models: A systematic review and narrative synthesis

BACKGROUND

Hemorrhage is a leading cause of preventable death in trauma. Accurately predicting a patient's blood transfusion requirement is essential but can be difficult. Machine learning (ML) is a field of artificial intelligence that is emerging within medicine for accurate prediction modeling. This systematic review aimed to identify and evaluate all ML models that predict blood transfusion in trauma.

METHODS

This systematic review was registered on the International Prospective register of Systematic Reviews (CRD4202237110). MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials were systematically searched. Publications reporting an ML model that predicted blood transfusion in injured adult patients were included. Data extraction and risk of bias assessment were performed using validated frameworks. Data were synthesized narratively because of significant heterogeneity.

RESULTS

Twenty-five ML models for blood transfusion prediction in trauma were identified. Models incorporated diverse predictors and varied ML methodologies. Predictive performance was variable, but eight models achieved excellent discrimination (area under the receiver operating characteristic curve, >0.9) and nine models achieved good discrimination (area under the receiver operating characteristic curve, >0.8) in internal validation. Only two models reported measures of calibration. Four models have been externally validated in prospective cohorts: the Bleeding Risk Index, Compensatory Reserve Index, the Marsden model, and the Mina model. All studies were considered at high risk of bias often because of retrospective data sets, small sample size, and lack of external validation.

DISCUSSION

This review identified 25 ML models developed to predict blood transfusion requirement after injury. Seventeen ML models demonstrated good to excellent performance in silico, but only four models were externally validated. To date, ML models demonstrate the potential for early and individualized blood transfusion prediction, but further research is critically required to narrow the gap between ML model development and clinical application.

LEVEL OF EVIDENCE

Systematic Review Without Meta-analysis; Level IV.

Evaluation of the prehospital administration of tranexamic acid for injured patients: a state-wide observational study with sex and age-disaggregated analysis

BACKGROUND

Tranexamic acid (TXA) decreases mortality in injured patients and should be administered as soon as possible. Despite international guidelines recommending TXA in the prehospital setting, its use remains low. The aim of this study was to assess the prehospital administration of TXA for injured patients in a Swiss region.

METHODS

We conducted a retrospective observational study in Switzerland between 2018 and 2021. Inclusion criteria were injured patients ≥18 years for whom an ambulance or helicopter was dispatched. The exclusion criterion was minor injury defined by a National Advisory Committee for Aeronautics score <3. The primary outcome was the proportion of patients treated with TXA according to guidelines. The European guidelines were represented by the risk of death from bleeding (calculated retrospectively using the Bleeding Audit for Trauma and Triage (BATT) score). Factors impacting the likelihood of receiving TXA were assessed by multivariate analysis.

RESULTS

Of 13 944 patients included in the study, 2401 (17.2%) were considered at risk of death from bleeding. Among these, 257 (11%) received prehospital TXA. This represented 38% of those meeting US guidelines. For European guidelines, the treatment rate increased with the risk of death from bleeding: 6% (95% CI 4.4% to 7.0%) for low risk (BATT score 3-4); 13% (95% CI 11.1% to 15.9%) for intermediate risk (BATT score 5-7); and 21% (95% CI 17.6% to 25.6%) for high risk (BATT score ≥8) (p<0.01). Women and the elderly were treated less often than men and younger patients, irrespective of the risk of death from bleeding and the mechanism of injury.

CONCLUSION

The proportion of injured patients receiving TXA in the prehospital setting of the State of Vaud in Switzerland was low, with even lower rates for women and older patients. The reasons for this undertreatment are probably multifactorial and would require specific studies to clarify and correct them.

A comparative analysis of tranexamic acid dosing strategies in traumatic major hemorrhage

INTRODUCTION

Tranexamic acid (TXA) is a life-saving treatment for traumatic hemorrhage, but the optimal dosing regimen remains unknown. Different doses and treatment strategies have been proposed, including single bolus, repeated bolus, or bolus plus infusion. The aim of this study was to determine the effect of different TXA dosing strategies on clinical outcomes in bleeding trauma patients.

METHODS

Secondary analysis of a perpetual cohort study from a UK Level I trauma center. Adult patients who activated the local major hemorrhage protocol and received TXA were included. The primary outcome was 28-day mortality. Secondary outcomes were 24-hour mortality, multiple organ dysfunction syndrome, venous thromboembolism, and rotational thromboelastometry fibrinolysis.

RESULTS

Over an 11-year period, 525 patients were included. Three dosing groups were identified: 1 g bolus only (n = 317), 1 g bolus +1 g infusion over 8 hours (n = 80), and 2 g bolus (n = 128). Demographics and admission physiology were similar, but there were differences in injury severity (median Injury Severity Score, 25, 29, and 25); and admission systolic blood pressure (median Systolic Blood Pressure, 99, 108, 99 mm Hg) across the 1-g, 1 g + 1 g, and 2-g groups. 28-day mortality was 21% in each treatment group. The incidence of multiple organ dysfunction syndrome was significantly higher in the bolus plus infusion group (84%) vs. 1 g bolus (64%) and 2 g bolus (62%) group, p = 0.002, but on multivariable analysis was nonsignificant. Venous thromboembolism rates were similar in the 1-g bolus (4%), 2 g bolus (8%) and bolus plus infusion groups (7%). There was no difference in rotational thromboelastometry maximum lysis at 24 hours: 5% in both the 1-g and 2-g bolus groups vs. 4% in bolus plus infusion group.

CONCLUSION

Clinical outcomes and 24-hour fibrinolysis state were equivalent across three different dosing strategies of TXA. Single bolus administration is likely preferable to a bolus plus infusion regimen.

LEVEL OF EVIDENCE

Therapeutic/Care Management; Level III.

Nationwide analysis of prehospital tranexamic acid for trauma demonstrates systematic bias in adherence to treatment guidelines: a retrospective cohort study

BACKGROUND

Prehospital (PH) tranexamic acid (TXA) improves survival from trauma haemorrhage. Injury mechanism, physiology, and sex demographics vary with patient age. The authors hypothesised that these factors influence TXA guideline compliance and examined national trends in PH use to identify any systematic biases in bleeding management.

MATERIALS AND METHODS

The UK Trauma Audit and Research Network data for TXA eligible patients admitted to major trauma centres were divided into two cohorts: 2013-2015 ( n =32 072) and 2017-2019 ( n =14 974). Patients were stratified by PH, emergency department or no TXA use. Logistic regression models explored interaction between PH variables and TXA administration. Results are presented as odds ratios with a 95% CI.

RESULTS

PH TXA use increased from 8% to 27% over time ( P <0.001). Only 3% of eligible patients who fell less than 2 m received PH TXA versus 63% with penetrating injuries ( P <0.001). Older patients eligible for PH TXA were less likely to receive it compared to younger patients [≥65 years old: 590 (13%) vs. <65 years old: 3361 (33%), P <0.001]. There was a significant interaction between age and sex with fewer older women receiving PH TXA. In shocked patients, one third of females compared to a fifth of men did not receive TXA ( P <0.001). There was a decrease in PH TXA use as age increased ( P <0.001).

CONCLUSIONS

Despite a threefold increase in use, treatment guidance for PH TXA is not universally applied. Older people, women, and patients with low energy injury mechanisms appear to be systematically under treated. Training and education for PH providers should address these potential treatment biases.

Early identification of bleeding in trauma patients: external validation of traumatic bleeding scores in the Swiss Trauma Registry

BACKGROUND

Early identification of bleeding at the scene of an injury is important for triage and timely treatment of injured patients and transport to an appropriate facility. The aim of the study is to compare the performance of different bleeding scores.

METHODS

We examined data from the Swiss Trauma Registry for the years 2015-2019. The Swiss Trauma Registry includes patients with major trauma (injury severity score (ISS) ≥ 16 and/or abbreviated injury scale (AIS) head ≥ 3) admitted to any level-one trauma centre in Switzerland. We evaluated ABC, TASH and Shock index (SI) scores, used to predict massive transfusion (MT) and the BATT score and used to predict death from bleeding. We evaluated the scores when used prehospital and in-hospital in terms of discrimination (C-Statistic) and calibration (calibration slope). The outcomes were early death within 24 h and the receipt of massive transfusion (≥ 10 Red Blood cells (RBC) units in the first 24 h or ≥ 3 RBC units in the first hour).

RESULTS

We examined data from 13,222 major trauma patients. There were 1,533 (12%) deaths from any cause, 530 (4%) early deaths within 24 h, and 523 (4%) patients who received a MT (≥ 3 RBC within the first hour). In the prehospital setting, the BATT score had the highest discrimination for early death (C-statistic: 0.86, 95% CI 0.84-0.87) compared to the ABC score (0.63, 95% CI 0.60-0.65) and SI (0.53, 95% CI 0.50-0.56), P < 0.001. At hospital admission, the TASH score had the highest discrimination for MT (0.80, 95% CI 0.78-0.82). The positive likelihood ratio for early death were superior to 5 for BATT, ABC and TASH. The negative likelihood ratio for early death was below 0.1 only for the BATT score.

CONCLUSIONS

The BATT score accurately estimates the risk of early death with excellent performance, low undertriage, and can be used for prehospital treatment decision-making. Scores predicting MT presented a high undertriage rate. The outcome MT seems not appropriate to stratify the risk of life-threatening bleeding.

TRIAL REGISTRATION

Clinicaltrials.gov, NCT04561050 . Registered 15 September 2020.