Establishing the Standardized EMS Metrics for Survival in Transfusion and Advanced Resuscitation: the SEMSTAR project

Abstract

Background

Prehospital blood transfusion is increasingly recognized as an important early resuscitation intervention for patients with hemorrhagic shock. However, comprehensive evaluations of such programs have been limited by heterogeneity in data collection, outcome definitions, and reporting methodologies. This impedes effective benchmarking, quality improvement initiatives, research efforts, and the creation of protocols and policies. The Standardized Emergency Medical Service (EMS) Metrics for Survival in Transfusion and Advanced Resuscitation (SEMSTAR) project sought to develop consensus-driven data elements and standardized outcome definitions to facilitate consistent reporting of prehospital blood transfusion programs.

Methods

Initial data metrics were identified through a literature review and surveyed across US EMS systems that perform prehospital transfusions. A modified Delphi methodology was then used by a multidisciplinary panel of 28 subject-matter experts in EMS, trauma surgery, transfusion medicine, and resuscitation science. Predefined thresholds analyzed metric inclusion, classification as either core or expanded elements, and endorsement of standardized outcome definitions.

Results

89 EMS systems completed the initial survey of 208 potential data elements. Of these, 193 (93%) advanced to expert review. Experts reached consensus on 168 data elements: 86 core metrics for universal reporting and 82 expanded metrics for comprehensive analysis. Consensus was also achieved on standardized definitions for hemorrhagic circulatory collapse, including stratification by pretransfusion circulatory collapse status and survival after prehospital transfusion. Wherever possible, the resulting framework draws from existing data infrastructure, including the National Emergency Medical Services Information System and trauma registry variables.

Conclusion

SEMSTAR establishes the first national, consensus-driven framework for standardized data collection and outcome reporting among prehospital blood transfusion programs. By defining core and expanded metrics with standardized survival definitions, this framework enables benchmarking, quality improvement, and multicenter research across diverse EMS systems. SEMSTAR adoption will enable rigorous program evaluation and support the development of a national registry to advance evidence-based care for patients with hemorrhagic shock.

Level of evidence

IV

WHAT IS ALREADY KNOWN ON THIS TOPIC

• Prehospital blood transfusion programs vary widely in their data elements, definitions, and outcome measures. This lack of standardization impedes meaningful cross-system comparisons and pooled analyses.

WHAT THIS STUDY ADDS

• Standardized data elements and definitions for hemorrhagic circulatory collapse and survival after prehospital transfusion will facilitate uniform outcome measurement across settings and patient populations, enabling reproducible, system-level comparisons and benchmarking across emergency medical service transfusion programs.

HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY

• Uniform definitions enable data aggregation across jurisdictions, supporting multicenter observational studies and comparative effectiveness research. Additionally, the results of this project serve to establish a reporting framework and provide a foundation for structured quality improvement, registry development, and evidence-informed policy in prehospital resuscitation.

Introduction

Prehospital blood transfusion programs have become increasingly prevalent in the early management of critically ill and injured patients to help mitigate death from hemorrhagic shock.¹,³ Early transfusion of blood products significantly impacts survival rates, particularly in cases of severe trauma.⁴,⁷ The large-scale integration of prehospital transfusion guidelines into emergency medical services (EMSs) practice, beyond aeromedical and critical care transport agencies, signifies a paradigm shift, emphasizing both rapid intervention and earlier initiation of hemostatic, damage-control resuscitation.^{8 9} Administering prehospital blood products is associated with improved outcomes, presumably by correcting shock and coagulopathy earlier, helping stabilize the endothelial glycocalyx, and restoring hemodynamic stability.¹⁰,¹² Prehospital blood transfusion reduces the time to initial transfusion, a crucial factor in managing severe hemorrhage. It has emerged as an essential element to the chain of survival and continuum of care for hemorrhagic shock.^{2 7 13 14}

In the USA, prehospital blood transfusion programs enable EMS clinicians to administer blood products in the field.¹⁵,¹⁹ Other countries have similarly incorporated prehospital transfusion protocols.^{20 21} Prehospital blood transfusion programs have historically used red blood cells and more recently liquid plasma, reflecting our evolving understanding of balanced resuscitation strategies and damage-control resuscitation in trauma care.^{22 23} The introduction of whole blood, particularly low-titer group O-positive whole blood and liquid plasma, in civilian prehospital settings has streamlined logistics for blood administration during resuscitation.^{24 25} As prehospital blood transfusion programs continue to evolve and proliferate, ongoing research and guideline refinement remain essential to improving outcomes, maximizing effectiveness, and ensuring patient safety.

A fundamental need has emerged for standardized data-reporting elements, metrics, and definitions, including outcome measures. A 2021 systematic review of prehospital transfusion studies highlighted the heterogeneity in both outcome reporting and definitions, as well as the absence of patient-reported outcomes. It recommended developing a clearly defined minimum core outcome set for prehospital trauma transfusion trials.²⁶ The implementation of standardized prehospital blood program metrics is imperative to serve as a universal criterion for reporting such programs. To address this need and to establish consensus-based metrics for the field, we launched the Standardized EMS Metrics for Survival in Transfusion and Advanced Resuscitation (SEMSTAR) project in January 2025. The conceptual model for this initiative is derived from analogous standardized models for prehospital resuscitation metrics, notably the Utstein criteria for reporting cardiac arrest outcomes.²⁷ We convened a panel of subject-matter experts (SMEs) from the EMS, trauma, transfusion, and resuscitation medicine communities across the USA. To be eligible to serve as an SME for this project, candidates had to meet at least one of the following criteria: direct experience with the implementation of a prehospital transfusion program; direct clinical experience with prehospital transfusion; multiple publications on prehospital transfusion; or expertise in prehospital damage-control resuscitation. “The purpose of this panel was to identify metrics and outcomes that should serve as the basis for standardized, universal reporting criteria.” The objective of this study was to establish a consensus list of data elements related to prehospital transfusion and to develop a limited set of outcome variables and definitions relevant to survival.

Methods

A modified Delphi technique was used to attain consensus on clinical and operational metrics for prehospital blood transfusion programs. The process began with a broad solicitation of input from EMS systems that perform prehospital transfusions. This was followed by three rounds of iterative ratings from a panel of 28 SMEs, selected based on documented expertise in EMS, trauma, prehospital transfusion, and resuscitation medicine, with predefined consensus thresholds applied to each round. The SME panel’s composition, by EMS system role, is listed in table 1.

Table 1. Subject-matter expert panel breakdown by role.

Primary EMS system role	N
EMS medical director/chief medical officer	7
Trauma surgeon and critical care physician	4
Researcher	3
EMS program analyst	3
EMS agency blood program manager	2
EMS associate/assistant medical director	2
EMS department chief	2
Emergency physician (non-EMS admin/medical director)	2
EMS operations chief	1
Operational EMS physician	1
EMS quality improvement specialist	1

EMS, emergency medical service.

During the preparatory phase, the study team conducted a comprehensive review of the existing literature to identify pertinent metrics for the performance and operations of prehospital blood programs. The identified metrics were then refined and converted into a Delphi survey instrument. In round 1, participation and recruitment were open to any EMS system that performs prehospital transfusions. Recruitment announcements were distributed to over 400 recipients via the Prehospital Transfusion Coalition listserv, the American College of Emergency Physicians Prehospital and EMS Medicine listserv, and to attendees of the 2025 National Prehospital Blood Symposium (San Antonio, Texas, USA). Only one response from each EMS system was permitted. In subsequent rounds of the Delphi process, the 28 SME team members voted to include or exclude metrics and to categorize them as either core or expanded data elements.

Modified-Delphi procedure

Round 1: EMS system survey. The initial poll presented each candidate metric with a 5-point Likert scale ranging from “extremely important” to “not important at all.” Respondents were asked to rate each metric’s importance independently. Consensus for advancement to Round 2 was defined a priori as a simple majority (≥50%) of respondents rating a metric as “moderately important” (Likert scale≥3) or higher.

Round 2: SME importance rating. Metrics that satisfied the Round 1 threshold for advancement were continued to the subsequent phase. SME panelists rated each metric independently, using the same importance scale. A consensus threshold of ≥75% of panelists’ rating of each metric as “moderately important” or higher was required for the metric to advance to Round 3.

Round 3: In the final round, SME panelists classified each metric as either a core metric that all EMS transfusion programs should report or an expanded metric that programs should ideally report (contingent on available resources). A ≥75% consensus threshold was applied to classification decisions. During this round, panelists also reviewed proposed definitions for standardized reporting of “circulatory collapse in hemorrhagic shock,” “raw survival following prehospital transfusions,” and “survival following prehospital transfusions in patients with circulatory collapse.” Panelists indicated either agreement or disagreement; if disagreeing, they could propose revisions. Final acceptance of the standardized definitions required ≥85% of agreement.

Data collection and management

All surveys were conducted using Qualtrics Survey Software.²⁸ Responses were closely monitored to ensure that only one submission per EMS system was received in Round 1. Item-level data, including Likert scale ratings and vote classifications, were exported for subsequent analysis.

Statistical analysis

Analyses were conducted using SAS version 8 software (SAS Institute).²⁹ For each metric and round, we calculated the proportion of respondents meeting the predefined consensus criterion. Descriptive statistics (eg, frequency distributions of ratings) summarized item-level responses. Consensus was operationalized as the proportion of respondents who rated a metric as “moderately important” or higher (Rounds 1 and 2) or who agreed on essential versus expanded classification and definition acceptance (Round 3). Metrics achieving consensus were either advanced or designated accordingly.

Results

The initial public survey instrument was developed through a literature review and contained 208 data elements (online supplemental table 1). The survey was distributed publicly to EMS systems in spring/summer 2025, and 89/400 (22%) responses were received. Of the initial data elements, 193 achieved the ≥50% consensus threshold for inclusion and advanced to the first round of expert consensus voting (online supplemental table 2). During round 2 (SME importance rating), 24 of the 28 (86%) SMEs evaluated these elements, and 168/193 achieved ≥75% consensus for inclusion (online supplemental table 3). In the second round of expert voting, 28 of 28 (100%) of SMEs responded. SMEs were asked to stratify the 168 selected elements into two categories: core (data elements that all EMS agencies performing PHT must measure) and expanded (data elements that agencies should measure if resources permit). This stratification process yielded 86 core data elements (online supplemental table 4) and 82 expanded data elements (online supplemental table 5), all of which achieved ≥75% consensus. Figure 1 summarizes the number of data elements selected in each voting round. Throughout all survey rounds, respondents were allowed to suggest additional data elements not included in the original lists. Additionally, during the last round of expert consensus voting, consensus (≥85%) was obtained on the definitions for circulatory collapse in hemorrhagic shock, raw survival after prehospital transfusions, and survival after prehospital transfusions in patients with circulatory collapse. By incorporating these variables into the SEMSTAR dataset, we aim to provide a robust basis for comparing EMS systems and minimizing heterogeneity in definitions. Ultimately, this standardized approach will enable accurate categorization and comparison across participating EMS systems, facilitating evidence-based conclusions.

Figure 1. Proposed data elements by round of voting. SMEs, subject-matter experts.

Hemorrhagic circulatory collapse

A state of profound hypoperfusion, in the setting of life-threatening hemorrhage, that results in the sudden loss of adequate circulation, characterized by significant mental status change, apnea or agonal respirations, and absence of a palpable central pulse.

Survival after prehospital transfusion

The proportion of patients who received prehospital blood products and survived to the specified endpoints of hospital arrival, 6 hours, 12 hours, 24 hours, 72 hours, and either 30 days postinjury or hospital discharge, whichever occurred first.

Survival of transfused prehospital patients without pretransfusion circulatory collapse (SEMSTAR Survival)

The proportion of patients, excluding those who experienced prehospital circulatory collapse before blood administration, who received prehospital blood products and survived to the specified endpoints of hospital arrival, 6 hours, 12 hours, 24 hours, 72 hours, and either 30 days postinjury or hospital discharge, whichever occurred first.

Discussion

As prehospital blood transfusion programs expand nationwide, a gap in the ability to examine epidemiology, practice patterns, and outcomes has emerged due to the absence of standardized data-collection methodologies. This lack of uniform metrics and consistent measurement approaches impedes the scientific rigor needed to evaluate and compare individual programs, assess their success, benchmark outcomes against peers, and meaningfully contribute to evidence-based outcomes and further research. This fragmentation threatens the ability to demonstrate program efficacy, secure and sustain funding, and optimize patient care protocols. The SEMSTAR project addresses this critical need as the inaugural comprehensive national initiative to establish standardized data elements designed explicitly for prehospital blood transfusion programs.

The SEMSTAR approach follows the successful precedent established by standardized data-collection frameworks in prehospital emergency care. The Utstein criteria serve as a standardized framework for reporting cardiac arrest and resuscitation outcomes, initially developed in 1991 and subsequently updated to enhance comparability across studies and settings.³⁰,³² These criteria emerged from the recognition that significant variations in cardiac arrest outcome reporting hindered the drawing of meaningful conclusions across disparate studies. The wide acceptance and implementation of Utstein-style guidelines has demonstrated measurable benefits, improving outcomes across various settings through enhanced care-system benchmarking and improved understanding of survival factors.^{33 34} The framework’s success has extended beyond cardiac arrest, with effective adaptation for trauma registries that standardize data collection and reporting practices across trauma centers.³³³⁵,³⁷

The SEMSTAR consensus process project yielded 168 carefully selected data elements, identified through comprehensive stakeholder engagement and expert consensus. The elements are divided into two strategic categories: 86 elements that serve as core metrics for fundamental program evaluation and quality assurance, and 82 expanded elements that provide supplemental metrics for comprehensive analysis and research. This distinction helps programs prioritize their data-collection efforts based on available resources and operational maturity, and acknowledging that all elements contribute valuable insights to the broader understanding of prehospital transfusion effectiveness. Prehospital blood transfusion programs should regard these elements as a framework for progressive implementation rather than a rigid hierarchy, allowing for growth and adaptation as capabilities evolve. For example, the 82 expanded elements should not be interpreted as elective or unnecessary, but rather as a secondary priority after efforts are made to implement and obtain the core elements.

The SEMSTAR framework leverages existing data infrastructure wherever possible to minimize implementation burdens and accelerate adoption across diverse emergency healthcare systems. For example, 100 of the combined core and expanded data elements can be directly obtained from the National Emergency Medical Services Information System (NEMSIS) V.3.5, which is already widely used by EMS agencies nationwide.³⁸ For patients with traumatic conditions, 30 of the remaining elements can be sourced from established trauma registries. This pragmatic approach maximizes data utility and reduces the administrative workload on participating programs, making standardized data collection feasible even for smaller or resource-constrained operations. However, targeted manual data entry will be needed for the remaining 38 metrics not captured in existing systems until more robust data collection platforms can be established for prehospital transfusion. Additionally, the project yielded standardized clinical definitions for hemorrhagic circulatory collapse and survival.

The SEMSTAR team envisions these standardized metrics as the foundational framework for developing a dedicated prehospital blood transfusion registry, akin to the Cardiac Arrest Registry to Enhance Survival, which has improved out-of-hospital cardiac arrest care through systematic data collection and analysis.³⁹ A prehospital blood transfusion registry would enable nationwide benchmarking, facilitate collaborative quality improvement initiatives, and support evidence-based program development through robust data analysis. Of note, such a registry would need to include both medical and trauma-related causes. This systematic approach will ultimately advance patient care in prehospital settings, catalyze the expansion of life-saving blood transfusion programs nationwide, and provide the necessary evidentiary foundation to refine protocols, justify resource allocation, and demonstrate the clinical and economic value of prehospital blood transfusion programs to stakeholders and policymakers.

Limitations

This study has several limitations that warrant consideration. Despite significant efforts to comprehensively survey the literature and be as inclusive as possible regarding existing metrics used by prior authors and EMS systems, some metrics may not have been identified during the initial phase. We attempted to mitigate this limitation by providing write-in options at each voting phase. SMEs with significant experience in prehospital blood program design, implementation, registry development, and operations were sought for our consensus panel. However, it is important to acknowledge that ground-based prehospital blood programs are relatively new, and expertise is often being developed in real-time as programs evolve. We acknowledge that significant variability exists among EMS systems across the USA. Efforts were made to ensure program representation across both urban and rural settings, various EMS system designs, and both ground-based and aeromedical EMS systems to ensure generalizability and broad applicability for both medical and trauma patients. As prehospital blood transfusion programs evolve and mature, expert opinions and priorities may change. Finally, we acknowledge that some metrics, such as in-hospital data, may be difficult to capture, especially early on, but nonetheless are important.

Conclusion

The SEMSTAR project establishes the first standardized data collection framework for prehospital blood transfusion programs. Through expert consensus, the project developed 168 categorized data elements that leverage existing infrastructure, including NEMSIS and trauma registries, to provide a pragmatic implementation pathway for programs of all sizes. SEMSTAR’s framework will enable nationwide benchmarking, quality improvement, and evidence-based program development. The ultimate vision of a dedicated national registry will transform prehospital blood transfusion care through systematic data collection and analysis. As these programs continue to expand, SEMSTAR’s standardized elements will serve as the foundation for measuring success, driving improvement, and providing the evidence base needed to refine protocols, justify resources, and demonstrate program value—ultimately advancing patient care and improving outcomes for patients with hemorrhagic shock.

The views expressed here are those of the author(s) and do not necessarily reflect the official policy or position of any agencies under the US government.

Data availability statement

All data relevant to the study are included in the article or uploaded as supplementary information.