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Abstract

While there are different protocols for in-hospital transesophageal echocardiography, there is no existing protocol for prehospital usage during out-of-hospital cardiac arrest. Herein, the “assess-improve-detect-guide” protocol is described.

This protocol includes four mid-esophageal views to address the most time-sensitive aspects during out-of-hospital cardiac arrest. This protocol can be used in services with and without the capability for eCPR, with the benefit of profiting from additional diagnostic and personal resources.

This protocol provides a standardized approach for performing transesophageal echocardiography during out-of-hospital cardiac arrest and reporting the results.

Background

Ultrasound has become more available in the past decades, and since 2015, it has been recommended to detect reversible causes of cardiac arrest [1]. Different protocols for transthoracic echocardiography (TTE) during out-of-hospital cardiac arrest (OHCA) are in place [2, 3]. Although not specified in current guidelines, TTE should be performed during rhythm checks to obtain the best possible images and limit chest compression interruptions.

Consideration should be made when interpreting the images outside a rhythm check [1]. However, TTE views can be limited due to gastric inflation, defibrillation pads, and hand positioning, potentially resulting in the inability to use this technique.

Further, extensive experience is necessary to obtain the desired images [1]. In comparison, transesophageal echocardiography (TEE) helped to detect reversible causes and the area of maximal compression (AMC) during emergency department treatment (ED) of OHCA [4,5,6].

In cases of uncertainty, TEE can help to characterize fine ventricular fibrillation [7]. Additionally, pulse checks were shortest with TEE compared to TTE and manual pulse checks [8]. TEE can facilitate goal-directed resuscitation with fluids, blood products, or inotropes [9].

In the absence of fluoroscopy, TEE has shown to be reliable during extracorporeal membrane oxygenation (ECMO) placement with a 100% success rate and without the need for repositioning [10].

Method

We conducted a narrative literature review to understand where in-hospital experience might be translated to pre-hospital practices. Search terms for PubMed were “cardiopulmonary resuscitation”, “out-of-hospital cardiac arrest”, “echocardiography”, and “ultrasound”.

Additionally, the practical experience of the author’s advanced prehospital response team was used to provide a comprehensive TEE protocol with a focus on adult non-trauma OHCA.

Conclusions

One observational study, two case reports, and our preliminary experience have demonstrated the feasibility of prehospital TEE. Building on this foundation, the proposed protocol offers a structured approach to integrating prehospital TEE into EMS systems.

However, future work is critical to evaluate and refine this protocol further. Testing the protocol across diverse EMS systems, including urban, rural, and international contexts, will ensure its adaptability and external validity.

Additionally, studies should focus on assessing the feasibility of protocol implementation, including provider training requirements, operational challenges, and patient safety considerations.

By standardizing reporting and sharing findings from these studies, the protocol can serve as a valuable tool to enhance prehospital diagnostics and improve patient outcomes.

Future research should also explore the clinical impact of prehospital TEE on decision-making, resource utilization, and survival rates.

READ MORE HERE: https://theultrasoundjournal.springeropen.com/articles/10.1186/s13089-025-00418-4

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