Characteristics of Patients With Traumatic Cardiac Arrest in Denmark Assessed by the Danish Helicopter Emergency Medical Services

Background Traumatic cardiac arrest (TCA) is associated with a poor prognosis, [1-3] and prompt, evidence-based treatment is paramount for increasing survival rates.

Cardiac arrest from traumatic origin is characterised as the end state of decompensated haemorrhagic shock, hypoxemia and/or obstructive shock.[1,4] Hypovolaemia and traumatic brain injury account for most cases, accounting for almost 90% of all TCAs.[5] Managing TCA relies on a time-critical assessment of reversible causes, which takes priority over chest compressions and simultaneous management of reversible causes.[1] Thus, TCA mandates urgent action in specialised prehospital treatment and further in-hospital advanced care in specialised trauma centres. [1] Potentially reversible causes of TCA include hypoxaemia, hypovolaemia and obstructive shock.[1,4] Earlier, resuscitation from TCA was considered futile due to meagre survival rates, yet survival has improved through the last decades. [5] Still, substantial variations in survival are seen across different populations. [4-7] Rapid transportation to specialised capacity, the role of the HEMS as an integrated function of the trauma system and the expertise of the helicopter crew are all factors that have been used to explain the benefits associated with using the HEMS in the trauma setting. [8-10] In-depth knowledge of the epidemiology of TCA is essential to improve care within this diverse subgroup of cardiac arrests. The hypothesis is that this novel data on TCA provide new and central data on reversible causes and treatment of these, which are linked to enhanced survival of cardiac arrest of traumatic origin.

Thus, the primary objective of the present study is to investigate the characteristics of patients to whom the Danish HEMS was dispatched who suffered from TCA. This assessment will be done by assessing the incidence, prognostic factors, critical care interventions, and survival from cardiac arrest of traumatic origin.

Materials and Methods This retrospective population-based cohort study with 30-day follow-up includes data from the national HEMS database on patients with traumatic cardiac arrest between 2014 and 2022. Patients will be included if the HEMS physician clinically assessed them and diagnosed them with OHCA from traumatic origin. Hence, patients declared dead on scene by the HEMS will be included. The traumatic aetiology will be supported by secondary diagnoses and free text descriptions from the HEMS database. Trigger words are developed using consecutive text search algorithms in a predefined subgroup of all OHCAs in the Danish Cardiac Arrest Registry note fields. The text search algorithm has been manually validated until no further relevant cases came up.

Data acquisition The HEMS file data were linked to the Danish Civil Registration System and, finally, to the prehospital patient record through the personal civil identification number. The HEMS file database was established in October 2014 and comprises information on all HEMS dispatches in Denmark.[12] Variables included