The FEMART-1 Pilot Study is focused on evaluating the feasibility, safety, and procedural timing of prehospital femoral arterial sheath placement in patients with non-traumatic out-of-hospital cardiac arrest (OHCA), both during ongoing cardiopulmonary resuscitation and after return of spontaneous circulation (ROSC).

The primary objective of the study is to enable invasive arterial blood pressure monitoring for targeted and continuous hemodynamic management using vasopressor therapy in the prehospital setting. The study evaluates the feasibility, safety, and procedural performance of invasive arterial monitoring with the aim of improving assessment of the patient's hemodynamic status and enabling more accurate titration of vasopressor support. This approach may reduce episodes of hypotension and decrease the risk of recurrent cardiac arrest while allowing safer transport to specialized cardiac arrest centers.

Femoral arterial access enables more precise monitoring of perfusion pressure, targeted vasopressor titration, and early recognition of impending circulatory collapse. The intervention may contribute to improved early organ perfusion and could be associated with more favorable neurological and overall clinical outcomes after cardiac arrest. In accordance with the ERC Guidelines 2025, which emphasize active hemodynamic optimization after ROSC and acknowledge the potential role of invasive arterial pressure monitoring during ongoing resuscitation, the study evaluates not only feasibility, safety, and procedural timing, but also the potential clinical benefit of continuous hemodynamic-guided management in the prehospital phase, including (1) early identification of hypotension, (2) targeted vasopressor administration, and (3) prevention of re-arrest.

The study is conducted by the Prague Air Rescue Service Kryštof 01 (Prague Emergency Medical Services) in collaboration with the Central Bohemian Emergency Medical Service, the Second Department of Internal Medicine - Cardiology and Angiology of the General University Hospital in Prague and First Faculty of Medicine, Charles University, and the Department of Anesthesiology, Resuscitation and Intensive Care Medicine of the General University Hospital in Prague and First Faculty of Medicine, Charles University.

FEMART-1 is designed as a prospective pilot study without external funding.

Inclusion Criteria:

* Non-traumatic out-of-hospital cardiac arrest (OHCA).

Patients meeting criteria for one of the following clinical scenarios:

Group A - ECPR-like group:

• Refractory cardiac arrest, including cardiac arrest occurring in the presence of the EMS crew.
• Age 18-70 years.
• Effective bystander cardiopulmonary resuscitation.
• Initial rhythm of ventricular fibrillation (VF), pulseless ventricular tachycardia (pVT), or pulseless electrical activity (PEA).

Group B - post-ROSC group:

• Return of spontaneous circulation (ROSC) after non-traumatic OHCA.
• Age 18-70 years.

Exclusion Criteria:

• Trauma as the probable primary cause of cardiac arrest.

• Known severe comorbidity, including:

  • terminal stage of incurable disease (advanced malignancy, advanced dementia, terminal pulmonary disease, terminal heart failure, or palliative care status),
  • established do-not-resuscitate (DNR) status,
  • severe pre-existing neurological disability (CPC 3 or CPC 4),
  • known severe peripheral arterial disease or known occlusion of lower limb arteries,
  • suspected pulmonary embolism with indication for thrombolytic therapy,
  • known severe hematological disease associated with severe thrombocytopenia,
  • morbid obesity.

• Known or suspected pregnancy.

Individual participant data sharing has not yet been determined. Future data sharing decisions will depend on data protection requirements, institutional policies, ethical considerations, and the feasibility of adequate anonymization of prehospital and hospital clinical data.