This study will test if a sustained Return of Spontaneous Circulation (ROSC) in patients with cardiac arrest is more frequent when patients receive advanced cardiac life support (ACLS) alone or when they receive ACLS plus a balloon occlusion of the thoracic aorta.

Patients with in-hospital cardiac arrest (IHCA) outside the operating room, the coronary angiography suite and the intensive care unit (ICU) will be attended to by the hospitals resuscitation team and provided with advanced cardiac life support (ACLS) as per usual practice.

A research team will be deployed simultaneously and, when patients meet inclusion criteria, will randomize patients to ACLS alone or to ACLS plus balloon occlusion of the descending thoracic aorta by means of a resuscitative endovascular occlusion of the aorta (REBOA) catheter.

Inclusion criteria:

• patients suffering from in hospital cardiac arrest (IHCA), including patients with out of hospital cardiac arrest (OHCA) and return of spontaneous circulation (ROSC), transported to the emergency department, where they suffer a second arrest (IHCA)
• successful placement of a femoral artery introducer sheath
• any electrical cardiac activity seen in the initial rhythm analysis
• ongoing effort of resuscitation as determined by study-independent resuscitation lead

Exclusion criteria:

• IHCA in the operating room, on intensive care unit or in the cardiac catheter laboratory
• hospital visitors suffering from cardiac arrest
• asystole seen in the initial rhythm analysis
• (presumed) age under 18 years
• known "do not resuscitate"-order
• known or obvious pregnancy
• traumatic cardiac arrest
• known aortic pathologies that render cannulation impossible
• known allergies to radiographic contrast agents