Long Term Follow-up of Cardiac Arrest Survivors Exposed to Ultra-rapid Cooling

Long Term Follow-up of Cardiac Arrest Survivors Exposed to Ultra-rapid Cooling, a Prospective Non-interventional Cohort

Less than 10% of patients eliciting out-of-hospital cardiac arrest (OHCA) survive, although 30% can be resuscitated by Emergency services before admission in Intensive Care Units (ICU). The majority succumb to Post-Cardiac Arrest Syndrome (PCAS). PCAS is associated with high mortality (60-70%) and morbidity.

One proposed method of preventing the neurological and cardiac consequences of PCAS is to lower the body temperature to 33°C as quickly as possible. This approach is known as therapeutic hypothermia or Targeted Temperature Management (TTM). The Vent2Cool system, developed by Orixha, is a novel approach that enables the rapid induction of therapeutic hypothermia by using hypothermic Total Liquid Ventilation (TLV) to reach a protective temperature of 33°C within minutes.

The OverCool feasibility study, which started in April 2025, is designed to validate the clinical performance and safety of an ultra-rapid cooling approach combining ultra-rapid hypothermia induction using the Vent2Cool system, and maintenance and rewarming using the ArcticSun system.

The AfterCool study aims to evaluate long-term outcomes during a five-year follow-up of cardiac arrest survivors who were treated with ultrarapid cooling in the OverCool study.

Fewer than 10% of patients experiencing out-of-hospital cardiac arrest (OHCA) survive, although 30% can be resuscitated by emergency services before being admitted to intensive care units (ICUs). Many cardiac arrest patients who are initially resuscitated by first responders and/or EMS, however, are condemned to a 'second death' in the ICU due to severe neurological and multi-visceral sequelae from post-cardiac arrest syndrome (PCAS).

One proposed method of preventing the neurological and cardiac complications of PCAS is to lower the body temperature to 33°C as quickly as possible. This approach is known as therapeutic hypothermia or Targeted Temperature Management (TTM). However, the cooling power of available technologies is insufficient to induce therapeutic hypothermia, and they do not improve outcomes for most patients. Conversely, experimental reports clearly demonstrate that therapeutic hypothermia can dramatically improve clinical outcomes if applied within two to three hours of resuscitation.

The devices currently available for TTM are mostly external cooling devices, such as blankets, pads and suits. These devices have a cooling performance of less than 1°C per hour in the body's core and in vital organs with high blood flow. Orixha's Vent2Cool is a novel approach that enables the induction of ultra-rapid therapeutic hypothermia (URTH) by using hypothermic total liquid ventilation (TLV) to reach a protective temperature of 33°C within minutes.

The OverCool feasibility study, which has been approved by the French authorities and began enrolment in early 2025, is designed to test the feasibility of ultra-rapid cooling. It aims to validate the clinical performance and safety of an ultra-rapid cooling approach combining ultra-rapid hypothermia induction using the Vent2Cool system, and maintenance and rewarming using the ArcticSun system. OverCool will pave the way for other clinical investigations to demonstrate the superior clinical benefits of this new approach to hypothermic TTM compared to the standard of care.

The AfterCool study will follow cardiac arrest survivors who were treated with ultrarapid cooling in the Overcool study for five years. The AfterCool approach aligns with the need to evaluate long-term outcomes after cardiac arrest, as endorsed by the French AfterROSC network, which supports research into post-cardiac arrest patients.

Eligible subjects, after having received clear, impartial and complete information, and not having objected to participation in the study, will be included. At the inclusion visit, a detailed questionnaire regarding life status, quality of life, putative rehospitalization, cardiovascular, neurological and respiratory status will be administered.

At 6±1 months and 12±1 months after inclusion, and then yearly during a total period of 5 years, the patients or trusted persons or the close relatives or parents will be interviewed by phone, using the same questionnaire regarding life status, quality of life, putative rehospitalization, cardiovascular, neurological and respiratory status.

Inclusion Criteria:

• Age of 18 years and over
• Cardiac arrest patient included in and alive at the end of the OverCool clinical investigation (28 days after the cardiac arrest)
• Non-opposition from the patient or the trusted person or the close relative or parent obtained within 3 months after the end of the OverCool study

Exclusion Criteria:

• Follow-up refusal from patient of trusted person or the close relative or parent
• Having being included in the OverCool clinical investigation but not submitted to the Vent2Cool procedure
• Impossibility to reach the patient or the trusted person or the close relative or parent