Targeted Temperature Management With Therapeutic Hypothermia Using Esophageal COOLing After Cardiac Arrest: THE COOL STUDY

Background The ability to control a patient's body temperature under a wide variety of conditions is extremely important, and is of particular importance after CA. TH targeted to 32-34°C as a targeted temperature management (TTM) demonstrably improves outcomes in at least two clinical conditions: adults resuscitated from CA and neonates suffering from hypoxic ischemic encephalopathy.1-7 TH is recommended for CA patients by major organizations that provide resuscitation guidelines, including the American Heart Association, the European Resuscitation Council, and the International Liaison Committee on Resuscitation.8-10 This indication was confirmed by a non-expert jury who provided clinical recommendations for five professional and international critical care societies (the American Thoracic Society, the European Respiratory Society, the European Society of Intensive Care Medicine, the Society of Critical Care Medicine, and the Société de Réanimation de Langue Française): the jury strongly recommends TTM to a target of 32-34°C as the preferred treatment (vs. unstructured temperature management) of out-of-hospital adult CA victims with a first registered electrocardiography rhythm of ventricular fibrillation or pulseless ventricular tachycardia and still unconscious after restoration of spontaneous circulation.11 Additional evidence exists, albeit lower level, for use of TH for comatose survivors of CA initially associated with non-shockable rhythms.8-10 The debate regarding the optimal level of TTM has been recently evaluated in a large randomized controlled trial comparing 2 different levels of TTM performed during 28 hours.12 In this study similar results regarding neuroprotection and survival have been obtained using either a 36°C target or a 33°C target (i.e. "real" TH).13 Consequently these 2 different levels of TTM can be used as it have been recently recalled by experts in the field. These treatments should be started as soon as possible, especially within the first 4 hours after CA. However this delay could be prolonged until 6 to 10 hours after CA.8-11 To date, however, available modalities for inducing precise TTM and TH have a number of technical, logistical, and financial barriers, including difficulties in placement, risks of use (such as needle sticks, infections, blood clots, and skin damage), and high cost. The Esophageal Cooling Device (ECD) is a disposable device that potentially improves the effectiveness of 32-34°C targeted TH while minimizing the risks of other existing methods such as invasive methods.14 The ECD is a multichambered silicone heat exchanger that is placed in the esophagus to provide highly efficient heat transfer to a patient while simultaneously maintaining access to the stomach to allow gastric suctioning, decompression, and drainage, as usually performed in such patients hospitalized in ICUs. The esophagus is in close proximity to blood flow from the heart and great vessels, and the ECD is designed to take advantage of this heat exchange environment. The ECD's ability to decompress the stomach and avoid distention of the esophagus away from the device ensures good contact with the esophageal mucosa, and thus maximizes heat transfer from the patient. The ECD replaces the standard gastric tube which is placed in the target patient population as a routine standard of care, is made of standard medical-grade silicone, and is generally similar in size and shape to the gastric tubes currently used. Initial mathematical and animal studies have shown strong support for the efficacy and safety of the ECD.14-16

Study design: Prospective, interventional study evaluating the feasibility (efficacy) and safety of the ECD in patients resuscitated from CA and treated with TH.

Patient population: Patient population will consist of patients suffering resuscitated out-of-hospital or in-hospital CA with stable return of spontaneous circulation (ROSC) and hemodynamic conditions with an indication to TH implementation according to standard recommendations.

Data collection: All clinical and biological parameters will be recorded according to the Utstein-style recommendations for reporting resuscitation outcomes. Neurologic outcome will be assessed according to the Cerebral Performance Category (CPC) score. Initial temperatures will be measured via a tympanic and naso-pharyngeal temperature sensors in the prehospital field and the inhospital cath-lab respectively. Continuous temperature measurement (specifically during cooling, maintenance, and rewarming) will be measured by bladder temperature sensors, and arterial temperature monitoring (Picco®) if available. Time of ECD placement and potential side effects will be recorded.

Specific treatment: The placement of the ECD will follow standard recommendations as per Instructions for Use. The ECD will be connected to the Gaymar console (Meditherm III, Gamida, France). In our institution, TH is performed in all patients resuscitated from an OHCA except those presenting exclusion criteria. TH can be initiated as soon as possible by administration of cold saline at 4°C if necessary followed by application of the available cooling device (blankets, endovascular methods, etc) aiming a target temperature of 32-34°C for 24 hours as recommended. 8-11,13 For all enrolled patient, the ECD will hereby replace the other cooling device usually used in our ICU.