Study on Optimal Temperature During Cardiopulmonary Bypass (THERMIC-4)

Normothermic Versus Hypothermic Cardiopulmonary Bypass in Adult Cardiac Surgery: a Multicentre Feasibility Randomised Controlled Trial

In order to perform heart surgery, a machine called cardiopulmonary bypass (CPB), or more commonly known as a heart-lung machine, is used to maintain the circulation of oxygenated blood needed by the rest of the body and its organs.

Historically, when a patient is connected to CPB, their body is cooled below the normal body temperature. This is known as hypothermia. This is because scientific studies have previously shown that reduced body temperature lowers metabolism and therefore offers more protection to the brain and other organs due to the reduced oxygen requirement. The evidence supporting this practice, however, has been challenged throughout the history of cardiac surgery, with studies supporting that normothermia, or normal body temperature, is a safe alternative. Despite this, the practice of hypothermia has persisted. Published data from a survey of 139 cardiac surgeons in the United Kingdom showed that 84% still routinely employ hypothermic CPB during surgery.

To assess whether normothermic or hypothermic CPB is safer, a clinical trial requiring a large sample size and high recruitment rates will be required. Therefore, the investigators aim to assess firstly the feasibility of trial recruitment and allocation adherence in this study. 100 adults across 10 different cardiac surgery centres in the United Kingdom will be recruited to a multicentre feasibility randomised controlled trial comparing normothermia (active comparator) against hypothermia (control comparator) during cardiopulmonary bypass in cardiac surgery. This study will also test the ability of the Cardiothoracic Interdisciplinary Research Network (CIRN), a trainee-led research collaborative, to collect pilot data on Major Adverse Cardiac and Cerebrovascular Events (MACCE) using a regulation-approved electronic application HealthBitⓇ. Participants will also be asked to complete quality of life surveys. The results of this study will subsequently inform a large, adequately powered randomised controlled trial for optimal temperature management during CPB.

Primary Objective

To assess the feasibility of trial recruitment and delivery to target in the United Kingdom of a multicentre randomised controlled trial on normothermia versus hypothermia during cardiopulmonary bypass in adult cardiac surgery.

Secondary Objective

To assess the feasibility of conducting a multicentre randomized controlled trial (RCT) using a novel Good Clinical Practice (GCP) approved remote data capture as the primary trial database alongside analysis of routinely collected healthcare data.

To obtain pilot data, undertaken by the Cardiothoracic Interdisciplinary Research Network (CIRN), to inform a subsequent large, adequately powered RCT for optimal temperature management during CPB.

INCLUSION CRITERIA

Participants may enter the trial if all of the following apply

1. Adult patients (≥ 18 years) scheduled for coronary artery bypass surgery and/or valve replacement/ repair, either in the elective or urgent setting.
2. European System for Cardiac Operative Risk Evaluation (EuroSCORE) II of 2 or higher.
3. Able to understand and communicate to provide informed consent.
4. Able to read and understand the English language.

EXCLUSION CRITERIA

Participants may not enter the trial if any of the following apply:

1. Patients undergoing coronary artery bypass surgery in combination with other procedures including cardiac or vascular procedures that require deep hypothermic arrest.
2. Patients undergoing emergency or salvage surgery.
3. Patients undergoing off-pump cardiac surgery.
4. Patients who are participating in another interventional trial.
5. Unable to provide informed consent.