In high-income countries, coronary artery bypass grafting (CABG) remains a common procedure, with approximately 36.7 operations per 100,000 inhabitants annually, corresponding to about 136,000 procedures in the European Union. This highlights the substantial healthcare burden and the need to optimize surgical outcomes. Cardiopulmonary bypass (CPB) is a fundamental component of cardiac surgery, ensuring extracorporeal perfusion of vital organs.
Hypothermic CPB has historically been widely used for organ protection due to its presumed neuroprotective mechanisms. However, evidence demonstrating its superiority over normothermic CPB remains inconclusive. In its 2024 guidelines, the European Association for Cardio-Thoracic Surgery recommends considering normothermia (≥35 °C) to reduce postoperative neurocognitive dysfunction (Class II, Level A). This recommendation is primarily based on two meta-analyses, but the underlying studies show methodological heterogeneity, outdated practices, and limited applicability to contemporary cardiac surgery. Importantly, the guidelines acknowledge the need for large randomized controlled trials to define optimal target temperature management (TTM) during CPB.
Previous diffusion-weighted MRI studies have demonstrated silent ischemic brain lesions in approximately 30% of CABG patients, with postoperative neurocognitive decline occurring in a similar proportion. However, no significant differences have been shown between normothermic and hypothermic CPB. Diffusion tensor imaging (DTI) extends conventional diffusion imaging by enabling detailed assessment of white matter microstructure and tractography. Fractional anisotropy (FA), a key DTI metric, has demonstrated prognostic value in various neurological conditions but has not yet been applied in CABG patients.
Blood-based biomarkers, including glial fibrillary acidic protein, neurofilament light chain, neuron-specific enolase, and total tau, offer complementary insights into brain injury but have not been studied in combination with DTI in this population.
This study will compare mild hypothermic (33-34 °C) and normothermic (36.5 °C) CPB to evaluate their neuroprotective effects using advanced MRI techniques and blood-based biomarkers. The primary aim is to determine whether mild hypothermia provides superior neuroprotection following CABG. Secondary objectives include assessing white matter injury evolution, global ischemic burden, associations with biomarkers and neurocognitive decline, and developing integrated prognostic models to improve outcomes in CABG patients.
Informed consent obtained
Age of >18 years
Undergoing elective or subacute coronary artery bypass grafting
An emergency case
A history of stroke
A history of intracranial bleeding
A history of transient ischemic attack (TIA)
Parallel
Normothermic cardiopulmonary bypass
Procedure/Surgerynormothermic cardiopulmonary bypass with nasopharyngeal temperature of 36.5 ± 0.2°C
Hypothermic cardiopulmonary bypass
Procedure/Surgerymild hypothermic cardiopulmonary bypass with nasopharyngeal temperature of 33 ± 0.2°C
Global fractional anisotropy of brain white matter of diffusion tensor imaging (DTI)
Fractional anisotropy measures white matter microintegrity. It is assessed with brain magnetic resonance diffusion tenson imaging (DTI)
Change in hippocampal volume in milliliters (ml) from preoperative day 4 (+/- 3 days) to postoperative day 6 (+/-1 day) between the control and the intervention group
The volume of hippocampus will be measured with voxel-based morphometry of magnetic resonance imaging at preoperative day 4 +/- 3 days and at postoperative day 6 +/- 1day.
Number of participants with treatment related adverse events as assessed by CTCAE v 4.0
Change in hippocampal ischemic injury from preoperative day 4 +/- 3 days to postoperative day 6 +/- 1 day between the control group and the intervention group.
The ischemic injury in the hippocampus will be measured with magnetic resonance diffusion tensor imaging
Change in ischemic injury of basal ganglia from preoperative day 4 +/- 3 days to postoperative day 6+/- 1 day between the control group and the intervention group
The ischemic injury in basal ganglia will be measured with the magnetic resonance diffusion tensor imaging
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