Neuroprotective Effect of Mild Hypothermia Versus Normothermia During Cardiopulmonary Bypass of Coronary Artery Surgery

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recommendation is primarily based on two meta-analyses, but the underlying studies show methodological heterogeneity, outdated practices, and limited applicability to contemporary cardiac surgery.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 inj