Evaluation of the Relationship Between Bilateral Optic Nerve Sheath Diameter (ONSD) Measurements and Postoperative Cognitive Functions in Bentall Surgeries: A Prospective Observational Study

Bentall procedure is a complex cardiac surgery involving replacement of the ascending aorta, aortic root, and aortic valve using a mechanical or bioprosthetic valve conduit and vascular graft. It is commonly performed for aortic aneurysm, aortic dissection, or connective tissue disorders such as Marfan syndrome. The procedure carries a mortality rate of 2-10% and a neurological complication rate of 3-8%, including stroke and postoperative cognitive dysfunction (POCD).Postoperative neurological complications in Bentall surgery are influenced by both patient-related and surgery-related factors. Patient-related risk factors include advanced age (>70 years), low educational level, pre-existing cognitive impairment, carotid artery stenosis, and acute type A dissection. Surgery-related risk factors include prolonged CPB and deep hypothermic arrest duration, cerebral perfusion technique, prosthesis type, prolonged mechanical ventilation, postoperative infection, low cardiac output, and anticoagulation compliance.

The optic nerve sheath (ONS) is a continuation of the intracranial dura mater surrounding the subarachnoid space. It expands in response to elevated intracranial pressure (ICP), particularly in the anterior retrobulbar region. Ultrasound measurement of ONSD is a well-validated, non-invasive bedside method for detecting elevated ICP and has been studied in various clinical settings.

Bentall surgeries involving CPB may affect intracranial dynamics through multiple mechanisms including oxygenation fluctuations, electrolyte disturbances, hemodilution, blood transfusion requirements, temperature variations, total circulatory arrest, prolonged surgical duration, and embolic events. Therefore, perioperative monitoring of intracranial status is of particular importance in these patients.

Study Procedures:

All patients will have the following baseline data recorded: age, sex, BMI, ASA classification, comorbidities, smoking and alcohol use, medications, ejection fraction (EF), EuroSCORE, and educational level.Preoperative assessments (T0) will include MoCA test, bilateral NIRS-based cerebral oximetry, and bilateral ONSD measurement by ultrasound while breathing room air.