Selective Antegrade Cerebral Perfusion and Perioperative Optic Nerve Sheath Diameter in Ascending Aortic Surgery

In ascending aortic surgery the distal anastomosis may be constructed with the aortic cross-clamp maintained, or, where the extent of the aortic pathology and the geometry of the graft require it, after release of the cross-clamp during a period of systemic circulatory arrest. Both are established surgical approaches. Where the cross-clamp is released, selective antegrade cerebral perfusion (SACP) is an established cerebral protection technique and is applied for that purpose. Where release of the cross-clamp is not required, systemic circulatory arrest is avoided and SACP is not applied. Optic nerve sheath diameter (ONSD) measured by ocular ultrasonography is a non-invasive marker of raised intracranial pressure. Cardiopulmonary bypass may increase blood-brain barrier permeability through hypoperfusion, non-pulsatile flow, hemodilution and systemic inflammation, predisposing to cerebral edema. Perioperative increases in ONSD have been reported after open heart surgery and have been associated with postoperative delirium. Data on how SACP influences perioperative ONSD dynamics in ascending aortic surgery, and whether such changes relate to postoperative delirium, are limited.

Inclusion Criteria: * Age 18 years or older * Planned or urgent, hemodynamically stable ascending aortic surgery, including supracoronary ascending aortic replacement, aortic root replacement (Bentall procedure) or valve-sparing root surgery (David procedure), limited to cases involving the ascending aortic segment * Perfusion planned through axillary artery cannulation * Written informed consent Exclusion Criteria: * History of intracranial procedure or intracranial pathology * Previous carotid intervention, or carotid artery stenosis of 50 percent or more on preoperative Doppler ultrasonography * Advanced chronic obstructive pulmonary disease, defined clinically as advanced stage disease with long-term oxygen therapy or a history of frequent exacerbations * Baseline arterial carbon dioxide tension of 55 mmHg or higher on preoperative arterial blood gas analysis * Ocular pathology, ocular surgery or ocular trauma that could affect measurement of the optic nerve sheath or optic nerve, including glaucoma and retinal detachment or fibrosis * Severe preoperative neurological deficit, including major stroke or severe dementia, or active psychiatric illness * Hemodynamic instability, or a requirement for extracorporeal membrane oxygenation or intra-aortic balloon counterpulsation, of a degree that prevents measurements during the first 24 postoperative hours * Known contraindication to any component of the protocol-specified anesthesia regimen