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

Selective Antegrade Cerebral Perfusion as a Cerebral Protection Strategy in Ascending Aortic Surgery: Perioperative Changes in Ultrasonographic Optic Nerve Sheath Diameter. A Single-Center Prospective Observational Cohort Study

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.

This single-center prospective study will enroll adults undergoing elective or urgent ascending aortic surgery with planned axillary artery cannulation. Participants are grouped according to whether release of the aortic cross-clamp is required to construct the distal anastomosis, and therefore whether selective antegrade cerebral perfusion is applied. Group membership follows from the intraoperative surgical requirement and is not assigned by the investigators. All participants receive a single protocol-specified general anesthesia and ventilation regimen, identical in both groups, so that variables known to act on optic nerve sheath diameter, in particular arterial carbon dioxide tension, volatile agent concentration and airway pressure, are held constant. Because this regimen is assigned by the protocol, the study is registered as interventional. Bilateral optic nerve sheath diameter and optic nerve diameter will be measured by ultrasonography, and middle cerebral artery mean flow velocity by transcranial Doppler, at three time points: before anesthesia induction (T0), at the end of surgery after hemodynamic stabilization in the operating room (T1), and at postoperative hour 24 in the intensive care unit (T2). Regional cerebral oxygen saturation by near-infrared spectroscopy and the electroencephalographic suppression ratio derived from bispectral index monitoring will be recorded intraoperatively. Delirium will be screened at postoperative hour 24 using the Nursing Delirium Screening Scale (Nu-DESC), with a total score of 2 or more considered a positive screen. The primary outcome is the change in bilateral mean optic nerve sheath diameter across T0, T1 and T2, evaluated as the group-by-time interaction in a linear mixed-effects model.

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