Carotid artery stenosis accounts for approximately 15-30% of ischemic strokes,
highlighting the importance of carotid endarterectomy (CEA) as a preventive surgical
strategy. One of the most critical intraoperative concerns during CEA is cerebral
hypoperfusion at the time of carotid cross-clamping, when antegrade ipsilateral blood
flow is interrupted. Monitoring cerebral oxygenation and collateral circulation during
this period is essential to reduce the risk of ischemic complications. Traditionally,
carotid stump pressure (SP) measurement has been used as a surrogate of collateral flow,
whereas near-infrared spectroscopy (NIRS) provides a continuous, non-invasive estimate of
regional cerebral oxygen saturation (rSO₂). While both tools are widely used, each has
limitations, and there is no universal consensus on their predictive thresholds. Recent
interest has shifted toward analyzing interhemispheric asymmetry in rSO₂ as a potentially
physiological marker of cerebral perfusion adequacy in other clinical conditions.
This prospective, single-center observational cohort study will evaluate the association
between carotid stump pressure and interhemispheric rSO₂ asymmetry in patients undergoing
awake CEA under regional anesthesia. All patients will undergo awake CEA under regional
anesthesia (superficial cervical plexus block) with bilateral NIRS monitoring and
intraoperative stump pressure measurement. Data will be collected at baseline (before
cross-clamping) and 3 minutes after carotid cross-clamp application. Patients will be
stratified into two groups based on interhemispheric ΔrSO₂ asymmetry (>10% vs. ≤10%).
The primary objective is to determine whether stump pressure values differ significantly
between patients with interhemispheric rSO₂ asymmetry greater than 10% (asymmetry group)
compared with those with asymmetry of 10% or less (symmetry group).
Secondary objectives include:
Interhemispheric asymmetry difference;
Assessing the correlation between SP and interhemispheric ΔrSO₂ difference;
Assessing the correlation between SP and ipsilateral ΔrSO₂;
Identifying a carotid SP threshold predictive of significant interhemispheric asymmetry
using receiver operating characteristic (ROC) curve analysis;
Evaluating the independent predictive value of SP for cerebral asymmetry using
multivariable logistic regression adjusted for age, sex, degree of carotid stenosis, and
intraoperative hemodynamic variables;
Comparing intraoperative hemodynamic parameters (PaO₂ (partial pressure of arterial
oxygen), SpO₂ (peripheric oxygen saturation), systolic blood pressure, and heart rate)
and procedural variables (need for shunt, cross-clamp duration, surgical time) between
groups;
Documenting postoperative complications, including neurological deficits or bleeding,
within 30 days of surgery.
A power analysis based on preliminary data (SP = 56 ± 15 mmHg in the symmetry group vs.
44 ±13 mmHg in the asymmetry group) yielded an effect size (Cohen's d) of 0.855. With α =
0.05 and 90% power, a minimum of 30 patients per group (60 total) are required to detect
a significant difference in stump pressure between groups.
The findings of this study may refine intraoperative brain monitoring practices during
CEA by clarifying the physiological relationship between stump pressure and cerebral
oxygenation asymmetry.
