Correlation Between Carotid Stump Pressure and Interhemispheric rSO₂ Asymmetry During Awake Carotid Endarterectomy

Izmir Katip Celebi University60 enrolled

Overview

This study aims to better understand how well the brain is perfused (supplied with blood and oxygen) during a specific type of surgery called carotid endarterectomy (CEA), which is performed to prevent strokes in people with stenosis of carotid arteries. During this surgery, the surgeon temporarily clamps the carotid artery to remove a blockage, which can reduce blood flow to the brain. Monitoring brain oxygen levels during this time is important to prevent brain injury. Two common monitoring methods are: Stump pressure (SP) - a pressure measurement taken from the carotid artery during surgery. Near-infrared spectroscopy (NIRS) - a non-invasive technique that tracks brain oxygen levels in real time. This study focuses on the relationship between carotid stump pressure and differences in brain oxygenation between the two sides of the brain (interhemispheric asymmetry), as measured by NIRS. The study will include patients undergoing awake CEA (under regional anesthesia) at a single center university hospital. Oxygen levels in both hemispheres of the brain will be monitored before and after the carotid artery is clamped after 3 minutes. Stump pressure will also be measured. The researchers will examine whether low stump pressure is linked to greater differences in brain oxygen levels between the two sides. The primary goal is to determine whether a large difference in brain oxygenation between the two hemispheres (greater than 10%) is associated with low carotid stump pressure. Secondary goals include identifying a stump pressure threshold that predicts significant asymmetry and analyzing the influence of patient and surgical factors. The findings may help improve how surgeons and anesthesiologists monitor and protect the brain during CEA, particularly in patients who are awake and can be observed for neurological changes.

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.

Outcomes

Primary Outcomes

Difference in Carotid Stump Pressure Between Interhemispheric rSO₂ Symmetry and Asymmetry Groups

The primary outcome is the comparison of intraoperative carotid stump pressure (SP) between patients with significant interhemispheric cerebral oxygenation asymmetry (\>10% ΔrSO₂ difference) and those with nonsignificant asymmetry (≤10%).