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.
Adults aged 18 years or older
Scheduled for elective carotid endarterectomy (CEA)
Able to tolerate surgery under regional anesthesia (superficial cervical plexus block)
Availability of bilateral regional cerebral oxygen saturation (rSO₂) measurements by near-infrared spectroscopy (NIRS)
Incomplete NIRS or SP recordings
Conversion from regional to general anesthesia
Intraoperative technical complications preventing monitoring
History of prior ipsilateral carotid endarterectomy or carotid artery stenting
Adult patients (≥18 years) undergoing elective carotid endarterectomy (CEA) under regional anesthesia at a single tertiary academic hospital. All participants must be able to tolerate awake surgery with regional anesthesia (superficial cervical plexus block) and undergo bilateral near-infrared spectroscopy (NIRS) monitoring and carotid stump pressure measurement during the procedure.
Cohort
Prospective
Not listed
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%).
Interhemispheric asymmetry difference
This outcome is the absolute difference in percentage change (ΔrSO₂) between the ipsilateral (surgical) and contralateral hemispheres during carotid cross-clamping, measured using near-infrared spectroscopy (NIRS). Interhemispheric asymmetry is defined as: ΔrSO₂ = (Post-clamp rSO₂ - Pre-clamp rSO₂) / Pre-clamp rSO₂ × 100 Interhemispheric asymmetry difference = ΔrSO₂ Ipsilateral - ΔrSO₂ Contralateral
Correlation Between Carotid Stump Pressure and Interhemispheric ΔrSO₂ Difference
This outcome evaluates the relationship between carotid stump pressure and the absolute ΔrSO₂ difference between hemispheres (interhemispheric asymmetry) during carotid cross-clamping. The analysis will determine whether lower stump pressure values are significantly associated with increased interhemispheric cerebral oxygenation asymmetry.
Correlation Between Carotid Stump Pressure and Ipsilateral ΔrSO₂
This outcome examines the association between carotid stump pressure and the percentage change in regional cerebral oxygen saturation (ΔrSO₂) specifically on the ipsilateral (surgical) hemisphere. ΔrSO₂ is calculated as the relative change from pre-clamp to post-clamp values using near-infrared spectroscopy (NIRS). The aim is to determine whether lower stump pressures are associated with greater ipsilateral desaturation, indicating impaired cerebral perfusion.
Carotid Stump Pressure Threshold Predictive of rSO₂ Asymmetry Using ROC Curve Analysis
This outcome evaluates whether a specific carotid stump pressure threshold can predict significant interhemispheric cerebral oxygenation asymmetry (\>10% ΔrSO₂ difference). Receiver operating characteristic (ROC) curve analysis will be used to calculate sensitivity, specificity, and area under the curve (AUC) for predictive accuracy.
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