Evaluation of the Correlation Between Carotid Stump Pressure and Interhemispheric rSO₂ Asymmetry in Awake Carotid Endarterectomy: A Prospective Cohort Study
Conditions: Carotid Artery Stenosis Symptomatic, Carotid Endarterectomy (CEA) Surgical Patients, Cerebral Hypoperfusion
Sponsor: Izmir Katip Celebi University

Study Protocol and Statistical Analysis Plan 
 
Brief Title: Correlation Between Carotid Stump Pressure and Interhemispheric rSO₂ 
Asymmetry During Awake Carotid Endarterectomy 
 
Official Title: Evaluation of the Correlation Between Carotid Stump Pressure and 
Interhemispheric rSO₂ Asymmetry in Awake Carotid Endarterectomy: A Prospective Cohort 
Study 
 
Document Date: August 2025 
NCT Number: [to be assigned upon registration] 
 
Background and Rationale 
 
Carotid artery stenosis accounts for 15–30% of ischemic strokes. Carotid 
endarterectomy (CEA) reduces recurrent stroke risk in patients with significant stenosis but 
carries intraoperative risk of cerebral hypoperfusion during carotid cross-clamping. Carotid 
stump pressure (SP) is used as a surrogate for collateral circulation, while near-infrared 
spectroscopy (NIRS) provides a continuous, non-invasive estimate of regional cerebral oxygen 
saturation (rSO₂). Limitations exist with both, and no universal threshold has been validated. 
Recent interest has shifted toward interhemispheric rSO₂ asymmetry as a marker of perfusion 
adequacy with different clinical conditions. This study investigates whether SP differs 
significantly between patients with asymmetry >10% and those with asymmetry ≤10% 
Study Objectives 
 

Primary Objective 
 
To determine whether stump pressure values differ significantly between patients with 
interhemispheric rSO₂ asymmetry >10% vs. ≤10% during awake CEA. 
 
Secondary Objectives 
 
1. Interhemispheric asymmetry difference. 
2. Assess correlation between SP and interhemispheric ΔrSO₂ difference. 
3. Assess correlation between SP and ipsilateral ΔrSO₂. 
4. Identify a carotid SP threshold predictive of significant asymmetry using ROC curve 
analysis. 
5. Evaluate the independent predictive value of SP for asymmetry using multivariable 
logistic regression (adjusted for age, sex, carotid stenosis, intraoperative 
hemodynamics). 
6. Compare intraoperative hemodynamic parameters (PaO₂ (partial pressure of arterial 
oxygen), SpO₂ (peripheric oxygen saturation), systolic blood pressure, heart rate) and 
procedural variables (need for shunt, cross-clamp duration, surgical time) between 
groups. 
7. Document postoperative complications (neurological deficit, bleeding) within 30 days. 
 
Study Design 
 
Type: Single-center, prospective observational cohort study 
Setting: Tertiary academic hospital (Cardiovascular Surgery Department) 

Population: Adult patients undergoing elective awake CEA under regional anesthesia 
(superficial cervical plexus block) 
Sample Size: ~60 patients (based on power analysis) 
 
Groups: 
Asymmetry group: >10% interhemispheric ΔrSO₂ difference 
Symmetry group: ≤10% interhemispheric ΔrSO₂ difference 
Time Perspective: Prospective, 30 days. 
Masking: None (open-label observational study) 
 
Eligibility Criteria 
Inclusion Criteria: 
1. Age ≥18 years 
2. Elective CEA under regional (superficial cervical plexus block) anesthesia 
3. Bilateral rSO₂ monitoring with NIRS 
4. Successful SP measurement after cross-clamping 
5. Written informed consent 
Exclusion Criteria: 
1. Incomplete SP or NIRS data 
2. Conversion to general anesthesia 
3. Intraoperative technical complications 
4. Prior ipsilateral CEA or stenting 
5. Major disabling stroke 
6. MI within 3 months 
7. Traumatic brain injury within 6 months 

Intervention and Monitoring 
Anesthesia: Superficial cervical plexus block. 
Monitoring: ECG, SpO₂, invasive arterial pressure, bilateral frontal NIRS (INVOS 5100C). 
Procedure: Standard CEA under regional anesthesia; SP measured 3 min after cross-clamping 
with 22G catheter. 
Data Collection Points: 
T1: Baseline (before cross-clamping) 
T2: 3 minutes after cross-clamp 
 
Outcome Measures 
 
Primary Outcome: 
Difference in carotid stump pressure between asymmetry (>10% ΔrSO₂) and symmetry 
(≤10% ΔrSO₂) groups. 
Time frame: 3 minutes post-cross-clamp. 
 
Secondary Outcomes: 
 
1. Interhemispheric asymmetry difference. 
2. Correlation between SP and interhemispheric ΔrSO₂ difference (3 min post-clamp). 
3. Correlation between SP and ipsilateral ΔrSO₂ (3 min post-clamp). 
4. ROC curve threshold analysis for SP predicting asymmetry. 
5. Logistic regression model (SP + covariates). 
6. Comparison of intraoperative hemodynamics and procedural characteristics between 
groups. 

7. Postoperative neurological or bleeding complications within 30 days. 
 
Statistical Analysis Plan 
 
Descriptive statistics: Continuous data as mean ± SD or median (IQR); categorical as 
frequency/%. 
Normality test: Shapiro–Wilk. 
Primary outcome: Independent t-test (SP difference between groups). Mann–Whitney U if non-
parametric. 
Secondary outcomes: 
Spearman’s correlation (SP vs. ΔrSO₂, ipsilateral ΔrSO₂). 
ROC analysis to determine SP cutoff for asymmetry (>10%). 
Logistic regression (Model 1: SP; Model 2: adjusted for age, sex, stenosis; Model 3: + 
intraoperative variables). 
Hemodynamic/procedural comparisons: t-test, Mann–Whitney, or Fisher’s exact test. 
30-day complications compared between groups (Fisher’s exact). 
Significance threshold: p < 0.05. 
Software: IBM SPSS v26. 
 
Power Analysis 
 
Preliminary data: 
Symmetry group SP: 56 ±15 mmHg 
Asymmetry group SP: 44 ±13 mmHg 
Cohen’s d = 0.855 

Sample size calculation (two-sample t-test, α = 0.05, power = 0.90, two-tailed): 
Required per group = ~30 patients 
Total = ~60 patients 
Software: G*Power 3.1 
 
Ethics 
 
Approval: Izmir Katip Celebi University Health Research Ethics Committee 
Approval No: 0442 (17 July 2025) 
Conducted per the Declaration of Helsinki. 
Written informed consent required. 
 
Data Sharing 
 
Plan: De-identified IPD (SP values, rSO₂ data, intraoperative hemodynamics, outcomes) will 
be available upon reasonable request for academic purposes. 
Access: Requests subject to institutional and ethical approval.