The Effect of Thyroid Lobe Volume on the Common Carotid Artery Blood Flow

Overview

The goal of this observational study is to evaluate how thyroid lobe volume affects carotid artery blood flow dynamics in adult patients undergoing elective thyroidectomy. The study includes male and female participants aged 18 years and older who have euthyroid function and are scheduled for elective thyroidectomy. The main questions it aims to answer are: * Does thyroid lobe volume influence carotid artery blood flow characteristics, particularly systolic/diastolic flow time ratios, during thyroidectomy? * What is the optimal thyroid lobe volume cutoff for predicting altered systolic/diastolic flow time ratios (\<0.3)? Participants will: * Undergo Doppler ultrasound measurements at three time points: before anesthesia induction, after anesthesia induction, and after surgical positioning. * Have their carotid artery blood flow and regional cerebral oxygenation values assessed. No comparison groups are involved, as all participants will be observed under the same conditions.

This observational study investigates how the size of the thyroid gland affects blood flow in the common carotid artery during thyroidectomy, a surgical procedure to remove part or all of the thyroid gland. The thyroid gland is anatomically close to the carotid artery, a major blood vessel supplying blood to the brain. Enlarged thyroid lobes may compress the artery, potentially altering blood flow dynamics, particularly during the semi-Fowler's position required for the surgery. By examining these effects, this study aims to provide insights into the interplay between thyroid anatomy and carotid blood flow, which could have implications for surgical and anesthetic management. Study Objectives The primary objective is to determine the relationship between thyroid lobe volume and carotid artery blood flow during thyroidectomy. Specifically, the study seeks to: 1. Evaluate how thyroid lobe volume influences systolic and diastolic blood flow in the carotid artery. 2. Identify a thyroid lobe volume cutoff associated with significant alterations in systolic/diastolic flow time ratios (\<0.3). Study Population The study includes adult patients aged 18 years and older scheduled for elective thyroidectomy. Participants must be in a euthyroid state, as thyroid hormone abnormalities may influence recovery and perioperative outcomes. Patients with conditions such as anemia, labile hypertension, or prior thyroid surgeries, as well as pregnant or emergency cases, are excluded. Study Design This is a prospective observational study conducted at a tertiary academic hospital. Measurements are obtained from each participant at three critical time points: 1. Baseline (T0): Before anesthesia induction. 2. After anesthesia induction (T1). 3. After surgical positioning (T2): In the semi-Fowler's position with head extension. Doppler ultrasound is used to assess carotid artery diameters and flow velocities. Regional cerebral oxygenation is also measured using a cerebral oximeter to evaluate the impact of altered blood flow on brain perfusion. Study Methods Participants undergo the following procedures during the study: * Ultrasound Measurements: The diameters of the common carotid artery at systole and diastole are measured, and Doppler flow velocities (peak systolic velocity, end-diastolic velocity) are recorded. These values are used to calculate mean velocity, Gosling pulsatility index, and Pourcelot resistance index. * Manual Tracing of VTI: In cases with altered systolic/diastolic flow ratios, manual tracing is used to ensure accuracy.