Comparison of Age-Based Formula and Ultrasound-Guided Subglottic Diameter Measurement for Endotracheal Tube Sizing in Single Ventricle Patients

To compare the accuracy of ultrasound-guided subglottic diameter measurement versus age-based formulas in determining optimal ETT size in pediatric patients with single ventricle physiology to avoid post-extubation complications. All legal guardians will provide written informed consent after a full explanation of the study. During the pre-anesthetic evaluation, demographic data, ASA physical status, relevant comorbidities, and a recent echocardiogram confirming single ventricle physiology will be documented. In the operating room, patients will be monitored using standard ASA monitors including ECG, non-invasive blood pressure, pulse oximetry, and capnography, followed by preoxygenation with 100% oxygen. If intravenous access is available, anesthesia will be induced with ketamine, fentanyl, and rocuronium. If IV access is not available, inhalational induction with sevoflurane will be used until IV access is secured, after which fentanyl and rocuronium will be administered. Following induction, ventilation will continue with FiO₂ 100% and sevoflurane 1.5% for 3 minutes.

Patients will be divided into two groups:

Group A (Age-Based Formula):

In neonates and infants under 1 year, a weight-based sizing is used:

• Infants <1 kg (Preterm): 2.5 mm ETT
• Infants 1-2 kg: 3 mm ETT
• Infants 2-3 kg (Full Term): 3-3.5 mm ETT
• Infants >3 kg (3 months to 1 year): 3.5-4 mm ETT