Comparison of Gastric Volume Changes Via Ultrasound After Ventilation With Endotracheal Tube, First-Generation Supraglottic Airway, and Second-Generation Supraglottic Airway in Pediatric Patients: A Prospective Observational Study

All participants will receive a standard preoperative intravenous (IV) dose of 0.1 mg/kg midazolam in the preparation room. Upon arrival at the operating room, routine monitoring will be established for all patients, including electrocardiography (ECG), non-invasive blood pressure (NIBP), and peripheral oxygen saturation (SpO2). Before the induction of anesthesia (T0), the gastric antral area will be evaluated using ultrasound in the right lateral decubitus (RLD) position. A high-frequency linear probe will be placed sagittally in the epigastric region to visualize the stomach antrum, located posterior to the left lobe of the liver and anterior to the abdominal aorta. The largest and smallest diameters (d1 and d2) of the elliptical antrum will be measured. The Antral Cross-Sectional Area (ACSA) will be calculated using the formula: ACSA = d1*d2*pi/4. Gastric volume will then be derived using the validated pediatric formula: [0.035*ACSA (mm2) + 0.127*age (months) - 7.8] / body weight (kg). Standard general anesthesia induction will be performed using sevoflurane and oxygen inhalation, 1 mcg/kg IV fentanyl, and 0.5 mg/kg IV rocuronium. Following induction, patients will be managed with either endotracheal intubation or a supraglottic airway device (SAD). The choice of airway management will follow routine clinical practice. SAD size and cuff inflation volume will adhere to the manufacturer's recommendations. Any volume leakage during ventilation will be recorded as a percentage. Anesthesia maintenance will be provided with 1 MAC sevoflurane in an oxygen/air mixture. The gastric antral area will be re-evaluated via ultrasound in the RLD position at two additional time points: T1: Immediately after the airway device is secured and ventilation is established, before the start of surgery. T2: At the end of the surgical procedure, before the patient emerges from anesthesia. All relevant clinical data will be recorded in the patient follow-up form, including age, gender, height, weight, duration of surgery, vital signs, type of airway device used, perioperative airway pressures, and any observed complications. Following the final measurement, patients will be emerged from anesthesia and transferred to the postoperative recovery room according to standard protocols.