a Comparive Study of Ketamine-Propofol Versus Dexmedetomidine-Propofol Sedation in Pediatric Patients Undergoing Cardiac Catheterization for Device Closure of Simple Left-to-right Shunts

Inclusion Criteria: * Age 2-12 years, male or female * Weight ≥ 10 kg * Scheduled for elective transcatheter device closure of a simple left-to-right shunt, including: * Secundum atrial septal defect (ASD) suitable for device closure * Small muscular ventricular septal defect (VSD) eligible for percutaneous device closure * Patent ductus arteriosus (PDA) closure * Procedure performed with transthoracic or transesophageal echocardiographic guidance according to the cardiology team's practice * ASA physical status II-III * Written informed consent obtained from a parent or legal guardian Exclusion Criteria: * Cyanotic congenital heart disease * Complex congenital cardiac lesions * Risk of pulmonary hypertensive crisis * Requirement for general anesthesia and cuffed endotracheal tube at the discretion of the cardiology or anesthesia team * Baseline oxygen requirement \> 2 L/min * Use of noninvasive ventilation * Known allergy or intolerance to ketamine, dexmedetomidine, or propofol * Significant hepatic impairment * Significant renal impairment * Advanced atrioventricular block * Clinically significant bradyarrhythmia * Uncontrolled epilepsy * Raised intracranial pressure * Severe obstructive sleep apnea * Craniofacial anomalies associated with anticipated difficult airway management * BMI \> 97th percentile when judged to confer high risk of sedation-related airway obstruction * Current beta-blocker use * Current clonidine use * Acute upper respiratory tract infection within 2 weeks before the procedure * Emergency or add-on procedures * Anticipated procedure duration \< 20 minutes * Anticipated procedure duration \> 3 hours