Evaluation of Analgesia for Cardiac Elective Surgery in Children

Inclusion Criteria: * Children aged 3-years - \<18 years * ASA physical status 1, 2, or 3 * Participant or legal guardian can speak and read English or Spanish * Undergoing the following cardiac surgeries (Categories 1 \& 2) that are associated with significant acute surgical pain STS Category 1: * ASD, PFO closure * VSD repairs, * Aortic stenosis sub-valvular repair * ASD and Partial anomalous venous return repair * AV canal transitional * Conduit replacement * Valve replacement (AVR, PVR) * TOF repair without ventriculostomy STS Category 2: * Glenn shunt (on Bypass only) * Fontan surgery (on Bypass only) * Pulmonary artery plasty (main) * Left Atrium (LA) to Pulmonary Artery (PA) conduit replacement. Exclusion Criteria: * Pregnant patients * Methadone allergy * Preoperative prolonged QTc more than 460 msec (-30 days to 0 day) * Subjects undergoing concomitant treatment with known cytochrome P450 inhibitors included in methadone labeling (i.e. macrolides (e.g. erythromycin), azole-antifungal agents (e.g. ketoconazole, voriconazole), protease inhibitors (e.g. ritonavir), fluconazole, SSRIs (e.g. sertraline, fluvoxamine) * Preoperative opioid use within 30 days before surgery * History of severe sleep apnea (have a sleep study with an AHI index score more than 10 or clinical signs of sleep disordered breathing - snoring, daytime drowsiness) * Significant liver, kidney, neurological disease, developmental delay, or any other co-existing medical condition per discretion o…