Evaluation of Analgesia for Cardiac Elective Surgery in Children

The purpose of this study is to look at a standardized methadone-based enhanced recovery after surgery protocol following pediatric cardiac surgery. This study will consist of randomly assigning children to receive the methadone-based recovery procedures or to receive current standard of care recovery procedures. Randomly assigning means that there is a 50/50 chance, like a coin flip, of being assigned to either research group.

The investigator's long-term goal is to proactively improve the safety and efficacy of surgical pain control while reducing opioid AEs (adverse events) and the opioid epidemic burden in all children undergoing inpatient surgeries. The investigator's central hypothesis is that a standardized, multidose, methadone-based ERAS (Enhanced Recovery After Surgery) protocol will reduce acute surgical pain, overall opioid use, RD (Respiratory Depression), PONV (Postoperative Nausea and Vomiting), and CPSP (Chronic Persistent Surgical Pain) compared with standard-of-care short-acting opioid-based analgesia in children undergoing CS (Cardiac Surgery) (Aim 1). Investigators will use PK (Pharmacokinetic) and genetic variations along with CPB (Cardiopulmonary Bypass) related dilution and clinical factors to develop optimal intra- and post-operative methadone dosing in children to enable precision analgesia in the future (Aim 2). The investigators will identify patient profiles with genetic, epigenetic, PK, clinical, and psychological factors to predict benefit from assigned analgesia for optimal clinical outcomes (Aim 3). The investigators expert multidisciplinary and multicenter team will enroll a total of 500 children to conduct two parallel randomized clinical trials for CS (500 children 1 month-10 years from 5 clinical sites). In this study, specifically, the investigators will:

Aim 1. Conduct two randomized clinical trials in CS to compare acute pain relief, opioid-sparing efficacy, and safety of standardized perioperative multidose methadone-based ERAS vs. standard-of-care non-methadone-based analgesia. Acute surgical pain, opioid needs (morphine equivalents), RD, PONV, and CPSP will be lower in methadone-based analgesia compared to short-acting opioid-based analgesia.

Aim 2. Develop precision methadone dosing based on age, CYP2B6 and ORM1 variants, AAG, and CPB. Age, CYP2B6 and ORM1 variants, AAG levels, and CPB-related dilution will explain methadone's PK variability and dose adjustments that correlate with optimal clinical outcomes among 500 children receiving methadone.

Aim 3. Identify patient profiles that predict benefits from the assigned analgesia protocol to optimize clinical outcomes. Personalized risk prediction models will be developed and validated including genetic variants (i.e., CYP2B6, CYP2D6, ABCB1, OPRM1, and FAAH), and psychological and clinical factors to predict benefit with the assigned treatments (methadone or non-methadone) for pre-specified clinical endpoints.

Overall Impact: The investigators will develop actionable evidence for the efficacy of standardized, multidose, methadone-based ERAS protocols and will harness genetic, clinical, and psychological factors contributing to variability in methadone and oxycodone PK, acute surgical pain, transition to CPSP, opioid-induced PONV, RD, and dependence to develop personalized analgesia strategy and dosing for children undergoing CS. Implementation of evidence-based standardized methadone-based ERAS pain management and individualized risk prediction will maximize acute surgical pain relief while minimizing opioid use and AEs in millions of children.

Eligibility Criteria:
Inclusion Criteria:

* Children aged 1 month - \<18 yrs
* ASA physical status 1\&2
* 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:

* Adults \>18 years
* Pregnant patients \<18 years
* American Society of Anesthesiologists (ASA) Physical Status 3 or above
* Methadone/oxycodone allergy
* Severe sleep apnea
* Baseline prolonged QTc
* Developmental delay
* Liver or kidney disease
* Neurological disease
* Preoperative opioid use