Tonsillectomy ± adenoidectomy (T&A) is one of the most common surgical operations with over 500,000 pediatric T&As performed annually in the United States. Unfortunately, despite advances in anesthetic and surgical techniques, moderate-severe post-tonsillectomy pain (PTP) remains a significant problem affecting up to 62% of children. PTP is thought to arise from pharyngeal mucosal inflammation, which produces local nerve irritation and pharyngeal muscle spasm. Patient factors and surgical techniques also play major roles. Race is an important phenotypic risk factor for moderately severe early PTP. The underlying molecular basis of this differential pain experience is presently unknown. This gap in knowledge means that therapies are poorly targeted and often unsuccessful. Indeed, treatment options for PTP have not advanced substantively for many years. Metabolomics provides novel opportunities to investigate common and unique "metabolic signature" of PTP through the analysis of low molecular weight compounds produced in response to tissue injury. Therefore, the central themes of this proposal are that (1) PTP is a complex process that may be determined by molecular level factors such as preoperative systemic inflammation and metabolic profile, and (2) these molecular level factors may explain the excess burden of PTP among minority children. Here the investigators seek to utilize a combined clinical, biological and untargeted metabolomics approach to identify candidate small and large serum molecules that may influence the frequency and severity of PTP in children across racial groups. This approach to exploring the molecular basis of PTP is novel and knowledge from the study should substantially enhance understanding of the mechanisms underlying pediatric PTP - and narrow the racial disparities in post-operative pain.

Inclusion Criteria:

• Consenting (or assenting) patients age 4-17yr and American Society of Anesthesiologist's (ASA) physical status I-III who are scheduled for elective tonsillectomy ± adenoidectomy (T&A).

Exclusion Criteria:

• Age > 18 years old
• Children below 4 years of age because they are routinely admitted following T&A in our institution and may not be able to clearly self-report their pain
• Children on chronic preoperative analgesic medications
• Children with Cushing's syndrome, or nephrotic syndrome
• Children on chronic systemic steroids
• Children with concurrent surgical procedures that could prolong the duration of anesthesia and surgery
• Children that do not speak English or cannot self-report their pain after surgery (significant cognitive impairment, anticipated or unplanned postoperative endotracheal intubation, and sedation)

Children undergoing tonsillectomy ± adenoidectomy at Nationwide Children's Hospital.