Gastric Assessment of Pediatric Patients Undergoing Surgery

The goal of this pilot prospective cohort study is to examine the reproducibility of gastric volume and emptying as measured by gastric ultrasound and its correlation to a gold-standard test for gastric emptying in the perioperative period in pediatric patients. The main questions it aims to answer are: * What is the reliability (inter-rater variability between expert and novice assessors, and intra-rater variability) of a) the gastric antral cross-sectional area (CSA) and b) gastric volume using the Perlas US qualitative grading assessment, measured by using an ultrasound device in pediatric patients undergoing general anesthesia for elective surgery? * What is the correlation between ultrasound assessment of gastric emptying by the antral-CSA and gastric emptying determined by the acetaminophen absorption test (AAT), the gold standard? The study will include two cohorts. Cohort assignment will be based on age and anesthesia induction plan. Subjects \>7yrs of age and expected to get an IV induction will be assigned to Cohort #1. Subjects \<7yrs of age and not expected to get an IV induction will be assigned to Cohort #2. * Cohort 1 will include abdominal ultrasound for gastric assessment AND the acetaminophen absorption test which includes administering enteral acetaminophen (tylenol) with 6 oz of water and drawing of blood samples through a peripheral intravenous line. * Cohort 2 will include subjects for whom a peripheral intravenous line placement is not part of routine pre-operative care. Procedures for Cohort 2 will include abdominal ultrasound only in the pre-op area (no tylenol). This cohort is included to examine the reliability of measurements across age groups.