Cohort 1 will include subjects who have a peripheral intravenous line placed in the pre-op area per routine care. This cohort is on average age 7 years and older. Procedures for cohort 1 will include: (a) gastric US measurement of the antral CSA and gastric volume using the Perlas US qualitative grading assessment by an expert and a novice operator to determine the inter-rater class reliability and repeat measurements by each operator to assess the intra-rater reliability (Aim 1), and (b) serial abdominal ultrasounds for gastric assessment and the acetaminophen absorption test to determine the correlation between gastric US and a gold-standard for gastric emptying (Aim 2). The acetaminophen absorption test requires administering a single weight-based enteral dose of acetaminophen with 6 oz of water and drawing of blood samples through a peripheral intravenous line.
The patient’s abdomen will be scanned using the ultrasound device by an expert scanner and novice scanner for baseline assessment of the antral CSA and gastric volume using Perlas US qualitative grading assessment.
Diagnostic Test: Acetaminophen Absorption Test (AAT)
Prior to starting the AAT, a baseline plasma acetaminophen level (250 microliters) will be obtained from the intravenous catheter. The subject will then be given 12.5 mg/kg or max 650mg of single batch 32mg/mL acetaminophen followed by 6oz of water PO. Up to 3 additional small volume blood samples will be drawn for acetaminophen levels.
These additional blood samples (250 microliters each) will be obtained to measure acetaminophen plasma levels at the following goal intervals after acetaminophen administration.T1:10-20 mins, T2:35-45 mins, T3: 60mins. At the time of each lab draw gastric ultrasound will be assessed by the expert scanner to correlate gastric ultrasound with the acetaminophen absorption test as a gold-standard of gastric emptying.
Diagnostic Test: Gastric Ultrasound Serial Scans
Cohort 1 will have multiple scans as part of assessing gastric emptying. These sequential scans after the baseline assessment will be done in line with the Acetaminophen Absorption Test timeline (T1:10-20 mins, T2:35-45 mins, T3: 60mins) and will be performed by an expert scanner only.
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