Early experiences with the stable isotope method in children.

Area of Science:

• Pediatric Gastroenterology
• Isotope Tracers
• Gastrointestinal Physiology

Background:

• Accurate assessment of gastrointestinal water absorption is crucial for infant health.
• Existing methods for measuring water uptake can be invasive or lack precision.
• Developing non-invasive, sensitive techniques is essential for pediatric research.

Purpose of the Study:

• To evaluate a new stable isotope (H2O18) technique for quantifying water absorption in the infant gastrointestinal tract.
• To determine the feasibility and sensitivity of using breath and blood analysis to track water flux.
• To establish a non-invasive method for assessing gastrointestinal water dynamics in infants.

Main Methods:

• Infants undergoing elective surgery were randomly assigned to receive either sterile water or a glucose-electrolyte solution labeled with stable isotope H2O18.
• Blood and breath samples were collected at 5-minute intervals post-administration.
• Mass spectrometric analysis was used to detect O18 enrichment in blood and breath CO2.

Main Results:

• Isotopic O18 rapidly equilibrates with plasma bicarbonate and appears in breath as C18O2.
• O18 enrichment in blood and breath was detectable within 5 minutes, reaching a plateau between 30 and 90 minutes.
• The rate of enrichment increase correlated with the unidirectional flux of water from the gut lumen.

Conclusions:

• The H2O18 stable isotope technique provides a sensitive and non-invasive method for estimating gastrointestinal water uptake in infants.
• This method allows for real-time monitoring of water absorption dynamics.
• The findings support the hypothesis that enrichment rate reflects water flux, offering a valuable tool for pediatric fluid balance studies.