title: The measurement of whole body water by H2(18)O dilution in newborn pigs.
abstract: Whole body water was measured in newborn piglets by isotope dilution with H2(18)O. The results were compared with those obtained by direct analysis of whole body water made by freeze-drying. When the tracer dose of H2(18)O was given to 30 piglets by intragastric gavage, post-equilibration values measured in urine were highly variable (average equilibration error equalled 9%) and the random error of the technique in predicting body water was 13%. When the dose was given to 49 animals intravenously, the post-equilibration values in urine were less variable (equilibration error equalled 4%), the random error of the technique was 7%, and body water was overestimated by 2%. The random error was reduced to 6% if data from animals in which equilibration errors exceeded 10% were excluded. When 18O enrichment in plasma instead of urine was measured, the technique was less precise (random error 11%). The estimation of body water from H2(18)O overestimates body water by 2%. Isotope dilution with 18O is a safe, accurate and repeatable method for the estimation of whole body water, and is suitable for use in adult and newborn humans.
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D001834:Body Water / Q000032:analysis*; D055598:Chemical Phenomena; D002621:Chemistry; D005069:Evaluation Studies as Topic; D007201:Indicator Dilution Techniques; D007275:Injections, Intravenous; D007441:Intubation, Gastrointestinal; D008433:Mathematics; D010103:Oxygen Isotopes; D013552:Swine
chemical_list: D010103:Oxygen Isotopes