Article Title



M Golloshi


Mateo Golloshi. Georgia Institute of Technology, Atlanta, GA.

Deuterium oxide (D2O) appearance in blood is utilized as a biomarker of fluid bioavailability (reflecting both gastric emptying and intestinal absorption). New technology, cavity ring down spectroscopy (CRDS), has emerged and how it compares to traditional methodologies is unclear. Purpose: To compare biomarkers of D2O appearance obtained via isotope ratio mass spectroscopy (IRMS) to CRDS. Methods: After overnight fast, eight men ingested non-carbohydrate electrolyte fluid (6 ml/kg body mass) containing 0.15 g/kg D2O. Serial venous blood was obtained before and over 45 min post-ingestion. D2O was analyzed by independent labs: IRMS on water (purified by diffusion from plasma) (IRMS-WAT); IRMS on plasma (IRMS-PLA); and CRDS on plasma (CRDS-PLA). Two methods were used to determine absorption speed based on D2O half-time to peak[MM1] (t1/2max), a modified one-compartment model and asymmetric triangle model. Results: Background [D2O] were different (P = 0.000) among IRMS-WAT, IRMS-PLA and CRDS (152.2 ± 0.8, 147.2 ± 1.5 ,137.7 ± 2.2 ppm). Differences in peak [D2O] were observed (P=0.001) but after correcting for the dilutions in IRMS methods, there were no differences (P=0.24) in peak enrichment. D2O appearance curves were consistent across methods, plateauing after 15 min with no difference from 20-45 min. Bland-Altman analysis indicated better agreement (lower mean error ±SD) between D2O (delta ppm) obtained via the two IRMS methods (-4.17 ± 9.9) than between values obtained with CRDS and either IRMS-WAT or IRMS-PLA (-7.62 ± 25.3, -11.8 ± 25.4, respectively). Mean calculated t1/2max (11 min) did not differ by the three spectroscopic or the two analytical t1/2max methods; however, the difference between analytical t1/2max methods was significantly less (P=0.039) when t1/2max was below the mean (<11 min) compared to those with slower absorption (> 11 min). Conclusion: Although absolute D2O background and peak values may differ among methods (IRMS vs. CRDS) and infusate (purified water vs. plasma), D2O appearance curves of fluid uptake are independent of analytic methods. However, the appropriate analytical model to determine hydration speed depends upon the individual’s absorption profile.

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