The use of a deuterium tracer technique to follow the fate of fluids ingested by human subjects: effects of drink volume and tracer concentration and content

Abstract

summaryDeuterium oxide (ÂHµO) has been added to drinks as a tracer for water to estimate the availability to the body water pool of ingested fluids, but doubts have been raised as to the reliability of the method. The present investigation evaluated the effects of systematic variations in the volume of fluid consumed and the amount and concentration of added tracer on the rate of accumulation of tracer in arterialized blood after ingestion of a labelled drink. Three separate experiments were undertaken. In expt 1, six healthy men ingested on separate occasions 200, 400 and 800 ml of a dilute glucose-electrolyte solution: all test drinks contained the same concentration (40 g l¢) of ÂHµO. In expt 2, six healthy men ingested 200, 400 and 800 ml of the same glucose-electrolyte drink: each drink contained 8 g of ÂHµO so that the concentration, but not the amount, of ÂHµO differed between treatments. In expt 3, six healthy men ingested 400 ml of the same drink on three separate occasions: each drink contained 8, 16 or 32 g of tracer so that amount and concentration of ÂHµO both varied. Arterialized venous blood samples were collected for the determination of deuterium (ÂH) concentration before ingestion of the test drink and at intervals for 120 min after ingestion. All trials for each of the experiments were conducted in the morning after an overnight fast and trials were in randomized order and separated by 7 days. In expt 1, the blood ÂH concentration at all time points from 2 min after ingestion of the test drink onwards was higher for the drink containing 32 g ÂHµO than for the drink containing 16 g ÂHµO, which in turn was higher than after ingestion of the drink containing 8 g of ÂHµO. In expt 2, no significant differences between treatments were observed at any time. In expt 3, the rate of ÂH accumulation was greater after ingestion of the drink containing 32 g of ÂHµO than after either of the other two drinks, and the ÂH accumulation rate was greater after ingestion of the drink containing 16 g of ÂHµO than after the drink containing 8 g of ÂHµO. When data from all three experiments were combined, significant correlations were observed between the rate of accumulation of ÂH in the circulation (p.p.m. min¢) and the amount (rs = 0·75, P < 0·001) and concentration (rs = 0·69, P < 0·001) of ÂHµO in the test drink, but there was no relationship (rs = 0·09, P = 0·5) between the rate of ÂH accumulation in the blood and the volume of the drink consumed. The results suggest that the rate of tracer accumulation in the blood after ingestion of different volumes of test drinks is not a reliable indication of the availability of the ingested fluid, but that the method gives at least a qualitative measure of the sum of the effects of gastric emptying and intestinal water absorption. introduction Techniques that measure either gastric emptying or intestinal absorption have been used extensively to assess the fate of ingested fluids and to assess the efficacy of oral rehydration solutions intended for the treatment of diarrh...

Thickened Fluids and Water Absorption in Rats and Humans

“…Intervening sampling was performed using saliva. Our data agree with those of others [42][43][44] that showed that salivary isotopic enrichment is a suitable surrogate for enrichment of tracer in blood, allowing calculation of total fluid absorption. This sampling route, however, was not suitable for the determination of uptake rates because despite exhortations to rinse the mouth thoroughly, the initial peak in D 2 O enrichment in saliva seen in some subjects indicated that some isotope in the ingested fluid remained in the oral cavity.…”

Transition duration of ingested deuterium oxide to eccrine sweat during exercise in the heat

“…After ingestion the water is readily transported across the mucosal membrane of the alimentary canal and diffuses into the blood within 2 min (Davis et al, 1985;Lambert et al, 1999). Next, the water moves via capillary fluid exchange from the intravascular to the extravascular space in approximately 30 s (Cao et al, 2005;Oppenheimer et al, 1983).…”

“…It is well documented, that following ingestion, water is rapidly absorbed by the gastrointestinal mucosa and within 2 min starts to appear in the plasma, thus maintaining blood volume (Davis et al, 1985;Lambert et al, 1999). However, it is currently unknown how long it takes following ingestion for water to start to appear as sweat on the skin surface, which would be available for evaporative cooling.…”

Appearance of D2O in Sweat after Oral and Oral-Intravenous Rehydration in Men

“…Although it does not directly measure net fluid movement across the intestinal wall, it still provides a useful index of fluid availability (13). The accumulation of D 2 O in plasma, urine, and saliva has been used as an index of the in vivo kinetics of these fluids (1,10,16,18). It rapidly equilibrates with these media and can be used to compare fluid availability during rest and exercise.…”