Bromide dilution in adults: optimal equilibration time after oral
administration.
Lichtenbelt, Wouter D. Van Marken, Arnold Kester, Erica M. Baarends,
and Klaas R. Westerterp.
Department of Human Biology, University of Limburg, PO box 616,
6200 MD Maastricht, The Netherlands
APStracts 3:0200A, 1996.
Extracellular water (ECW) is often estimated by bromide dilution. The
time interval between oral administration of the dose and the blood
sampling varies considerably between studies. Since at least two
processes are involved during equilibration (1: distribution of the
dose, 2:bromide leaving the body), we performed a bromide dilution
experiment and analyzed the decay data by fitting a bi-exponential
curve. The experiment was carried out in 11 healthy adults (8
females, 3 males, age 21-39 year). Bromide ingestion (60 mg Br/L
estimated total body water) was followed by blood sampling at 2, 3,
4, 6, 10, 25, and 105 (or 170) h. Bromide concentration [Br] in serum
ultra-filtrate was determined with HPLC. [Br] in serum after dose
intake showed a significant decrease over time. One-exponential
functions significantly fitted the data. The two-exponential
functions fitted the data significantly better (F-test:
p<0.0001). A model, combining the data from all subjects, fitted
just as well. Equilibration time can be defined as the time at which
the first exponential function, which represents distribution of the
dose, has decreased 5% of its starting balue. According to this model
the equilibration time of orally administered bromide should be 8.5
-11.7 hours. This can be achieved by an overnight equilibration.
Received 14 June 1995; accepted in final form 11 March 1996.
APS Manuscript Number A640-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 23 April 96