Oral Rehydration or Intravenous Drip? - A Volume Kinetic Study of Glucose Solutions to Young and Old

Background: The aim of this study was to use a volume kinetic model to compare oral versus intravenous fluid administration of glucose solutions in young and elderly healthy volunteers. We investigated differences in the absorption, distribution and elimination of the administered fluid. Methods: The study had a randomized, crossover design and all experiments were performed when subjects had been fasting overnight indicating a state of dehydration. Twenty-four healthy volunteers received an isotonic 2.5% glucose solution, 7 ml/kg during 15 minutes, both orally and intravenously at separate occasions. Repetitive blood tests over 120 minutes showed changes in body fluid volumes using volume kinetic principles. Results: There were significant different lag times of absorption between oral and intravenous administration of fluid. In the young, a plasma volume decrease was shown in the beginning of the oral rehydration experiments but they retained fluid at the end of the experiment. The elderly had a consistent slow elimination of glucose and retained water after oral rehydration. The two administration routes showed different patterns for the elderly’s fluid volume expansion with steeper slopes for intravenous rehydration. Conclusions: It was possible to model the absorption, distribution and elimination of glucose fluids given both orally and intravenously in both age groups.