Background: Ringer's solution might be used to treat volume depletion (extracellular dehydration) and hemorrhage, but there is no integrated view of how these fluid balance disorders influence the kinetics of the infused volume.
Methods: Acute dehydration (mean 1.7 L) was induced by repeated doses of furosemide (5 mg) in 10 healthy male volunteers, and 0.5 L and 0.9 L of blood was withdrawn in random order on different occasions in another 10 male volunteers, just before administration of Ringer's acetate solution. Infusions performed in the normovolemic state served as controls. Measurements of blood hemoglobin and urinary excretion were used to create volume kinetic profiles that were analyzed using mixed-effects modeling software.
Results: Infusions over 15 to 30 min showed a marked distribution phase during which the plasma volume transiently increased by 50% to 75% of the administered volume. Dehydration and hemorrhage accelerated redistribution but retarded the elimination; the half-life of the infused fluid increased from 36 to 51 min (mean) from 1 L of dehydration and to 95 min from 1 L of hemorrhage. Extravascular accumulation decreased with the dehydration volume and increased with the hemorrhage volume.Simulations show that 60% as much Ringer is needed to replace volume depletion amounting to 1 L as compared with hemorrhage over a 2-h period. A continued but slower drip after the initial fluid resuscitation prevents rebound hypovolemia.
Conclusions: Furosemide-induced dehydration and blood withdrawal in normotensive volunteers had modest effects on the Ringer's acetate kinetics. Urinary excretion was inhibited more by hemorrhage than by dehydration.