Restoration of hemorrhaged plasma volume by gastrointestinal fluid in the dog

Conscious, intact and splenectomized, male dogs were hemorrhaged 35 percent of their blood volumes (23 +/- 3 and 25 +/- 4 ml/kg, respectively) from carotid loop cannulas. Isotonic saline or glucose solutions were administered by gastric tube in volumes equal to the blood volume hemorrhaged. Plasma volume, mean arterial blood pressure, venous hematocrit, plasma protein concentration, and interstitial fluid pressure were monitored after hemorrhage and after fluid treatment. The magnitudes of plasma volume restoration 8 h after hemorrhage in the nontreated dogs averaged 56 +/- 9 percent of the hemorrhaged volume and did not differ significantly between intact and splenectomized dogs. Plasma volumes, however, were increased significantly by enterally administered fluids. The maximum rates of plasma volume restoration occurred within the 1st h after fluid treatment. Approximately 46 percent and 28 percent of the hemorrhaged plasma volume was replaced by saline and glucose solutions, respectively, during this period. Results support the hypothesis that fluid is absorbed from the gastrointestinal tract following hemorrhage, and that enterally administered fluids restore plasma volume at a rate and to an extent exceeding that provided by net interstitial fluid exchange alone.