Intercompartmental fluid shifts after dextran infusion in rabbits.

Abstract

Intercompartmental fluid shifts were studied in New Zealand White rabbits after infusion of hyperoncotic dextran solution with a mean molecular weight of 64,200 and osmolality of 220 mosmol/kg H2O. In comparison with the control period, it was found that 1) plasma volume increased by a net volume of 83 +/- 12 ml; 2) systemic blood pressure increased slightly but significantly and central venous pressure increased markedly (this was accompanied by a reduction of interstitial fluid pressure from a control of -1 to -8 cmH2O after dextran); 3) plasma volume expansion was not accompanied by plasma sodium and chloride dilution when they were expressed in meq/kg of plasma water; and 4) plasma osmolality did not change after dextran infusions. The increase in plasma volume unaccompanied by any change in plasma sodium, chloride, or osmolality may be explained by a transcapillary fluid shift from the interstitial space to the bloodstream caused by an increase in plasma oncotic pressure. Because the more negative interstitial fluid pressure did not seem to attract any appreciable amount of fluid from the cells, we concluded that the interstitial space did not hydrodynamically couple the intravascular space to the cellular compartment.