Transvascular fluid shift after blood volume modification in relation to compliances of the total vascular bed and interstitial fluid space.

The transvascular fluid shift after blood volume modification was analyzed by means of continuous blood volume determination and stimulation analysis. On splenectomized dogs, 15% of the circulating blood was withdrawn and retransfused, while the circulating blood volume, hematocrit and colloid osmotic pressure were continuously monitored. Based on the results, the transvascular fluid shift was stimulated by a two-compartment model. The compliance of the intravascular and interstitial fluid spaces as well as the transvascular filtration coefficient was determined on the whole body, simultaneously. No statistically significant differences were found between any of the values for blood withdrawal and retransfusion. The compliance of the vascular space, 4.62 +/- 0.82 ml/mmHg . kg of body weight, was almost identical with that of the interstitial fluid space, 4.75 +/- 1.52 ml/mmHg . kg of body weight. The whole body capillary filtration coefficient was 0.74 +/- 0.39 ml/min . mmHg . kg of body weight, which is within the range of the reported values of the capillary filtration coefficient for muscle and intestine. It is suggested that the rapid transvascular fluid shift after blood volume modification is provided with the fact that the compliances of intravascular and interstitial fluid spaces are almost identical.