Transvascular osmotic flow reflected by changes in plasma oncotic pressure of anesthetized dog

To assess overall bodily transvascular fluid flow due to osmotic imbalance between blood and interstitial fluid during or after addition of hypertonic saline, sugar-, albumin- and dextran solutions or CO2 mixture to blood, arterial blood colloid osmotic pressure (COP) of anesthetized dogs was continuously measured with a needle-type colloid osmometer. Plasma volume change (delta Vp) was estimated from the changes in either the equivalent albumin concentration (C) or the albumin concentration equivalent to plasma COP, which was well confirmed in inanimate model experiments. Carbon dioxide inhalation caused RBC swelling (1.5% volume increase/10 mmHg of PCO2). Intravenous injection of hypertonic solutions resulted in transient osmotic flow (8.5 +/- 2.2 ml/g of solute per kg of animal weight by NaCl, and 1.7 +/- 0.4 by glucose), and albumin and dextran also induced fluid flow (1.3 +/- 0.4 by albumin and 2.2 +/- 0.7 by dextran), which depended on van't Hoff's law and reflection coefficient of solutes.