Reflection coefficient for albumin and capillary fluid permeability in cat calf muscle after traumatic injury.

Surgery and traumatic injury are often followed by tissue oedema and a low plasma albumin concentration, indicating leakage of fluid and proteins from the intravascular to the interstitial space. Transcapillary leakage can be referred to as an increase in capillary hydraulic conductance and/or a decrease in the reflection coefficient for plasma macromolecules. This study evaluates if time-dependent variations in the reflection coefficient for albumin and capillary hydraulic conductance can be confirmed experimentally following a surgical trauma using a blood perfused cat skeletal muscle in vivo preparation. The hydraulic conductance was estimated by the capillary filtration coefficient, and was used to evaluate variation in capillary fluid permeability. According to the Starling fluid equilibrium, the ratio between the reflection coefficients for albumin on two occasions can be calculated from the maximum osmotic absorption rates induced by a fixed intravenous bolus infusion of albumin (0.5 g kg(-1)) and from the capillary filtration coefficients. We found a decrease in the reflection coefficient of about 30% up to 10 h after the preparation. The capillary filtration coefficient showed no significant change over time, but decreased by 5-10% following the albumin infusion. We conclude that: (1) the reflection coefficient for albumin is reduced after a trauma, whereas the effects on the capillary fluid permeability are small, (2) albumin in plasma contributes to preserve normal capillary fluid permeability and, (3) the model seems to be useful for evaluation of relative variations in the reflection coefficient for albumin.