Effects on capillary fluid permeability and fluid exchange of albumin, dextran, gelatin, and hydroxyethyl starch in cat skeletal muscle

Objective: To evaluate the peripheral hemodynamic effects in a skeletal mus cle in vivo model of the four commercially available colloid solutions, 20% human albumin, 6% dextran-70, 6% hydroxyethyl starch 200/0.5 (HES), and 3. 5% urea-linked gelatin. Design: Controlled laboratory study. Setting: University research laboratory. Subjects: Fifteen adult cats. Interventions: The isolated, autoperfused, and denervated calf muscles of t he cat hindlimb were placed in a plethysmograph. The colloids tested were g iven intra-arterially to the muscles in increasing rates of clinically rele vant doses. Measurements and Main Results: Arterial blood flow, arterial and venous blo od pressures, total vascular resistance, tissue volume changes, and capilla ry filtration coefficient were measured before, during, and after the collo id infusions. The altered capillary filtration coefficient reflects a chang e in capillary fluid permeability. The capillary filtration coefficient was decreased by albumin and dextran, not affected by HES, and increased by ur ea-linked gelatin. Albumin induced transcapillary fluid absorption, gelatin induced transcapillary filtration, and no transcapillary fluid exchange wa s observed with dextran and HES. After discontinuation of the infusions, HE S and gelatin induced a rebound transcapillary filtration. No such effect w as seen after dextran and albumin. All colloids increased muscle blood flow . Conclusion: We conclude that capillary fluid permeability is decreased by a lbumin and dextran, unchanged by HES, and increased by gelatin. This and th e differences in the rebound effect may contribute to the differences in th e plasma volume expanding properties of the respective colloid. The increas ed blood flow induced by the colloids was more an effect of reduced vascula r tone than of lowered blood viscosity.