Dextran Modulates Microvascular Permeability: Effect in Isotonic and Hypertonic Solutions

Hypertonic saline solutions with Dextran (HSD) have been advocated for rapid restoration of intravascular volume. Dextran is thought to increase the duration of action of hypertonic saline (HS) by selectively partitioning the water in the vascular space that has been drawn out of cells by HS. The goal of this study was to define the microvascular permeability modulating activity of Dextran in both isotonic and hypertonic solutions. We hypothesized that Dextran would decrease hydraulic permeability (Lp). Using the modified Landis micro-occlusion technique, single rat mesenteric venules were perfused with either normal Ringers (NR) with 135 mM NaCl or HS with 185 mM NaCl. In sequential cannulations of the venules, 1%, 2%, and 3% of Dextran was added to the NR perfusion (n = 6) and the HS perfusion (n = 6). The Lp was measured at baseline and after perfusion with each Dextran concentration. Baseline Lp measurements for NR and HS solutions were 1.01 +/- 0.034 and 5.14 +/- 1.02, respectively. In the NR group, the 2% and 3% Dextran decreased permeability below baseline levels to 0.79 +/- 0.028 (P < 0.0001) and 0.66 +/- 0.028 (P < 0.0001), respectively. In the HS group, the 2% and 3% Dextran decreased permeability to 1.65 +/- 0.53 (P < 0.0001) and 0.99 +/- 0.2 (P < 0.0001), respectively. All values for Lp are x10(-7) cm s(-1) x cm H2O(-1). The addition of Dextran to isotonic and hypertonic solutions results in a decrease in microvessel permeability. This effect is more pronounced with the perfusion of hypertonic solutions. The results demonstrate the oncotic potential of Dextran and its ability to hold water in the vascular space. Dextran may have a beneficial effect when used for resuscitation with HS by decreasing microvascular permeability and augmenting intravascular volume.