Resuscitation of hypovolemic sheep with hypertonic saline/Dextran: the role of Dextran.

We evaluated the role Dextran-70 plays in small volume resuscitation of hemorrhage using hypertonic saline dextran solutions. Sheep were hemorrhaged (1.5 to 2 liters) over 2 hr to an arterial pressure of 50 mm Hg and were then resuscitated with 100 ml of either 7.5% NaCl (HS/0% Dex) alone, 7.5% NaCl/6% Dextran-70 (HS/6% Dex), or 7.5% NaCl/24% Dextran-70 (HS/24% Dex). During hemorrhage cardiac output was reduced to 40-50% of baseline levels. The major effect of the added dextran was a greater initial increase and more sustained normalization of plasma volume and cardiac output. At 15 min post-infusion, plasma volume was expanded 17 +/- 2% with HS/0% Dex; 27 +/- 2% with HS/6% Dex; and 56 +/- 8% with HS/24% Dex. A dose response effect of the added dextran was also apparent in the post-resuscitation increases in arterial pressure and cardiac output. At 3 min post-infusion, both variables improved with all solutions, but baseline levels were reached and exceeded only in the HS/24% Dex. The increased cardiac output correlated significantly with the degree of vascular expansion. Regression and extrapolation of the post-resuscitation data of plasma volume expansion and increased cardiac output to no volume expansion suggests that the hypertonic saline also augments cardiac output by an additional mechanism independent of volume. Our data show that the addition of dextran to hypertonic saline can play an important role in small volume hypertonic resuscitation by improving both the initial cardiovascular response and the sustainment of that response. Higher concentrations of dextran than currently used in hypertonic formulations may make small volume resuscitation more efficacious.