The effect of the type of colloid on the efficacy of hypertonic saline colloid mixtures in hemorrhagic shock: dextran versus hydroxyethyl starch.

Colloids increase and prolong the efficacy of hypertonic saline solutions in hemorrhagic shock. We compared the efficacy of dextran 60 and hydroxyethyl starch (HES) 200,000/0.5 at iso-oncotic concentrations of 6.5 or 6% in a 7.5% NaCI solution. Thirty-two rabbits were bled to maintain a mean arterial pressure at 35 mmHg. Twenty-five percent of the shed blood volume was replaced after 40 min by bolus infusion either with hypertonic dextran (HS-DEX) (n = 16) or with hypertonic hydroxyethyl starch (HS-HES) (n = 16). The animals were then observed for a 120-min period. In both groups immediate and complete restoration of cardiovascular function was achieved in up to 30 min and adequate restoration maintained for 60 min after infusion. During the subsequent 60 min signs of insufficient oxygen supply indicated the recurrence of near shock levels. Greater stability of hemodynamic efficacy was observed when dextran was added to hypertonic saline. The decrease in mean arterial pressure was lower in the dextran group (P < 0.05). The subsequent increase in avDO2 (v. cava sup.) was approximately 50% lower with dextran (1 ml/dl compared to 1.8 ml/dl); (P < 0.05). These differences occurred primarily within the initial 15 min although the differences in mean arterial pressure were recorded only after 30-60 min. A 50% reduction in lactate levels (1.1 compared to 2.0 mmol; P < 0.05) in immediate response to reinfusion indicates an increased lactate absorption and thus improved perfusion of poorly perfused tissue in the dextran group. A further, important difference may be due to the different effects on the microcirculation. As evidenced by a decline in the end-expiratory arterial CO2 gradient, dextran effected a significant (P < 0.01) improvement in decreased pulmonary CO2 emission during shock. This indicates a greater rise of blood flow in poorly perfused, ventilated pulmonary areas. In summary, in our model dextran appeared to be the superior colloid compared to HES, particularly during the first hour after initiation of treatment, although direct proof of an improved long term outcome has not been demonstrated.