The efficacy of iso- and hyperosmotic fluids as volume expanders in fixed-volume and uncontrolled hemorrhage.

Rapid blood volume expansion is the goal in prehospital hemorrhage resuscitation. A comparison was made for fixed volume and uncontrolled hemorrhage between three fluid regimes: Ringer's lactate (RL), Macrodex (MD), or a small volume of a hyperosmotic solution (HSD, 7.5% NaCl/6% dextran 70) followed by RL. A mathematical model was developed to simulate blood volume restoration for these given hemorrhage and resuscitation situations. Model predictions for a fixed hemorrhage (35%) and reinfusion of each fluid regime (1 mL.min-1.kg-1) were found to agree with hematocrit and osmolality changes from experiments on anesthetized rabbits. HSD gave the quickest volume expansion after the controlled hemorrhage, which is a useful experimental model; however, it is not realistic of many trauma injuries. The model suggests for severe uncontrolled hemorrhage that HSD/RL initially hastens the bleed, yet the blood volume expansion is still more effective than RL alone for the first 20 minutes, making it an effective prehospital expander for most urban trauma situations.