Small volumes (4 ml/kg) of 2400 mOsm NaCl restore cardiac output and mean arterial pressure to 80% of baseline after
hemorrhage (65% of blood volume) in unanesthetized sheep. An equal volume of
normal saline is less effective. To identify an optimal
hypertonic solution, we screened six 2400 mOsm solutions in 18 randomized experiments in 8 sheep: NaCl, NaHCO3, NaCl/
sodium acetate, NaCl/
mannitol, NaCl/6%
Dextran 70, and
glucose. Cardiovascular function, as determined by cardiac output and mean arterial pressure, was restored best with NaCl, NaCl/NaAc, and NaCl/Dex. These three solutions were then evaluated using 18 sheep in 36 experiments. Following a 1-hr baseline period, the sheep were bled to a mean arterial pressure of 50 mm Hg for 2 hr. One of the solutions was then given in a volume of 4 ml/kg over 2 min and the sheep were monitored for 3 hr. Within 3 min of the infusion, cardiac output increased to greater than 100% of baseline for all three solutions. The NaCl-Dex
solution sustained a significantly higher cardiac output over the 3-hr observation period than the other solutions. Plasma volume increased for all solutions following infusion. NaCl-Dex maintained plasma volume significantly better than the other solutions. As a further control, an isotonic
solution of 6%
Dextran 70 in
normal saline was studied. It was not as effective as the hypertonic NaCl-Dex in maintaining cardiac output, mean arterial pressure, or plasma volume. Osmolality increased 10% (309 to 326 mOsm/kg H2O), plasma [NA] increased 7% (151 to 161 meq/liter), and plasma [K] decreased from 3.9 to 2.6 meq/liter following the hypertonic infusions. The sheep appeared to tolerate these
electrolyte changes well. We conclude that a single bolus infusion of 2400 mOsm NaCl with 6%
Dextran 70 best resuscitates sheep that have been subjected to a moderate degree of
hemorrhagic shock compared to several other solutions. Its beneficial effects are caused in part by a sustained reestablishment of plasma volume. More studies are needed to document the safety of
dextran in the clinical setting of
hemorrhagic shock. Small volumes of
hypertonic solutions may be valuable in the initial fluid
resuscitation of patients in
hemorrhagic shock.