The effect of heat load and dehydration on hypertonic saline solution treatment of controlled hemorrhagic shock

Small volume hypertonic saline solution has been suggested for initial effective resuscitation of hemorrhagic shock. The effect of hypertonic saline solution in controlled hemorrhagic shock was studied in rats subjected to dehydration or heat, or both. The rats were randomly divided into four groups--group 1 (n = 19), normal rats; group 2 (n = 21), water deprivation for 12 hours; group 3 (n = 20), heating at 37 degrees C. for five hours, and group 4 (n = 19), water deprivation for 12 hours and heating at 37 degrees C. for five hours. Controlled hemorrhagic shock was induced in all rats by arterial bleeding of 15 milliliters per kilogram and the rats were divided into three treatment subgroups--group a was untreated, group b was treated with 5 milliliters per kilogram 0.9 percent NaCl and group c was treated with 5 milliliters per kilogram 7.5 percent NaCl. Arterial bleeding of 15 milliliters per kilogram in group 1 resulted in decrease in mean arterial pressure (MAP) to 44 +/- 2 millimeters of mercury (p < 0.001) and pulse rate to 280 +/- 13 per minute (p < 0.01). A similar decrease in MAP and pulse rate was observed in all four groups. Infusion of hypertonic solution (HTS) in group 1c was followed by an increase in MAP to 89.0 +/- 9.7 milliliters of mercury (p < 0.01) in 15 minutes. This was significantly higher than infusion of normal saline solution in group 1b (p < 0.01) or untreated group 1a (p < 0.01). This difference remained significant also after 45 minutes from infusion (p < 0.05 and p < 0.05, respectively). The increase in MAP in response to HTS in group 1c after 15 minutes was significantly higher than the rise in groups 2c (p < 0.05), 3c (p < 0.05) and 4c (p < 0.05). This difference in response to HTS remained significant 45 minutes from infusion in groups 3c (p < 0.05) and 4c (p < 0.05), but not in dehydrated rats in group 2c. Arterial bleeding did not alter serum sodium significantly in all four groups. Infusion of HTS in group 1c was followed by an increase in serum sodium from 149.1 +/- 1.4 to 161.1 +/- 2.4 milliequivalent per liter (p < 0.001), while infusion of HTS in group 4c, where serum sodium was initially elevated to 157.1 +/- 3.0 milliequivalent per liter, did not further elevate the serum sodium level.(ABSTRACT TRUNCATED AT 400 WORDS)