THE EFFECT OF HEAT LOAD AND DEHYDRATION ON HYPERTONIC SALINE SOLUTIONTREATMENT OF CONTROLLED HEMORRHAGIC-SHOCK

Small volume hypertonic saline solution has been suggested for initial effective resuscitation of hemorrhagic shock. The effect of hypertoni c saline solution in controlled hemorrhagic shock was studied in rats subjected to dehydration or heat, or both. The rats were randomly divi ded into four groups-group 1 (n=19), normal rats; group 2 (n=21), wate r deprivation for 12 hours; group 3 (n=20), heating at 37 degrees C. f or 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 kil ogram 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 minut e (p<0.01). A similar decrease in MAP and pulse rate was observed in a ll four groups. Infusion of hypertonic solution (HTS) in group Ic 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 n ormal saline solution in group lb (p<0.01) or untreated group la (p<0. 01). This difference remained significant also after 45 minutes from i nfusion (p<0.05 and p<0.05, respectively). The increase in MAP in resp onse 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 dif ference in response to HTS remained significant 45 minutes from infusi on in groups 3c (p<0.05) and 4c (p<0.05), but not in dehydrated rats i n group 2c. Arterial bleeding did not alter serum sodium significantly in all four groups. Infusion of HTS in group 1c was followed by an in crease 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 s odium was initially elevated to 157.1+/-3.0 milliequivalent per liter, did not further elevate the serum sodium level. It is concluded that the immediate hemodynamic response to infusion of HTS in controlled he morrhagic shock is limited after water deprivation or heat stress, or both. Infusion of HTS in hypernatremic rats did not further elevate se rum sodium to dangerous levels.