Treatment of hyperthermia-induced extravasation with hypertonic saline (7.5%) in 6% dextran 70 (HSD) in Wistar/Furth rats

This study determined the effectiveness of hypertonic saline (7.5%) in 6% Dextran 70 (HSD) in reducing hyperthermia-induced extravasation in Wistar/Furth (WF) rats and compared this extravasation with that previously reported in Sprague-Dawley (SD) rats. Wistar/Furth rats (male, n = 12/group, 300-325 g) were placed unrestrained in a chamber (41.5 degrees C) until a core temperature (Tc) of 42.6 degrees C was attained. Immediately following heat exposure, HSD or normal saline (4 mL/kg) was administered via jugular catheter, followed 15 min later by Evan's blue (Eb, 25 mg/kg) in normal saline. After another 15-min interval, animals were anesthetized, exsanguinated, tissues removed and washed in normal saline, and Eb was extracted with formamide. Another group of normothermic WF rats were also given Eb and had tissues harvested. Comparisons were made to extravasation in normothermic and hyperthermic SD rats. In hyperthermic SD rats, Eb content increased significantly in liver, kidney, and intestinal tissues. In hyperthermic WF rats compared to normothermic WF rats, Eb content of kidney and spleen was increased; however, Eb content of heart, skeletal muscle, and intestine was significantly decreased. HSD-treated WF rats had increased extravasation in intestinal tissue compared to that of saline-treated rats. However, HSD treatment resulted in significant decreases in wet weight/dry weight ratios of heart (4.34 +/- 0.10 versus 4.51 +/- 0.11) and skeletal muscle tissue (3.78 +/- 0.08 versus 3.91 +/- 0.08). Findings of this study indicate that HSD did not prevent the hyperthermia-induced extravasation of Eb in kidney and spleen; that the increase in plasma volume following HSD administration is most likely due to the movement of fluid into the vasculature from the skeletal muscle mass; and that the WF strain may have limited value for the study of extravasation.