0.45-PERCENT SALINE AND 5-PERCENT DEXTROSE IN WATER, BUT NOT 0.9-PERCENT SALINE OR 5-PERCENT DEXTROSE IN 0.9-PERCENT SALINE, WORSEN BRAIN EDEMA 2 HOURS AFTER CLOSED-HEAD TRAUMA IN RATS

In this study, we examined the effect of four IV fluids (250 mL/kg) on blood glucose and osmolality and brain tissue specific gravity after closed head trauma (CHT) in rats. CHT was delivered at Time O; blood w as sampled at 60 min; fluid infusion began at 75 min and ended at 105 min. Blood was again sampled at 105 and 120 min, and brain tissue spec ific gravity was determined at 120 min. Five groups (one control and f our fluid-treated groups) received CHT, and five other groups (one con trol and four fluid-treated) did not (n = 9 in each group). 0.45% sali ne (1/2 NS) and 5% dextrose in water (D5W) accentuated the decrease of brain tissue specific gravity (1.0366 +/- 0.0025 and 1.0368 +/- 0.002 8, respectively; mean +/- SD) caused by CHT (1.0395 +/- 0.0036), but 5 % dextrose in 0.9% saline (D5NS) and 0.9% saline (NS) did not (1.0431 +/- 0.0042 and 1.0389 +/- 0.0049, respectively). In addition, 1/2 NS d ecreased blood osmolality (248 +/- 6 mOsm/L), D5W increased blood gluc ose (1095 +/- 173 mg/dL), D5NS increased blood osmolality (350 +/- 5 m Osm/L) and glucose (1695 +/- 76 mg/dL), and NS caused no significant c hange. We conclude that administering hypoosmolar IV fluids after CHT causes a significant worsening of cerebral edema 2 h after CHT. Implic ations: We previously reported worse neurological outcome and/or morta lity after closed head trauma in rats when 5% dextrose in water or 0.4 5% saline was given IV compared with 0.9% saline or 5% dextrose in 0.9 % saline. The present results and our previous findings indicate that worsening of outcome after closed head trauma in rats may be caused mo re by edema formation than by hyperglycemia.