The effect of total parenteral nutrition on vasogenic edema development following cold injury in rats

Total parenteral nutrition (TPN) has been shown to decrease mortality and to increase the rate of recovery in head-injured patients. However, a recent short-term animal experiment has raised concern over the potential enhancement of vasogenic edema by TPN. The experiment described here was undertaken to examine longer-term effects of TPN infusion on vasogenic edema development. Twenty-four rats received an infusion of a TPN solution (35% glucose) or 0.9% saline at 4 ml/kg/hr for 4 or 26 hours following cold injury. In the 4-hour experiment, TPN increased the serum glucose level to 772 +/- 57 mg/dl compared to 160 +/- 14 mg/dl in the saline-treated animals (p = 0.0001) and increased serum osmolality to 312 +/- 3 mOsm/kg compared to 291 +/- 3 mOsm/kg in the saline-treated group (p = 0.0006). In the 26-hour experiment, TPN-infused rats were also hyperglycemic and hyperosmotic by 4 hours postinjury and remained hyperglycemic at 26 hours postinjury (serum glucose level 374 +/- 97 mg/dl compared to 141 +/- 3 mg/dl in saline-treated animals; p = 0.0371). Although by 26 hours the TPN-infused rats appeared hyperosmotic compared to the saline-treated rats, high variability in the TPN group prevented statistical confirmation of this observation (serum osmolality 337 +/- 35 mOsm/kg in the TPN group compared to 287 +/- 6 mOsm/kg in the saline group). A three-way analysis of variance with repeated measures was used to analyze the effect of infusion (saline vs. TPN), time (4 vs. 26 hours), and cold injury on the specific gravity of the five brain regions studied. Cold injury significantly increased edema development in the injured versus uninjured hemisphere for every region studied (p less than or equal to 0.0034, all five regions), and edema development increased significantly between 4 and 26 hours in three of the five regions (p less than or equal to 0.0207, all three regions). The infusion fluid was not a significant factor in any of the analyses. In conclusion, TPN infusion produced hyperglycemia and hyperosmolality in cold-injured rats but did not enhance vasogenic edema development in any brain region studied.