PRESSIONE INTRACRANICA ED EDEMA CEREBRALE IN CORSO DI EMODILUIZIONE NORMOVOLEMICA

The effects of isovolemic hemodiluition (IVH) with either colloid or crystalloid solutions on plasma osmolality, intracranial pressure (ICP) and various indices of brain and body water content, were examined in twenty-four albino rabbits. In the experimental animals, the hematocrit was reduced from 45 ± 1 % to a value of 19 ± 1 % (SD) over a one hour period by the gradual removal of blood and simultaneous volume replacement with either hydroxyethyl starch (n = 6), lactated Ringer's (n = 6) or a solution of diluted lactated Ringer's (207 mOsm/l, n = 6). In each group, the rate of fluid administration was adjusted to maintain central venous pressure and blood pressure at control values. Six animals served as control (no hemodilution). Electrolytes and osmolality decreased only in the group given hypo-osmolar solution. IVH with crystalloid solutions resulted in significant increases in ICP in both group, while ICP was not significantly different from control in colloid treated animals. In spite of these ICP changes, brain water content (5 hours after starting IVH), measured with either microgravimetric or wet-dry methods, was significantly increased only in the group given hypo-osmolar crystalloid solution.