Cerebrospinal fluid dynamics and brain tissue composition following intravenous infusions of hypertonic saline in...

This study examined brain tissue, cerebrospinal fluid (CSF), and plasma composition following intravenous infusion of two doses of 3% saline to rabbits anesthetized with halothane. The low dose of 3% saline consisted of infusion for 10 min at 1.0 ml/min at 1.0 ml/min and then thereafter at 7.0 ml/h. Infusion of either dose caused no significant change in CSF pressure, brain tissue water content, the concentration of sodium in CSF, or the concentration of potassium in CSF or plasma. Brain tissue sodium and potassium concentrations increased (by 8.5 and 8.6%, respectively), and CSF and plasma osmolalities increased (by 11-18 mOsm/kg) following both doses of 3% saline. Resistance to reabsorption of CSF increased by 56 +/- 22% (mean +/- SD) with the low dose of 3% saline and plasma sodium concentration increased by 5-11 mEq/L with the high dose of 3% saline. Both doses decreased the rate of CSF formation from 0.010 +/- 0.002 to 0.007 +/- 0.002 ml/min. It is concluded that 3% saline may not favor reduction of cerebral edema or decrease CSF pressure if it is given while the CSF pressure is normal, in part because of the large volume load imposed (22 ml/kg).