A comparison of the cerebral and haemodynamic effects of mannitol and hypertonic saline in an animal model of brain injury.

There has recently been an increased interest in the use of hypertonic saline solutions in the fluid resuscitation of trauma victims and to control intracranial hypertension. In this study, the cerebral and haemodynamic effects of a 3.2% hypertonic saline solution were compared with those of either a 0.9% saline or 20% solution were compared with those of either a 0.9% saline or 20% mannitol solution in a rabbit model of brain injury. Forty-five minutes following the creation of a left hemispheric cryogenic brain lesion, equal volumes of hypertonic saline, 0.9% saline, or mannitol were infused over a 5 minute period. Monitored variables over the ensuing 120 minutes included mean arterial pressure, central venous pressure, intracranial pressure, hematocrit, serum osmolality and oncotic pressure. Upon conclusion of the two hour study period, hemispheric water contents were determined by the wet/dry weight method. There were no significant differences in mean arterial pressure between the three groups at any point during the experiment. Plasma osmolality was significantly increased by 10-11 mOsm/kg in both the mannitol and hypertonic groups. The infusion of either mannitol or hypertonic saline produced a transient decrease in intracranial pressure lasting approximately 60 minutes whereas animals in the saline group demonstrated a continual increase in intracranial pressure. The lesioned hemisphere demonstrated a significantly greater water content than the non-lesioned hemisphere.