Effects of resuscitation from hemorrhagic shock on jerebral hemodynamics in the presence of an intracranial mass

This study compares intracranial pressure, cerebral blood flow, and cerebral oxygen transport during hemorrhagic shock and following fluid resuscitation with crystalloid or colloid solution in a canine model with an epidural mass lesion. After placement of an epidural balloon, intracranial pressure was increased to 30 mm Hg for 5 minutes and then permitted to vary without further manipulation. Hemorrhagic shock was produced by the rapid removal of blood to achieve a mean arterial pressure of 55 mm Hg for 30 minutes. Resuscitation then was performed with intravenous lactated Ringer’s solution, 60 ml/kg, or with 6.0% hetastarch, 20 ml/kg. Following both solutions mean arterial pressure and cardiac output were increased and hemoglobin concentration was reduced. Intracranial pressure was significantly lower immediately after resuscitation in the hetastarch group; it then gradually increased so that the difference was much less 1 hour later. Cerebral blood flow decreased during shock and was not restored by either fluid; cerebral oxygen transport fell further with resuscitation in both groups due to hemodilutional reductions in hemoglobin. Although colloid resuscitation improved systemic hemodynamics and maintained lower intracranial pressure, it failed, as did crystalloid resuscitation, to restore cerebral oxygen transport to prehemorrhagic shock levels.