ObjectivesA 2400-mOsm/L hypertonic solution (Isosal) with a lower sodium content, compared with conventional 7.5% hypertonic saline, was formulated using a mixture of sodium chloride, glucose, and mixed amino acids. This solution was developed to minimize hypernatremia during resuscitation. We assessed the effects of Isosal on hemodynamics, brain edema, and plasma sodium concentration after head injury associated with hemorrhagic shock.DesignProspective, randomized laboratory study.SettingUniversity research laboratory.SubjectsTwenty-one adult female Suffolk sheep, weighing 39 to 49 kg.InterventionsAnimals were subjected to a 2-hr period of hemorrhagic shock to a mean arterial pressure (MAP) of 40 to 45 mm Hg in the presence of a freeze injury to the cerebral cortex. The hemorrhagic shock/head injury phase was followed by 2 hrs of resuscitation with Isosal, a new 2400-mosm/L low-sodium hypertonic fluid, 2400 mosm/L of 7.5% hypertonic saline, or lactated Ringer's solution. Initial resuscitation was with a bolus injection of 8 mL/kg of the study solution; subsequent resuscitation in all three groups was with lactated Ringer's solution as needed to maintain baseline cardiac output.Measurements and Main ResultsSerial hemodynamics, intracranial pressure, electrolytes, and osmolarity were measured. At the end of resuscitation, the animals were killed and brain water content (mL H2O/g dry weight) of the injured and uninjured areas was determined.Resuscitation volumes were significantly lower in the Isosal (19 plus minus 5 mL/kg) and 7.5% hypertonic saline (14 plus minus 2 mL/kg) groups compared with the lactated Ringer's solution (35 plus minus 5 mL/kg) group. Intracranial pressure after 2 hrs of resuscitation was significantly lower in the Isosal (7 plus minus 1 mm Hg) and hypertonic saline groups (4 plus minus 1 mm Hg), compared with the lactated Ringer's solution group (11 plus minus 2 mm Hg). Water content in all areas of the brain was significantly lower in the hypertonic saline group compared with the lactated Ringer's solution group. Brain water content in the Isosal group was lower than in the lactated Ringer's solution group only in the cerebellum. Plasma sodium content was lower in the Isosal group than in the hypertonic saline group.ConclusionsAfter combined head injury and shock, Isosal and 7.5% hypertonic saline have similar effects on hemodynamics and intracranial pressure. Hypertonic saline induces a greater degree of brain dehydration; Isosal resuscitation results in smaller increases in plasma sodium.(Crit Care Med 1996; 24:1226-1232)