Combined hemorrhagic shock and head injury: effects of hypertonic saline (7.5%) resuscitation. Hypertonic saline resuscitation was compared to isotonic fluid resuscitation in a large animal model combining hemorrhagic shock with head injury. Sheep were subjected to a freeze injury of one cerebral hemisphere as well as 2 hours of hypotension at a mean arterial pressure (MAP) of 40 mm Hg. Resuscitation was then carried out (MAP = 80 mm Hg) for 1 hour with either lactated Ringer's (LR, n = 6) or 7.5% hypertonic saline (HS, n = 6). Hemodynamic parameters and intracranial pressure (ICP) were followed. At the end of resuscitation brain water content was determined in injured and uninjured hemispheres. No differences were detected in cardiovascular parameters; however, ICPs were lower in animals resuscitated with HS (4.2 +/- 1.5 mm Hg) compared to LR (15.2 +/- 2.2 mm Hg, p less than 0.05). Additionally, brain water content (ml H2O/gm dry weight) in uninjured brain hemispheres was lower after HS resuscitation (HS = 3.3 +/- 0.1; LR = 4.0 +/- 0.1; p less than 0.05). No differences were detected in the injured hemispheres. We conclude that hypertonic saline abolishes increases in ICP seen during resuscitation in a model combining hemorrhagic shock with brain injury by dehydrating areas where the blood-brain barrier is still intact. Hypertonic saline may prove useful in the early management of multiple trauma patients. 