Hemodynamic effect of mannitol in a canine model of concomitant increased intracranial pressure and hemorrhagic shock.

The use of mannitol in the management of head injury has been considered a threat to hemodynamic stability in hypotensive multiply injured patients. To evaluate this contention, we compared mannitol with normal saline administration in a canine model combining elevated intracranial pressure (ICP) and hemorrhagic shock. Mongrel dogs were bled to and maintained at a mean arterial pressure (MAP) of 60 mm Hg for 30 minutes. Following this, ICP was elevated to and sustained at 25 mm Hg for 45 minutes by inflating an epidural balloon. The dogs were then randomized to resuscitation with 2 g/kg of mannitol in saline (total volume, 20 mL/kg; n = 5) or 20 mL/kg of normal saline alone (n = 5). All dogs were successfully resuscitated, and MAP returned to baseline levels in both groups. ICP was significantly lower and urine output significantly higher in the mannitol group than in saline controls (P less than .01). Moreover, cerebral perfusion pressure, cardiac index, and left ventricular stroke work index were significantly improved in dogs given mannitol versus controls during the first hour of resuscitation (P less than .05). Mannitol ameliorates increases in ICP without compromising hemodynamic resuscitation in a canine model of concomitant increased ICP and shock.