Treatments to support blood pressure increases bleeding and/or decreases survival in a rat model of closed head trauma combined with uncontrolled hemorrhage

Hemorrhagic hypotension may aggravate the detrimental effects of head traum a on neurologic outcome. Our study examined whether using phenylephrine or large volumes of saline IV to increase mean arterial blood pressure (MAP) t o 70, 80, or 90 mm Hg during the combination of head trauma and uncontrolle d hemorrhage would improve neurologic outcome. Rats were assigned to one of 17 groups. In Groups 1-5, the variables were head trauma (yes/no), hemorrh age (yes/no), 0 or 3 mL saline per milliliter of blood lost, and no target MAP. In Groups 6-11, hemorrhage was or was not combined with head trauma, a nd large volumes of saline were given IV to achieve target MAPs of 70, 80, or 90 mm Hg. Groups 12-17 were similar to Groups 6-11 except that phenyleph rine was used rather than saline to achieve target MAPs. Saline increased b lood loss at 2 h to approximately 16 and 25 mL at a MAP of 80 and 90 mm Hg respectively, increased (worsened) the neurodeficit score but not cerebral edema at 24 h, and decreased survival rate at 2 and 24 h. Because phenyleph rine was fatal for 62 of 63 rats, group mean values for blood loss, neurode ficit score, and brain tissue specific gravity could not be calculated. We conclude that supporting MAP with either phenylephrine or large volumes of saline worsened the neurodeficit score and/or survival and did not affect c erebral edema formation in our rat model of head trauma combined with hemor rhage. Implications: The results of this study indicate that maintaining me an arterial blood pressure at 70, 80, or 90 mm Hg with either phenylephrine or large volumes of saline worsened the neurodeficit score and/or survival and did not affect cerebral edema formation in our rat model of head traum a combined with hemorrhage.