Physiology and Pharmacology of Cerebral Blood Flow and Metabolism

Advances in the early management of patients with head injury

The last decade has seen continual improvement in our skills of visualizing and diagnosing the many types of human head injury. As we continue to unravel the complex biochemistry and molecular changes caused by trauma, we expect to find new methods and agents to enhance the extracellular milieu of injured but salvageable neurons and supporting cells, resulting in continued improvement in outcome for patients with severe head injury.

Colloid infusion after brain injury: effect on intracranial pressure, cerebral blood flow, and oxygen delivery

OBJECTIVES

We sought to determine the effects of colloid osmotic pressure on cerebral edema formation after brain injury. We hypothesized that an increase in plasma oncotic pressure accompanying a colloid infusion would be associated with a decrease in intracranial pressure and increases in cerebral blood flow and oxygen delivery when compared with isotonic crystalloid.

DESIGN

Prospective, laboratory study.

SETTING

University surgical research laboratory.

SUBJECTS

Adult swine, both genders.

INTERVENTIONS

Cryogenic brain injury with intravenous fluid infusion of either lactated Ringer's solution or 6% dextran-70 in normal saline. The effect of this intervention was monitored for 24 hrs.

MEASUREMENTS

Mean arterial pressure, central venous pressure, intracranial pressure, hemoglobin concentration, plasma oncotic pressure, serum osmolality, cerebral blood flow, and specific gravity of cortical biopsies.

RESULTS

Cryogenic injury significantly increased the cortical water content and the intracranial pressure and significantly decreased the cerebral blood flow and oxygen delivery (p < .05). Dextran infusion significantly increased the colloid oncotic pressure. There were no differences between the lactated Ringer's solution and dextran groups in intracranial pressure, cerebral oxygen delivery, or cortical water content after 24 hrs.

CONCLUSIONS

Colloid infusion after a focal cryogenic injury does not increase cerebral oxygen delivery or reduce either cerebral edema formation or intracranial pressure when compared with lactated Ringer's solution. Colloid is not superior to isotonic crystalloid in the management of isolated brain injury.