A simplified organ donor model produced by permanent complete central nervous system ischemia in dogs

Abstract

The physiologic and pathophysiologic changes of the potential organ donor in the brain-dead state are poorly understood. We have developed a canine model of complete brain death by infusing saline into the subdural space and elevating intracranial pressure above systolic arterial pressure. A snare on the inferior vena cave decreased venous return and limited the Cushing response to 1 to 2 minutes. The electroencephalogram became isoelectric as soon as intracranial pressure was elevated and maintained above systolic arterial pressure. The brain-dead state was confirmed by several means. No return of electroencephalogram activity was seen throughout the study. Neurologic examination failed to document any cranial nerve or spinal cord reflexes after the induction of brain death. Pharmacologic challenges failed to document any baroreceptor function or autonomic cardiovascular control in this state. Blood flow to the central nervous system using the microsphere technique was determined at 1 hour post-brain death. The mean calculated flows were not statistically different than zero. The model provides a simple, controlled, consistent, and relatively noninvasive model of complete brain death. It should facilitate the investigation of the mechanisms leading to somatic death in the brain-dead state and ultimately lead to improved clinical supports.