Orthostatic hypotension in the anesthetized rabbit in the sitting position exceeds cerebral autoregulation.

Abstract

BACKGROUND: Orthostatic hypotension and cerebral autoregulation have been extensively studied in the rabbit. However, these physiologic responses have not been previously studied utilizing a rabbit in the sitting position under anesthesia. METHODS: This unusual position was obtained as the preferred orientation based on geometry requirements of associated equipment for a study of osteoarthritis of the knee. Rabbits for this experiment did not survive and an additional experimental condition was developed to elucidate the mechanism and cause of death. The carotid artery pressure was measured under general anesthesia with incremental tilt testing to achieve the sitting position. RESULTS: Under this condition, rabbits developed orthostatic hypotension and did not survive. CONCLUSIONS: According to previous studies of orthostatic hypotension and limits of cerebral autoregulation, it is concluded that orthostatic hypotension in the anesthetized rabbit in the sitting position exceeds cerebral autoregulation.