Controlled hypotension during anesthesia for otologic operations. An ultrastructural study of the brain in an experimental animal model.

We have studied the fine structure of the cerebral cortex, the cerebellar cortex, the thalamus, the caudate nucleus, the amygdala, the putamen, the vestibular nuclei, the substantia nigra, the hippocampus and the centrum semiovale in a canine model following 20 min controlled hypotension by the administration of sodium nitroprusside. The neurons and the astrocytes of all structures were intact morphologically. The synapses in the cerebral and cerebellar cortex were all unremarkable. Sensitive areas such as the molecular layer of the cerebellum did not demonstrate any ultrastructural alterations. We believe that carefully controlled sodium-nitroprusside-induced hypotension might be applied in middle ear microsurgery in otherwise healthy patients as an effective and innocuous method without causing any anoxic insult to sensitive areas of the central nervous system.