[Experimental study of safe limits of retrograde cerebral perfusion]

Safe limits of retrograde cerebral perfusion (RCP) which is now used as an adjunctive method in the surgical treatment of the aortic arch aneurysm were examined experimentally using adult mongrel dogs. After the brain was cooled to 20 degrees C by extracorporeal circulation, RCP was performed from the bilateral maxillary veins, and later, the brain was warmed up to the initial temperature. Experimental groups were divided into two groups; Group I (n = 5) were subjected to cerebral perfusion for 60 minutes, and Group II (n = 8) for 90 minutes. Cerebral function was evaluated using somatosensory evoked potentials (SEP). Cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRO2) were measured, and histopathological examination was conducted SEP disappeared immediately after the initiation of RCP. In Group I, all the wave forms were recovered by rewarming in every animals, but the amplitude was only 35.0 +/- 16.6% of the preoperational value. In Group II, wave forms were not recovered in 3 animals of 8. CBF during RCP was minimal and about 2% of CBF observed before operation in either group. CMRO2 after being rewarmed up in Group II was lower than that in Group I, but this difference was statistically insignificant. In the histopathological examination, no ischemic change was found in Group I, while many cells indicating ischemic change were found in Group II. These findings indicate that RCP at 20 degrees C could not supply sufficient blood to brain tissues, and the brain can be injured irreversibly when the RCP exceeds more than 60 minutes.