A novel protocol of retrograde cerebral perfusion with intermittent pressure augmentation for brain protection

OBJECTIVES: We examined a novel protocol of retrograde cerebral perfusion with intermittent pressure augmentation to improve the clinical usefulness of this procedure, in a canine model, because a high retrograde cerebral perfusion pressure may be required to open cerebral vessels. METHODS: Eighteen dogs (25.2 +/- 4.1 kg) were randomly divided into the following 3 groups: circulatory arrest group (circulatory arrest alone), conventional-retrograde cerebral perfusion group (conventional retrograde cerebral perfusion at 25 mm Hg), and intermittent-retrograde cerebral perfusion group (retrograde cerebral perfusion at 15 mm Hg with intermittent pressure augmentation to 45 mm Hg). The animals were cooled down to 26 degrees C under cardiopulmonary bypass and underwent 60 minutes of circulatory arrest with or without retrograde cerebral perfusion in accordance with the protocol described. They were weaned from cardiopulmonary bypass after rewarming and observed for 12 hours after the procedures. The retinal vessels were observed as a means of noninvasive direct visualization of the cerebral vascular system. The level of Tau proteins in the cerebrospinal fluid was measured as a marker of neuronal damage. RESULTS: While the retinal vessels were fully distended with blood (100%) at a retrograde cerebral perfusion pressure of 45 mm Hg in the intermittent-retrograde cerebral perfusion group, full distension of the retinal vessels was not observed in the conventional-retrograde cerebral perfusion group (67%). The level of Tau proteins, measured 12 hours after the operation, was lower in the intermittent-retrograde cerebral perfusion group (247 +/- 70 pg/mL) than in the circulatory arrest group (1313 +/- 463 pg/mL; P < .05) or the conventional-retrograde cerebral perfusion group (1449 +/- 693 pg/mL; P < .05). Histopathologic examination revealed that the most effective brain protection was obtained in the intermittent-retrograde cerebral perfusion group (P < .05). CONCLUSIONS: Intermittent-retrograde cerebral perfusion effectively opens up cerebral vessels to allow adequate blood supply to the brain, thereby minimizing brain damage. This novel method may protect the cerebral system effectively from ischemia during circulatory arrest.