Effect of pH management on brain perfusion during retrograde cerebral perfusion

This study was undertaken to determine the effects of different pH management strategies during retrograde cerebral perfusion on the relationship between retrograde perfusion pressure and brain tissue perfusion. Six pigs were subjected to an alpha-stat strategy and another 6 to a pH-stat strategy during hypothermic (15 degrees C) retrograde cerebral perfusion at perfusion pressures of 10 to 70 mm Hg, in increments of 10 mm Hg every 20 min. Regional cerebral blood flow was significantly higher in the pH-stat group than in the alpha-stat group. The cerebral blood flow peaked at perfusion pressures of 40-50 mm Hg (18.6% +/- 10.8% in the pH-stat group vs. 3.6% +/- 1.2% in the alpha-stat group). In both groups, the intracranial pressure remained below the critical level of 25 mm Hg, even at a retrograde perfusion pressure of 70 mm Hg. Cerebral lactate production was higher in the alpha-stat group than the pH-stat group during retrograde cerebral perfusion at pressures of 10-30 mm Hg. Compared to the alpha-stat strategy, the pH-stat strategy significantly improved brain tissue perfusion. With an open inferior vena cava, the optimal perfusion pressure seems to be 40-50 mm Hg.