Increased pressure during retrograde cerebral perfusion in an acute porcine model improves brain tissue perfusion without increase in tissue edema

Background. There is a significant lack of scientific data to support the clinically accepted view that 25 to 30 mm Hg is the maximum safe perfusion pressure during retrograde cerebral perfusion (RCP). This study was designed to investigate whether perfusion pressure greater than 30 mm Hg during RCP is beneficial to the brain during prolonged HCA in an acute porcine model. Methods. Sixteen pigs underwent 120 minutes of circulatory arrest in conjunction with RCP at a perfusion pressure of either 23 to 29 mm Hg (group L, n = 8) or 34 to 40 mm Hg (group H, n = 8) at 15°C, followed by 60 minutes of normothermic cardiopulmonary bypass. Cortical blood flow and oxygenation were measured continuously with a laser flowmeter and near-infrared spectroscopy, respectively. Tissue water content was measured at the end of the experiments. Results. Brain tissue blood flow was significantly higher in group H than in group L (16.8% ± 4.1% vs 4.8% ± 0.9% of baseline, p < 0.01) during RCP. Brain oxygen extraction in group L reached a maximum (not, vert, similar70%) immediately after starting RCP, whereas in group H it increased gradually and reached a maximum at 120 minutes of RCP, indicating a greater supply of oxygen to tissue in group H than in group L. After RCP, the ability of brain tissue to use oxygen was better preserved in group H than in group L, as indicated by tissue oxygen saturation and the deoxyhemoglobin level. There was no significant increase in tissue water content in either group (group H 79.2% ± 0.3%, group L 79.1% ± 0.4%) relative to normal control pigs (78.7% ± 0.1%). Conclusions. In this acute porcine model, increasing perfusion pressure from 23–29 to 34–40 mm Hg during RCP increases tissue blood flow and provides better tissue oxygenation, without increasing tissue edema. The optimal perfusion pressure for RCP needs to be further investigated.