RETROGRADE CEREBRAL PERFUSION RESULTS IN FLOW DISTRIBUTION ABNORMALITIES AND NEURONAL DAMAGE - A MAGNETIC-RESONANCE-IMAGING AND HISTOPATHOLOGICAL STUDY IN PIGS

Background-In the past few years, although significant efforts have be en made to assess flow distribution during retrograde cerebral perfusi on with microspheres, dye, or hydrogen clearance, flow distribution in real time is still undefined, We used MR perfusion imaging to monitor flow distribution in the brain during and after deep hypothermic circ ulatory arrest (DHCA) with antegrade or retrograde cerebral perfusion (ACP or RCP). Methods and Results-Thirteen pigs were divided into 2 gr oups and exposed to 120 minutes of either RCP (n=7) or ACP (n=6) at 15 degrees C, followed by 60 minutes of cardiopulmonary bypass (CPB) at 37 degrees C, During DHCA, the brain was perfused antegradely through the common carotid artery or retrogradely through the superior vena ca va at pressures of 60 to 70 mm Hg and 20 to 25 mm Hg in the ACP and RC P groups, respectively. Esophageal temperature was monitored continuou sly. MR perfusion images were acquired every 30 minutes before, during , and after DHCA, The brain was perfusion-fixed with formaldehyde solu tion for histopathology at the completion of each experiment, During i nitial normothermic CPB, MR perfusion imaging showed a nearly uniform distribution of flow in the brain. The same pattern was maintained wit h a significant increase in regional cerebral blood volume during ACP and reperfusion in the ACP group. RCP provided little or no detectable blood distribution to the brain, resulting in poor reperfusion of man y areas of the brain on reflow with CPB at 37 degrees C. The total are a suffering poor reperfusion was significantly higher in the RCP group than the ACP group. Histopathology showed no morphological changes in any area of the brain in the ACP group, whereas varying severity of n euronal damage was observed in different regions of the brain in the R CP group. Conclusions-ACP preserves uniform blood distribution and nor mal morphology of brain tissue after prolonged DHCA, RCP provides very little blood to the tissue of the brain. A 120-minute period of RCP r esults in abnormal flow distribution and neuronal damage during reperf usion. The damage resulting from shorter periods of RCP remains to be assessed.