Experimental Study on Free Radical Changes in Cerebral Tissue During Deep Hypothermic Circulatory Arrest With Retrograde Cerebral Perfusion and Selective Antegrade Cerebral Perfusion

Objective:To study the free radical changes in cerebral tissue during deep hypothermic circulatory arrest with retrograde cerebral perfusion and selective antegrade cerebral perfusion. Methods: Fifteen healthy adult hybrid canines were divided into three groups at random: simple-DHCA group (n = 5), DH-CA-RCP group ( n = 5) and DHCA-SCP group ( n = 5 ) . Immediately before, and 30, 60, and 90 minutes after DHCA, and 30 min after DHCA reperfusion, a little cerebral cortex was tested for oxygen free radical parameters, such as superoxide dismutase ( SOD) and malondialdehyde ( MDA) . At point DHCA 90 min, some cerebral cortex was cut out and changes of ultrastructure of the brain were observed with electron microscope. Results:SOD was decreased and MDA increased over time in simple-DHCA group. Compered with points DHCA 60 min, 90 min, and reperfusion 30 min, there were significant differences at the point before DHCA ( P 0. 05 ) . The contents of SOD and MDA in DHCA-RCP group and DHCA-SCP group had no obvious changes (P 0. 05 ) . There were significant differences between the three groups at points DHCA 30, 60, 90 min, and reperfusion 30min(P 0. 01-0.001). And at points DHCA 90 min and reperfusion 30 min, the content of SOD was higher and MDA was lower in DHCA-SCP group than in DHCA-RCP group (P 0. 05-0. 01). At point DHCA 90 min, in simple-DHCA group, the ultrastructure of the brain changed obviously. The number of mitochondria was decreased. Some mitochondria showed vacuolar degeneration or electron density alteration. In DHCA-RCP group, the ultrastructure of nerve cells changed. The mitochondria were ruptured, but less change was found than those of simple-DHCA group. In DHCA-SCP group, there were no obvious changes ultrastructure of the brain. Conclusions :①RCP and SCP can both minimize or eliminate free radical reaction and reduce brain injury.②DHCA-SCP is able to minimize or eliminate free radical reaction and provide better brain protection than simple-DHCA or DHCA -RCP.