| Recently, there has been a great advance in the therapy for severe and complicated great vascular malformation. The effective technique of deep hypothermic circulatory arrest (DHCA) has been used widely in operation on great vessels, especially involving transverse arch of the aortas. However, when the operation time is beyond of the safe time limit of total circulatory arrest, it is still harmful for central nerve system becaue of hypoxia-ischemia injury. According to the anatomy of Willis circle of cerebrum, continuous cerebral perfusion via right subclavian artery (RSA) can increase brain oxygen supply, lessen hypoxia-ischemia induced brain injury, and reduce nervous system complication after operation. So, to provide objective foundations for clinical application, the present study that based on cat cardiopulmonary bypass (CPB) mode investigated the continuous selective cerebral perfusion via RSA and compared it with pure deep hypothermic circulatory arrest and retrograde cerebral perfusion via superior vena cava (SVC). Sequentially, we can make an synthetic evaluation on the cerebral protection from the changes of structure and energy metabolism of cerebral tissue as well as the variety of nitrogen monoxide synthetase by means of histological method and transmission electron micrography analysis..Materials and methodsThirty-six hybrid cats with both sexes, weighing 3.0 ± 0.5 kg, were randomly divided into 3 groups with 12 cats in each. Group I (DHCA group): regular CPB with temperature reduced to 20℃, then circulation is arrested for 45 min and 90 min respectively. Group II (SVC perfusion group): CPB with temperature reduced to 20℃, then with retrograde perfusion through superior vena cava for 45 min and 90 min respectively. Group III (RSA perfusion group): right subclavian artery and right atria were cannulated for establishing CPB, temperature was reduced to 30℃, and ascending aorta was obstructed. When temperature reached to 20℃, left subclavian artery and left common carotid artery were obstructed, with circulatory arrest for 45 min and 90 min respectively.Results1. Ultrastructure changes of cerebral tissueWith transmission electron microscope, we can see: in DHCA group, hypoxia-ischemia changes manifested as swelling of neuron, widely doffing beads of rough endoplasmic reticulum, dispersion of organelles, and swelling of mitochondria; Especially in group of circulatory arrest for 90 min, heavy hypoxia changes was found as widely and severe doffing beads of rough endoplasmic reticulum, fragmentation of organelles, severe swelling of mitochondria, severe vacuolation, and abnormal changes of nuclei. In SVC and RSA perfusion group, light hypoxia changes were characterized by gentle oedema of neuron, gentle swelling of mitochondria and rough endoplasmic reticulum, nearly intact cell structure, and mostly normal chromatin and nucleolus. In SVC perfusion group with circulatory arrest for 90 min, breaking of mitochondrial crista could be seen in a few cells and vacuoles occasionally occurred. 2. Changes in energy metabolism of cerebral tissue(1) Lactate content in venous return blood Lactate (LAC) content in venous return blood can indicate the degree of anaerobic metabolism in cerebral tissue. Compared with SVC and RSA perfusion group , the LAC content in DHCA group was markedly increased at the beginning of rewarming and when rewarming to 37℃. However the product of anaerobic metabolism LAC was not increased in SVC and RSA perfusion group and no significant difference between them. It was clear that there was continuous perfusion of oxygenated blood to supply oxygen to cerebrum in these two groups, that is, with aerobic metabolism. (2) ATP content in cerebral tissueATP content of cerebral tissue implies the cerebral energy store. When circulation is arrested for 45 min then rewarming to 37℃, ATP content in SVC and RSA perfusion group was statistically increased compared with pure DHCA group, indicated that these two groups can provide sufficient blood supply to cer...
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