Influence of various deep hypothermic circulatory arrest treatments on brain metabolism

AIM To observe the influence of deep hypothermic circulatory arrest treatments on cerebral construction and its metabolism.METHODS Eighteen dogs were randomly divided into three groups of 6 dogs each: the group of deep hypothermic circulatory arrest(DHCA),the group of DHCA with retrograde cerebral perfusion(RCP)and the group of DHCA with intermittent antegrade cerebral perfusion(IACP).When their nasopharynx temperature was lowered to 18℃ through cardiopulmonary bypass,deep hypothermic circulatory arrest was started and kept on for 90min.When the circulation reopened,the body temperature was gradually restored until the nasopharynx temperature reached 36℃ and the machine was turned off.Before(T1),and 45 min(T2) and 90 min(T3) after the circulatory arrest,and 15 min(T4) and 30 min(T5) after reopening the circulation,blood samples from all the dogs were obtained by artery and jugular tube inserting for pH and lactate testing.When the surgery was completed,the hippocampus was removed from the brain,and the transmission electron microscope was used to observe the changes in the ultrastructure brain and nerve cells.RESULTS There was no significant difference in pH before circulatory arrest among all the dogs.After circulatory arrest,DHCA and RCP groups showed an significant decrease in brain pH compared with IACP group which showed no significant difference.No significant lactate difference was found in the 3 groups before arrest.After circulatory arrest,DHCA and RCP groups showed a great increase in brain lactate compared with IACP group which showed an increase only at 90 min after circulatory arrest.CONCLUSION Long time DHCA brain produces large amount of lactic acid,which causes brain damage.Although RCP treatment can provide some protection for the brain,it will in some cases lead to dropsy of brain and nerve.IACP treatment has the best brain protection with less dropsy of brain and nerve cells.