Relationship Between Cerebral Injury And Early Changes Of Excitatory Amino Acid In Rabbit Hippocampus Due To Cardiopulmonary Bypass And Deep Hypothermic Circulatory Arrest

Objective: To set up a completely clinical simulated rabbit model of cardiopulmonary bypass (CPB) and deep hypothermic circulatory arrest (DHCA) with small priming volume by ascending aorta cannulation. Cerebral microdialysis was established based on the rabbit model of cardiopulmonary bypass and sampling in awake condition was performed to continuously monitor the neurobiological macromolecular changes in the brain extracellular fluid..Method: Sixteen New Zealand rabbits were randomized into the CPB group and the DHCA group. Implantable cerebral microdialysis cover was used after locating the hippocampus CA1 region and in vivo sampling. CPB was initiated 36 hours after the implantation. Double purse-string suture was done to cannulate the ascending aorta and specially designed membrane oxygenation was used to set up bloodless, small priming volume CPB. The temperature in CPB group was lowered to 30℃ and DHCA group to 18 to 20℃, mild or deep hypothermic CPB or DHCA was kept for 60 minutes, hypothermia was reversed or circulation was restored for 90 minutes respectively. Arterial blood pressure and heart rate were continuous monitored, while blood gas analysis on PaCO₂, PaO₂, Hemoglobulin (Hb) and Hemocrit (Hct) were intermittently determined. Microdialysis location was examined after the operation.Results: There were 2 failures in each group. The percentage of failure ascribable to microdialysis and operation was 12.5% respectively and the success rate of this model was 75%. The Hb concentration before operation and at the end of experiment were 7.0 ± 1.4 g/dl and 7.2 ± 1.0 g/dl in CPB group, and 7.5 ± 1.3 g/dl and 7.2 ± 1.0 g/dl in DHCA group, respectively. The percentage of heart beat restoration (100%) in CPB group is higher than DHCA group (66.6%). During the CPB, the perfusion flow remained stable with a mean perfusion pressure of 60 to 85 mmHg. PaO₂ remained above 150 mmHg. Among all the investigated parameters, there were no significant differences between the two groups in all phases of the operation. Upon postoperative examination, all microdialysis locations were exact and he cerebral microdialysis cover remained firm.Conclusions: The rabbit model of bloodless, small priming volume CPB by ascending aortic cannulation and using specially made membrane oxygenation is a...