Efficacy Evaluation Of Extracorporeal Cardiopulmonary Resuscitation Model In Rats And Exploration Of Its Protective Mechanism On Neurons In Hippocampal CA1 Area

Background and objective:Cardiac arrest refers to the sudden loss of the normal pumping function of the heart,resulting in loss of consciousness,lack of breathing and circulation signs of the patient.If not given timely treatment,the patient will die suddenly in a short time.Even though cardiopulmonary resuscitation（CPR）has been widely popularized and the return of spontaneous circulation（ROSC）rate of CA patients has been increased,the discharge survival rate is extremely low.It is often accompanied by severe post-cardiac arrest syndrome（PCAS）.With the development of extracorporeal membrane oxygenation（ECMO）,a new treatment method has been provided for patients with CA,which is called extracorporeal cardiopulmonary resuscitation（ECPR）.Clinical studies have suggested that ECPR,compared with conventional CPR（CCPR）,helps to reduce the can achieve better curative effect than conventional CPR in the treatment of patients with cardiac arrest,and reduce occurrence of complications of severe nervous system injury,but the specific mechanism of action is still not clear.Therefore,the purpose of our study was to establish a robust rat model of extracorporeal cardiopulmonary resuscitation,to compare the supporting efficacy of ECPR and CCPR in rats,and to preliminary explore the mechanism of ECPR’s protective effect on hippocampal CA1 region.Methods:Adult male SD rats were randomly divided into Sham operation group（Sham group）,conventional cardiopulmonary resuscitation（CCPR）group and extracorporeal cardiopulmonary resuscitation（ECPR）group.Sevoflurane was inhaled to induce anesthesia,tracheotomy was performed and self-made tracheal intubation was placed,and hemodynamics was monitored through the right femoral artery.In the Sham group,only surgical operation and ligation of corresponding blood vessels were performed;in the CCPR group,only conventional cardiopulmonary resuscitation was performed;in the ECPR group,the right jugular-caudal artery V-A ECMO loop was established,and performed extracorporeal cardiopulmonary resuscitation.Respiration,anal temperature and hemodynamics were continuously monitored in all three groups.Blood gas analysis was performed before asphyxia and 30 minutes after observation/resuscitation.Vital signs and internal environment of each group were compared.After the experiment,the rats were sacrificed,blood samples were collected,and paraffin sections were made for hematoxylin-eosin staining and Nissl staining.The number and morphological changes of neurons and Nissl bodies in hippocampal CA1 region of the three groups of rats were observed.Small molecular metabolites in hippocampal CA1 region of rats were analyzed based on microdialysis technology,and the metabolism of ATP and neurotransmitters in CA1 region of rats in each group was detected.Western blotting was used to detect the expression of apoptosis-related proteins in each group.Ultrasensitive electrochemiluminescence was used to detect inflammatory factors and to detect systemic inflammatory response of rats in each group.Result:There were seventeen rats successfully survived.Among them,all the Sham group survived to the end of the experiment,and all the ECPR groups survived to ROSC successfully,with stable hemodynamics and good blood gas results.In the CCPR group,5 rats were succeeded in ROSC,1 died due to rescue failure,and the residual circulation was stable,one rat was added in the CCPR group according to the principle of randomization.There were no statistically significant differences in the general conditions before CA among the three groups,such as body weight,anal temperature,heart rate,MAP,time to CA induced by asphyxia and CA duration（P>0.05）.the time of cardiopulmonary resuscitation in the ECPR group was shorter than that in the CCPR group（P<0.05）.The hemodynamics and blood gas of ECPR and CCPR groups at 30 min after resuscitation were compared with those of Sham group,the differences of heart rate,MAP,anal temperature,p H,PO2,PCO2 and BE were statistically significant（P<0.05）.In addition,compared with CCPR group,there were statistically significant differences in MAP,heart rate,PH,BE,PO₂,HCT and HB in ECPR group after resuscitation（P<0.05）.In HE staining and Nissl staining,both ECPR and CCPR groups showed obvious neuronal cell damage compared with Sham group,but the number of neurons and Nissl bodies in ECPR group was better than that in CCPR group.The results of small molecule metabolites detection showed that compared with Sham group,the Asp and Gly in CCPR group and ECPR group were significantly increased,while the ATP in CCPR group was decreased.Compared with CCPR group,Asp and Gly of ECPR group were decreased.Western blotting showed that the expression of Bcl-2 and the ratio of Bcl-2/Bax in the hippocampus of rats in ECPR group were higher than those in CCPR group（P<0.05）.Compared with the Sham group,TNF-αin ECPR group was significantly increased（P<0.001）,and increased IL-6（P<0.05）,TNF-αin CCPR group was increased（P<0.05）.Conclusion:In this experiment,the ECPR model of rats was successfully established and the efficacy was better than that of conventional CPR.In the treatment of cardiac arrest in rats,ECPR can protect the hippocampal CA1 region after CA,and the mechanism may be related to the improvement of brain energy metabolism,the reduction of neurotransmitter damage to brain tissue and the inhibition of neuronal cell apoptosis.