The Dynamic Changes Of Brain Structure And Metabolism After Cardiopulmonary Resuscitation In Rats And The Effect Of Glibenclamide In Treating Brain Edema

BackgroundCardiac arrest(CA)is still a serious public health problem.Cardiopulmonary resuscitation(CPR)occurs after the success of systemic pathophysiological changes,known as "post-cardiac arrest syndrome(PCAS)." In recent years,the rate of return of spontaneous circulation(ROSC)in out-of-hospital cardiac arrest(OHCA)is increasing,yet the survival rate and prognosis have not been significantly improved.Because of the limited tissular tolerance to hypoxia and ischemia and the ischemia/reperfusion response,brain injury results in serious pathological edema that affects the prognosis of PCAS.During the aggravation of PCAS brain injury,it was found that ischemic and hypoxic internal environment lead to the onset of cytotoxic edema,while cerebral edema can inhibit the transmission and utilization of oxygen in return.These repeating secondary damages can last for several hours to several days,leads to the the status quo of cardiac arrest patients' long ICU stay with invalid treatment,and it's difficult to predict the process of edema as well as patients' condition.So that the treatment and prognosis of cerebral edema after cardiac resuscitation became the critical focus area among clinical and experimental researchers for years.Although ischemia and hypoxia is the main cause of cell edema,the existing experimental methods to detect cerebral edema of rodent CA model are still insensitive and extremely unreliable.With the development of neuro-imaging of small animals,more methods can provide ways and evidence for the analysis of cerebral edema and other brain pathological phenomena.To establish stable and noninvasive measurable cerebral edema and structural/metabolic changes of brain injury by magnetic resonance diffusion imaging,we can better understand the CA/CPR model and simulate cerebral edema pathological situation in patients with cardiac arrest,provide objective and credible evidence to examine the experimental drug or treatment of neuroprotection,which has great significance in the future.PurposeThis study was to establish a 5 minutes cardiac arrest/cardiopulmonary resuscitation model with asphyxia(ACA-5min/CPR)in rats,to observe the structural damage and metabolism of cerebral tissue after CA/CPR,and to assess whether glibenclamide has an efficacy on the structure and metabolism of brain edema by small animal MRI.MethodsSixteen male SD rats underwent asphyxial CA/CPR modeling(n = 11)and sham operation(n = 5)while the CA/CPR modeling rats were randomly assigned to vehicle control group(CA/CPR or Veh)and glibenclamide treatment group(GBC)after ROSC achieved for 10 minutes.All criteria-met rats were scanned in 7.0T high-intensity magnetic field MRI with diffusion weighted imaging(DWI)and hydrogen proton magnetic resonance spectroscopy(~1H-MRS)sequences at 6,24,48,72h after ROSC and baseline of sham-operated group as well.The progress of brain injury and brain edema were analyzed by apparent diffusion coefficient(ADC),the changes of metabolites and the neurological deficit score(NDS).After 72 hours,nissl staining as well as immunohistochemistry of MAP2,GFAP and Iba-1 were implemented to observe the histopathological changes in order to being comparisons of MRI as traditional methods.Results(1)Water diffusion became abnormal and time-fluctuated after cardiac arrest/cardiopulmonary resuscitation in rats.Whole brain high signal was showed on DWI with ADC value significantly lower than baseline at ROSC6h.after ROSC 24h,the whole brain ADC value was significantly increased compared to ROSC6h,with abnormal signal on DWI and dimishing ADC value limited to the cerebral cortex and hippocampus.ADC values of the rest brain region such as brainstem did not change significantly during 24?72h.The signal intensity of the cerebral cortex and hippocampus was gradually increased from dayl to day3,and the signal intensity in hippocampal CA1 region was significantly higher than that in other hippocampal regions at 72 h.Compared with the vehicle control,glibenclamide treatment significantly reduced the range and signal intensity of high signal area on DWI at 72 h after CA/CPR,and increased the ADC value of the region.The difference between the two modeling groups was statistically significant(P<0.05).(2)~1H-MRS results showed that glutamate&glutamine was significantly higher in hippocampus after CA/CPR than before.NAA+NAAG was significantly decreased and decreased with time after resuscitation.Outstanding lactate peak arose at ROSC6h.The trend of several metabolites synchronously changes with pathologic findings and neuronal deficit.(3)Morphological and neurofunctional results were consistent with those of DWI and MRS-the delayed loss sensitive neurons,the diffuse injury of dendrites,markedly increase and activation of astrocytes in the hippocampal CA1 region after 72 hours of resuscitation response.Glibenclamide can reduce neuronal loss,dendritic damage and inhibit the activation of astrocytes and microglia.The NDS(Normal = 80,death = 0)decreased significantly at ROSC24h of CA/CPR,while the recovery of neurological function was more significant after glibenclamide treatment(P<0.05).Conclusions(1)DWI and ADC can reflect the presence of global ischemia and hypoxia-induced cell edema at very early stage(within a few hours)of CA/CPR and progressive cytotoxic edema associated with pathological delayed loss of neurons that due to the integrated systemic brain injury during reperfusion-phase(1-3 days).Glibenclamide can effectively relieve the delayed cytotoxic edema,reduce the loss of neurons in hippocampal CA1 region,and optimize the recovery of neurological function in rats.(2)~1H-MRS reflects the abnormality of brain metabolism after CA/CPR.The presence of lactate peak reflects the glycolytic and energy metabolism disorder due to hypoxia in the early stage of the CA/CPR model,and the decrease of tNAA is consistent with the pathological changes of neuronal loss,indicating that ~1H-MRS can reflect the pathological damage process of CA/CPR model by metabolic changes,and provide more evidence for the development and application of the model and the validation of drug efficacy.