Effect Of Hypertonic Saline On Rats With Acute Ammonia Intoxication: A Study Utilizing Diffusion-weighted And Perfusion-weighted Magnetic Resonance Imaging

PartⅠ:Effect of hypertonic saline on rats with acute ammonia intoxication:a study utilizing diffusion-weighted magnetic resonance imagingPurpose:To investigate the value of Apparent diffusion coefficient in rats with acute ammonia intoxication before and after using hypertonic saline.Materials and Methods:twelve male SD rats were randomly divided into two groups.12 rats were performed MR diffusion-weighted imaging before and after they were injected intraperitoneally with ammonium acetate;and then 6 rats were injected by femoral vein with hypertonic saline and the other 6 control rats were injected by femoral vein with saline.After 15min MR imaging were performed.Apparent diffusion coefficient(ADC)topographical maps were archived by the Workstation(AW4.0-05,GE).The values of ADC of the right or left sensory cortex,caudate-putamen,thalamus, cerebellar hemisphere and the motor cortex were measured.Results:We measured ADC in 10 brain regions,ADC decrease only in bilaeral caudate-putamen.The using hypertonic saline dose not influence the values of ADC in 15min.Conclusion:The values of ADC decrease in bilaeral caudate-putamen suggested ammonia induced cytotoxic edema in rats with acute ammonia intoxication.Hypertonic saline dose not influence the values of ADC in short time period.PartⅡ:Study of rats with acute ammonia intoxication with magnetic resonance perfusion imagingPurpose:To investigate the change of the value of NEI (negative enhanced integral),MSD(maximum slope of decrease) and MTT (mean transit time) in rats with acute ammonia intoxication.Materials and Methods:twelve male SD rats were randomly divided into twogroups.6 rats were performed MR perfusion-weighted imaging after they were injected intraperitoneally with ammonium acetate;and then the other 6 control rats were performed MR perfusion-weighted imaging.NEI,MSD and MTT topographical maps were archived by the Workstation(AW4.0-05,GE). The values of NEI,MSD and MTT of the right or left sensory cortex, caudate-putamen,thalamus,cerehellar hemisphere and the motor cortex were measured.Then take mean NEI,MSD and MTT of two-sides of cerebellar hemisphere ROIs in every rat,the relative NEI,MSD and MTT(rNEI,rMTT and rMSD) were calculated as ratios to the averged left and right cerebellar values.Take the ratios of two groups into statistical analysis.Results:relative MTT prolonged in everv ROIs after poisoning, had statistical significance(P＜0.05),which compared with pre-poisoning;relative NEI and MSD of poisoned rats compared with pre-poisoning have no significant differences.Conclusion:Rats with acute ammonia intoxication can be obvered cerebral hyperemia in all ROIs. MR perfusion weighted imaging can reflect changes of the microcirculation of the poisoned rats' brain,which suggest that brain microcirculation severe disturbance is possibly one of the causes which aggravate brain injury and induce delayed encephalopathy.PartⅢ:Effect of hypertonic saline on rats with acute ammonia intoxication:a study utilizing perfusion - weighted magnetic resonance imagingPurpose:To apply MR perfusion weighted imaging to reflect the changes of the perfusion of rat in acute ammonia poisoning before and after using hypertonic saline.Materials and Methods:24 male SD rats were randomly divided into four groups,ammonia plus hypertonic saline,ammonia plus saline,saline and hypertonic saline.12 rats were injected intraperitoneally with ammonium acetate;and then 6 rats were injected by femoral vein with hypertonie saline and the other 6 control rats were injected by femoral vein with saline,after 15min MR perfusion-weighted imaging were performed.the other group were injected by femoral vein with hypertonic saline and saline,after 15min MR perfusion-weighted imaging were performed too.NEI,MSD and MTT topographical maps were archived by the Workstation(AW4.0-05,GE).The values of NEI,MSD and MTT of the right or left sensory cortex, caudate-putamen,thalamus,cerebellar hemisphere and the motor cortex were measured.Then take mean NEI,MSD and MTT of two-sides of cerebellar hemisphere ROIs in every rat,the relative NEI,MSD and MTT(rNEI,rMTT and rMSD) were calculated as ratios to the averged left and right cerebellar values.Take the ratios of four groups into statistical analysis.Results:Relative MTT and MSD had no remarkable changes in four groups.Relative NEI(rNEI) decreased in group of ammonia plus hypertonic saline in the caudate-putamen ROIs,which compared with that of ammonia plus saline;had statistical significance(P＜0.05). The values of relative NEI(rNEI) in groups of saline and hypertonic saline are low than that of in group of ammonia plus hypertonic saline in the caudate-putamen ROIs,had statistical significance(P＜0.05).Conclusion:The values of relative NEI decrease in group of ammonia plus hypertonic saline in eaudate-putamen suggested perfusion cut down.So hypertonic saline can relieve brain hyperemia in rats with acute ammonia intoxication.