Effect Of Dexmedetomidine On Acute Kidney Injury In Patients With Aortic Dissection Undergoing Sun’s Procedure With Cardiopulmonary Bypass

BackgroundIn recent years,aortic dissection（AD）has become one of the most serious diseases in Cardiac Surgeryas a result of the increasing incidence rate of hypertensionand aged populations.The incidence rate is increasing year by year,and there is a trend of younger age.A possible mechanism of aortic dissection is the cystic necrosis of the aorta,tearing of the intima,and pressure of the pulsation of the blood vessels to cause blood in the lumen to enter the middle layer of the aorta at the lesion..The Stanford scheme classifies aortic dissections into two groups.Aortic dissections that involve the ascending aorta（The Stanford type A）are considered as surgical emergencies（ACC/AHA class I recommendation;Level of evidence B）.Immediate surgical intervention significantly improves the mortality rate,especially among patients younger than 80 years.Sun’s surgery is recognized as the standard procedure for the treatment of complex aortic dissection and involvement of aortic arch and descending aortic dilatation.During aortic arch replacement insurgery,deep hypothermia circulatory（DHCA）is needed to temporarilyblock systemic perfusion,and retrograde cerebral perfusion（RCP）.The physiologic basis for deep hypothermia as a neuroprotection strategy is to decrease the cerebral metabolic rate and oxygen demands to increase period that the brain can tolerate circulatory arrest.Due to temporary interruption of blood flow and reperfusion injury,the risk of renal ischemia is very significant.Nephrotoxicity,inflammation and sympathetic over-excitation caused by elevated renin levels,are also the main cause of kidney injury.The etiology of renal injury is mainly due to elevation of renin levels as a result of sympathetic overactivity in addition to nephrotoxic,inflammatory,and hemodynamic.In recent years,both animal and clinical studies have reported that dexmedetomidinecan be used for perioperative organ protection in patients undergoing complex surgery and major organ dysfunction.Itimproves the myocardial oxygen supply-demand balance,inhibites cardiomyocyte apoptosisandreduces postoperative delirium and cognitive kinetics in patients undergoing neurosurgery.And it has a certain lung protection effect by reducing the production of inflammatory factors in the lungs.The explanation was reported by an animal study in rat model of renal ischemia-reperfusion injury.Itconcluded that dexmedetomidine decreased the number of apoptotic tubular epithelial cells through suppression of injury-mediated activation of JAK/STAT signaling pathway.It has been reported in the literature that dexmedetomidine has a certain protective effect on the kidney of patients undergoing heart valve replacement.However,there are few studieson renal protection and corresponding mechanisms in patients with aortic dissection.ObjectiveTo evaluate the effect of dexmedetomidine on acute kidney injury（AKI）in patients with Stanford type A aortic dissection undergoing Sun’s procedure with cardiopulmonary bypass.MethodsApproved by the ethics committee of the Second Affiliated Hospital of Zhengzhou University.Sixty patients with Stanford type A aortic dissection undergoing Sun’s procedure with cardiopulmonary bypass（CBP）were randomly divided into two groups（n=30）:control group（group C）and dexmedetomidine group（group D）.Dexmedetomidine was intravenously injected in group D with a dose of 1μg/kg,10minutes before the induction of conventional anesthesia,followed by slowly intravenous pumping at a rate of 0.5μg·kg^-1·h^-1 to the end of the operation.The same procedure was also employed by using normal saline instead of dexmedetomidine.General surgical conditions of the two groups and the changes of hemodynamics related indices at different time points in the two groups were recorded,as well as bleeding volume.Blood samples and urine samples were taken before induction（T₀）,at the end of operation（T₂）,24 hours（T₃）and 48 hours（T₄）after operation to determine Cr,BUN,NAG/Cr andβ₂-MG/Cr levels.SPSS 21.0 statistical software was used to analyze the measured data to compare the occurrence and severity of acute kidney injury.Results1.There was no statistical significant difference between the two groups of patients whose general situations were compared（P>0.05）.2.There were no statistical significant differences in the general conditions of Sun’s operation,intraoperative blood loss,RBC infusion and fluid infusion between the two groups of patients（P>0.05）.3.There were no significant differences in perioperative hemodynamic parameters between the two groups（P>0.05）.There were significant differences in urine volume between the two groups at T₃ and T₄（P<0.05）.The two groups showed a significant downward trend between T₂ and T₃.T3-T4 saw a significant increase in group D,and group C was basically flat with the previous one,with no obvious increase.4.Comparison of renal function markers in serum and urine samples between the two groups at four time points.4.1.Comparison of serum Cr changes between the two groupsThe Cr values of the two groups were in the normal range at T₁,and there were differences in serum Cr between the two groups at T₂,T₃ and T₄（P<0.05）.The Cr value of Group C showed an overall upward trend,and exceeded the normal value at T₃.The rising trend of the D group is relatively flat,the peak value is reached at the T₃ time point,and the T₄ time point has a downward trend,which is basically reduced to the normal value.4.2.Comparison of serum BUN changes between the two groupsThere were differences in BUN values between the two groups（P<0.05）.Within the group,the BUN values of the D and C groups were statistically significant at the time of T₁ and T₂（P<0.05）.On the whole,the C group showed a continuous upward trend.The T₁-T₃ points in the D group showed a slow upward trend,and the T₃ showed a downward trend.4.3.Comparison of changes in urine NAG/Cr between the two groupsThere was a statistically significant difference in T₂-T₄ between the two groups of patients with NAG/Cr values（P<0.05）.The measured values of D and C groups at T₂were compared with the rest of the time points,and the difference was statistically significant（P<0.05）.The two groups showed an upward trend during the period from T₁ to T₂,and reached a peak at T₂,then showed a downward trend,and then decreased gradually after T₃.The fluctuation trend of group C in the whole trend was more severe than that in group D.4.4.Comparison of changes in urineβ2-MG/Cr between the two groupsThere was a statistically significant difference in T₂-T₄ between the two groups in theβ2-MG/Cr group（P<0.05）.Theβ2-MG/Cr values of the two groups showed a significant upward trend at T₁,peaked at T₂,and increased significantly in group C compared with group D.After T₂,the trend showed a downward trend,and T₃-T₄slowed down.Theβ₂-MG/Cr at each time point in Group C was higher than that in Group D.5.Comparison of AKI changes within 48 hours after operation in both groupsThe incidence of AKI in group C was much higher than that in group D within 48hours after operation.And the incidence of group A was mainly concentrated in AKI2.The incidence of AKI in group C was mainly in AKI 3.6.The 48-hour Cr,BUN,NAG/Cr,andβ₂-MG/Cr measurements were considered as risk factors for AKI in aortic dissection（P<0.05）.ConclusionFor patients undergoing Sun’s procedure,dexmedetomidine can alleviate the effects of cardiopulmonary bypass and surgical methods on various renal function--related indicators,thereby reducing the risk and severity of AKI and improve prognosis.