Effect Of Dexmedetomidine Combined With Remote Ischemic Preconditioning On Myocardial Ischemia-reperfusion Injury In Patients Undergoing Heart Valve Surgery Under CPB

Objective:To study the effect of dexmedetomidine combined with remate ischemic preconditioning on myocardial ischemia reperfusion injury and to explore its effect on apoptosis.Methods:80 patients scheduled for heart valve replacement under cardiopulmonary bypass were randomly divided into 4 groups?n=20?:Centrol group?group C?,limb ischemia preconditioning group?group R?,dexmedetomidine pretreatment group?group D?,and dexmedetomidine pretreatment combined with limb ischemia preconditioning group?group DR?.Group R received upper limb ischemic preconditioning after induction of anaesthesia.Attach the mercury sphygmomanometer cuff to the right upper limb elbow2³cm,inflate the cuff to the mercury column scale up to 200 mmHg,close the inflatable balloon,and time it for 5 minutes to make it ischemic.The success criteria of ischemia:limb radial artery The pulsation could not be touched,and the oxygen saturation of the fingertip could not be measured.Opening the balloon to ventilate the ischemic limb for 5min;the above operation was performed for 3 cycles for 30 min.In group D,dexmedetomidine was intravenously as a loading dose of 1ug/kg for 10min and then intravenously as 0.4ug·kg^-1·h^-1until the end of the operation.In DR group,limb ischemic preconditioning was performed simultaneously with dexmedetomidine infusion.The method was the same as that in D group and R group.The plasma troponin I?cTnI?levels were measured before surgery?T₀?,24 hours after operation?T₁?and 48hours after operation?T₂?.The contents of Bcl-2 and Bax protein and cardiomyocyte apoptosis index?AI?were measured before aortic occlusion and at the end of cardiopulmonary bypass.Early postoperative cardiovascular complications were recorded in each group.Results:1.There were no significant differences in general conditions,left ventricular ejection fraction,duration of surgery,duration of cardiopulmonary bypass,ICU stay,and early postoperative cardiovascular complications in the four groups?P>0.05?.2.Compared with T₀,the plasma cTnI concentrations in T₁ and T₂ were significantly increased in each group?P<0.05?.Compared with before aortic occlusion,Bcl-2,Bax protein content and AI increased,and Bcl-2/Bax decreased in the four groups after cardiopulmonary bypass?P<0.05?.3.Comparison between groups:at T₁ and T₂,plasma troponin-I was decreased in each group compared with the control group?P<0.05?.Compared with group D and group R,the concentration of cTnI in DR group decreased?P<0.05?,and there was no significant difference between group D and group R?P>0.05?.Compared with group C,Bcl-2 and Bcl-2/Bax were increased in group D,group R and DR,and Bax and AI were decreased?P<0.05?.Compared with group R and group D,group Bcl-2 and Bcl were compared with group D and group D.Bcl-2/Bax increased,Bax and AI decreased?P<0.05?.Conclusion:1.Patients with rheumatic heart disease undergoing CPB descending heart valve replacement,dexmedetomidine preconditioning,limb remote ischemic preconditioning and their combination can alleviate myocardial ischemia-reperfusion injury.The mechanism may be related to the inhibition of apoptosis.2.The effect of dexmedetomidine combined with remote ischemic preconditioning is better than single action,which may be related to the further inhibition of apoptosis.3.The effect of dexmedetomidine combined with remote ischemic preconditioning on cardiovascular complications in patients requires further study.