Cardioprotection induced by combination of dexmedetomidine and limb ischemic preconditioning in patients undergoing coronary artery bypass grafting with cardiopulmonary bypass / 中华麻醉学杂志

ABSTRACT

Objective To evaluate the cardioprotection induced by combination of dexmedetomidine and limb ischemic preconditioning in the patients undergoing coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB).Methods Eighty American Society of Anesthesiologists physical starus Ⅱ or Ⅲ patients of both sexes,aged 52-64 yr,weighing 51-78 kg,with New York Heart Association Ⅱ or Ⅲ,scheduled for elective CABG with CPB,were divided into 4 groups (n =20 each) using a random number table method:control group (group C),limb ischemic preconditioning group (group L),dexmedetomidine group (group D) and dexmedetomidine plus limb ischemic preconditioning group (group DL).Limb ischemic preconditioning was induced by 3 cycles of 5-min unilateral lower limb ischemia followed by 5-min reperfusion starting from 30 min before aortic clamping in L and DL groups.Dexmedetomidine was injected via the central vein in a loading dose of 1 μg/kg after induction of anesthesia,followed by an infusion of 0.4 μg · kg-1 · h-1 until the end of operation in D and DL groups.Venous blood samples were obtained immediately before aortic clamping,at the end of CPB and at the end of operation for determination of plasma concentrations of cardiac troponin Ⅰ (cTnI) by enzyme-linked immunosorbent assay.Myocardial tissues were obtained from the right auricle immediately before aortic clamping and at the end of CPB for determination of the expression of Bcl-2 and Bax (by immunohistochemistry) and apoptosis index (AI) (using TUNEL).The restoration of spontaneous heart beat was recorded.Bcl-2/Bax ratio was calculated.Results Compared with group C,the plasma cTnI concentrations were significantly decreased,the Bcl-2 expression was up-regulated,the Bcl-2/Bax ratio was increased,Bax expression was down-regulated,and AI was decreased in the other three groups (P＜0.05).Compared with L and D groups,the plasma cT-nI concentrations were significantly decreased,the Bcl-2 expression was up-regulated,the Bcl-2/Bax ratio was increased,Bax expression was down-regulated,and AI was decreased in group DL (P＜0.05).The rate of restoration of spontaneous heart beat was significantly increased in group DL as compared with the other three groups (P＜0.05).Conclusion Combination of dexmedetomidine and limb ischemic preconditioning can mitigate myocardial injury,it provides better efficacy than either alone,and the mechanism is related to inhibiting cell apoptosis in the patients undergoing CABG with CPB.