The effect of dexmedetomidine on renal function in patients undergoing cardiac valve replacement under cardiopulmonary bypass: A double-blind randomized controlled trial

•The SOD activity was significantly declined at 12h, 24h in Dex group after operation.•The postoperative level of NGAL at 24h and 72h was significantly lower in Dex group than controls.•The levels of BUN and Cr were significantly increased in all of the patients.•The incidence of AKI was significantly lower in Dex group than in placebo group.