Comparison between the Effects of Dexmedetomidine and Midazolam on Postoperative Cognitive Impairment after Coronary Artery Bypasses Graft Surgery: A Randomized Clinical Trial

Postoperative cognitive decline is a common complication observed frequently after general anesthesia in the immediate postoperative phase. We studied the effects of dexmedetomidine versus midazolam during coronary artery bypass graft (CABG) surgery on cognitive and memory function.  In this clinical trial, 42 elective on-pump CABG candidates under general anesthesia, aged between 40 and 65 years, were enrolled randomly in 2 groups. Group A received 0.05–0.1 mg/kg of midazolam and Group B received 1 µg/kg of dexmedetomidine. One day before surgery, all the participants underwent the Persian version of the Mini-Mental State Examination (MMSE) and the Persian version of the Wechsler Memory Scale (WMS) test for a comparison of cognitive impairment and memory functions. Both groups were given fentanyl and propofol for the induction of anesthesia and muscle relaxants. The MMSE and WMS tests were repeated 5 and 30 days after surgery. The mean±SD of age was 55.47±7.18 y in Group A and 55.39±6.08 y in Group B. Eighty percent of the participants were men in both groups. There were no significant differences between Group A and Group B in the MMSE and WMS before surgery (89.04±14.30 vs. 97.10±18.10, respectively;  P=0.059), but the WMS was significantly different 30 days after surgery (87.60±14.30 vs. 103.53±19.93, respectively; P=0.005). Group A showed high cognitive impairment and low WMS scores compared with Group B (P=0.005). Additionally, the MMSE results were not statistically different between the 2 groups postoperatively (24.80±3.18 vs. 23.55±4.18, respectively; P=0.394). Our results showed that dexmedetomidine might have a lower impact on cognitive function than might midazolam among patients undergoing CABG.