Objective:To investigate the dosage of dexmedetomidine(Dex)and its effect on microcirculation during valve replacement under the guidance of EEG monitoring during cardiopulmonary bypass(CPB).Method:A total of 85 patients who underwent elective CPB valve replacement in our hospital from June 2020 to December 2022 were selected for the study.The patients were randomly divided into three groups:low dose group(n=28),high dose group(n=28)and control group(n=29).Before anesthesia induction,0.2μg/kg·h-1Dex,0.4μg/kg· h-1 Dex and normal saline were infused into 10min until the end of operation.The hemodynamics and microcircula-tion indexes were compared after anesthesia induction(T1),before the start of CPB bypass(T2),1 hour after CPB bypass(T3),when CPB bypass stopped(T4),4 hours after operation(T5)and 24 hours after operation(T6).The effect of Dex infusion time on bispectral index(BIS)and postoperative recovery were analyzed.Results:The BIS values of 12min,15min and 1min after intubation in low dose group and high dose group were lower than those in control group.The levels of HR at T2-T4,MAP at T2-T5,LA and cTnI at T2-T6,postoperative cardio-vascular adverse events,time for nasal and anal warming,and N terminal pro B type natriuretic peptide(NT-proB-NP)at 24h post surgery in the low dose group were lower than those in the control group.The ScvO2 and urine volume and the rate of automatic cardiac resuscitation at T2-T6 in the low dose group were higher than those in the control group.HR and MAP at T2 in high dose group were lower than those in low dose group.The nasal and anal rewarming time and postoperative 24hNT-proBNP in the high dose group were higher than those in the low dose group.Conclusion:Low dose of Dex can achieve a good sedative effect and maintain hemodynamic stability.Infusion of 0.2μg/kg·h-1 Dex at 10min before anesthesia induction can effectively improve the effect of valve replacement under CPB on microcirculation.Low dose of Dex can reduce the levels of LA and cTnI,increase ScvO2 and urine volume,and shorten the rewarming time of nasal and anal temperature.
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