RESUMO
Objective To evaluate the effects of dexmedetomidine on the cerebral oxygen metabolism in elderly patients undergoing general anesthesia.Methods Sixty ASA physical status Ⅰ or Ⅱ patients,aged 60-87 yr,scheduled for elective abdominal surgery under general anesthesia,were randomly divided into 2 groups (n =25 each) using a random number table:control group (group C) and dexmedetomidine group (group D).Anesthesia was induced with iv injection of midazolam,fentanyl,atracurium and propofol.The patients were tracheally intubated and mechanically ventilated.In group D,dexmedetomidine 1.0μg/kg was infused intravenously over 20 min before induction of anesthesia,while the equal volume of normal saline was given in group C.Before induction of anesthesia,at 0 and 10 min after tracheal intubation and at the end of operation (T0-3),blood samples were taken from the radial artery and jugular bulb for blood gas analysis.Arteriovenous blood O2 content difference (DajvO2) and cerebral O2 extraction rate (CERO2) were calculated at the same time.The development of emergence agitation and postoperative delirium within 48 h after surgery were recorded.Resets Compared with the baseline values at T0,the Da-jvO2 and CERO2 were significantly decreased at T1-3 in the two groups (P ＜ 0.05).Compared with group C,the Da-jvO2 and CERO2 were significandy decreased at T2-3,and the incidence of emergence agitation and postoperative delirium within 48 h after surgery was decreased in group D (P ＜ 0.05).Conclusion Dexmedetomidine can improve the cerebral oxygen metabolism and reduce the development of postoperative delirium in elderly patients undergoing general anesthesia.