Effect Of Dexmedetomidine On Regional Cerebral Oxygen Saturation And Postoperative Cognitive Function In Elder Patients Undergoing Laparoscopic Radical Resection Of Rectal Cancer

Objective:To observe effect of dexmedetomidine on regional cerebral oxygen saturation and postoperative cognitive function in elder patients undergoing laparoscopic radical resection of rectal cancer.Methods:Fifty elderly patients who underwent laparoscopic radical resection of rectal cancer under general anesthesia were selected with ASA gradeⅠ-Ⅲ,age 65-80years old.These patients were randomly divided into two groups:dexmedetomidine group（group A n=25）and control group（group B n=25）.In group A,200μg dexmedetomidine was diluted to 4μg/ml.The loading dose of 0.5μg/kg was given into15min after endotracheal intubation induced by general anesthesia,and then continuously pumped with 0.5μg/kg/h.30 min was stopped before the end of operation,and the infusion rate was adjusted at any time according to the changes of HR and BP.The patients in group B were pumped with the same amount of 0.9%sodium chloride solution at the same time under the same conditions,and all patients stopped using anesthetic drugs after the operation.Anesthesia maintenance:intravenous infusion of propofol 4-10mg/kg/h and remifentanil 0.05-0.20μg/kg/min,inhaled sevoflurane 1%-2%.intermittent intravenous injection of cisatracurium besylate（powder）0.2 mg/kg to maintain muscle relaxation,according to hemodynamic changes,vasoactive drugs were given to maintain hemodynamic stability.The bispectral index（BIS）was maintained at 40-60.After operation,the patient was sent to the anaesthesia recovery room for further observation until the anesthesia regained consciousness.rSO₂ was monitored by Covidien cerebral oxygen and regional monitoring system during operation.MAP,rSO₂,PaCO₂ and PaO₂were monitored and recorded at the time of entering the operating room（T1）,after general anesthesia induction and intubation（T2）,after the establishment of pneumoperitoneum（T3）and after awakening（T4）.MAP,rSO₂,PaCO₂ and PaO₂ were recorded.One day before operation,one day after operation,three days after operation and seven days after operation,the patients were scored with mini-mental state examination scale（MMSE）.At the same time,the number of patients with postoperative cognitive impairment（POCD）was recorded.Results:In each group,rSO₂ and PaO₂ at T2,T3 and T4 were significantly higher than those at T1（p<0.05）,but there was no significant difference in rSO₂ and PaO₂between the two groups at T1,T2,T3 and T4（p>0.05）.One day after operation,the MMSE score of A group was significantly higher than that of B group（p<0.05）.One patient（4%）in A group had POCD,which was significantly lower than that in B group（24%）（p<0.05）.Conclusion:Dexmedetomidine did not significantly affect rSO₂ in elder patients undergoing laparoscopic radical resection of rectal cancer but can reduce the incidence of early POCD.