Effects Of Different Induction Rates Of Propofol On The Early Postoperative Cognitive Function In Elderly Patients Undergoing Laparoscopic Inguinal Herniorrhaphy

Objective This study aims to investigate the effect of different induction rates of propofol monitored by bispectral index(BIS)on the early postoperative cognitive function in elderly patients undergoing laparoscopic inguinal herniorrhaphy.Methods 180 elderly patients scheduled for elective laparoscopic inguinal herniorrhaphy were selected and randomly divided into three groups(n=60):the induction rate of propofol was 30 mg/(kg·h)(group A),100 mg/(kg·h)(group B),300 mg/(kg·h)(group C).Anesthesia was induced using a microinfusion pump,and the depth of anesthesia was monitored using BIS.The end point of propofol induction was the first drop in BIS to 60 or below,the end point of propofol induction was that the patient’s BIS value dropped to 60 or below,or the induction dose of propofol reached 2.5 mg/kg.The primary result of this study was the incidence of postoperative cognitive decline(POCD)in elderly patients on postoperative day 1 and 7,mainly by Mini-Mental State Examination(MMSE)and Montreal Cognitive assessment(Montreal Cognitive Assessment,MoCA)scale to assess in this study.Secondary results included the induction dose of propofol,the incidence of burst suppression and the use of vasoactive agents during induction of anesthesia,the maximum electroencephalogram(EEG)effect(BIS-min)of propofol during the induction period.The determined levels of biomarkers(S-100β,IL-6)related to postoperative cognition in serum.Multivariate regression analysis of possible risk factors related to the occurrence of POCD in this study was conducted in order to find the risk factors related to POCD.Results The incidence of POCD on the first day after surgery(group A:5 cases,8.6%VS.group B:7 cases,11.9%VS.group C:10 cases,16.9%;P=0.389)and the incidence of POCD at 7 days after surgery(group A:2 cases,3.4%VS.group B:3 cases,5.1%VS.group C:5 cases,8.5%;P=0.493)were similar,the serum levels of S-100βand IL-6 in the three groups were similar,and there was no significant difference among the three groups.However,with the increase of propofol induction rate,the dose of propofol required for induction,the incidence of burst suppression during the induction period,the number of patients requiring vasoactive agents during the induction period,and the maximum EEG effect of propofol were significantly increased(P<0.001).Regression analysis found that age[OR,1.11(1.01-1.23);P=0.043]and hospital stay[OR,1.71(1.29-2.27);P<0.01]were independent risk factors for POCD.Conclusion Reducing the induction rate of propofol did not improve the incidence of early POCD in elderly patients undergoing laparoscopic inguinal herniorrhaphy,but it can reduce the induction dose of propofol,the incidence of burst suppression and the use of vascular agents during the induction period.Age and length of hospital stay were independent risk factors for POCD.In clinical practice,slow induction rate[such as 30 mg/(kg·h)]is recommended for propofol anesthesia in elderly patients.