To explore the effect of Narcotrend (Nt) monitoring on postoperative delirium in the elderly after hip and knee replacements.

The patients with unilateral hip or knee arthroplasty in the First Affiliated Hospital of Chongqing Medical University and aged over 60 years were included in the study. They were randomly divided into the Nt monitoring group (n=65, the anesthesia depth was controlled by the Nt index to D1-E0) and the control group (n=71, the anesthesia depth was controlled by the experience of anesthesiologists). The data were recorded, including the operation position, education level, the dosage of general anesthesia, nerve block rate, the postoperative hospital stay, the confusion assessment method(CAM) scores and incidence of postoperative nausea and vomiting on the postoperative first and third day, the level of serum CRP on the first day before operation and the first, third and fifth day after operation, and the level of serum IL-6 on the first day before operation and the third and fifth day postoperation. According to the type of data, independent-sample t test or chi-square test were used to compare the differences between groups. Rank sum test was used to analyze the difference of inflammatory factors. Spearman and binary logistic regression analysis were used for correlation analysis.

When compared with the control group, the POD in the Nt group on the first and third day after operation had no difference 21.1% vs 9.2% (χ²=3.678, P >0.05)on the first postoperative day; 22.5%vs 18.5% on the third postoperative day (χ²=0.344, P >0.05). The dosage of propofol in Nt group was less than that in the control group (245.63±84.48)mg vs (303.64±127.38)mg(t=-3.131, P<0.01). There was no difference in the levels of serum IL-6(U=505, 590, 445, all P>0.05) and CRP(U=2 090, 2 165, 1 687, 505, all P>0.05) after operation between Nt group and the control group. Regression analysis suggested that nerve block and age could independently influence the risk of POD.

Nt monitoring can reduce the dosage of propofol when compared with usual monitoring for the hip and knee replacement in the elderly, but it can not decrease the incidence of POD.