Relationships between preoperative neutrophil/lymphocyte ratio and postoperative delirium in elderly patients / 中华麻醉学杂志

ABSTRACT

Objective:To evaluate the relationship between the preoperative neutrophil/lymphocyte ratio(NLR) and postoperative delirium (POD)in elderly patients.Methods:Nine hundred and thirty-seven patients, undergoing elective knee or hip arthroplasty under combined spinal and epidural anesthesia, in whom Mini-Mental State Examination was completed at 1 day before operation, with Mini-Mental State Examination score≥24, were selected. Elbow venous blood samples were collected before surgery, neutrophils and lymphocytes were counted, and the ratio of neutrophils to lymphocytes was calculated.Cerebrospinal fluid (CSF) 2 ml was extracted after successful spinal-epidural puncture for measurement of preoperative amyloid beta40 (Aβ40), amyloid beta42 (Aβ42), total Tau (T-tau), and phosphorylated Tau (P-tau) by enzyme-linked immunosorbent assay. POD was assessed by Confusion Assessment Method, and the severity of POD was assessed by the Memorial Delirium Assessment Scale.The logistic regression equation was used to identify the risk factors for POD, and the mediating effect of CSF biomarkers was analyzed. Sensitivity analysis was used to test the stability of the results. The receiver operating characteristic curve was introduced, and the area under the curve was calculated to evaluate the accuracy of preoperative NLR in predicting POD.Results:A total of 853 patients were finally enrolled in this study, and 17.4% patients developed POD. Logistic regression analysis showed that the increased levels of NLR ( OR 1.141, 95% confidence interval [ CI] 1.033-1.260, P=0.010), P-tau in CSF ( OR 1.093, 95% CI 1.076-1.110, P<0.001) and T-tau in CSF( OR 1.003, 95% CI 1.001-1.005, P<0.001) were risk factors for POD, while the increased level of Aβ42 in CSF( OR 0.998, 95% CI 0.997-1.000, P=0.028) was a protective factor for POD after adjusting for multiple confounding factors. Analysis of mediating effect: T-tau and P-tau in CSF were the mediating factors in the relationship between NLR and POD with the mediating effects of 0.011 9 and 0.020 0 respectively, and the proportion of mediating effect was 46.1% and 53.1% respectively.The receiver operating characteristic curve showed that the area under the curve of NLR and combination of NLR and CSF biomarkers in predicting POD was 0.711 and 0.939 respectively. Conclusions:Increased preoperative NLR level is a risk factor for POD, and combination of NLR and CSF biomarkers shows a higher accuracy in predicting POD. T-tau and P-tau in CSF serve as the key mediators in the relationship between NLR and POD.