Accuracy of plasma and urine neutrophil gelatinase-associated lipocalin concentrations in predicting postoperative delirium in elderly patients

Abstract

Objective To evaluate the accuracy of plasma and urine neutrophil gelatinase-associated lipocalin (NGAL) concentrations in predicting postoperative delirium in elderly patients. Methods From November 2014 to March 2015, 70 patients of either sex who underwent total unilateral hip or knee replacement, aged 65-85 yr, with body mass index of 18-25 kg/m2, of American Society of Anesthesiologists physical status Ⅱ or Ⅲ, were selected.The Confusion Assessment Method for the Intensive Care Unit was used to assess the development of postoperative delirium at 24, 48 and 72 h after operation.The patients were divided into either delirium group or non-delirium group according to whether or not postoperative delirium occurred.At 5 min before anesthesia induction, immediately after extubation, and at 24 and 72 h after operation, the midstream urine samples and peripheral venous blood samples were collected for determination of the urine and plasma NGAL concentrations by immuno-enhanced turbidimetry.At 5 min before anesthesia induction, and 24 and 48 h after operation, the serum creatinine and cystatin C concentrations were detected, and the development of postoperative acute kidney injury was recorded.The receiver operating characteristic curve for urine and plasma NGAL concentrations in diagnosing postoperative delirium was plotted, and the area under the curve and 95% confidence interval were calculated.The critical value and sensitivity and specificity were calculated according to the corresponding concentrations of NGAL in urine and plasma when Youden index reached the maximal value. Results The incidence of postoperative delirium was 15%.Compared with non-delirium group, the plasma NGAL concentrations were significantly increased immediately after extubation, and the urine NGAL concentrations were significantly increased immediately after extubation and at 24 h after operation in delirium group(P 0.05). Postoperative acute kidney injury was not found in the two groups.The area under the curve (95% confidence interval) for urine NGAL concentrations measured immediately after extubation in predicting postoperative delirium was 0.736 (0.509-0.946), the critical value was 149.1 ng/ml, the sensitivity 60%, and the specificity 97%.The area under the curve (95% confidence interval) for urine NGAL concentrations measured at 24 h after operation in predicting postoperative delirium was 0.785 (0.565-0.998), the critical value was 131.5 ng/ml, the sensitivity 60%, and the specificity 82%.The area under the curve (95% confidence interval) for plasma NGAL concentrations measured immediately after extubation in predicting postoperative delirium was 0.772 (0.580-0.965), the critical value was 107.9 ng/ml, the sensitivity 80%, and the specificity 79%.The area under the curve (95% confidence interval) for plasma NGAL concentrations at 24 h after operation in predicting postoperative delirium was 0.679 (0.524-0.835), the critical value was 153.65 ng/ml, the sensitivity 70%, and the specificity 90%. Conclusion The plasma and urine NGAL concentrations measured immediately after extubation can accurately predict the development of postoperative delirium in elderly patients. Key words: Proto-oncogene proteins; Forecasting; Delirium; Postoperative complications; Aged