Association of Preoperative Neutrophil-to-Lymphocyte Ratio with Postoperative Acute Kidney Injury and Mortality Following Major Noncardiac Surgeries

BACKGROUND: Acute kidney injury (AKI) is a major complication that occurs following an operation. Therefore, there is an increasing need to discover new predictors of AKI. We hypothesized that the preoperative neutrophil-to-lymphocyte ratio (NLR) was associated with postoperative AKI and in-hospital mortality following noncardiac surgery. METHODS: This is a retrospective observational study of patients who underwent noncardiac surgery at Sichuan University West China Hospital from 2018 to 2020. Multivariable logistic regression was performed as the major analytic method. In addition, sensitivity and subgroup analyses were performed to validate the results. RESULTS: A total of 44,065 patients were included in this study. The prevalence of postoperative AKI was 5.62%, and the in-hospital mortality was 1.58%. Multivariable analysis demonstrated that NLR ≥ 5 was independently associated with the development of postoperative AKI (OR 1.42, 1.24–1.73; P < 0.001) and in-hospital mortality (OR 2.03, 1.63–2.52; P < 0.001). Similar results were achieved when propensity-score matching was performed for patients with NLR ≥ 5 and < 5 on the baseline. In stratified analysis, the associations remained persistent in most subgroups. For the sensitivity analysis, we took NLR as a continuous variable and demonstrated the potential linear relationship between NLR and postoperative AKI and mortality. CONCLUSIONS: Our results indicated that preoperative NLR is associated with the prevalence of postoperative AKI and in-hospital mortality that occur after major noncardiac surgery. These findings suggest that NLR has the potential to be a significant correlation biomarker associated with perioperative risk assessment of patients undergoing noncardiac surgeries.