The neutrophil-lymphocyte ratio is associated with postoperative mortality of cardiac surgery

BACKGROUND: The neutrophil-lymphocyte ratio (NLR) has been recognized as a useful marker of poor prognosis in non-cardiac surgery patients. But, the prognostic function of NLR in cardiovascular surgery patients still largely unknown. The aim of this study was to explore the relationship between postoperative NLR and mortality in cardiac surgery patients. METHODS: Clinical data were extracted from the Medical Information Mart for Intensive Care III (MIMIC-III) database. Postoperative day 1 (POD-1) NLR of the patients was calculated. All patients were divided into two groups according to the cut-off value of NLR, which was determined using the receiver operating characteristic (ROC) curve and Youden Index. The primary death outcomes were 30-day, 90-day and 1-year mortality. Cox proportional hazard analysis was performed to assess the associations between NLR and 1-year mortality. Logistic analysis was performed to assess the associations between NLR and other outcomes. Multivariate analyses were used to control for confounders. RESULTS: A total of 2,707 cardiac surgery patients were included in this study. The cut-off value of postoperative NLR was 7.28. Elevated postoperative NLR was associated with increased death outcomes including 30-day mortality [adjusted odds ratio (OR) 2.25, P=0.019], 90-day mortality (adjusted OR 2.49, P=0.001) and 1-year mortality [adjusted hazard ratio (HR) 1.58, P=0.03] of cardiac surgery in cox proportional hazard model. Elevated NLR was also associated with increased risk of continuous renal replacement therapy (CRRT) rate (adjusted OR 3.01, P=0.004), prolonged ICU stays (adjusted OR 2.55, P<0.001), prolonged hospital stays (adjusted OR 3.32, P<0.001) and duration of ventilatory support (adjusted OR 4.16, P<0.001) after adjusting confounders. CONCLUSIONS: Elevated postoperative NLR was significantly associated with increased short-term and long-term mortality, CRRT rate, longer ICU and hospital stay, prolonged ventilation in patients undergoing cardiac surgery. NLR is promising to be a readily available and independent prognostic biomarker for patients with cardiac surgery.