Neutrophil–lymphocyte ratio as predictor of mortality and morbidity in cardiovascular surgery: a systematic review

BACKGROUND: Neutrophil-lymphocyte ratio (NLR) is an emerging biomarker of inflammation and predicts poorer outcome in cancer surgery. The prognostic value of NLR in cardiovascular surgery is unclear. METHODS: Systematic review and meta-analysis of studies of in cardiovascular surgical patients were conducted to assess the role of perioperative NLR in predicting post-operative mortality and morbidity. Electronic searches were conducted on Ovid Medline, EMBASE, Cochrane Central Register of Controlled Trials and Cochrane Database of Systemic Reviews for all prospective clinical studies reporting on NLR and post-operative morbidity and mortality in cardiovascular surgical patient population. Our primary end point was all-cause post-operative mortality and the secondary end point was post-operative morbidity. Mortality outcome from prospective studies were pooled for a meta-analysis using a random-effect model. RESULTS: Of the 999 citations identified, five studies with 3487 patients met the inclusion criteria. In a pooled analysis of three prospective studies of 3108 patients, a preoperative increase in NLR (>3.3 in cardiac surgery, >5 in vascular surgery) was associated with increased mortality at a mean follow-up of 34.8 months (hazard ratio 1.85, 95% confidence interval 1.46-2.36; P < 0.00001). Raised NLR value was also associated with increased cardiac mortality, amputation in vascular operations and raised risk of post-operative re-intubation. CONCLUSIONS: Elevated NLR were associated with increased long-term mortality and morbidity after major cardiac and vascular surgery. NLR may guide perioperative management and risk-stratification of patients.