Neutrophil-To-Lymphocyte Ratio as a Predictive Tool for Post-Operative Outcomes in Patients Undergoing Open Lower Extremity Revascularization Procedures

Abstract

Elevated neutrophil-to-lymphocyte ratio (NLR), a marker of systemic inflammation, has been shown to correlate with worse outcomes in patients undergoing vascular surgery. Limited data exists on the association of NLR and outcomes in patients undergoing lower extremity vascular surgery. We sought to investigate whether preoperative NLR correlates with outcomes in patients undergoing open lower extremity revascularization procedures. We conducted a retrospective analysis of a prospectively maintained database of patients who underwent open lower extremity revascularization procedures from January 2011 to January 2017 (N=535). Preoperative NLR was calculated within 6months of surgery. Primary outcomes were major adverse limb event (MALE) or death. The maximally-ranked statistic method was used to determine the NLR cut-off point. Kaplan-Meier analyses of death and MALE and NLR were used to compare the groups by NLR cut-off point. We conducted a multivariate analysis of the association between NLR and mortality using Cox proportional hazard models, including confounding variables such as age, smoking status, and diabetes. P-values <0.05 were considered statistically significant. Two hundred and fifty four patients undergoing surgery from January 2011 to January 2013 were analyzed. The median NLR was 3.6 interquartile range [IQR 2.5-6.7]. The analysis showed a negative correlation between elevated NLR and mortality (P<0.001), but not MALE (P=0.8). Controlling for multiple comorbidities including gender, age, smoking, body mass index (BMI), diabetes, hyperlipidemia, hypertension, and infection, the NLR cut-off point was a significant independent predictor of mortality (P<0.0001), but not MALE (P=0.551). Elevated NLR was also correlated with statistically and clinically significant longer hospital stays (6.5 [IQR 3.0-12.8] days vs. 4.0 [IQR 2.0-8.0] days, P=0.027). This study suggests that NLR is an independent predictor of mortality and hospital length of stay in patients undergoing open lower extremity revascularizations. Going forward, we plan to expand this study to include more patients and to compare NLR to other risk assessment tools.