Association of neutrophil-to-lymphocyte ratio with outcomes after elective abdominal aortic aneurysm repair

Abstract

Data are lacking regarding real-time prediction of postoperative complications after elective aneurysm repair. The neutrophil-to-lymphocyte ratio (NLR) has been evaluated as a predictor of outcomes after cardiac and infrapopliteal interventions and is associated with poor outcomes for critical limb ischemia. We examined NLR and outcomes after abdominal aortic aneurysm (AAA) repair. Inpatients undergoing elective AAA repair (2008 to 2015) were selected from the Cerner Health Facts database using International Classification of Disease (9th edition) procedure codes. Postoperative outcomes were identified using data from patient records within 1week after surgery. NLR was calculated by dividing the absolute neutrophil count by the absolute lymphocyte count. The receiver operating characteristic curve was analyzed to define low and high postoperative NLR groups. Chi-square analysis and multivariable logistic regression models were used to identify characteristics (demographics, diagnoses, postoperative NLR) associated with postoperative complications. Elective AAA repair occurred in 5,655 patients. Of these, we could calculate postoperative NLR for 1,908 (34%), with 1,529 undergoing endovascular repair and 379 undergoing an open repair. Compared with patients with low postoperative NLR, patients with high postoperative NLR experienced longer hospital stays (5.7 vs 2.6days, P<.0001); higher rates of in-hospital death (2.9% vs 1.4%, P=.002); higher rates of renal failure (11.6% vs 3.9%, P<.0001); cardiac problems or myocardial infarction (3.8% vs 1.2%, P=.0002); respiratory problems (13.3% vs 5.8%, P<.0001); and infection (8.9% vs 2.9%, P<.0001). The association between high postoperative NLR and adverse postoperative outcomes persisted on multivariable analysis. This included infection (odds ratio [OR], 2.59; 95% confidence interval [CI], 1.65-4.07), renal failure (OR, 2.19; 95% CI, 1.45-3.31), cardiac events (OR, 2.41; 95% CI, 1.21-4.77), and respiratory problems (OR, 1.73; 95% CI, 1.22-2.45).NLR was associated with adverse outcomes after elective endovascular and open AAA repair. An elevated NLR within 1week after surgery was strongly associated with postoperative complications, and may identify at-risk patients who require closer follow-up. Given the perilous nature of vascular surgery and the risk-benefit ratio for prophylactic aneurysm repair, future study of postoperative outcome and preoperative NLR is needed to provide clinically important risk profiles before treatment decisions.