Neutrophil-Lymphocyte Ratio as a Risk Factor for Early Postoperative Cognitive Dysfunction in Off-Pump Coronary Surgical Patients 

Background and Goal of study 
Postoperative cognitive dysfunction (POCD)　is a devastating complication. While the underlying cause of the POCD is multifactorial, systemic inflammation has been implicated in the development of cognitive dysfunction. Neutrophil-lymphocyte ratio (NLR) is an available marker of systemic inflammation. We hypothesize that patients with excessive and prolonged elevated NLR have increased risk of cognitive dysfunction 1 week after off-pump coronary artery bypass grafting (OPCAB).
Materials and Methods
One hundred twenty-seven Japanese patients (>60 y.o.) scheduled for OPCAB were enrolled from 2004 to 2014. All patients underwent preoperative brain magnetic resonance imaging (MRI) and angiography, and intraoperative epiaortic ultrasound to assess prior cerebral infarcts, white matter lesions, craniocervical artery stenosis, and atherosclerosis of the ascending aorta. NLR of preoperative, postoperative day 1 and 6-8 were retrospectively reviewed. Four cognitive tests were performed preoperatively and 1 week after surgery. POCD defined as a decrease of at least 20% from baseline in performance in more than two tests. Statistical comparisons between the POCD and no POCD group were performed using the x2 test and one-way analysis of variance. To assess the predictors of POCD, stepwise logistic regression analysis was performed. 
 Results and Discussion 
POCD was identified in 25 of the 127patients (20%). Although preoperative NLR and NLR of postoperative day 1 were not different between the two groups, patients with POCD had significantly higher NLR during postoperative day 6-8 than those without POCD (5.9+4.7 vs. 3.7+2.4, P<0.01). In the multivariate model, periventricular white matter lesions [odds ratio (OR) 2.3], age>75 y.o. (OR 3.8), male (OR 3.4), and NLR of postoperative day 6-8 (OR: 4.2 [1.4-13.0], P=0.01) were significantly associated with early POCD in OPCAB patients. Systemic inflammation triggers a neuroinflammatory response involving blood-brain barrier, glia and neurons. POCD is likely the consequence of this inflammatory cascade.
Conclusions
The incidence of POCD was 20% (25/127). Periventricular white matter lesions, age>75 y.o., male, and NLR of postoperative day 7 were independent predictors of POCD. Prolonged systemic inflammation is associated with early POCD in off-pump coronary surgical patients. .

Neutrophil-lymphocyte ratio as a risk factor for early postoperative cognitive dysfunction after off-pump coronary surgery