Preoperative and early postoperative neutrophil-to-lymphocyte ratio for predicting delirium after laparoscopic gynecologic surgery in elderly women: a retrospective cohort study with an outcome-matched nested case-control analysis and internal validation.

BACKGROUND: Postoperative delirium (POD) is a common complication in older surgical patients. Neutrophil-to-lymphocyte ratio (NLR) is an inexpensive marker of systemic inflammation; however, its role in predicting POD after laparoscopic gynecological surgery has not been well-characterized.

METHODS: POD on postoperative days 0-7 was assessed using the Confusion Assessment Method (CAM) or the CAM-intensive care unit (ICU). Inflammatory indices determined preoperatively and on postoperative day 1, including the NLR, were evaluated in a retrospective cohort (n = 356). Outcome-matched (nested case-control) 1:1 propensity score-matched cohort of patients with and without POD (111 per group) was constructed, and the associations were examined using multivariate logistic regression. Model discrimination was assessed using area under the receiver operating characteristic curve (AUC).

RESULTS: POD occurred in 111 of the 356 patients (31.2%). In the matched cohort, the preoperative NLR was higher in patients with POD than in those without POD (7.7 vs. 3.2). In multivariate analyses, both preoperative NLR (adjusted odds ratio [OR]: 1.29 per unit increase) and postoperative NLR (adjusted OR: 1.08 per unit increase) were associated with POD. AUC of the clinical prediction model was 0.68, which increased to 0.78 with the addition of preoperative NLR and to 0.84 with the inclusion of both pre- and postoperative NLR. The optimal preoperative cutoff NLR was 7.1.

CONCLUSIONS: In elderly women undergoing laparoscopic gynecologic surgery, the preoperative NLR was associated with POD within 7 days postoperatively. Incorporation of the NLR into clinical prediction models may facilitate perioperative risk stratification.