Preoperative Geriatric Nutritional Risk Index Score as a Novel Predictor of Postoperative Acute Kidney Injury in...

Malnutrition could be a risk factor for postoperative acute kidney injury (AKI). The geriatric nutritional risk index (GNRI) is a simple indicator of malnutrition, and this study examined the association of preoperative GNRI with postoperative AKI in noncardiac surgery.

A retrospective cohort study.

Adults who underwent noncardiac surgery under general anesthesia from 2007-2011 were included. Obstetric or urologic surgery, missing serum creatinine, baseline estimated glomerular filtration rate <15 mL/min/1.73 m², and preoperative dialysis were excluded.

Preoperative GNRI.

AKI within 7 days after surgery.

Multivariable logistic regression and restricted cubic spline analysis were performed to examine the association of preoperative GNRI with AKI.

Among 5,148 patients, 301 (5.8%) developed AKI. After adjustment for potential confounders, preoperative lower GNRI scores were independently associated with higher incidence of postoperative AKI (adjusted OR [95% confidence interval], 1.20 [0.84-1.73], 1.37 [0.91-2.06], and 1.88 [1.11-3.20] for those with mild [92 ≤ GNRI < 98], moderate [82≤ GNRI <92], and severe [GNRI <82] malnutrition, respectively (P for trend = 0.02]). Restricted cubic spline analysis confirmed a monotonous increase in ORs for AKI at GNRI levels <98. Subgroup analyses suggested the association was similar across age, different reasons for surgery, and C-reactive protein levels (P for interaction = 0.78, 0.55, and 0.84, respectively). In sensitivity analyses, the association of GNRI with AKI was consistent using multiple imputations on missing data. Multinomial logistic regression indicated severe malnutrition tended to be associated with more severe AKI.

The presence of residual unknown confounders is a concern although a maximal effort was made to adjust for possible confounders.

Lower GNRIs were independently associated with postoperative AKI irrespective of patients' age, malignancy, or inflammation. Improvement of preoperative malnutrition may reduce postoperative AKI.