Impact of body mass on outcomes of geriatric postoperative acute kidney injury patients.

Abstract

Acute kidney injury (AKI) frequently occurs in hospitalized patients, particularly in the elderly. However, studies on outcome-modifying factors in geriatric patients with AKI are absent, especially the influence of body mass index (BMI). We performed a retrospective analysis of a prospectively collected multicenter observational cohort, which enrolled elderly (≥65 years) who developed AKI after major surgery in the intensive care units. We analyzed in-hospital mortality within BMI category utilizing Cox proportional hazard regression analysis and generalized additive modeling. Data of a total of 2,015 postoperative elderly patients were retrieved and analyzed. Generalized additive modeling showed that elderly AKI patients with a BMI between 21 and 31 kg/m(2) ("normal") had a lower mortality risk than those with a BMI of less than 21 kg/m(2) ("underweight") or 31 kg/m(2) or greater ("obese"). Both "underweight" and "obese" individuals had a greater risk of mortality compared with patients with "normal" BMI. The U-shaped association of BMI with hospital mortality in geriatric AKI patients contains a widened base and a shifted nadir comparing with chronic dialysis and other AKI patients. This finding is interesting and warrants our attention.