Recurrent acute kidney injury in elderly patients is common and associated with 1-year mortality.

Background: Acute kidney injury (AKI) is common among elderly patients after a first hospitalized AKI. Patients who recover are at risk for recurrence, but recurrent geriatric AKI is not well-studied. Methods: This was a retrospective, 12-month cohort study using data from the National Clinical Research Center for Geriatric Diseases. Recurrent AKI was defined as a new spontaneous rise of ≥ 0.3 mg/dl (≥ 26.5 µmol/L) within 48 h or a 50% increase in serum creatinine (Scr) from the baseline within 7 days after the previous AKI episode. The outcome measured was 12-month mortality. Results: Among 1711 study patients, 652 developed AKI. Of the 429 AKI survivors in whom recovery could be assessed, 314 patients recovered to their baseline renal function, and 115 patients developed chronic kidney disease (CKD). Of the group that recovered renal function, 90 patients (28.7%) subsequently developed recurrent AKI, while 224 (71.3%) did not. Of the 429 survivors with AKI, 103 patients (24.0%) died within 12 months. Multivariate logistic regression analysis revealed that recurrent AKI was significantly associated with coronary disease (odds ratio [OR = 2.008; 95% confidence interval [CI] 1.024–3.938; P = 0.042), a need for mechanical ventilation (OR = 2.265; 95% CI 1.267–4.051; P = 0.006) and high blood urea nitrogen levels (OR = 1.036; 95% CI 1.002–1.072; P = 0.040) at the first AKI event. Kaplan–Meier curves showed the 12-month survival of patients with non-recurrent AKI was better than that of patients with CKD, and survival of patients with recurrent AKI was worse than that of patients with CKD (log rank P < 0.001). In the multivariate Cox regression analysis, mortality at 12 month was higher in the patient with recurrent AKI as compared with those with a single episode (HR = 3.375; 95% CI 2.241–5.083; P < 0.001). Conclusion: Recurrent AKI is common among elderly patients who recovered their renal function post-AKI and is associated with significantly higher 12-month mortality compared with CKD patients. [ABSTRACT FROM AUTHOR]