Clinical outcomes of acute kidney injury developing outside the hospital in elderly

Although various studies have improved our knowledge about the clinical features and outcomes of acute kidney injury developing in the hospital (AKI-DI) in elderly subjects, data about acute kidney injury developing outside the hospital (AKI-DO) in elderly patients (age ≥ 65 years) are still extremely limited. This study was performed to investigate prevalence, clinical outcomes, hospital cost and related factors of AKI-DO in elderly and very elderly patients.

We conducted a prospective, observational study in patients (aged ≥ 65 years) who were admitted to our center between May 01, 2012, and May 01, 2013. Subjects with AKI-DO were divided into two groups as “elderly” (group 1, 65–75 years old) and “very elderly” (group 2, >75 years old). Control group (group 3) consisted of the hospitalized patients aged 65 years and older with normal serum creatinine level. In-hospital outcomes and 6-month outcomes were recorded. Rehospitalization rate within 6 months of discharge was noted. Hospital costs and mortality rates of each group were investigated. Risk factors for AKI-DO were determined.

The incidence of AKI-DO that required hospitalization in elderly and very elderly patients was 5.8 % (136/2324) and 11 % (100/905), respectively (p < 0.001), with an overall incidence of 7.3 % (236/3229). Chronic kidney disease (CKD) was developed in 43.4 % of group 1 and 67 % of group 2 within the 6 months of discharge (p < 0.001). Progression to CKD was significantly lower in the control group than in groups 1 and 2 (p < 0.001). Mortality rates for groups 1, 2 and 3 were 23.5 % (n = 32), 31 % (n = 31) and 4.2 % (n = 8), respectively (p < 0.05). Rehospitalization rate within the 6 months of discharge for the groups with AKI-DO was higher than for the control group (p < 0.001). Hospital cost of groups 1 and 2 was significantly higher than that of the control group (p < 0.001). Nonsteroidal anti-inflammatory drugs (NSAIDs) (OR: 6.839, 95 % CI = 4.392–10.648), angiotensin-converting enzyme inhibitors (ACEI) (OR: 7.846, 95 % CI = 5.161–11.928), angiotensin receptor blockers (ARB) (OR: 6.466, 95 % CI = 4.813–8.917), radiocontrast agents (OR: 8.850, 95 % CI = 5.857–13.372), hypertension (OR: 4.244, 95 % CI = 2.729–6.600), diabetes mellitus (OR: 2.303, 95 % CI = 1.411–3.761), heart failure (OR: 3.647, 95 % CI = 2.276–5.844) and presence of infection (OR: 3.149, 95 % CI = 1.696–5.845) were found as the risk factors for AKI-DO in elderly patients (p < 0.001 for all). Patients with AKI-DO had higher 6-month mortality rate (HR 1.721, 95 % CI: 1.451–2.043, p < 0.001). Mortality risk increased 0.519 times at 20th day.

The incidence of AKI-DO requiring hospitalization is higher in very elderly patients than elderly ones, especially in male gender. Use of ACEI, ARB, NSAID and radiocontrast agents is the main risk factors for the development of AKI-DO in the elderly.