The impact of transient and persistent acute kidney injury on short-term outcomes in very elderly patients

Objectives: Acute kidney injury (AKI) is a common complication in elderly patients and is associated with poor outcomes. However, the effect of transient and persistent geriatric AKI on short-term mortality is unclear. We aimed to study the incidence, clinical characteristics, and prognostic impact of transient and persistent AKI in such patients. Methods: We retrospectively enrolled very elderly patients (>= 75 years) from the geriatric department of the Chinese PLA General Hospital between 2007 and 2015. AKI was defined according to the 2012 Kidney Disease: Improving Global Outcomes criteria. AKI patients were divided into transient or persistent AKI groups based on their renal function at 3 days post-AKI. Renal function recovery was defined as a return to the baseline serum creatinine (SCr) levels. Results: In total, 668 geriatric patients (39.0%) experienced AKI, and 652 satisfied the inclusion criteria. Of these 652 patients, 270 (41.4%) had transient AKI, and 382 (58.6%) had persistent AKI. The 90-day mortality was 5.9% in patients with transient AKI and 53.1% in patients with persistent AKI. Multivariate analysis revealed that low hemoglobin levels (odds ratio [OR] = 0.989; 95% CI: 0.980-0.999; P=0.025), low mean aortic pressure (OR =0.985; 95% CI: 0.971-1.000; P=0.043), peak SCr (OR =1.020; 95% CI: 1.015-1.026; P<0.001) levels, high uric acid (OR = 1.002; 95% CI: 1.000-1.003; P=0.040) levels, high blood urea nitrogen (OR =1.028; 95% CI: 1.000-1.056; P=0.047) levels, and mechanical ventilation requirements (OR =1.610; 95% CI: 1.012-2.562; P=0.044) were associated with persistent AKI. Persistent AKI (hazard ratio [HR] = 5.741; 95% CI: 3.356-9.822; P<0.001) and more severe AKI stages (stage 2: HR = 3.363; 95% CI: 1.973-5.732; P<0.001 and stage 3: HR =4.741; 95% CI: 2.807-8.008; P<0.001) were associated with 90-day mortality. Conclusion: AKI is common in very elderly patients, with transient renal injury representing close to 42% of all cases of geriatric AKI. More frequent SCr measurements may be helpful for the early diagnosis of transient geriatric AKI. Persistent geriatric AKI is independently associated with a significantly higher risk of 90-day mortality.