Hospital-acquired acute kidney injury in very elderly men: clinical characteristics and short-term outcomes

Objectives We explored the risk factors for, and the clinical characteristics of, acute kidney injury (AKI), and the causes of death 28 days after such injury, in very elderly men. Methods This was a retrospective cohort study using data from the Geriatric Department of the Chinese PLA General Hospital. A total of 3464 elderly patients (>= 75 years) were enrolled from January 2007 to December 2015. All patients were followed for 28 days or until death after AKI. Results In total, 668 patients (39.0%) developed AKI, and 623 men were included for the final analysis. The median age was 87 years. The 28-day mortality rate was 25.7%. The AKI etiologies were infections (39.6%), hypovolemia (23.8%), cardiovascular events (15.9%), nephrotoxicity (12.0%), and surgery (7.1%). Multiple organ dysfunction syndrome (46.4%) and pulmonary infection (22.5%) were the principal causes of death. Multivariate analysis revealed that time for AKI to develop (HR = 0.865; 95% CI 0.799-0.937;P < 0.001), low mean arterial pressure (HR = 0.970; 95% CI 0.958-0.981;P < 0.001), low serum prealbumin (HR = 0.924; 95% CI 0.894-0.955;P < 0.001) level, oliguria (HR = 2.261; 95% CI 1.424-3.590;P = 0.001), mechanical ventilation (HR = 1.492; 95% CI 1.047-2.124;P = 0.027), blood urea nitrogen (HR = 1.037; 95% CI 1.025-1.049;P < 0.001) level, magnesium (HR = 2.512; 95% CI 1.243-5.076;P = 0.010) level, and more severe AKI stages (stage 2: HR = 3.709; 95% CI 1.926-7.141;P < 0.001 and stage 3: HR = 5.660; 95% CI 2.990-10.717;P < 0.001) were independent risk factors for 28-day mortality. Conclusions The incidence of AKI increases significantly as age advanced. Identification of risk factors might lead to more intensive monitoring and early prevention, and might improve AKI patients' outcomes in the very elderly.