Background and aims: Follow-up observation was performed on elderly acute kidney injury (AKI) patients to analyze the short-term prognosis and risk factors of AKI patients in the 48-h diagnostic window and 7-day diagnostic window of the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines.
Methods: Inpatients aged ≥ 75 years in the geriatric ward of the People's Liberation Army General Hospital, China, between January 2007 and December 2015 were selected as the research subjects. According to two diagnostic criteria in the KDIGO guidelines, patients were divided into a 48-h diagnostic window group and a 7-day diagnostic window group. The medical data of the patients were divided into the death group and the survival group for analysis based on the survival condition of the patients after 90 days of AKI. Factors that affected the 90-day survival of patients in the 48-h diagnostic window and 7-day diagnostic window groups were analyzed using multivariate Cox regression.
Results: During the follow-up period, a total of 652 patients were enrolled in this study. Among them, 623 cases were men, accounting for 95.6% of the patients. The median age was 87 (84-91) years. According to the KDIGO staging criteria, there were 308 (47.2%) cases in AKI stage 1, 164 (25.2%) cases in stage 2, and 180 (27.6%) cases in stage 3. Among the 652 patients, 334 (51.2%) were diagnosed with AKI based on the 48-h diagnostic criteria window, and 318 (48.8%) were diagnosed with AKI based on the baseline 7-day diagnostic criteria. The 90-day mortality of AKI patients was 42.5% in the 48-h diagnostic window and 24.2% in the 7-day diagnostic window. The multivariate Cox analysis results showed that low mean arterial pressure (HR = 0.966; P < 0.001), low serum prealbumin level (HR = 0.932; P < 0.001), infection (HR = 1.448; P = 0.047), mechanical ventilation (HR = 1.485; P = 0.038), high blood urea nitrogen (BUN) level (HR = 1.026; P < 0.001), blood magnesium level (HR = 2.560; P = 0.024), and more severe AKI stage (stage 2: HR = 3.482; P < 0.001 and stage 3: HR = 6.267; P < 0.001) were independent risk factors affecting the 90-day mortality of elderly patients in the 48-h diagnostic window, whereas low body mass index (HR = 0.851; P < 0.001), low mean arterial pressure (HR = 0.980; P = 0.036), low serum prealbumin level (HR = 0.950; P = 0.048), low serum albumin level (HR = 0.936; P = 0.015), high BUN level (HR = 1.046; P < 0.001), and more severe AKI stage (stage 2: HR = 4.249; P = 0.001 and stage 3: HR = 9.230; P < 0.001) were independent risk factors affecting the 90-day mortality of elderly patients in the 7-day diagnostic window.
Conclusions: The clinical differences of AKI and risk factors for 90-day mortality in elderly AKI individuals vary depending on the definition used. An increment of Scr ≥ 26.5 μmol/L in 48 h (48-h KDIGO window) alone predicts adverse clinical outcomes.
Keywords: AKI diagnosis window; Acute kidney injury; Short-term mortality; Very elderly.