Acute kidney injury in nonagenarians: clinical characteristics and mortality.

Introduction: Nonagenarians constitute a rising percentage of inpatients, with acute kidney injury (AKI) being frequent in this population. Thus, it is important to analyze the clinical characteristics of this demographic and their impact on mortality.

Methods: Retrospective study of nonagenarian patients with AKI at a tertiary hospital between 2013 and 2022. Only the latest hospital admission was considered, and patients with incomplete data were excluded. A logistic regression analysis was conducted to define risk factors for mortality. A p-value < 0.05 was considered statistically significant.

Results: A total of 150 patients were included, with a median age of 93.0 years (91.2-95.0), and males accounting for 42.7% of the sample. Sepsis was the most common cause of AKI (53.3%), followed by dehydration/hypovolemia (17.7%), and heart failure (17.7%). ICU admission occurred in 39.3% of patients, mechanical ventilation in 14.7%, vasopressors use in 22.7% and renal replacement therapy (RRT) in 6.7%. Death occurred in 56.7% of patients. Dehydration/hypovolemia as an etiology of AKI was associated with a lower risk of mortality (OR 0.18; 95% CI 0.04-0.77, p = 0.020). KDIGO stage 3 (OR 3.15; 95% CI 1.17-8.47, p = 0.023), ICU admission (OR 12.27; 95% CI 3.03-49.74, p < 0.001), and oliguria (OR 5.77; 95% CI 1.98-16.85, p = 0.001) were associated with mortality.

Conclusion: AKI nonagenarians had a high mortality rate, with AKI KDIGO stage 3, oliguria, and ICU admission being associated with death.