Determination of Risk Factors, Incidence, and Mortality Rates of Acute Kidney Injury in COVID-19 Patients Hospitalized in the Intensive Care Unit

TL;DR

This study finds that acute kidney injury is common in ICU patients with severe COVID-19 and is linked to higher mortality and longer hospital stays.

Contribution

The study identifies risk factors and clinical markers for acute kidney injury in ICU COVID-19 patients and evaluates its impact on mortality.

Findings

AKI occurred in 54.6% of ICU COVID-19 patients.

Mortality rates increased with more severe AKI stages.

Lymphopenia and elevated inflammatory markers were associated with severe AKI.

Abstract

Background: Although the main target of SARS-CoV-2 is the respiratory system, in some patients, it may affect multiple organ systems, leading to multi-organ failure. Acute kidney injury (AKI) remains one of the most frequent and clinically significant complications of severe COVID-19, with clinical importance extending beyond the acute phase due to its association with long-term renal outcomes and persistent morbidity. The incidence of AKI is particularly high among patients admitted to the intensive care unit (ICU), where its development has been consistently associated with prolonged hospitalization and increased mortality. The primary aim of this study was to determine the incidence of COVID-19-associated AKI, identify factors related to its development and severity, and evaluate mortality as a clinical outcome. Methods: Data from 238 COVID-19 patients monitored in the Intensive Care Unit of Ankara University Ibni Sina Hospital (ISH-ICU) between 1 January 2021 and 1 January 2022 were retrospectively reviewed. Patients were divided into two groups according to the presence of AKI. Those with AKI were staged according to KDIGO criteria (stages 1–2–3). Demographic characteristics, comorbidities, disease severity scores, laboratory parameters, and mortality outcomes were analyzed and compared between groups. Results: AKI was identified in 54.6% of patients. Of the patients with AKI, 32 (13.4%) had stage 1, 25 (10.5%) had stage 2, and 73 (30.7%) had stage 3 AKI. Thirteen patients (5.5%) had already developed AKI at ICU admission. AKI developed at a median of 11 days after symptom onset and 3 days after ICU admission. Advanced age, hypertension, cardiovascular disease, and chronic kidney disease were more frequent in patients with AKI (p < 0.001). Higher Charlson Comorbidity Index (CCI) and Acute Physiologic Assessment and Chronic Health Evaluation II (APACHE II) scores were observed in patients with stage 3 AKI. Lymphopenia and elevated levels of D-dimer, ferritin, IL-6, CRP, and procalcitonin were significantly higher in patients with stage 3 AKI than in patients with other AKI stages and the non-AKI group. Mortality rates were higher in patients with AKI and increased with advancing AKI stage (p < 0.001). ICU length of stay was significantly longer in the AKI group (p < 0.001). Conclusions: AKI is a common complication among critically ill patients with COVID-19 and is associated with prolonged ICU stay and higher mortality rates, particularly in advanced stages. Early identification of clinical and laboratory factors associated with AKI may support timely risk stratification and targeted management in this high-risk population.