Acute Kidney Injury Developed in the Intensive Care Unit: A Population-based Prospective Cohort Study in the Brazilian Amazon

Abstract Background The Brazilian Amazon is a vast area with limited health care resources and scarce data on the epidemiology of acute kidney injury (AKI). We aimed to assess the epidemiology of critically ill AKI patients in this area. Methods This was a prospective cohort study of patients aged > 18 years with residential addresses in the Acre state who stayed ≥ two days in one of the three intensive care units (ICUs) of Rio Branco city, the capital of Acre state. The incidence, risk factors and outcomes of AKI (Kidney Disease: Improving Global Outcomes (KDIGO) criteria) developed in ICU were evaluated. Admitted patients were followed for up to seven days or until discharge or death, whichever occurred first. Results Of 1,494 patients admitted, 1,029 met the inclusion criteria. The incidence of AKI was 53.3% (37.8% had maximum KDIGO stage 3); 7.7% received kidney replacement therapy. Most cases of incident ICU AKI (74.1%) developed in the first three days of ICU hospitalization, and 68.1% were transient. The majority of patients (84.5%) had at least one comorbidity, 19.6% were hemodynamically unstable, and 15.3% had respiratory failure at ICU admission. Only 1.7% of the patients had tropical diseases. Risk factors for AKI included higher age, nonsurgical patients, admission to the ICU from the ward, higher Acute Physiology and Chronic Health Evaluation (APACHE) II scores at ICU admission, and positive fluid balance > 1500 ml/24 hours in the days before AKI development in the ICU. AKI was associated with higher ICU mortality (adjusted odds ratio 2.04, 95% confidence interval (CI) 1.30–3.18). AKI mortality was independently associated with higher age, nonsurgical patients, sepsis at ICU admission, mechanical ventilation and mean positive fluid balance in the ICU > 1500 ml/24 hours during ICU follow-up. Adjusted hazard ratios for AKI mortality 30 and 180 days after ICU discharge were 2.52, 95% CI 1.39–4.56 and 2.01, 95% CI 1.05–3.85, respectively. Conclusions AKI incidence was strikingly high among critically ill patients in the Brazilian Amazon. Hospitalizations due to tropical diseases were rare. The AKI etiology, risk factors and outcomes were similar to those described in high-income countries, but mortality rates were higher.