Clinical implications of persistently increased blood urea nitrogen/serum creatinine ratio (PI-BUN/Cr) in severe COVID-19 patients

Patients with COVID-19 may experience a persistent increase in the blood urea nitrogen over creatinine ratio (PI-BUN/Cr). Its elevation could reflect multiple underlying pathophysiological processes beyond prerenal injury but also warrants nuanced interpretation due to its complex interplay with various factors, underscoring the importance of investigating its effects on mortality and acute kidney injury in this population. We analized a retrospective and longitudinal cohort of patients admitted to a single center in Mexico City for patients with severe COVID-19. Between March 5, 2020 and August 25, 2021, we included patients with confirmed positive diagnosis for SARS-CoV-2, age > 18 years, disease severity was defined by clinical data of respiratory distress syndrome and a ratio of partial oxygen pressure to inspired oxygen fraction 30 in more than 60% of measurements in the hospital. The outcomes included: risk factors to mortality and AKI in-hospital. The cohort included 3,007 patients with a median age of 54.6 ± 14.5 years. 35% of patients died; 44.6% developed PI-BUN/Cr ratio and 71.4% AKI. Mortality was associated with older age > 60 years [Hazard ratio (HR)] = 1.45, 95% CI: 1.28-1.65; p