Blood urea nitrogen to creatinine ratio and in-hospital mortality in cardiac intensive care units
N Benameur, Y Bennouna, A Molina, B Elboussaadani, Z RaissuniAbstract
Introduction
Renal dysfunction is a major prognostic factor in patients admitted to cardiac intensive care units (CICU). While estimated glomerular filtration rate (eGFR) is a well- established prognostic marker (1), the prognostic value of blood urea nitrogen (BUN) and the blood urea nitrogen–to–creatinine ratio (BCR) remains less clearly defined in this setting (2). Elevated BUN has been linked to increased mortality in acute cardiac conditions (2), and BCR has emerged as a potential biomarker reflecting renal hypoperfusion and neurohormonal activation (3). However, the overall prognostic role of BCR in unselected CICU populations remains underexplored.
Objective
To determine whether an elevated BUN/Creatinine ratio (BCR ≥ 20) at admission is independently associated with increased in-hospital mortality among CICU patients, and to evaluate its potential role as a simple, integrative prognostic biomarker in a real-world population of 1,885 patients.
Method
We conducted a retrospective observational study over 2 years that included all consecutive adult patients admitted to the Cardiac Intensive Care Unit (CICU) of the University Hospital Centre for acute cardiac conditions. Exclusion criteria were pregnancy, chronic haemodialysis, missing baseline urea or creatinine values, and early transfer out of USIC (to general ICU or cardiology ward). Blood urea (g/l) was converted to BUN (mg/dL), and the BUN-to-creatinine ratio (BCR) was calculated at admission. Patients were categorised into two groups based on BCR: <20 and ≥20. The primary outcome was in-hospital all-cause mortality. Data were analysed using SPSS software.
Results
An elevated BUN/Creatinine ratio (BUN/Cr ≥20) was significantly associated with higher in-hospital mortality. Patients with higher BUN/Cr were older and more frequently presented with dyspnoea, peripheral oedema, and chest pain, as well as haemodynamic compromise characterised by lower blood pressure and higher heart rate. Elevated BUN/Cr was also associated with a higher incidence of ST-segment elevation myocardial infarction. Echocardiography showed a higher prevalence of wall-motion abnormalities, reduced left ventricular ejection fraction, left ventricular dilation or hypertrophy, dilated inferior vena cava, and elevated filling pressures in patients with high BUN/Cr. Biologically, these patients had higher C-reactive protein levels, lower potassium levels, and lower creatinine levels.
Conclusion
Overall, BUN/Cr serves as a straightforward, integrative marker of haemodynamic severity and neurohormonal stress, accounting for its strong association with mortality in our CICU population.