Objectives: Serious complications are seen after cardiac surgery operations. Postoperative pneumonia is one of the most important of these complications. Some biomarkers have been examined in the prediction of mortality in special groups such as hospital-acquired pneumonia or aspiration pneumonia. In addition to parameters such as blood-urea nitrogen and albumin, the blood urea nitrogen to albumin ratio obtained by the ratio of these two parameters is also used as a mortality predictor. In this study, it was aimed to investigate the effect of the blood urea nitrogen to albumin ratio at the time of diagnosis of pneumonia on mortality in patients who developed pneumonia in the early period after cardiac surgery. Methods: In this study, 138 patients who developed pneumonia in the early period after cardiac surgery were examined. Complete blood count and biochemical test results were analyzed for all patients, and differences between groups were investigated. The patients who developed in-hospital pneumonia and were discharged as survivors were classified as Group 1, and non-survivor patients were determined as Group 2. Results: Patients who did not develop in-hospital mortality were included in Group 1 (n = 105, mean age = 63.7 ± 9.2 years), and those with non-survivor were included in Group 2 (n = 33, mean age = 66.9 ± 9.6 years). At the time of diagnosis neutrophil-lymphocyte ratio, C-reactive protein, blood-urea nitrogen and blood urea nitrogen to albumin ratio values were significantly higher in Group 2 (p < 0.001, p < 0.001, p = 0.004 and p < 0.001; respectively) ROC curve analysis was performed to evaluate blood urea nitrogen to albumin ratio in predicting mortality. The cut-off value of blood urea nitrogen to albumin ratio was 4.1 (Area under the curve [AUC]: 0.740, 95% CI: 0.690-0.820, p < 0.001, with sensitivity of 72.5% and specificity of 68.6%). Conclusions: In pneumonia developing after cardiac surgery, we found that the peripheral blood blood urea nitrogen to albumin ratio at the time of the first symptom in the patient has a high predictive power for the development of mortality in this particular patient group.
