INTRODUCTION: Cardiopulmonary bypass is known to be a cause of systemic inflammatory response. The systemic inflammatory response affects albumin and lymphocyte levels and is associated with the development of complications. Serum albumin and lymphocyte concentrations have been used to create inflammation-based risk scores, which predict prognosis in different patient groups. One of these risk scores is called the Prognostic Nutritional Index (PNI). In this study, our objective was to examine how changes in PNI values, measured at different times before and after surgery, impact clinical outcomes and hospital mortality. METHODS: One hundred and sixty-four patients were retrospectively scanned and included in the study. Patients were divided into aortic valve replacement (AVR) and mitral valve replacement (MVR) groups. The patient's preoperative and postoperative PNI values were examined. Duration of cross-clamping, cardiopulmonary bypass time, length of hospital and intensive care unit stay, postoperative mortality, atrial fibrillation, and acute kidney injury (AKI) development were evaluated. RESULTS: Preoperative and second PNI values were lower in the patients that developed AKI and non-survivors. The PNI cutoff value was ≤ 28.01 in non-survivors (P=0.001). In the MVR group, the decrease in PNI value over time was statistically significant (P<
0.001). There was a negative correlation between preoperative PNI value and length of stay in intensive care unit, cross-clamping, and cardiopulmonary bypass duration (P<
0.05, P<
0.01). CONCLUSION: A correlation was determined between the PNI value and development of postoperative AKI and mortality. PNI value, an easy method to use, can be used in the follow-up of these patients.