CONCLUSION
The European Society for Clinical Nutrition and Metabolism defined malnutrition as a condition resulting from a lack of nutrition or intake that leads to changes in body composition (reduction of lean mass) and body cell mass, resulting in reduced physical and mental function and impaired clinical outcomes from the disease. Additionally, cardiac cachexia triggers impaired neuroendocrine and immunological function, and it is considered an indicator of poor prognosis regardless of age and disease severity16,17.
Malnutrition is generally associated with humoral and cellular immune dysfunction, inflammatory response change, and the wound healing process delay or failure. It is well known that malnutrition is closely related to the incidence of postoperative complications, length of hospital stay, quality of life, and increased mortality of malignant tumors18. Besides, the negative impact of long-term calorie and protein deficiencies on critically ill surgical patients’ outcomes has recently been demonstrated19. The decreased response of albumin and lymphocytes to acute disease indicates low immunonutritional status. The PNI was calculated based on the serum albumin concentration and lymphocyte count of peripheral blood. Therefore, the PNI score should be considered a clinical element and indicator of disease severity in patients undergoing cardiac surgery. Some studies recently reported that a lower PNI level was significantly associated with higher mortality in patients with cardiovascular diseases20-23. One of the most beneficial aspects of PNI is not time-consuming, and no special equipment is required. Therefore, it can be easily integrated into routine clinical practice. Although the prognostic significance of the PNI has been reported previously in several types of abdominal or gastrointestinal surgery, its relevance in cardiovascular surgery has not been proven. The surgery’s success depends not only on technical surgical skills but also on the preoperative nutritional status.
Keskin et al.24 showed a significant relationship between PNI level and mortality (in-hospital and long-term) in coronary artery disease patients undergoing CABG. In addition, Hyashi et al.25 retrospective study showed that a high PNI value was found to decrease mechanical ventilation duration, ICU stays, and infection rates. In the multivariate analysis, in addition to age and female gender, a low PNI value was determined as an independent predictor for mortality. Recent published Lee et al.26study is the first to assess the usefulness of the PNI in adult cardiac surgery using only CPB and showed that a lower PNI was an independent predictor of early morbidity and mortality, and was also related to prolonged mechanical ventilation support and ICU stays.
In cardiac surgery, an increasing number of older people are accepted for elective surgery. When low preoperative PNI is detected in elderly patients, postoperative nutritional management such as serum albumin supplementation, dietary maintenance, or nutritional supplementation should be considered to improve patients’ nutritional status27.
Our research demonstrated that the PNI value was statistically low in the mortality group. There was significantly different a higher tendency for postoperative hospital-acquired infection and stroke in the mortality group. PNI may be used to predict patients’ outcomes before cardiac surgery and select an adequate surgical strategy. In that case, it must be useful for choosing the biological or mechanical materials for valvular surgery and determining graft materials in coronary surgery. In the case of patients with a low PNI, less invasive surgery may be suitable if possible.
Our study does not include the effects of preoperative nutritional support on postoperative mortality and morbidity in patients with low PNI values. Further studies are needed to show the results of preoperative nutritional support in elective cases.
Preoperative low PNI level was evaluated as an independent predictor of long-term cardiovascular outcomes. Also, it was statistically significantly associated with postoperative mortality and morbidity in cardiac surgery. According to the results we obtained in our study, we firmly believe that PNI is a useful and suitable parameter for preoperative assessment of nutritional status and should be regarded in managing the indication and strategy in on-pump cardiac surgery.
Authors’ contributions The authors’ responsibilities were as follows: AG, OAO and SAS conceived the study and designed the search strategy; AG and OAO conducted the study selection; SAS and NK conducted data extraction; AG, NK and DD evaluated the risk of bias of included studies; AG, OAO and SAS conducted the data analysis and interpretation of results; AG, OAO and IBS wrote the first draft of the manuscript; AG and OAO revised the manuscript; all authors read and approved the final version of the manuscript.