Nutritional indices for screening sarcopenia before adult cardiac surgery

Malnutrition can increase and exacerbate sarcopenia, and preoperative nutritional indices could have potential use as screening tools for sarcopenia in all patients, not only those with limited activity. Muscle strengths, such as grip strength, chair stand test, are used to screen for sarcopenia, but these measurements are time-consuming and cannot be applied to all patients. This retrospective study was conducted to determine whether nutritional indices can predict the presence of sarcopenia before adult cardiac surgery.

The study subjects were 499 patients aged ≥18 who had undergone cardiac surgery using a cardiopulmonary bypass (CPB). Bilateral psoas muscle mass areas at the top level of the iliac crest were measured by abdominal computed tomography. Preoperative nutritional statuses were evaluated using COntrolling NUTritional status (CONUT) score, Prognostic Nutritional Index (PNI), and Nutritional Risk Index (NRI). Receiver operating characteristic (ROC) curve analysis was used to identify the nutritional index that best predicted the presence of sarcopenia.

The 124 patients (24.8%) in the sarcopenic group were older (69.0 vs. 62.0 years; P<0.001), and had a lower mean body weight (58.90 vs. 65.70 kg; P<0.001) and body mass index (BMI) (2.22 vs. 2.49 kg/m²; P<0.001), and a poorer nutritional status than the 375 patients in the non-sarcopenic group. ROC curve analysis showed that NRI [area under the curve (AUC) 0.716, confidence intervals (CI): 0.664-0.768] better predicted the presence of sarcopenia than CONUT score (AUC 0.607, CI: 0.549-0.665) or PNI (AUC 0.574, CI: 0.515-0.633). The optimal NRI cut-off value was 105.25, which provided a sensitivity of 67.7% and a specificity of 65.1% for the prevalence of sarcopenia. The median durations of mechanical support (17 vs. 16 hours; P=0.008) and intensive care unit stay (3 vs. 2 days; P=0.001) were significantly longer in the sarcopenic group.

NRI offers a more straightforward, faster, and reproducible screening tool than muscle strength or mass measurement for identifying sarcopenia, and an alternative means of assessment in patients with limited activity before adult cardiac surgery.