The bioelectrical impedance phase angle as an indicator of undernutrition and adverse clinical outcome in cardiac surgical patients

Background & aims: In cardiac surgical patients, undernutrition increases the risk of adverse clinical outcome. We investigated whether the bioelectrical impedance phase angle is an indicator of undernutrition and clinical outcome in cardiac surgery. Methods: In 325 cardiac surgical patients, we prospectively analyzed the associations between a preoperative low phase angle, measured by bioelectrical impedance spectroscopy, and well-established indicators of undernutrition such as body mass index (kg/m(2)), unintended weight loss, and fat free mass index (kg/m(2)), and muscle strength (handgrip strength (kg)), immune function (C-reactive protein and albumin), and adverse clinical outcomes. Results: A low phase angle (<5.38 degrees) was present in 29.8% (n = 96) of the patients, and was associated with low body mass index (p < 0.001), low fat free mass index (p < 0.001), and less handgrip strength (p = 0.063), but not with unintended weight loss or immune function. Furthermore, a preoperative low phase angle was associated with a prolonged intensive care unit and hospital stay (adj. hazard ratio: 0.68; 95%CI: 0.49-0.94; p = 0.020 and adj. hazard ratio: 0.74; 95%CI: 0.55-0.99; p = 0.048, respectively). Conclusions: A preoperative low bioelectrical impedance phase angle is associated with undernutrition, and increases the risk of adverse clinical outcome after cardiac surgery. The phase angle might help to identify undernourished cardiac surgical patients. (C) 2012 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.