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美国明尼苏达大学双城分校、美国明尼苏达大学医学中心、加拿大金斯顿总医院、荷兰阿姆斯特丹自由大学医疗中心、加拿大滑铁卢大学、美国宾夕法尼亚大学、美国拉什大学医疗中心对71例重症监护病房（ICU）成人患者进行研究，以CT第三腰椎平面的骨骼肌横断面积来定义肌肉发达程度减低（男性＜55.4cm²/m²，女性＜38.9cm²/m²），发现相位角（PA）和阻抗比（IR）对重症患者肌肉发达程度和ICU住院时间均有较好的预测价值，联合体重指数（BMI）、年龄、性别等因素后预测价值增加，这为肌肉不发达患者筛查提供新的手段。 JPEN J Parenter Enteral Nutr. 2016;40(4):139-140. An Evaluation of Multifrequency Bioimpedance Phase Angle and Impedance Ratio as Markers of CT-Measured Low Muscularity and Live ICU Discharge in Critically Ill Patients: Preliminary Results From the VALIDation of Bedside Ultrasound of Muscle Layer Thickness of the Quadriceps in the Critically Ill Patient (VALIDUM Study). Adam Kuchnia; Carrie Earthman; Abigail Cole; Gregory Beilman; Andrew Day; Roger Leung; Willem Looijaard; Peter Weijs; Heleen Oudemans-van Straaten; Marina Mourtzakis; Michael Paris; Charlene Compher; Rupinder Dhaliwal; Sarah Peterson; Hannah Roosevelt; Daren Heyland. University of Minnesota-Twin Cities, Minneapolis-St Paul, MN, USA; University of Minnesota Medical Center, Minneapolis, MN, USA; Kingston General Hospital, Kingston, Ontario, Canada; VU University Medical Center Amsterdam, Amsterdam, Netherlands; University of Waterloo, Waterloo, Ontario, Canada; University of Pennsylvania, Philadelphia, PA, USA; Rush University Medical Center, Chicago, IL, USA. Purpose: Lean tissue depletion has been associated with increased morbidity and mortality, infections, and hospital length of stay. Moreover, loss of lean tissue in clinical populations is often masked by increased adiposity, lending to the exacerbation of this issue. Estimation of lean tissue is not commonly performed in hospital settings in part due to the limited availability of valid bedside methods. Inaccuracies in whole-body lean tissue estimates have led to the investigation of raw bioelectrical impedance analysis (BIA) parameters (eg, 50-kHz phase angle [PA] and 200/5-kHz impedance ratio [IR]) as potential markers of nutrition status, prognosis, and clinical outcomes. Our objective was to test whether PA and IR could be similarly used to assess low muscle index measured by computed tomography (CT) and evaluate whether these BIA parameters are independent predictors of live intensive care unit (ICU) and hospital discharge. Furthermore, we assessed whether PA and IR cut points, created on the basis of low fat free mass index as measured by dual-energy X-ray absorptiometry in a healthy population, could be used to further predict live ICU and hospital discharge. Methods: This was a multicenter prospective observational study, which included all patients greater than 18 years of age admitted to the ICU. Further inclusion criteria consisted of having an abdominal CT scan performed for clinical reasons less than 24 hours prior to admission and up to 72 hours after admission. Moribund patients not expected to survive were excluded. CT scans were landmarked at the third lumbar vertebra and were analyzed for skeletal muscle cross-sectional area. Multifrequency BIA was performed according to standard protocol within 72 hours following the abdominal CT scan. Results: Of our 71 patients, 62% were male. Overall, patients were 57 ± 16 years old and had a BMI of 29 ± 8 kg/m² (mean ± SD). Mean APACHE II score was 16 ± 7. According to BMI, 39% were classified as normal weight; 31% were overweight; and 30% were class I obese. CT scans revealed that 57% of patients had lower-than-normal muscularity, defined as CT-derived muscle index <55.4 cm²/m² for males and <38.9 cm²/m² for females. Based on linear regression, PA alone was able to predict 28% of the variance in CT muscle index and 58% of the variance when covariates were added to the model (age, sex, BMI, Charlson comorbidity index, and admission type; Table 27-1). Similarly, IR alone was also able to predict 26% of the variance in CT muscle index and 57% of the variance when covariates were added. The area under the receiver operator curve (c index) to predict CT-defined low muscle mass index was 0.73 for both PA and IR. With covariates added to logistic regression models including PA and IR, the c indexes were 0.87 and 0.86, respectively (Figures 27-1 and 27-2). PA and IR were both able to predict live ICU discharge. When low fat free mass index cut points for PA and IR were used, they were able to predict live ICU discharge with greater certainty (c index = 0.77, 0.79 and P = .04, .01, respectively; Table 27-2). Conclusions: Despite the fact that 61% of the patients were overweight or obese, PA and IR were useful tools in predicting low muscularity defined by abdominal CT scans. When information such as BMI, age, sex, and comorbidity index were known, PA and IR were strong predictors of muscularity and live ICU discharge. Our preliminary results illustrate the potential utility of PA and IR as markers to identify patients with low muscularity who could benefit from early and rigorous intervention. |
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