Assessment of body cell mass at bedside in critically ill patients

Abstract

Critical illness affects body composition profoundly, especially body cell mass (BCM). BCM loss reflects lean tissue wasting and could be a nutritional marker in critically ill patients. However, BCM assessment with usual isotopic or tracer methods is impractical in intensive care units (ICUs). We aimed to modelize the BCM of critically ill patients using variables available at bedside. Fat-free mass (FFM), bone mineral (Mo), and extracellular water (ECW) of 49 critically ill patients were measured prospectively by dual-energy X-ray absorptiometry and multifrequency bioimpedance. BCM was estimated according to the four-compartment cellular level: BCM ϭ FFM Ϫ (ECW/0.98) Ϫ (0.73 ϫ Mo). Variables that might influence the BCM were assessed, and multivariable analysis using fractional polynomials was conducted to determine the relations between BCM and these data. Bootstrap resampling was then used to estimate the most stable model predicting BCM. BCM was 22.7 Ϯ 5.4 kg. The most frequent model included height (cm), leg circumference (cm), weight shift (⌬) between ICU admission and body composition assessment (kg), and trunk length (cm) as a linear function: BCM (kg) ϭ 0.266 ϫ height ϩ 0.287 ϫ leg circumference ϩ 0.305 ϫ ⌬weight Ϫ 0.406 ϫ trunk length Ϫ 13.52. The fraction of variance explained by this model (adjusted r 2 ) was 46%. Including bioelectrical impedance analysis variables in the model did not improve BCM prediction. In summary, our results suggest that BCM can be estimated at bedside, with an error lower than Ϯ20% in 90% subjects, on the basis of static (height, trunk length), less stable (leg circumference), and dynamic biometric variables (⌬weight) for critically ill patients. critical illness; body composition; bioelectrical impedance; dualenergy X-ray absorptiometry OTHER THAN THE BASIC TWO-COMPARTMENT [fat and fat-free mass (FFM)] model, the composition of the human body can be described by multicompartment models from the atomic to the functional level (11). Body cell mass (BCM) is the metabolically active compartment of FFM that reflects the body's cellular components involved in oxygen consumption, carbon dioxide production, and resting metabolism (11,19,20). Thus, physiological modeling of body composition at the cellular level can be separated into different compartments associated with functions: energy store in fat mass (FM), energy expenditure and metabolism by BCM, exchanges in extracellular water (ECW), and support by bone mineral (Mo).In healthy adults, homeostasis maintains a stable body composition. Conversely, body composition is profoundly modified in acutely or chronically ill patients (28). BCM is altered by changes of nutritional status and the catabolic effects of disease (11,39,47). In this context, BCM could be a marker of malnutrition or prognosis of chronically or critically ill patients (14, 37). BCM is associated with resting energy expenditure (REE), and it has been shown that assessment of energy balance may have particular significance for the nutritional management of the...

The consequences of sudden fluid shifts on body composition in critically ill patients

“…Nutritional markers, such as body mass index (BMI), albuminemia or transferrin, are made unreliable in ICU practice because of systemic inflammation and fluid balance disturbances [11]. Moreover, estimation of body composition as fat-free mass (FFM) is subject to many variations caused by injury and stress conditions in the ICU [12,13]. Body cell mass (BCM), the metabolically active part of FFM, is reported to be more specifically correlated to changes in nutritional status [11,14-16].…”

“…In addition, a lower BCM/FFM ratio is associated with higher extracellular water/intracellular water (ECW/ICW) [17]. It has been suggested that assessing BCM, BCM/weight or BCM/FFM ratios could help to provide more valuable markers of nutritional status and may promote understanding of the metabolic consequences of energy deficit [11,12]. Because of fluid shifts and poor renal and intestinal function during critical illness, the isotope and tracer dilution methods used for BCM measurements are impractical in critically ill patients, at least in the first or second week after their admission [15,18,19].…”

Body cell mass evaluation in critically ill patients: killing two birds with one stone

“…They derived intra- and extracellular water volumes from low- and high-frequency resistances measured by multi-frequency bioelectrical impedance analysis (BIA) of body compartments, before and after hemodialysis. Moreover, they estimated body cell mass (BCM) from BIA parameters and anthropometric variables, based on a recently developed regression equation specific for ICU patients [2]. The investigation aimed at evaluating the consistency and clinical relevance of the current model for BCM calculation in case of massive changes in the external fluid balance.…”

“…BCM can be directly measured by isotope dilution methods (that is, 40  K), or estimated by predictive equations [2]. However, the gold standard methods based on radioactive tracer techniques are not amenable to routine use in the ICU.…”

Nutrition and Acute Lung Injury in Critical Care: Focus on Nutrition Care Process

“…There have been several questionnaires, e.g., short nutritional assessment questionnaire (SNAQ), developed to record recent involuntary weight loss or to determine patients at risk for undernutrition (Wijnhoven et al 2012). Interestingly, one study recently showed a technique to derive body cell mass (as a marker of skeletal muscle mass) from anthropometric data and weight change (Savalle et al 2012). This technique was validated with dual-energy X-ray absorptiometry (DEXA) scanning, showed an error of less than 20 %, and was found to be useful in identifying undernutrition in critical care.…”