Depletion of body cell mass (BCM) is a useful estimation of nutritional status.41 Decreased BCM before transplantation has been shown to correlate with a threefold increase in post-transplant mortality rates.5, 6 ISOTOPE DILUTION, measurement of WHOLE-BODY POTASSIUM, and in vivo neutron activation analysis are arguably the most accurate methods currently available to assess body composition; however, these techniques are costly and labor intensive, making them less practical for routine nutritional screening. BIOELECTRICAL IMPEDANCE is a more readily available tool for estimating BCM. Although this is a reliable tool in many patient populations, the accuracy of these measurements in patients with cirrhosis can be affected by fluid retention.42 Pirlich et al., however, showed that estimation of BCM using bioelectrical impedance correlated closely with BCM measured by total body potassium in patients with and without ascites.43 Figueiredo et al. studied whether the traditionally measured nutritional parameters correlate with BCM. Although depleted BCM correlated most closely with arm-muscle circumference and hand-grip strength, most parameters, nonetheless, did not correlate well with depleted BCM.44
An evaluation of the status of energy metabolism might be a reasonable component of a nutritional assessment, because there seems to be a correlation between hypermetabolism and malnutrition.6, 31 This evaluation can be accomplished using indirect calorimetry, a widely accepted tool that is used to estimate REE. Indirect calorimetry measures the consumption of oxygen and production of carbon dioxide, and REE is calculated using the Weir equation: [kcal/d = [3.941 times VO2(l/day)] + 1.106 times VCO2(l/day)].45 The measured REE is compared with the predicted energy expenditure, as calculated using the Harris–Benedict equation.46 A patient is generally considered to be hypermetabolic if the measured REE is more than 10–20% greater than the predicted REE.30, 31 In transplant recipients, hypermetabolism is associated with a decreased survival rate after transplantation.5 The use of indirect calorimetry enables the calculation of the nonprotein respiratory quotient, defined as the ratio of energy produced by carbohydrate metabolism to energy generated by fat oxidation, which confirms whether a patient has an altered pattern of fuel consumption.