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INTRODUCTION

  • Malnutrition is a consequence of nutrient imbalance resulting from inadequate intake, absorption, or utilization of protein and energy. Undernutrition can result in changes in subcellular, cellular, or organ function that increase the individual’s risks of morbidity and mortality.

  • For information on overnutrition or obesity, see Chapter 58.

  • Nutrition screening provides a systematic way to identify individuals in any care environment with preexisting malnutrition or those at risk for malnutrition for whom a detailed nutrition assessment is warranted.

  • Nutrition assessment is the first step in developing a nutrition care plan. Goals of nutrition assessment are to identify the presence of factors associated with an increased risk of developing undernutrition and complications, estimate nutrition needs, and establish baseline parameters for assessing the outcome of therapy.

  • This assessment should include a comprehensive medical, surgical, and dietary history and a nutrition-focused physical exam (NFPE) including anthropometrics and laboratory measurements.

  • The NFPE uses a system-based approach to assess for abnormal nutrition-related clinical and physical findings in each region of the body.

NUTRITION ASSESSMENT

Anthropometric Measurements

  • Anthropometric measurements are physical measurements of the size, weight, and proportions of the human body used to compare an individual with normative population standards. Common measurements are weight, stature, head circumference (for children younger than 3 years of age) and waist circumference. Measurements of limb size (eg, skinfold thickness and mid-arm muscle and wrist circumferences), along with bioelectrical impedance analysis (BIA), may be useful in selected individuals.

  • Interpretation of actual body weight (ABW) should consider ideal weight (IBW) for height, usual body weight (UBW), fluid status, and age. Change over time can be calculated as the percentage of UBW. Unintentional weight loss, especially rapid weight loss (5% of UBW in 1 month or 10% of UBW in 6 months), increases risk of nutrition-related poor clinical outcomes in adults.

  • The best indicator of adequate nutrition in children is appropriate growth. Weight, stature, head circumference (until 3 years), and body mass index (BMI) (after 2 years) should be plotted on the appropriate growth curve. Average weight gain for newborns is 10–20 g/kg/day (24–35 g/day for term infants and 10–25 g/day for preterm infants depending on gestational age).

  • BMI is another index of weight-for-height. Interpretation of BMI should include consideration of gender, frame size, race/ethnicity, and age. BMI values greater than 25 kg/m2 are indicative of overweight, and values less than 18.5 kg/m2 are indicative of undernutrition. BMI is calculated as follows:

Body weight (kg)/[height (m)]2 or [Body weight (lb) × 703]/[height (in.)]2

  • Measurements of skinfold thickness estimate subcutaneous fat, mid-arm muscle circumference estimates skeletal muscle mass, and waist circumference estimates abdominal (visceral) fat content.

  • BIA is a simple, noninvasive, and relatively inexpensive way to assess LBM, total body water (TBW), and water distribution. It is based on differences between fat tissue and lean tissue’s resistance to conductivity. Hydration status ...

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