PHYSICAL EXAMINATION

Nutritional deficiencies may be identified on physical examination, and these

findings may require further evaluation. Muscle and fat wasting (often noticed in the

temporal area), loss of subcutaneous fat and muscle in the shoulders, and loss of

subcutaneous fat in the interosseous and palmar areas of the hands are readily

identifiable. Other physical parameters that may be less obvious are assessment of

hair for color changes and sparseness, skin for turgor, pigmentation, and dermatitis,

mouth for glossitis, gingivitis, cheilosis, and color of the tongue, nails for friability

and lines, and abdomen for signs of ascites or enlarged liver. Additionally, the

patient’s fluid status must be evaluated as a part of the physical examination.

ANTHROPOMETRICS

Anthropometry is the science of body composition based on measurement of weight,

stature, body circumferences, and subcutaneous fat thickness. Physical examination

may include measurement of subcutaneous fat and skeletal muscle mass. Assessment

of fat stores provides information about fat loss or gain and assumes fat is gained or

lost proportionally throughout the entire body. The subcutaneous compartment

contains approximately 50% of body fat. Triceps skinfold and subscapular skinfold

thickness measurements are methods used to assess subcutaneous fat, allowing

associated estimations of total body fat.

Reference standards

26 are used to compare against values obtained in the

examination. Somatic protein mass or skeletal muscle mass can be estimated by

measuring mid-arm circumference and then calculating arm muscle circumference.

These values are also compared with standards, and the amount of muscle mass is

then estimated.

Anthropometric measurements accurately reflect total body fat and skeletal muscle

mass when used for the long-term comparisons of large, nutritionally stable

populations. However, anthropometric measurements of hospitalized patients are of

little value. Changes experienced during acute illness and stress may result in errors

of interpretation of subcutaneous fat and weight assessments, and peripheral edema

can result in inflated values for skinfold thickness and mid-arm circumference.

9,25

Biochemical Assessment

Biochemical assessment of nutritional status includes the examination of protein

status. No single test or group of tests can be recommended as a routine or reliable

indicator of protein status. It is a combination of measures—biochemical,

anthropometric, dietary, and clinical findings—that produce a more complete picture

of protein status.

The protein composition of the human body can be viewed as a two-compartment

model—somatic and visceral proteins. Somatic proteins are those constituting

skeletal muscle; they account for approximately 75% of total body protein. The

remaining 25% of total body protein are visceral proteins, which are found in the

internal organs and serum. Albumin, prealbumin, transferrin, and retinol-binding

protein are the most common visceral proteins used to assess nutritional status. These

proteins are produced by the liver and often reflect hepatic synthetic capability.

When hepatic insufficiency develops or when intake of substrates is inadequate for

synthesis of proteins, the serum concentration of visceral proteins decreases. During

stress or injury, inflammatory cytokines are released and substrates are shunted away

from the synthesis of these proteins to synthesize other acute-phase proteins such as

C-reactive protein, haptoglobin, fibrinogen, and others.

27 Serum protein

concentrations are altered during acute stress or inflammatory states and chronic

starvation.

25,27

Albumin is the classic visceral protein used to evaluate nutritional status and is a

prognostic indicator. Serum concentrations of less than 3 g/dL correlate with poor

outcome and an increased length of stay of hospitalized patients.

28 Albumin serves as

a carrier protein for fatty acids, hormones, minerals, and drugs, and is necessary for

maintaining oncotic pressure. Albumin has a large body pool of 3 to 5 g/kg, and 30%

to 40% is localized to the intravascular space. The normal hepatic rate of albumin

synthesis is 150 to 250 mg/kg/day. Because albumin has a half-life of 18 to 21 days,

a decrease in serum albumin concentrations is generally not observed until after

several weeks of inadequate nitrogen intake. Serum albumin concentrations decrease

rapidly in response to stress (which causes albumin to shift from the intravascular to

the extravascular space), burns, nephrotic syndrome, protein-losing enteropathy,

overhydration, and decreased synthesis with liver disease.

25,27

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Table 35-2

Visceral Proteins for Nutritional Assessment

Visceral Protein Half-Life (days) Normal Serum Concentration

Albumin 18–21 3.5–5 g/dL

Transferrin 8–10 250–300 mg/dL

Transthyretin (prealbumin) 2–3 15–40 mg/dL

Retinol-binding protein 0.5 2.5–7.5 mg/dL

Transferrin, which is involved in the transport of iron, has a half-life of 8 to 10

days and is more sensitive than albumin to acute changes in nutritional status. Normal

serum concentrations of transferrin are 250 to 300 mg/dL.

Even more sensitive to changes in energy and protein intake is prealbumin

(transthyretin), which has a small body pool (10 mg/kg) and a half-life of 2 to 3 days.

Prealbumin transports both retinol and retinol-binding protein. Normal serum

prealbumin concentrations are 15 to 40 mg/dL.

Retinol-binding protein has the shortest half-life, 12 hours; normal serum

concentrations are 2.5 to 7.5 mg/dL. However, because serum concentrations of

retinol-binding protein change rapidly in response to alterations in nutrient intake,

monitoring it has limited use in clinical practice. The visceral proteins commonly

used for nutritional assessment are summarized in Table 35-2.

Other proteins, such as fibronectin and somatomedin-C (insulin-like growth factor1), are also used as markers of nutritional status. Fibronectin is a glycoprotein found

in blood, lymph, and many cell surfaces. Somatomedin-C is important in regulating

growth. Both fibronectin and somatomedin-C have half-lives of less than 1 day and

respond to fasting and refeeding. Urinary measurement of 3-methylhistidine, a byproduct of muscle metabolism that is excreted unchanged, has been used to estimate

skeletal muscle mass. Although these markers have potential use in nutritional

assessment, they are used primarily as research tools and are not readily available

for routine clinical use.

25

The interpretation of serum protein concentrations in hospitalized patients may be

difficult because other factors more important than hepatic synthesis rate can alter

serum concentrations. These factors may include renal, hepatic, or cardiac

dysfunction, hydration status, and metabolic stress. Visceral proteins, as with any

nutritional assessment parameter, must be used in conjunction with other parameters

and comprehensive consideration of the patient’s clinical status. Practitioners should

evaluate markers of inflammation and stress, such as C-reactive protein, in

conjunction with visceral protein markers periodically to ensure that an accurate

assessment is made.

Nutritional assessment based on determinations of body composition using

anthropometric and biochemical parameters has many limitations. Newer techniques

(e.g., bioelectrical impedance, dual-energy X-ray absorptiometry, isotope dilution,

neutron activation) are increasingly being used to determine body composition. Other

parameters such as hand grip and forearm dynamometry may be used to assess

skeletal muscle function, which relates changes in body composition to body

function.

1,9,25

Another nutritional assessment method, subjective global assessment (SGA),

combines objective parameters and physiologic function.

29 This easy-to-use tool for

diagnosing malnutrition is based on a history of weight change, dietary intake,

presence of significant GI symptoms, functional capacity, and physical examination to

assess edema and the loss of subcutaneous fat and muscle. Using the SGA system,

patients are rated as well nourished, moderately malnourished, or severely

malnourished.

Classification of Malnutrition

Malnutrition is categorized through a variety of descriptive terms, each with varying

characteristics. Three classic categories include marasmus, kwashiorkor, and mixed

protein-calorie malnutrition. A chronic deprivation of energy (calories), or partial

starvation, leads to marasmus, which means a “dying away state.” For patients with

marasmus, physical examination reveals severe cachexia with loss of both fat and

muscle mass; however, visceral protein production is preserved, and serum levels

may remain at or near the normal range. Patients with chronic wasting diseases such

as cancer or anorexia are likely to present with marasmus malnutrition.

Classic kwashiorkor malnutrition results from diets devoid of adequate protein,

but with adequate caloric intake. Kwashiorkor-like malnutrition in hospitalized

patients often refers to patients who are extremely catabolic from their medical

complication (e.g., sepsis) or injury (e.g., trauma, thermal injury). Carbohydrate

metabolism involves endogenous production of insulin, which in turn prevents

lipolysis and promotes the movement of amino acids into muscle. To meet increased

protein demands, protein can be mobilized from internal organs and circulating

visceral proteins. Consequently, an individual with kwashiorkor-like malnutrition

may have adequate fat and muscle mass, but may demonstrate depleted serum

proteins.

Hospitalized patients commonly exhibit components of both marasmus and

kwashiorkor-like malnutrition and are classified as having mixed protein-calorie

malnutrition. This mixed condition occurs when an acute injury or stress compounds

chronic starvation or semistarvation, resulting in wasting of fat and muscle mass, as

well as depletion of serum proteins.

Estimation of Energy Expenditure

Estimating energy expenditure constitutes an important aspect of patient evaluation.

The most common approach used to determine energy requirements is based on body

weight in kilograms. Energy requirements are standardized and are determined by the

metabolic condition of the patient.

Many predictive equations for estimating expenditure have been described in the

literature.

30,31 The traditional method of assessing energy expenditure is the basal

energy expenditure (BEE): the amount of energy (kilocalories) needed to support

basic metabolic functions in a state of complete rest, shortly after awakening, and

after a 12-hour fast. BEE is most commonly calculated using the Harris–Benedict

equations (see Table 35-3). Alternatively, BEE can be estimated at 20 to 25

kcal/kg/day.

Basal metabolic rate (BMR) is the energy expended in the postabsorptive state,

approximately 2 hours after a meal. BMR is approximately 10% greater than BEE.

Calculations of BEE or BMR do not include additional energy required as a result of

stress or activity. The Harris–Benedict equations can be modified to include stress

and physical activity factors, or these variables are estimated at 20 to 35 kcal/kg/day

for moderate-to-severe stress (Table 35-3).

Indirect calorimetry determines energy expenditure using a machine known as a

metabolic cart that measures the patient’s breathing or respiratory gas exchange. The

cart measures oxygen consumption and carbon dioxide production when standard

testing conditions are maintained. The amount of oxygen consumed and carbon

dioxide produced for carbohydrate, fat, and protein is constant and known. Energy

expenditure, including that caused by stress, is measured for a defined time, and the

information is then subjected to a series of equations to extrapolate the estimated 24-

hour energy expenditure.

17,25 This is the measured energy expenditure (MEE).

Because the measurement is usually conducted while the patient is at rest, activity is

not included in MEE.

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Table 35-3

Estimation of Energy Expenditure

Basal Energy Expenditure (BEE)

Harris–Benedict equations

BEEmen

(kcal/day) = 66.47 + 13.75 W + 5.0 H – 6.76 A

BEEwomen

(kcal/day) = 655.10 + 9.56 W + 1.85 H – 4.68 A

Or

20–25 kcal/kg/day

Energy Requirements

Hospitalized patient, mild stress 20–25 kcal/kg/day

Moderate stress, malnourished 25–30 kcal/kg/day

Severe stress, critically ill 30–35 kcal/kg/day

A, age in years; BEE, basal energy expenditure; H, height in cm; kcal, kilocalories; W, weight in kg.

Indirect calorimetry is available to many clinicians and is considered the gold

standard for energy expenditure determination. Its usefulness is particularly valuable

in the energy assessment of critically ill or obese patients. In 2016, the Society of

Critical Care Medicine (SCCM) and American Society for Parenteral and Enteral

Nutrition (ASPEN) published guidelines for the provision and assessment of

nutritional support therapy for the adult critically ill patient.

32 Based on expert

consensus, the guidelines suggest that determination of nutritional risk be performed

on all ICU patients for whom volitional intake is anticipated to be insufficient. Highrisk patients would likely benefit from early enteral nutritional therapy. Additionally,