the guidelines suggest that the nutritional assessment should include evaluation of

comorbid conditions, function of the gastrointestinal tract, and risk of aspiration.

Traditional nutrition indicators or surrogate markers should likely not be used to

assess nutritional status in critically ill patients because they have not been validated

in the critically ill patient population.

Estimation of Protein Goals

Estimation of protein needs is necessary in nutritional assessment. Protein needs are

calculated based on body weight, degree of stress, and disease state. The initial

estimation is often made with a degree of subjectivity and clinical judgment, with

adjustments made based on patient response. The US-recommended dietary

allowance is 0.8 g of protein/kg/day. Well-nourished, hospitalized patients with

minimal stress need 1 to 1.2 g of protein/kg/day to maintain lean body mass. The

requirement for protein intake may be as high as 2 g/kg/day for a patient in a

hypermetabolic, hypercatabolic state secondary to trauma or burns. In addition,

protein provision may need to be adjusted and reduced in patients with renal or

hepatic dysfunction as a result of altered metabolism. Guidelines for protein needs

are summarized in Table 35-4.

Micronutrients

Micronutrients are the electrolytes, vitamins, and trace minerals needed for

metabolism. A complete assessment will include identification of risks for

deficiencies or toxicities with micronutrients based on the patient’s specific

nutritional status and concurrent disease processes. These nutrients are available

enterally and parenterally from various manufacturers as either single entities or in

combinations. It is important to be aware of the specific products available in each

institution to avoid providing inadequate or excessive amounts of various

micronutrients.

Table 35-4

Estimation of Protein Requirements

US-recommended dietary allowance 0.8 g/kg/day

Hospitalized patient, minor stress 1–1.2 g/kg/day

Moderate stress 1.2–1.5 g/kg/day

Severe stress 1.5–2 g/kg/day

PATIENT ASSESSMENT: WOMAN WITH

CROHN’S DISEASE

CASE 35-1

QUESTION 1: S.P., a 34-year-old cachectic woman, is admitted to the hospital with abdominal pain, nausea,

vomiting, and diarrhea. She has a history of moderate Crohn’s disease diagnosed 4 years ago. She has had

extensive treatment with medical therapy, but has not required surgical intervention since her diagnosis. She has

experienced extraintestinal symptoms including skin lesions and joint pain. She presents to the hospital with

increasing weight loss in the past 3 months, accompanied by regurgitation, vomiting, and poor appetite.

Approximately 6 months ago, S.P. weighed 120 lb. Her weight on admission is 92 lb; height is 60 inches. Past

medical history is also significant for peptic ulcer disease and occasional bouts of depression. Physical

examination reveals a thin woman with wasting of subcutaneous fat in the temporal area and square shoulders.

She reports noticing recent hair loss. Attempts at increasing her oral intake with enteral supplements have not

been successful owing to self-reported retching.

Admission laboratory values are as follows:

Sodium, 135 mEq/L

Potassium, 4.0 mEq/L

Chloride, 100 mEq/L

Bicarbonate, 25 mEq/L

Blood urea nitrogen, 4 mg/dL

Creatinine, 0.6 mg/dL

Glucose, 87 mg/dL

Calcium, 8.2 mg/dL

Magnesium, 1.7 mg/dL

Phosphorus, 2.8 mg/dL

Total protein, 6.0 g/dL

Albumin, 3.5 g/dL

Prealbumin, 14 mg/dL

Her white blood cell count is 12,600/μL. Based on history and physical findings, S.P.’s working diagnosis

includes Crohn’s disease exacerbation with cutaneous, joint, and GI involvement. What is her current nutritional

status?

To develop an accurate nutritional assessment of any patient, it is important to

elicit a thorough history and conduct an appropriate physical examination. Although

history and physical examination are of paramount importance, laboratory studies are

also integral components to the assessment of S.P.’s nutritional status. S.P.’s nutrition

history indicates that she is unable to eat because of vomiting, and the Crohn’s

diagnosis raises the question of nutrient malabsorption. Most striking about S.P.’s

history is her weight loss of 28 lb in 6 months. She is now 76% of

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her usual weight (Eq. 35-2). Another way of analyzing this is that she has lost 25%

of her original weight, which is characterized as severe weight loss. The physical

findings of cachectic appearance, temporal wasting, and loss of subcutaneous fat and

muscle in her shoulders are significant. No anthropometric measurements are

available. S.P.’s visceral proteins are also in low–normal ranges, indicating both

short-term (prealbumin) and long-term (albumin) malnutrition. Consideration of these

factors leads one to conclude that S.P. is severely malnourished. This assessment can

be further validated by using other tools such as the SGA.

29

Because nutritional assessment can often be difficult, a clinician may choose to use

the SGA to appropriately categorize their patients. Application of the SGA technique

classifies patients into three areas: class A (the well-nourished patient), with less

than 5% weight loss or more than 5% total weight loss but recent gains and

improvements in appetite; class B (moderately malnourished), identified by those

patients with 5% to 10% weight loss without recent stabilization or gain, poor

dietary intake, and mild loss of subcutaneous tissue; and class C (severely

malnourished), with an ongoing weight loss of more than 10% with severe

subcutaneous tissue loss and muscle wasting, often with edema. The utility of the

SGA is its simplicity for implementation and strong correlation with other subjective

and objective measures of nutrition.

Clinicians place patients into one of the three categories on the basis of their

subjective rating of two broad factors: history and physical examination. There are

four elements to the history: (a) weight loss in the 6 months before the examination,

expressed as a proportionate loss from previous weight, (b) dietary intake in relation

to the patient’s usual pattern, (c) presence of significant GI symptoms, and (d)

functional capacity or energy of the patient, ranging from full capacity to bedridden.

Applying these four elements to S.P., one first finds that S.P. is reporting a 25%

weight loss during the past 6 months. It is also important to recognize the pattern of

weight loss. Querying a patient regarding recent weight loss (in conjunction with the

weight change in 6 months), often in the past 2 weeks, can help establish a pattern of

chronic weight loss. In S.P.’s case, she reports increasing weight loss in the past 3

months, which confirms a progression. It is also recommended that clinicians explore

weight history by asking for the patient’s maximal weight at specific times, such as 1

year ago, 6 months ago, 1 month ago, and at the present time. Confirmation of weight

history can be conducted by having the patient to discuss about his/her change in

clothing size or how his/her clothes fit.

With respect to the second element regarding dietary intake, S.P. says she has a

poor appetite, and attempts to consume supplements have been unsuccessful. Using

the SGA, patients are classified as having either normal or abnormal intake in the

weeks to months before the examination. In this case, S.P. is clearly experiencing

abnormal intake; however, one can also ask S.P. certain questions such as “How has

the amount of food you have consumed over the past several weeks to months

changed?” or “Are there certain kinds of foods that you no longer can eat?” and

“Give me an example of a typical meal” to establish eating patterns. It is also

important to determine why a patient is eating less—intentional reduction or

unintentional reduction. S.P. is not communicating any intention of wanting to lose

weight, and her change in consumption is related to her chronic pathology.

In terms of the third element of the history, significant GI symptoms are those that

have persisted on virtually a daily basis for a period longer than 2 weeks. Given the

presentation of S.P. to the hospital with her history of 3 months of vomiting, it is

highly likely that she satisfies the definition for possessing significant GI symptoms.

However, a clinician can always clarify this by asking S.P. more specific questions.

The final element of S.P.’s history, functional capacity, is one that should be

explored further; yet, it is not likely to have an impact on the final nutritional

assessment given the prior objective findings of the patient. Patients who cannot eat

will often complain of weakness and fatigue—many times to the point of which they

are bedridden. Observation of the activity levels of patients, their overall mood,

skeletal muscle function, and their respiratory movements can all provide clues to the

clinician regarding functional impairment. Given the joint pain and squared-off

appearance of her shoulders from the combination of muscle and subcutaneous tissue

loss, functional capacity of S.P. is likely to be diminished.

Having completed the history component of the SGA, the clinician moves to the

second component of the SGA, or the physical. This section of the SGA essentially

asks the clinician to look for physical signs of malnutrition such as loss of

subcutaneous fat in the triceps and chest region, muscle wasting in areas like the

quadriceps and deltoids, presence of ankle or sacral edema, and finally any presence

of ascites. For each of the traits, the clinician should consider the severity, if anything

present. In the case of S.P., there is definite muscle wasting. Given the history and

physical components of the SGA, S.P. would be classified as severely malnourished

(class C) as there are obvious signs of malnutrition such as subcutaneous tissue loss

and muscle wasting in the presence of a clear and convincing pattern of ongoing

weight loss greater than 10%.

CASE 35-1, QUESTION 2: Is S.P. a candidate for specialized nutritionalsupport therapy?

The fundamental goal of specialized nutritional support therapy is to meet the

energy requirements of metabolic processes, to support the hypermetabolism

associated with critical illness, and to minimize protein catabolism. Crohn’s disease

is a form of inflammatory bowel disease that is associated with potentially great

nutritional insult. Nutritional abnormalities can arise in Crohn’s disease patients from

malabsorption, decreased food intake, medications, and intestinal losses. Disease

location along the GI tract, symptomatology, and dietary restrictions all contribute to

the development of protein energy malnutrition with specific nutritional deficiencies.

S.P. is admitted to the hospital for tests to evaluate her Crohn’s disease, weight loss,

and associated symptoms. The subjective and objective evidence points to a

nonfunctioning GI tract. If the diagnosis of advanced Crohn’s exacerbation is

accurate, S.P. may require parenteral nutritional therapy until enteral therapy can be

established (see Chapter 38, Adult Parenteral Nutrition). In addition, previous

attempts at enteral nutrition were unsuccessful with continued increased retching and

vomiting, indicating decreased GI motility. With her malnourished state, continued

inadequate nutrition in the hospital will result in further deterioration of her

nutritional status. Specialized nutritional support intervention should be implemented.

Goals of Therapy

CASE 35-1, QUESTION 3: Calculate calorie and protein goals for S.P.

Nutritional support begins with an estimation of the patient’s caloric

requirements.

30,31 Accurate determination of caloric needs is essential to obtain the

full benefits of nutritional therapy and aids in preventing the problems associated

with underfeeding as well as overfeeding. The Harris–Benedict equation is one of

the most commonly used methods for estimating caloric needs or BEE; however,

there is still controversy regarding the best method to accurately estimate the caloric

needs of a patient. The Harris–Benedict equation may overestimate or underestimate

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resting energy expenditure in certain critically ill patients, particularly when

clinical conditions are changing and when body weight fluctuates because of changes

in fluid status. The most common approach is based on body weight in kilograms.

The energy requirements are standardized and are determined by the metabolic

condition of the patient. S.P.’s initial calorie goals are to meet her current energy

expenditure needed for basal metabolism and activity of ambulating. S.P. would fall

into the category of “moderate stress, malnourished” requiring 25 to 30 kcal/kg/day.

For this calculation, S.P.’s actual weight of 92 lb (41.8 kg) should be used because

her metabolism and current energy expenditure reflect this decrease in body mass.

Using usual weight or IBW in patients who have severe weight loss may result in

overfeeding. For S.P., the caloric goal should be from 1,045 to 1,255 kcal/day.

Protein is the building block of life. Once hepatic glycogen stores are depleted,

muscle protein is degraded to provide three-carbon backbones for hepatic

gluconeogenesis. Initially, protein catabolism is resistant to the administration of

exogenous amino acids, and it can sometimes take weeks until a patient is found to be

in a state of positive nitrogen balance. In addition to protein catabolism, exogenous

protein is required for wound healing and to replace protein lost in wounds and

fistulae. Protein goals are estimated based on weight, degree of stress, and disease

state. The goal is to minimize the loss of lean body mass, and as a general rule this

requires anywhere from 1.0 to 1.5 g/kg/day of protein depending on the degree of

illness and injury. Because S.P. has not had surgery and her stress is minimal, her

protein goal should be based on the desire to maintain her current protein status.

Using the guidelines provided in Table 35-4, S.P.’s protein dose is 1.2 to 1.5

g/kg/day, or 50 to 63 g/day. As with energy expenditure, calculations of protein

needs are only estimates; the patient’s clinical course should be monitored, and the

protein dose should be adjusted accordingly. If S.P. requires surgery, her energy or

calorie goals should be reassessed to include an additional stress factor.

Micronutrients

CASE 35-1, QUESTION 4: What vitamin and mineral deficiencies would you expect to find in S.P.? What

options are available to the clinician to address them?

The therapeutic effects of specialized nutritional support accrue through the

combined provision of macronutrients and micronutrients. These elements support

vital cellular and organ functions, immunity, tissue repair, protein synthesis, and

capacity of skeletal, cardiac, and respiratory muscles. As with any medical therapy, a

nutritional support regimen should be adjusted based on the requirements, response,

and tolerance of the patient. Patients who have inflammatory bowel disease are

particularly at risk for developing altered levels of vitamins and other micronutrients.

The etiology of these micronutrient losses is multifactorial and encompasses

decreased oral intake, increased losses secondary to diarrhea, and malabsorption. In

particular, deficiencies in vitamin D, folate, vitamin B12