Malnutrition in hospitalized patients is common. Though exact prevalence is difficult to calculate due to a lack of uniform criteria, most studies suggest that 30-60% of all hospitalized patients are malnourished. Furthermore, malnutrition significantly affects patient’s mortality, morbidity and length of hospital stay.
Malnutrition can be defined as “an acute, subacute or chonic state of nutrition, in which varying degrees of overnutrition or undernutrition with or without inflammation activity have led to a change in body composition and diminished function”. This definition encompasses the most current understanding of links between inflammation and nutrition and highlights the importance of considering severity and duration of illness or trauma when diagnosing malnutrition.
II. Diagnostic Approach.
A. What is the differential diagnosis for this problem?
Hypo or hyperthyroidism
Viral or parasitic infections
B. Describe a diagnostic approach/method to the patient with this problem.
I. The initial step in evaluating the nutritional status of a patient is to perform a screening test to identify persons either malnourished or at risk for malnutrition. There is significant controversy in the literature regarding the ideal screening tool as few have been validated by well designed studies.
Commonly used screening tools backed by prominent nutrition societies (American Dietetic Association, European Society of Parenteral and Enteral Nutrition and the American Society of Parenteral and Enteral Nutrition) include: Nutritional Risk Screening (NRS), Malnutrition Universal Screening Tool (MUST), and the Malnutrition Screening Tool (MST). All three screening tools evaluate for weight loss and adequate intake; NRS and MST include severity of disease (metabolic stress), and MST also considers body mass index (BMI) in determining risk.
Laboratory tests, such as albumin and pre-albumin, have been proposed as screening tools. However, it should be noted that these tests have not been validated as a measurement of nutritional status and are influenced by factors independent of nutrtitional state as discussed below.
II. Once a patient has been identified as malnourished or at risk for malnutrition, a detailed assessment conducted by or in conjunction with trained clinicians (i.e. registered dietician, nutrition nurse or expert provider) is warranted. Nutrition assessment includes diet and medication history, clinical status, anthropometric measurements (i.e. weight, BMI, mid-arm circumference, etc), laboratory data and physical examination. The two nutrition assessment tools most commonly used and recommended are the Subjective Global Assessment (SGA) and the Mini Nutritional Assessment (MNA), which evaluate a combination of the above mentioned parameters.
III. The next step is to determine the etiology of malnutrition. Recently the American Society of Parenteral and Enteral Nutrition has proposed a classification system for malnutrition based on the cause and presence of inflammation. These include the following nutrition diagnoses:
(1) Starvation-related malnutrition, which is chronic starvation without inflammation:
(2) Chronic disease-related malnutrition, where inflammation is chronic and of mild-moderate degree:
Organ failure (heart, kidney, liver or lung)
Inflammatory bowel disease
Chronic infections (TB, HIV)
(3) Acute disease or injury-related malnutrition, where inflammation is acute and severe:
Sepsis/ major infections
IV. The final step is to develop a treatment plan based on the classification designated above.
Micronutrient deficiencies are another important cause of malnutrition. Iron, zinc, magnesium, folic acid, iodine, vitamin A and perhaps vitamin D are among the most common deficiencies found worldwide.
1. Historical information important in the diagnosis of this problem.
When obtaining a medical history to identify patients malnourished or at risk for malnutrition, particular attention should be given to:
>2% weight loss over 1 week (acute)
Unintentional weight loss over 6 months (chronic): >10% weight loss indicates need for a thorough nutritional assessment; 10-20% weight loss indicates moderate protein-calorie malnutrition; >20% loss indicates severe protein-calorie malnutrition
Diet history, including recent change in intake or type of diet
Gastrointestinal symptoms (nausea, vomiting, diarrhea)
Current and past medical and surgical history
Current and past medications
Social and environmental factors, including access to food, poverty, etc.
Unintentional weight loss and decreased intake have been found to have the highest sensitivity and specificity for identifying patients who may have nutritional problems in the acute setting.
2. Physical Examination maneuvers that are likely to be useful in diagnosing the cause of this problem.
Physical findings, with the exception of recent weight loss, are late findings in the spectrum of malnutrition, and include the following:
Anthropometric measurements, including weight, mid upper arm circumference, triceps skin fold and body mass index.
Decreased subcutaneous fat, particularly around the face, buttocks, arms and legs.
Muscle wasting, particularly around temples, clavicles, shoulders, scapulae, thigh and calf.
Edema, most commonly distal extremities and/or anasarca.
Skin changes with dry skin, flaking, raw chaffed skin.
Hair tends to thin out, become brittle, may change to reddish-brown, dull color.
Nails often ridged with fissures, brittle.
In the oral cavity, can see cheilosis, angular stomatitis or papillary atrophy.
Abdominal distention may occur from weak abdominal wall musculature. Hepatomegaly is possible from fatty infiltration.
Hand grip strength.
3. Laboratory, radiographic and other tests that are likely to be useful in diagnosing the cause of this problem.
Diagnostic tests for malnutrition can be categorized into (1) serum visceral proteins (2) immunologic markers (3) nitrogen balance, and (4) muscle function tests.
Serum visceral proteins include albumin, pre-albumin, retinol-binding protein, and transferrin. In general, these serum proteins are affected by capillary permeablility, medications, impaired liver function and inflammation, making them poor proxies for nutritional status. These proteins act as negative acute phase reactants meaning in the face of acute illness, these proteins are preferentially downgraded in exchange for positive acute phase reactants (C-reactive protein (CRP), ferritin, etc), further limiting their use in determining malnutrition in the face of inflammation.
Because of it’s long half-life (14-20 days), extravasation into extracellular spaces and low rate of synthesis (5% of albumin synthesized in liver daily), albumin should not be used as an index of nutrition in patients. Additionally, albumin levels may be normal in chronic starvation states and does not correlate with weight loss. Low albumin, however, is a predictor of prognosis.
Pre-albumin (PAB) has a shorter half life of 2-3 days and a smaller body pool than albumin. However, it is also a negative acute phase reactant and therefore is subject to similar variations in association with inflammation. Furthermore, since it is degraded by the kidneys, it may be falsely elevated in patients with renal dysfunction.
Retinol-binding protein has a half-life of only 12 hours, making it a tempting choice as an indicator of malnutrition. It, too, is degraded by the kidneys and so may be elevated in acute renal failure.
Theratio of CRP to PAB has been correlated in some studies with multi-organ dysfunction and postoperative infections and is therefore commonly used to determine nutritional status. It is important to remember that the rates at which CRP and PAB rise and fall independently and in relationship to each other is inconsistent, making their interpretation in the clinical settings difficult.
Immunologic markers of nutritional state include total lymphocyte count (TLC) and delayed cutaneous hypersensitivity, which consists of injecting an antigen under the skin with anergy indicating poor nutrition. However, TLC is affected by immunosuppressive agents and critical illness and delayed cutaneous hypersensitivity is no longer used because of difficulties creating a graded score and the associated scarring at the injection site.
Nitrogen balance is used to evaluate the adequacy of protein intake as proteins contain virtually all the nitrogen in the body. A positive nitrogen balance indicates an anabolic state while a negative balance indicates a catabolic state, with a net loss of protein. Nitrogen balance can be calculated using the formula:
Protein intake (g/day) / 6.25-Urine Urea Nitrtogen (g/day) + 4g
Urine urea nitrogen is determined from 24 hour urine collection
4g is added to account for miscellaneous (non-urinary) nitrogen losses
Hand grip strength as a measure of muscle function has shown to be a good marker for nutritional status and for predicting short and long-term morbidity and mortality. Studies have demonstrated it’s value as an indicator of increased postoperative complications, increased length of hospitalizations, increased rate of rehospitalization and decreased physical status.
C. Criteria for Diagnosing Each Diagnosis in the Method Above.
Distinguishing malnutrition from the conditions listed in the differential above is difficult as malnutrition is common within each of those conditions.
D. Over-utilized or “wasted” diagnostic tests associated with the evaluation of this problem.
Serum albumin is often used as a marker for nutritional status. However, because of it’s long half life, role as a negative acute phase reactant, influence by hydration status and low correlation with weight loss, albumin is not a representative surrogate of malnutrition and should not be used in this regard.
III. Management while the Diagnostic Process is Proceeding.
A. Management of Clinical Problem Malnutrition.
Potentially life treatening complications associated with treatment of malnutrition include fluid overload in severly malnourished patients and refeeding syndrome. Careful monitoring of electrolytes and frequent reassessment of clinical status is paramount to preventing these complications.
Goals of treatment and management of malnutrition is based on the underlying etiology according to the classifications mentioned above. Inflammation affects energy demands because of increased resting energy expenditure and protein needs due to increased nitrogen excretion. The presence or absence, severity and duration of inflammation are important considerations when formulating a nutrition treatment plan. Acute inflammation produces a rapid, catabolic state whereas loss of muscle mass and function from chronic inflammation occurs slowly over months to years.
Without inflammation, even the most advanced starvation-based malnutrition can be treated with nutritional resuscitation (enteral or parenteral feeds). However, muscle protein loss associated with inflammation is only partly halted or reversed by nutritional interventions, but inadequate intake may contribute to further loss of lean tissue, compounding the effects of inflammation. For acute, severe inflammatory conditions, the priority of nutrition intervention is to provide nutrients to support vital organ function and preserve host responses while acute medical treatment is provided. For chronic-disease related malnutrition with mild-moderate inflammation, nutrition therapy is supportive to facilitate effective medical treatment for the underlying condition.
In devising a nutrition plan, the first step is determining the patient’s energy/calorie requirements. This is done by calculating the basal energy expenditure (BEE) and the total energy expenditure (TEE). Then determine protein requirements, fluid needs and disease states.
Adult males: BEE (kcal/day)= 66 + (13.7 * wt in kg) + (5 *ht in cm) – (6.8*age)
Adult females: BEE (kcal/day)= 655 + (9.6*wt in kg) + (1.7*ht in cm)- (4.7-age)
60-80% of caloric provision should be in the form of glucose, with the remainder given as lipids. The role of protein calories in energy provision is controversial.
Protein requirements are typically 0.75g/kg/d- 2.2g/kg/d based on degree of stress placed on body.
Fluid needs are affected by patient’s functional cardiac, pulmonary, renal and hepatic status and increase with external losses (diarrhea, fever, burns, etc). Average adult requires 35-45 ml/kg/d of water. Most of the fluids are easily replenished as caloric, protein, and electrolyte needs of the patient are met.
Lastly, underlying disease guides specific nutritional therapies. For instance, protein needs in patients with renal failure are altered as nitrogen elimination is impaired or patient is placed on dialysis. Suggested protein requirements are 0.8-1.0g/kg/d for patients not on dialysis, 1-1.2g/protein/d for patients on hemodialysis, and 1.2-1.5g/protein/d for patients on peritoneal dialysis. Patients with liver failure may require additional carbohydrates as glycogen stores are depleted and risk of hypoglycemia increases.
Feeds are initiated either enterally or parenterally, with enteral feeds preferred when possible. Long term enteral feeds are accomplished with gastrostomy or jejunostomy tubes while short term enteral feeds are administered via nasogastric or nasodudodenal tubes.
B. Common Pitfalls and Side-Effects of Management of this Clinical Problem.
Patients receiving enteral and parenteral nutrition should be carefully monitored for complications, including nausea, vomiting, diarrhea, constipation, malabsorption, aspiration, or metabolic derangements. Refeeding syndrome is a potentially fatal complication associated with initiating feeds in severely malnourished patients. This occurs as a result of increased insulin release as the body shifts from fat to carbohydrate as the primary fuel source. The increased insulin causes intracellular shifts of electrolytes leading to hypophosphatemia, hypokalemia, and hypomagnesiumemia. Prevention of this life threatening complication involves slow initiation of feeds, correcting electrolyte abnormalities prior to starting treatment and frequent monitoring of clinical status and electrolytes.
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- I. Problem/Condition.
- II. Diagnostic Approach.
- D. Over-utilized or “wasted” diagnostic tests associated with the evaluation of this problem.
- B. Common Pitfalls and Side-Effects of Management of this Clinical Problem.