L 40 Nutrition Assessment and Clinical Nutrition Support - Study Notes
Introduction
- Nutrition Care Process (NCP) used by Registered Dietitian Nutritionists (RDN) in clinical settings to provide consistent, high-quality nutrition care and clinical nutrition support with predictable outcomes.
- Four interrelated steps of the NCP:
- Assessment: collect and document information such as food/nutrition history, biochemical data, medical tests/procedures, anthropometrics, nutrition-focused physical findings, and client history.
- Diagnosis: select the appropriate nutrition diagnosis (name the specific problem) based on assessment data.
- Intervention: choose nutrition interventions targeting the root cause (etiology) of the nutrition problem to alleviate signs/symptoms.
- Monitoring and Evaluation: determine if goals are achieved or progress is being made toward goals.
- Clinical nutrition support includes entering the GI tract via enteral nutrition (feeding tube to stomach or small intestine) or bypassing the GI tract via parenteral nutrition (nutrients delivered directly into the bloodstream).
- Key point: Nutrition assessment synthesizes information from clinical signs/symptoms, anthropometrics, labs, and dietary intake (when appropriate); nutrient needs are determined by various mechanisms.
- Goals of nutrition support: tailor caloric and nutrient delivery to patient condition; continuously monitor and adjust.
- Assigned readings include foundational resources on life with Life with Fred (parenteral nutrition case), consensus statements from major nutrition organizations, and academy guidelines.
1. Overview: Nutrition Assessment and Clinical Nutrition Support
- Four-step process reiterated:
1) Assessment of nutritional status
2) Determination of nutritional needs (nutrition-related diagnosis)
3) Provision of nutrition support (enteral or parenteral)
4) Monitoring and evaluation to ensure needs are met - Nutrition assessment components: clinical signs/symptoms, anthropometrics, laboratory tests, and food diaries when appropriate.
- Routes of nutrition support:
- Enteral nutrition: via feeding tube into stomach or small intestine.
- Parenteral nutrition: predigested nutrients delivered intravenously.
- Nutritional formulas and rate of delivery are tailored to patient needs and condition.
2. Assessment of Nutritional Status
The ABCDs of nutrition assessment summarize the four core domains:
- Anthropometric measures (weight, height, etc.)
- Biochemical laboratory tests (e.g., albumin, prealbumin, TLC, CHI, etc.)
- Clinical signs and symptoms (hair, skin, eyes, etc.)
- Diet history (recall, diaries, FFQ)
2.1 Anthropometric Measurements
- Body weight (BW): crude index of total energy reserves; unintentional weight loss signals malnutrition but fluid shifts can confound BW.
- Significant weight loss thresholds by time:
- 1 week: loss of 1-2% (mild), >2% (severe)
- 1 month: ≥5% (severe if >5%)
- 3 months: ≥7.5% (severe ≥7.5%)
- 6 months: ≥10% (severe ≥10%)
- % Weight loss formula: \%Loss = \frac{(\text{Usual BW} - \text{Current BW})}{\text{Usual BW}} \times 100
- Current BW as % of Ideal BW (IBW) and Usual BW:
- % IBW = \frac{\text{Current weight}}{\text{IBW}} \times 100
- % UBW = \frac{\text{Current weight}}{\text{Usual weight}} \times 100
- Ideal Body Weight (IBW) by Hamwi method (example values):
- Men: IBW = 106 lb + 6 lb per inch over 5 ft
- Women: IBW = 100 lb + 5 lb per inch over 5 ft
- Example: a 5'10" man: IBW = 166 lb; a 5'3" woman: IBW = 115 lb
- Example %IBW: current 145 lb in a 5'3" woman (IBW 115 lb) → \%IBW = \frac{145}{115} \times 100 = 126.1\%
- Example %UBW: usual 160 lb, current 145 lb → \%UBW = \frac{145}{160} \times 100 = 90.1\%
- Body Mass Index (BMI) is used to categorize overweight/obesity and can reflect malnutrition severity in some cases:
- BMI ranges (kg/m^2): 18.5–24.9 Normal; 25.0–29.9 Overweight; 30.0–34.9 Obesity I; 35.0–39.9 Obesity II; >40 Obesity III
- For malnutrition interpretation (in some contexts): 17.0–18.4 Malnutrition I; 16.0–16.9 Malnutrition II; <16 Malnutrition III
- Body composition measures (two simple methods):
- Triceps skin-fold thickness (TSF) estimates body fat via skinfold calipers
- Mid-upper arm circumference (MAC) used to calculate MAMC: \text{MAMC} = \text{MAC} - \text{TSF}
- Other body composition methods: Bioelectrical impedance analysis (BIA), underwater densitometry (UWW), DXA/DEXA, isotope dilution, MRI, CT, ultrasound, etc.
2.2 Biochemical (Laboratory) Measurements
- Common nutritional markers: serum albumin, prealbumin (transthyretin), prothrombin time (PT), RBC indices (MCV, MCH), total lymphocyte count (TLC), creatinine-height index (CHI)
- Serum albumin: liver-synthesized with amino acid supply; decreases with edema, hepatic disease, malabsorption, diarrhea, burns, ESRD, stress, over-hydration, cancer; not a reliable sole marker of malnutrition due to non-nutritional influences and long half-life (~21 days).
- Serum albumin ranges: Normal 3.5–5.0 g/dL; Mild malnutrition 2.8–3.4 g/dL; Moderate 2.1–2.7 g/dL; Severe <2.1 g/dL
- Non-nutritional factors affecting albumin and its limited utility as a malnutrition marker: hydration status, inflammation, disease state, vascular leakage, zinc status, etc.
- Other serum proteins: transferrin, transthyretin (prealbumin), retinol-binding protein (RBP)
- Prealbumin: a better indicator of dietary change; half-life ~2–3 days; decreases with stress, infection, surgery, malnutrition, low protein intake, overhydration; not affected by iron deficiency
- Prothrombin time (PT): indicator of extrinsic coagulation pathway; prolongation may reflect vitamin K deficiency or other factors; consider other influences beyond vitamin K status
- Red blood cell indices (MCV, MCH): anemia evaluation; macrocytic or microcytic patterns reflect various nutrient deficiencies (protein, iron, copper, B12, folate; other nutrients may also cause anemia)
- Total lymphocyte count (TLC): often decreases with malnutrition and low albumin; prognostic indicator in hospitalized patients; high day-to-day variation limits monitoring usefulness
- Creatinine-height index (CHI): marker of lean body mass via urinary creatinine excretion normalized to height; reduced CHI suggests muscle wasting but can be influenced by renal function, stool/meat intake, etc.
2.3 Clinical Signs and Symptoms
- Nutrition-focused history and physical examination tools (Tables 10.1 and 10.2 in referenced text) to identify potential deficiencies (e.g., hair, skin, mucous membranes, edema)
- These signs help triangulate nutritional status alongside labs and anthropometry
2.4 Diet History
- Common methods to obtain diet history: 24-hour dietary recall; food diaries (1–7 days); food-frequency questionnaires
- Practical notes: 24-hour recall often sufficient in hospitalized patients to determine whether more detailed dietary evaluation is necessary; limitations exist for recall bias and day-to-day variation
2.5 Subjective Global Assessment (SGA)
- SGA integrates patient history, physical examination, and limited labs to assess nutritional status rapidly at the bedside; when performed by experienced clinicians, SGA is at least as good as other methods for identifying nutritional risk
- Components of SGA (patient history, physical exam, labs) including determinants:
- Recent weight loss*
- Dietary intake relative to normal
- GI symptoms
- Functional capacity of patient
- Muscle wasting*
- Loss of subcutaneous fat*
- Edema/ascites
- Albumin
- Total lymphocyte count
- *Most significant determinants during SGA
- The seven-point SGA version provides increased objectivity and granularity (ratings from 1 to 7; 1 = severely malnourished, 7 = well nourished); includes a structured questionnaire with sections for Weight Change, Dietary Intake, GI symptoms, Functional Status, Disease State affecting nutritional requirements, Muscle Wasting, Fat Stores, Edema; Overall rating determines nutritional status (Well-nourished, Mild/Moderate Malnutrition, Severe Malnutrition)
- The seven-point SGA has been developed and refined to provide more nuanced bedside assessment (Lim et al., 2016)
2.6 Current Guidelines for Malnutrition Diagnosis
- Key references: White et al. (2012) Consensus Statement by Academy of Nutrition and Dietetics and American Society for Parenteral and Enteral Nutrition; other reviews (Marcason, 2017) discuss albumin/prealbumin limitations
- Recommendation: Malnutrition diagnosis should be based on meeting 2 or more of six criteria rather than relying on albumin/prealbumin alone:
- Insufficient energy intake
- Weight loss
- Loss of subcutaneous fat
- Loss of muscle mass
- Localized/generalized fluid accumulation that may mask weight loss
- Diminished functional status as measured by hand grip strength
- This approach reflects the multifactorial nature of malnutrition and the influence of inflammatory and fluid status on single biomarkers
3. Determination of Nutrient Requirements
After assessing nutritional status, determine requirements for fluid, calories, protein, and other needs
3.1 Energy
- ENERGY REQUIREMENTS can be estimated via two primary methods:
1) Indirect calorimetry (gold standard): measures gas exchange (VO2, VCO2) to compute resting energy expenditure (REE) and respiratory quotient (RQ)
- Weir equation for REE: \text{REE} = \left[ 3.9(\text{VO}2) + 1.1(\text{VCO}2) \right] \times 1.44
- RQ: \text{RQ} = \frac{\text{VCO}2}{\text{VO}2}; physiological range 0.65–1.25; RQ indicates fuel use (carbs ~1.00, fat ~0.70, protein ~0.80)
- Examples: carbohydrate metabolism has RQ ≈ 1.00; fat ≈ 0.70; protein ≈ 0.80; prolonged ketosis or fat storage can shift RQ outside normal range
2) Predictive equations (for when indirect calorimetry is not available): Harris-Benedict, Owen, Mifflin-St. Jeor, Ireton-Jones, Frankenfield, Fusco - Harris-Benedict REE:
- Men: REE = 66.47 + 13.75W + 5.00H - 6.76A
- Women: REE = 655.10 + 9.56W + 1.85H - 4.68A
- Total Energy Expenditure (TEE);
- TEE = REE \times AF \times IF \times TF
- Where AF = Activity factor (e.g., 1.25 for hospitalized patients), IF = Injury factor (ranges 1.1 to 2.0 depending on injury severity), TF = Thermal factor (e.g., 1.3 for hyperthermia/burns)
- Ireton-Jones equations (examples):
- EEE(s) (spontaneously breathing) = 629 - 11A + 25W - 609O
- EEE(v) (ventilator-dependent) = 1925 - 10A + 5W + 281S + 292T + 851B
- Note: Use clinically appropriate equation based on patient status; burn patients often require higher energy due to hypermetabolism
- ENERGY REQUIREMENTS can be estimated via two primary methods:
1) Indirect calorimetry (gold standard): measures gas exchange (VO2, VCO2) to compute resting energy expenditure (REE) and respiratory quotient (RQ)
3.2 Fluid
- Daily water requirement approximations:
- 30-35\ \text{mL/kg/day} for adults, or
- 1\ \text{mL/kcal/day} based on caloric intake
3.3 Protein (Nitrogen)
- General requirement: non-pregnant/non-lactating adults require approximately 0.8\ \text{g protein/kg body weight} to maintain nitrogen balance
- Alternative estimation: protein should comprise about 12-15\% of total daily calories
- Nitrogen balance equation:
- N-balance = N-intake - N-losses
- N-intake (g/day) = \frac{\text{Protein intake (g/day)}}{6.25}
- N-losses (g/day) = UUN + Non-urea urinary N + Fecal N + Misc N-losses = UUN + 4
- N-balance (g) = \frac{\text{Protein intake (g/day)}}{6.25} - (\text{UUN} + 4)
- Example question: A patient consuming 70 g protein/day with urinary urea loss of 7 g/day → compute nitrogen balance using the above formula
4. Enteral Nutrition Support
- Enteral nutrition provides nutrients through the GI tract via a feeding tube when the patient has partial or full functional intestine
- 4.1 Access Routes (key considerations before selecting route)
- Can the patient’s GI tract be used safely?
- How long will nutrition support be required?
- Is the patient at risk for pulmonary aspiration of feeding formula?
- 4.2 Enteral Formulas
- Formulary options vary byメーカー (e.g., Abbott, Nestlé) and differ in macro ratios and added nutrients (e.g., arginine, glutamine, immune support formulas)
- Example composition considerations:
- Carbohydrate: typically 40–80% of total calories
- Nitrogen (protein): essential for lean mass maintenance
- Fat: ~20–30% of total calories
- Water, micronutrients, fiber
- Questions:
- Besides energy, what are two other important nutritional roles of fat in enteral formulas?
- What are potential benefits of including fiber in formulas?
- 4.3 Complications
- Mechanical: tube size/placement issues, nasal irritation/necrosis, obstruction
- Infectious: usually Staphylococcus species
- Gastrointestinal: diarrhea or constipation
- Metabolic: dehydration, electrolyte imbalances, hyperglycemia, weight changes, loss of visceral protein
- Refeeding syndrome: a serious potential complication in susceptible patients receiving nutrition support (covered separately)
5. Parenteral Nutrition Support
- Parenteral nutrition bypasses the GI tract; solutions are regulated as drugs and require a prescription; RDNs collaborate with pharmacists/physicians for total kcal needs, formulas, and delivery rate
- 5.1 Access Routes
- Central venous catheter (terminating in distal Vena Cava or right atrium) or peripheral venous access (e.g., cephalic vein) depending on duration and needs
- 5.2 Parenteral Solutions
- Base solution: glucose + crystalline amino acids (typical 50:50 essential:non-essential amino acids)
- Lipid emulsion: oil-in-water emulsions (soybean and/or safflower oils)
- Total Nutrient Admixture (TNA): combination of base solution with lipid emulsion in a single bag (three-in-one admixture sometimes used)
- Included components: water, electrolytes, vitamins and minerals
- 5.3 Complications
- Mechanical: catheter misplacement
- Infection: catheter-related sepsis (Staphylococcus species common)
- Metabolic: list of common metabolic complications (early and late) including electrolyte disturbances and organ dysfunction
- Refeeding syndrome: occurs with rapid replenishment in malnourished patients; electrolyte disturbances (hypophosphatemia, hypomagnesemia, hypokalemia) can lead to arrhythmias, cognitive issues, respiratory failure, and death
- Populations at risk for refeeding syndrome include anorexia nervosa, chronic malnutrition, chronic alcoholism, morbid obesity with rapid weight loss, prolonged fasting, significant stress/depletion, or NPO status for 7–10 days
6. Refeeding Syndrome: Biochemical/Physiologic Basis and Prevention
- Definition: metabolic and physiologic consequences of depletion, repletion, shifts, and interrelationships of phosphorus, potassium, magnesium, glucose metabolism, vitamin deficiency, and fluid resuscitation
- Characteristic electrolyte abnormalities: hypophosphatemia, hypomagnesemia, hypokalemia
- Consequences: cardiac arrhythmias, confusion, respiratory failure, potential death
- At-risk populations: anorexia nervosa, chronic malnutrition, alcoholism, rapid weight loss, prolonged fasting, high-stress depletion, prolonged NPO
- Prevention strategies (Practical Handbook of Nutrition in Clinical Practice, 1994):
1) Understand refeeding syndrome and affected populations
2) Monitor electrolytes before and after starting nutrition support
3) Replete electrolyte deficiencies aggressively (K, P, Mg)
4) Maintain glucose control
5) Monitor vital signs, intake, and output while restoring circulatory volume carefully
6) Assess caloric needs with metabolic cart when possible; meet measured needs first, then gradually increase calories to support weight gain
7) Routinely provide vitamin and mineral supplements
7. Clinical Cases: Nutritional Assessment, Needs, Route, and Potential Complications
- Case 1 (21-month-old): eczema with feeding issues; weight 10.8 kg (10th percentile); height 81 cm (5th percentile); serum albumin 1.0 g/dL (low); largely breastfed until ~13 months; introduction of cow’s milk followed by rice milk due to concerns about eczema
- Case 2 (64-year-old man): 6 weeks of progressive blurred vision; diet-controlled celiac disease with persistent diarrhea despite a gluten-free diet
- Case 3 (14-year-old boy): jaundice, lethargy, anorexia, weight loss; dietary pattern dominated by white bread, junk foods; pale and icteric; Hgb 7.9 g/dL; MCV 117 fL; WBC normal; platelets 119×10^3/µL (thrombocytopenia)
- Case 4 (22-year-old male): bruising/petechiae with no trauma; poor oral hygiene, carbohydrate-heavy diet with no vegetables; smoking and episodic heavy alcohol use; blood smear shows hypochromic, microcytic RBCs
- Case 5 (31-year-old woman): refractory dermatitis and diffuse alopecia; prior Whipple procedure; steatorrhea with loose stools post-surgery; 10 kg weight loss over 6 years; beefy red tongue with papillary atrophy; edema
- Case 6 (JM, 39-year-old man, burn injury): extensive burns (~75% TBSA with 60% third-degree) and inhalation injury; resuscitated with IV fluids; enteric feeding via proximal duodenum within 8 hours of admission; energy needs discussed via multiple methods, including Harris-Benedict and Curreri equations; indirect calorimetry results (VCO2=253 mL/min, VO2=220 mL/min) and RQ calculation; PN formulation delivering 720 kcal/day from protein; nitrogen balance calculation; serum prealbumin low at 7.5 mg/dL; rationale for prealbumin use over albumin explained
7. Worked example topics from Case 6
- (a) Harris-Benedict REE calculation for JM: REE = 66 + 13.75W + 5H - 6.8A
- (b) Burn injury adjustments: TEE = REE × AF × IF × TF with
- AF (Activity Factor) = 1.0–1.1 (bedrest)
- IF (Injury Factor) = 2.1 (≥50% TBSA)
- TF (Thermal Factor) = 1.3 (temperature ~40°C)
- (c) Curreri equation for burn energy needs: TEE = (25 \text{ kcal} \times ext{kg}) + (40 \text{ kcal} \times \% TBSA)
- (d) Comparison and interpretation of energy needs across methods (Harris-Benedict vs Curreri)
- 2. Indirect calorimetry for JM: RQ interpretation and implications for energy needs and metabolic state; subsequent PN formulation considerations (high/low fat, protein emphasis based on metabolic state)
- 3. PN feeding: 720 kcal/day from protein: nitrogen content calculation:
- Protein provided = 720 kcal/day, assuming 4 kcal/g protein (typical), so protein grams = \frac{720}{4} = 180\ \text{g/day}
- Nitrogen from protein: N_{intake} = \frac{180}{6.25} = 28.8\ \text{g N/day}
- Urinary urea nitrogen (UUN) = 18 g/day; N-losses = UUN + 4 = 22 g/day
- Nitrogen balance: N{balance} = N{intake} - N_{losses} = 28.8 - 22 = 6.8\ \text{g/day (positive balance)}
- 4. Serum prealbumin interpretation: 7.5 mg/dL (normal range 9.5–46.6 mg/dL)
- Rationale for using prealbumin instead of albumin in this case: shorter half-life (~2–3 days) makes prealbumin a more responsive index of recent nutritional intake; albumin is less sensitive to short-term changes and is influenced by inflammation, hydration, and disease state
- Interpretation: low prealbumin suggests undernutrition or acute catabolic state despite other markers; context important (inflammation, fluid shifts, hepatic function)
Key formulas and references (for quick review)
- Weight loss percentage: \%Loss = \frac{(\text{Usual BW} - \text{Current BW})}{\text{Usual BW}} \times 100
- %IBW: \%IBW = \frac{\text{Current weight}}{\text{IBW}} \times 100
- %UBW: \%UBW = \frac{\text{Current weight}}{\text{Usual weight}} \times 100
- Hamwi IBW (examples):
- Men: \text{IBW} = 106 + 6\times\text{inches over 5 ft}
- Women: \text{IBW} = 100 + 5\times\text{inches over 5 ft}
- BMI: \text{BMI} = \frac{\text{Weight (kg)}}{\text{Height (m)}^2}
- BMI interpretation (standard): 18.5–24.9 Normal; 25.0–29.9 Overweight; 30.0–34.9 Obesity I; 35.0–39.9 Obesity II; >40 Obesity III; Malnutrition ranges may apply in some contexts (e.g., 17.0–18.4, 16.0–16.9, <16.0 for gradations of malnutrition)
- TSF/MAC/MAMC: \text{MAMC} = \text{MAC} - \text{TSF}
- Biochemical markers: Serum albumin (3.5–5.0 g/dL normal; often unreliable for malnutrition), Prealbumin (18–38 mg/dL normal; <10 mg/dL significant malnutrition), PT (coagulation), TLC, CHI
- N-balance: N{intake} = \frac{\text{Protein intake (g/day)}}{6.25}, \quad N{losses} = \text{UUN} + 4, \quad N{balance} = N{intake} - N_{losses}
- Indirect calorimetry: \text{REE} = \left[3.9(\text{VO}2) + 1.1(\text{VCO}2)\right] \times 1.44; \text{RQ} = \frac{\text{VCO}2}{\text{VO}2}
- Harris-Benedict REE and TEE: Men: REE = 66.47 + 13.75W + 5.00H - 6.76A; Women: REE = 655.10 + 9.56W + 1.85H - 4.68A; \text{TEE} = \text{REE} \times AF \times IF \times TF
- Ireton-Jones equations: EEE(s) = 629 - 11A + 25W - 609O; EEE(v) = 1925 - 10A + 5W + 281S + 292T + 851B
- Curreri equation: TEE = (25 \text{ kcal} \times \text{kg}) + (40 \text{ kcal} \times \% TBSA)
- Enteral vs Parenteral considerations and complications summarized in sections 4–5 above
Note: The content above consolidates all major and minor points from the transcript, emphasizing definitions, formulas, clinical reasoning, and practical implications for nutrition assessment and support. Use as a comprehensive reference for exam preparation and clinical case analysis.