BMI may be easily calculated using the equation provided above or standardized tables. When calculating BMI two intersystem conversions are important: 1 kg = 2.2 lb and 1 m = 39.37 in.

As an example, let us calculate the BMI for a person 5 ft & 1 in in height weighing 120 lb.

BMI = 22.7 kg/m². This is a normal weight individual according to the guidelines in Appendix 5 (Table A5.1), which shows the classification recommended by both the NIH (National Institutes of Health) and WHO (World Health Organization).

Calculate the BMI values for the following individuals:

A. An adult weighing 182 lb and measuring 5’5” in height.

B. A person 5’6” in height weighing 75 kg.

C. A subject weighing 110 kg and 64 inches in height.

Solutions.

A. 30.4 kg/m²

B. 26.6 kg/m²

C. 41.4 kg/m²

CALCULATIONS

ASSESSMENT OF MALNUTRITION

2. When nutritional needs are not met by oral intake because the patient does not want to eat or is unable to eat, malnutrition will result unless nutrition is provided in another way.

Critical assessment regarding nutritional requirements and adequacy of nutrition support depends on:

(a) Patient’s data related to disease state

(b) Dietary and drug intake history

(c) Laboratory results

Two alternatives are available for nutrition support: enteral nutrition (through a feeding tube placed into the stomach or small bowel) or parenteral nutrition (nutrition solution administered intravenously). Both methods will require initial nutrition assessment to determine the degree of malnutrition and calculations will be needed to determine specific nutrient requirements.

CALCULATION OF NUTRITIONAL REQUIREMENTS

3. Nutritional needs are primarily focused on caloric needs, as the body needs a constant energy supply to maintain physiological functions. Caloric (nonprotein) requirements vary depending on the patient’s physical state, age, height, weight, gender and medical condition, including degree of stress imposed by the disease.

Energy Requirement (Caloric Requirement)

4. Caloric requirement is measured in calories or kilocalories (kcal). One kilocalorie corresponds to the amount of heat required to raise the temperature of 1 kg of water by 1 °C at room temperature. Caloric requirement, also known as estimated total daily calorie (TDC), total daily energy (TDE) requirement, or anabolic goal (for maintenance of body weight) may be calculated through several methods described in Table 11.1.

TABLE 11.1 Usual methods to determine caloric requirements

Methods	Description/Equations
Nomogram	Basal metabolic requirements in function of age, sex, height and body weight
Indirect calorimetry	Measured estimate of energy utilization
Ideal body weight (IBW)	IBW rule of thumb or Hamwi equation^a: Males IBW = 106 lb (48 kg) + 6 lb (2.7 kg) for each inch (2.54 cm) over 5 ft (152 cm) Females IBW = 100 lb (45 kg) + 5 lb (2.3 kg) for each inch (2.54 cm) over 5 ft (152 cm) TDC = 45 kcal/kg/day × IBW^b (kg)
^cHarris–Benedict equation (BEE = basal energy expenditure)	Males BEE (kcal/day) = 66.5 + (13.75 × W_(kg)) + (5 × H_(cm)) − (6.76 × A_(yr)) Females BEE (kcal/day) = 655 + (9.56 × W_(kg)) + (1.85 × H_(cm)) − (4.68 × A_(yr)) TDC = BEE (kcal/day) × 1.25^d × stress factor^e
Rule of thumb	TDC = 25–35 kcal/kg/day
General guidelines	Anabolic goal (TDC) = 25 kcal/kg/day (mildly stressed) 30–35 kcal/kg/day (moderately stressed) 45 kcal/kg/day (postoperative) 60 kcal/kg/day (hypercatabolic)^f

^a In practice, when the Hamwi equation is used, the resultant weights are rounded to the nearest whole number.

^b Usually, the smaller value between IBW (ideal body weight) and ABW (actual body weight) is used for calculation of total daily calorie (TDC) or anabolic goal.
ABW is the patient’s real weight or the patient’s weight at time of consultation. IBW is also known as lean body mass (LBM). An important application of IBW is in the dosing of some drugs that are highly hydrophilic and do not distribute well into fat. For overweight and obese patients, dosing must be based on IBW or the patient will be overdosed.

^c The Harris-Benedict equation determines the Basal Metabolic Expenditure (BME), also known as Basal Energy Expenditure (BEE), Resting Metabolic Energy (RME) or Resting Energy Expenditure (REE).

^d 1.25 = activity factor (walking, sitting, physical therapy, treatment)

^e Stress factor = degree of stress imposed by the disease process and may be:
0.85 = simple starvation, hospitalization
1.05–1.15 = elective surgery
1.20–1.40 = sepsis
1.30 = closed head injury
1.40 = multiple trauma
1.50 = systemic inflammatory response syndrome
2.00 = major burn

^f Hypercatabolic states are sepsis, closed head injury, major trauma, and severe burn.

As a general rule, glucose, which is administered daily, is used to provide approximately 60–80% of estimated daily caloric requirement for maintenance of body weight. The remaining caloric requirement is complemented by the infusion of fat emulsion 2–3 times a week.

So Which Method Should I Use to Determine Caloric Requirements?

5. There are no definite rules as to which of the methods in Table 11.1 should be used. The Harris-Benedict equation and the Hamwi equation have traditionally been used and recommended by ASPEN (American Society of Parenteral and Enteral Nutrition) but some institutions consider indirect calorimetry a good guide to have an estimation of energy utilization by the patient. All methods listed above have been used repeatedly in several institutions and have provided relatively similar results (maintenance of patient’s body weight) when used as a guide for patient caloric requirement.

6. We will now apply the IBW rule of thumb or Hamwi equation to determine the actual body weight (ABW) and ideal body weight (IBW) in kg for a woman of 5’1” in height and weighing 120 lb. What would be the anabolic goal or total daily calorie requirement (TDC) for this patient?

The patient’s actual body weight in kg is:

Calculation of IBW in kg is:

We will use the smallest body weight (IBW, in this case) for calculation of TDC:

Based on IBW, calculate the total daily calorie requirement for a male patient weighing 198 lb and 5’6” in height.

Solution. 2880 kcal/day

CALCULATIONS

If we consider the patient’s actual body weight, it is 198/2.2 = 90 kg. The usual procedure is to calculate TDC using either ABW or IBW, whichever is smaller.

IBW = 106 lb (48 kg) + 6 lb (2.7 kg) for each inch (2.54 cm) over 5 ft (152 cm)

7. The weight of a male patient undergoing surgery is 110 lb and his height is 165 cm. What is the total daily energy requirement for maintenance of body weight of this patient? Use the IBW method.

Solution. 2250 kcal/day

CALCULATIONS

165 cm − 152 cm = 13 cm

IBW = 48 kg + (2.7 kg × 13) = 83.1 kg

8. Using the Harris-Benedict equation calculate the daily energy requirement for a 38 year old male patient undergoing elective surgery (use a stress factor of 1.10) weighing 132 lb and measuring 5’7” in height.

Solution. 2043 kcal/day

CALCULATIONS

BEE = 66.5 + (13.75 × W_(kg)) + (5 × H_(cm)) − (6.76 × A_(yr))

BEE = 66.5 + (13.75 × 60) + (5 × 170.2) − (6.76 × 38) = 66.5 + 825 + 851 − 256.9

BEE= 1486 kcal/day

TDC = BEE (kcal/day) × 1.25 × stress factor

TDC = 1486 × 1.25 × 1.10 = 2043 kcal/day

9. A 28 year old female patient with closed head injury (stress factor = 1.3) will need nutritional support. Calculate the TDC required for this patient using Harris-Benedict equation. Patient weight and height are 121 lb and 5’2”.

Solution. 2195 kcal/day

CALCULATIONS

BEE = 655 + (9.56 × W_(kg)) + (1.85 × H_(cm)) − (4.68 × A_(yr))

BEE = 665 + (9.56 × 55) + (1.85 × 157.5) − (4.68 × 28) = 665 + 525.8 + 291.4 − 131 = 1351 kcal/day

TDC = BEE (kcal/day) × 1.25 × stress factor

TDC = 1351 × 1.25 × 1.3 = 2195 kcal/day

10. Use the Harris-Benedict equation and calculate the caloric requirement for:

A. A 65 year old hospitalized male patient weighing 1301b and measuring 5’4” in height. Assume a stress factor of 0.85

B. A 25 year old hospitalized female patient weighing 1001b and measuring 5’2” in height. Consider that the patient has multiple trauma (stress factor of 1.4)

Solutions.

A. 1329 kcal/day

B. 2228 kcal/day

CALCULATIONS

A. BEE = 66.5 + (13.75 × W_(kg)) + (5 × H_(cm)) − (6.76 × A_(yr))

BEE = 66.5 + (13.75 × 59) + (5 × 162.6) − (6.76 × 65) = 66.5 + 811.3 + 813 − 439.4 = 1251 kcal/day

TDC = BEE (kcal/day) × 1.25 × stress factor

TDC = 1251 × 1.25 × 0.85 = 1329 kcal/day

B. BEE = 655 + (9.56 × W_(kg)) + (1.85 × H_(cm)) − (4.68 × A_(yr))

BEE = 665 + (9.56 × 45.4) + (1.85 × 157.5) − (4.68 × 25) = 665 + 434 + 291.4 − 117 = 1273 kcal/day

TDC = BEE (kcal/day) × 1.25 × stress factor

TDC = 1273 × 1.25 × 1.4 = 2228 kcal/day

11. Determine the TDC for a 32 year old male patient 158 cm in height and weighing 42 kg. Use IBW method, Harris-Benedict method, and rule of thumb method considering the patient is moderately stressed (35 kcal/kg/day or stress factor = 1.05). Analyze the results.

Solutions. See below.

CALCULATIONS

Using body weight:

158 cm − 152 cm = 6 cm

ABW = 42 kg

IBW = 48 kg + (2.7 kg × 6) = 64.2 kg

Using Harris-Benedict:

BEE = 66.5 + (13.75 × W_(kg)) + (5 × H_(cm)) − (6.76 × A_(yr))

BEE = 66.5 + (13.75 × 42) + (5 × 158) − (6.76 × 32) = 66.5 + 577.5 + 790 − 216.3 = 1218 kcal/day

TDC = BEE (kcal/day) × 1.25 × stress factor

TDC = 1218 × 1.25 × 1.05 = 1599 kcal/day

Using rule of thumb:

These results show that calculations using the Harris-Benedict equation and the rule of thumb produce similar results and seem to be more appropriate than using body weight only because they include a stress factor.

Protein (Nitrogen) Requirement

12. Amino acids, the building blocks of protein, provide the nitrogen necessary for protein synthesis (anabolism). While grams of protein are generally calculated in a nutritional plan, grams of nitrogen are occasionally used as an expression of the amount of protein received by the patient. In a nutrition regimen, amino acids are provided through amino acid solutions. Protein requirements may be reduced in certain disease states (renal failure, hepatic encephalopathy); thus specialized amino acid formulations have been developed for patients whose protein intake is restricted. Recommendations for amino and intake are summarized in Table 11.2.

TABLE 11.2 General recommendations for daily amino acid requirements

Patient Status	Daily Requirement Based on Actual Body Weight (g/kg)
Postoperative (uncomplicated)	0.8–1.0
Postoperative (unable to eat for >10 days)	1.0–1.5
Sepsis and stress	1.2–1.5
Multiple trauma	1.3–1.7
Major burn	1.8–2.5

M.S., 121 lb, will be hospitalized for 2 days after hernia surgery (uncomplicated). What is this patient’s daily amino acid requirement? (Assume a daily requirement of 1 g/kg.)

Solution. 55 g

CALCULATIONS

13. A patient weighing 1651b and presenting major burns is hospitalized. The nutrition pharmacist will need to calculate the daily amino acid requirement for this patient. Assuming the patient will receive this nutrient intravenously from a 15% (w/v) amino acid solution, how many milliliters will be required?

Solution. 1250 mL

CALCULATIONS

14. There are three sources of amino acids available in a hospital pharmacy: 3.5%, 7%, and 12.5% amino acid solutions (w/v). Which solution should the pharmacist choose and how many milliliters should be given to a patient weighing 991b and presenting sepsis? This patient is under fluid restriction (a patient under fluid restriction should receive the smallest volume of fluid possible).

Solution. 540 mL of the 12.5% solution

CALCULATIONS

Since the patient is under fluid restriction, the most concentrated solution must be chosen to allow the smallest volume. Thus,

Micronutrient Requirement

15. The requirements for vitamins, trace minerals and electrolytes (micronutrients) are basically empirical. In general, serum concentrations of electrolytes and trace minerals are measured regularly and adjusted accordingly. Blood concentrations of vitamins are measured in patients with a suspected deficiency. Electrolytes, multivitamins and trace elements are available as multiconcentrates or as individual units to be added to nutrition formulations. Table 11.3 provides guidelines for various micronutrients.

TABLE 11.3 General guidelines for daily electrolyte requirements

Electrolyte	Requirement (mEq/day)
Na (sodium)	80–100
K (potassium)	60–80
Mg (magnesium)	8–16
Ca (calcium)	5–10
PO₄ (phosphate)	15–30
Cl (chloride)	50–100
Acetate	50–100
Daily multivitamin requirement: 10 mL of standard multivitamin injection.
Daily trace elements requirement 1 mL of standard trace elements injection.

Fluid Requirement

16. Some general recommendations have been developed among practicing nutrition professionals and the choice of one of them for calculation of the total daily fluid (TDF) requirement is based on patient’s age, disease state and degree of dehydration. These are shown below in Table 11.4.

TABLE 11.4 Recommendations for fluid intake

Category	Patient Group	Recommendation
I	Adults	35 mL/kg/day
II	Adults with severe dehydration (e.g., burns over a large part of the body)	1500 mL (for first 20 kg) + 20 mL/kg/day (for additional kg > 20 kg)
III	Pediatrics and geriatrics	BW 0–10 kg: 100 mL/kg/day 10 kg < BW < 20 kg: 50 mL/kg/day BW > 20 kg: 20 mL/kg/day

An 8-year-old child was hospitalized after 4 days with diarrhea and vomiting. At consultation, the child weight was 66 lb. What would be the recommended total daily fluid (TDF) for this patient?

Solution. 600 mL

CALCULATIONS

Considering that the patient is a child, the best approach is to use category III, BW > 20 kg: 20 mL/kg

TDF = 20 mL/kg × 30 kg = 600 mL

17. A 35 year old male patient weighing 1101b and 5’3” in height has been admitted with severe burns (stress factor = 2.0). Calculate:

(a) The total daily calorie (TDC) using Harris-Benedict equation.

(b) The daily protein requirement for major burns = 2.5 g/kg. How many milliliters would be administered from a 15% a.a. solution?

(c) The total daily fluid (TDF) using recommendations I or II. Choose the most appropriate and explain your choice.

Solution.

(a) 3169 kcal/day

(b) 833 mL of 15%

(c) use category II recommendation

2100 mL should be used because the patient has major burns and severe dehydration will be present.

CALCULATIONS

(a) BEE = 66.5 + (13.75 × W_(kg)) + (5 × H_(cm)) − (6.76 × A_(yr)) W_kg = 110/2.2 = 50 kg

BEE = 66.5 + (13.75 × 50) + (5 × 150) − (6.76 × 35) = 1267 kcal/day

TDC = BEE (kcal/day) × 1.25 × stress factor

TDC = 1267 × 1.25 × 2 = 3169 kcal/day

(b) Daily protein =

= 833 mL of 15% a.a. solution.

(c)

TDF = 1500 mL (for 20 kg BW) + 20 mL/kg (additional kg > 20 kg)

TDF = 1500 + (20 × 30) = 2100 mL

18. An adult patient weighing 60 kg was admitted for an elective surgery. Considering the patient as mildly stressed calculate TDC (general guidelines = 25 kcal/kg/day).

Solution. 1500 kcal/day

CALCULATIONS

PARENTERAL NUTRITION

19. The term TPN or PN, which stands for total parenteral nutrition or simply parenteral nutrition, is frequently used to describe an intravenous infusion mixture that is expected to supply all needed fluid, electrolytes, calories, essential fatty acids, and vitamins: in short, everything needed to sustain life.

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Tags: Pharmaceutical Calculations

Jun 24, 2016 | Posted by admin in PHARMACY | Comments Off

Basicmedical Key

Fastest Basicmedical Insight Engine

Parenteral Nutrition

ASSESSMENT OF MALNUTRITION

CALCULATION OF NUTRITIONAL REQUIREMENTS

Energy Requirement (Caloric Requirement)

So Which Method Should I Use to Determine Caloric Requirements?

Protein (Nitrogen) Requirement

Micronutrient Requirement

Fluid Requirement

PARENTERAL NUTRITION

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Basicmedical Key

Fastest Basicmedical Insight Engine

Parenteral Nutrition

ASSESSMENT OF MALNUTRITION

CALCULATION OF NUTRITIONAL REQUIREMENTS

Energy Requirement (Caloric Requirement)

So Which Method Should I Use to Determine Caloric Requirements?

Protein (Nitrogen) Requirement

Micronutrient Requirement

Fluid Requirement

PARENTERAL NUTRITION

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