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NAPLEX Review > Calculations III > Flashcards

Calculations III Flashcards

1
Q

What is enteral nutrition?

A

Enteral nutrition (EN) uses the GI tract to deliver all or part of a patient’s caloric needs

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2
Q

What is parenteral nutrition?

A

Parenteral nutrition (PN), also referred to as total parenteral nutrition (TPN), delivers calories into a vein through a peripheral or central line

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3
Q

When is enteral nutrition preferred over parenteral nutrition?

A

When the GI tract is working, enteral nutrition is preferred; it is most physiologic, has fewer complications and is generally less expensive

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4
Q

When is parenteral nutrition preferred over enteral nutrition?

A

Parenteral nutrition can be used when the GI tract is not functioning, or in patients who cannot maintain nutritional status enterally

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5
Q

What is a calorie?

A

A calorie is a measurement of the energy, or heat, it takes to raise the temperature of 1 gram of water by 1 degree celsius

*Calories are associated with nutrition because humans obtain energy from the food they consume orally or from EN/PN

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6
Q

How are calories provided?

A

Calories are provided by these 3 components: carbohydrates, fat and protein (called macronutrients)

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7
Q

How is a calorie measured?

A

A calorie is a very small unit, and theses are therefore measured in kilocalories or kcals where 1000 calories = 1 kcal

*For pharmacy calculations, “calories” are meant to refer to kilocalories or kcals

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8
Q

How is PN different from EN?

A

Compared to EN, PN is more invasive, less physiologic and has a higher risk of complications (e.g. infection and thrombosis)

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9
Q

When is PN indicated?

A

PN may be indicated when the patient is not able to absorb adequate nutrition via the GI tract for > 5 days. Conditions that often require PN include bowel obstruction, ileus, severe diarrhea, radiation enteritis and untreatable malabsorption

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10
Q

What are the 2 types of PN admixtures and how are they similar?

A

The 2 types of PN admixtures are 2-in-1 formulations and 3-in-1 formulations. Both types contain sterile water for injection, electrolytes, vitamins and minerals

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11
Q

What are 2-in-1 formulations of PN?

A

2-in-1 formulations contain two macronutrients (dextrose and amino acids) in one container. Lipids are infused separately if needed.

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12
Q

What are 3-in-1 formulations of PN?

A

3-in-1 formulations contain three macronutrients (dextrose, amino acids and lipids) in one container. 3-in-1 formulations are also called total nutrient admixture (TNA) or “all-in-one” formulations

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13
Q

How are PN admixtures compounded?

A

PN admixtures are compounded sterile products (CSPs) and their preparation must comply with USP Chapter 797 requirements. They are also classified as high-alert medications by ISMP

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14
Q

How do large hospitals make PN admixtures?

A

Many large hospitals use automated compounding devices to combine the ingredients into a single container, but multi-chamber bags can be purchased for convenience. Two-chamber premixed PN products have an amino acid solution in one chamber and a dextrose solution in another chamber. The seal between the chambers is broken before administration to mix the solutions together

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15
Q

What is an example of a commonly used Multi-Chamber product?

A

Clinimix

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16
Q

What can be done if the PN is expected to be used short-term?

A

If the PN is expected to be used short-term (< 1 week), peripheral administration may be possible, but has a high risk of phlebitis and vein damage

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17
Q

What is the advantage of central line placement for PN?

A

Central line placement allows for a higher osmolarity and wider variation in pH

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18
Q

What are common types of central lines?

A

Peripherally inserted central catheters (“PICC” lines), Hickman, Broviac, Groshong etc.

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19
Q

What is required with administration of PN?

A

Administration of PN requires a filter due to the risk of a precipitate

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20
Q

What is refeeding syndrome?

A

An intracellular loss of electrolytes, particularly phosphate, that causes serious complications

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21
Q

What is the first thing that needs to be calculated when designing a PN regimen?

A

Fluid requirements are determined first when designing a PN regimen. Enough fluid needs to be given to maintain adequate hydration, but not cause too much accumulation

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22
Q

What formula can be used to calculate daily fluid needs?

A

When weight > 20 kg: 1500 mL + (20 mL)(weight in kg - 20)

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23
Q

What general guideline do some institutions use to estimate adult fluid requirements?

A

Some institutions estimate adult fluid requirements using a general guideline of 30-40 mL/kg/day

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24
Q

What is basal energy expenditure (BEE)?

A

The basal energy expenditure (BEE), otherwise referred to as the basal metabolic rate (BMR), is the energy expenditure in the resting state, exclusive and activity

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25
Q

What is the BEE formula for males?

A

66.47 + 13.75(weight in kg) + 5(height in cm) - 6.76(age in years)

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26
Q

What is the BEE formula for females?

A

655.1 + 9.6(weight in kg) + 1.85(height in cm) - 4.68(age in years)

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27
Q

What is total energy expenditure (TEE)?

A

Total energy expenditure is a measure of BEE plus excess metabolic demands as a result of stress, the thermal effects of feeding and energy expenditure from activity

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28
Q

What is the formula to calculate TEE?

A

TEE = BEE x activity factor x stress factor

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29
Q

What are the calories provided from carbs in EN?

A

4 kcal/gram

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30
Q

What are the calories provided from fat in EN?

A

9 kcal/gram

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31
Q

What are the calories provided from protein in EN?

A

4 kcal/gram

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32
Q

What are the calories provided from dextrose monohydrate in PN?

A

3.4 kcal/gram

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33
Q

What are the calories provided from glycerol/glycerin in PN?

A

4.3 kcal/gram

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34
Q

What are the calories provided from injectable lipid emulsion 10% in PN?

A

1.1 kcal/gram

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35
Q

What are the calories provided from injectable lipid emulsion 20% in PN?

A

2 kcal/gram

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36
Q

What are the calories provided from injectable lipid emulsion 30% in PN?

A

3 kcal/gram

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37
Q

What are the calories provided from amino acid solutions in PN?

A

4 kcal/gram

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38
Q

What is protein used for?

A

Protein is used either to repair or build muscle cells or as a source of energy

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39
Q

What is the typical protein requirement for a non-stressed, ambulatory patient?

A

0.8-1 k/kg/day

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40
Q

What is the typical protein requirement for a hospitalized or malnourished patient?

A

1.2-2 g/kg/day

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41
Q

How is nitrogen released and excreted?

A

Nitrogen is released during protein catabolism and is mainly excreted as urea in the urine

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42
Q

What is nitrogen balance?

A

Nitrogen balance is the difference between the body’s nitrogen gains and losses

43
Q

How much nitrogen is in protein?

A

There is 1 g of nitrogen (N) for each 6.25 g of protein

*Grams of nitrogen are used as an expression of the amount of protein received by the patient

44
Q

How do you calculate the grams of nitrogen in a certain weight of protein?

A

Nitrogen intake = grams of protein intake/6.25

45
Q

How do you calculate the non-protein calorie to nitrogen ratio (NPC:N)?

A

1) Calculate the grams of nitrogen supplied per day (1 g N = 6.25 g of protein)
2) Divide the total non-protein calories (dextrose + lipids) by the grams of nitrogen

46
Q

What is the desirable NPC:N ratio for most severely stressed patients?

A

80:1

47
Q

What is the desirable NPC:N ratio of severely stressed patients?

A

100:1

48
Q

What is the desirable NPC:N ratio of an unstressed patient?

A

150:1

49
Q

How many kcals do amino acids provide?

A

4 kcal/gram

50
Q

What are some examples of branded amino acid solutions commonly used for PN?

A

Aminosyn, FreAmine, Travasol, TrophAmine and Clinisol

51
Q

What is the primary energy source?

A

Glucose

52
Q

How is glucose obtained in the body?

A

Carbohydrates are consumed as simple sugars or complex “starchy” sugars. These are hydrolyzed by the gut into the monosaccharides fructose, galactose and glucose, which is absorbed. The liver converts the first two in glucose, and excess glucose is stored as glycogen

53
Q

How many calories do carbohydrates provide?

A

Carbohydrates from food or in enteral nutrition formulas provide 4 kcal/gram

54
Q

What provides the carbohydrate source in PN?

A

Dextrose monohydrate

55
Q

What can be used as an alternative to dextrose in patients with impaired insulin secretion?

A

Glycerol

56
Q

How many calories does glycerol provide?

A

Glycerol provides 4.3 kcal/gram and comes premixed with amino acids

57
Q

What is the usual distribution of non-protein calories?

A

70-85% as carbohydrate (dextrose) and 15-30% as fat (lipids)

58
Q

How is fat provided in food and EN formulas?

A

In food and EN formulas, fat is provided as four types: saturated, trans, monounsaturated and polyunsaturated

59
Q

How many calories does fat provide?

A

9 kcal/gram

60
Q

What is the fat source in PN?

A

Injectable lipid emulsion (ILE)

61
Q

How are fat calories in PN measured?

A

Fat calories are measured in kcal/mL due to the caloric contribution provided by the egg phospholipid and glycerol components in the ILE

62
Q

How many calories does 10% ILE provide?

A

1.1 kcal/mL

63
Q

How many calories does 20% ILE provide?

A

2 kcal/mL

64
Q

How many calories does 30% ILE provide?

A

3 kcal/mL

65
Q

Describe the lipid formulations available.

A

Lipids are available as 10%, 20% or 30% emulsions, with brand names Intralipid (all concentrations) and Smoflipid (20% only)

66
Q

How do you determine the daily amount of fat if lipids are given?

A

If lipids are given once weekly, divide the total calories by 7 to determine the daily amount of fat the patient receives

67
Q

What is the recommended hang time limit for ILE?

A

Due to the risk of infection, the recommended hang time limit for ILE is 12 hours when infused alone. An admixture containing fat emulsion may be administered over 24 hours

68
Q

What filters are used for lipid emulsions?

A

1.2 micron filters are commonly used for lipids

69
Q

What are some important notes about sodium?

A

Sodium is the principal extracellular cation. Sodium may need to be reduced in renal dysfunction or cardiovascular disease, including hypertension

70
Q

What preparations can add sodium to PN?

A

Sodium can be added to PN as either sodium chloride, sodium acetate, sodium phosphate or a combination of these

71
Q

Which sodium preparation should be used if acidosis is present?

A

If acidosis is present, sodium acetate should be used; sodium acetate is converted to sodium bicarbonate and may help correct the acidosis

72
Q

What are some important notes about potassium?

A

Potassium is the primary intracellular cation. Potassium may need to be reduced in renal or cardiovascular disease

73
Q

What preparations can provide potassium?

A

Potassium chloride, potassium phosphate, potassium acetate or a combination of these

74
Q

What is the normal range of potassium?

A

3.5-5 mEq/L

75
Q

What are some important notes about phosphorus?

A

Phosphorus is present in DNA, cell membranes and ATP. It acts as an acid-base buffer and is vital in bone metabolism

76
Q

What preparations can provide phosphorus?

A

Phosphate can be provided by the sodium phosphate or potassium phosphate

*The two forms do not provide equivalent amounts of phosphate

77
Q

How should the phosphate order in PN be written?

A

The PN order should be written in mmol of phosphate, followed by the type of salt form

*Phosphate will often need to be reduced in renal disease

78
Q

What functions is calcium important for?

A

Cardiac conduction, muscle contraction and bone homeostasis

79
Q

What is normal serum calcium level?

A

8.5-10.5 mg/dL

80
Q

What can low albumin lead to?

A

Low albumin will lead to a measured calcium concentration that is falsely low

*Almost half of serum calcium is bound to albumin

81
Q

What is the equation to correct calcium?

A

Ca(corrected) = calcium (reported serum) + [(4.0 - albumin) x (0.8)]

82
Q

What is the danger of combining phosphate and calcium?

A

Phosphate and calcium can bind together and precipitate, which cause a pulmonary embolus which can be fatal

83
Q

What steps can be done to help reduce the risk of calcium-phosphate precipitate?

A
  • Choose calcium gluconate over calcium chloride because it has a lower risk of precipitation with phosphates (calcium gluconate has a lower dissociation constant than calcium chloride, leaving less free calcium available in solution to bind phosphates)
  • Add phosphate first (after the dextrose and amino acids), followed by other PN components, agitate the solution, then add calcium near the end to take advantage of the maximum volume of the PN formulation
  • The calcium and phosphate added together (units must be the same to do this) should not exceed 45 mEq/L
  • Maintain a proper pH (lower pH = less risk of precipitation) and refrigerate the bag once prepared. When temperature increases, more calcium and phosphate dissociate in solution and precipitation risk increases
84
Q

What are other additives that can be added to PN?

A

Multivitamins and trace elements are usually added to the PN formula. Insulin and histamine-2 receptor antagonists are occasionally added

85
Q

What is in the standard MVI-13 mixture?

A

There are 4 fat-soluble vitamins (A, D, E, K) and 9 water soluble vitamins (thiamine, riboflavin, niacin, pantothenic acid, pyridoxine, ascorbic acid, folic acid, cyanocobalamin, biotin)

86
Q

What is the difference between MVI-13 and MVI-12 mixture?

A

The MVI-12 mixture does not contain vitamin K since certain patients may need less or more of this vitamin (e.g. patient taking warfarin must monitor INR)

87
Q

What is the standard mix of trace elements?

A

The standard mix includes zinc, copper, chromium and manganese (and possibly selenium. Manganese and copper should be withheld in severe liver disease. Chromium, molybdenum and selenium should be withheld in severe renal disease. Iron is not routinely given in PN

88
Q

Why can insulin required with a PN?

A

Because of the large carbohydrate component of PN, insulin may be required (even in patients without diabetes)

89
Q

How much insulin can be added to PN?

A

Half the sliding scale requirement from the previous day (or less) can be added to the PN as regular insulin to safely control blood glucose which can be supplemented by SC insulin as needed

90
Q

What are the advantages of EN over PN?

A

Lower cost, it uses the gut (which prevents atrophy and other problems) and it has a lower risk of complications (less infections, less hyperglycemia, reduced risk of cholelithiasis and cholestasis)

91
Q

What are some examples of EN formulas?

A

Ensure, Osmolite, Jevity, Glucerna, Novasource

92
Q

What is a nasogastric tube?

A

A tube in the nose to the stomach

93
Q

What is a PEG tube?

A

A percutaneous endoscopic gastrostomy tube is a tube that goes through the skin into the stomach

94
Q

What is a PEJ tube?

A

A percutaneous endoscopic jejunostomy (PEJ) tube is a tube into the small intestine

95
Q

What is the most common risk associated with tube feeding?

A

The most common risk associated with tube feeding is aspiration, which can lead to pneumonia

96
Q

What can happen for patients on tube feeds that have inadequate fluid intake?

A

If fluid intake is inadequate, it will be uncomfortable for the patient and put them at risk for complications, including hypernatremia

97
Q

What is important to remember with drug administration via feeding tubes?

A

Medications should never be added directly to the EN formula, and oral dosage forms (solid and liquid) are not always compatible with tube administration

98
Q

In general, which of the following types of drugs should not be crushed and administered via a feeding tube?

A

Enteric-coated products, delayed or extended release products, sublingual or buccal formulations, hazardous drugs

99
Q

What is the general rule of preventing drug/enteral feeding interactions?

A

The general rule for preventing drug/enteral feeding interactions is to hold the feedings 1 hour before and 1-2 hours after drug administration

100
Q

What is the recommendation of administration of enteral products and warfarin?

A

Many enteral products bind warfarin, resulting in low INRs and the need for dose adjustments. Hold tube feeds one hour before and one hour after warfarin administration

*EN formulas contain varying amounts of vitamin K, which can complicate warfarin dosing in some patients

101
Q

What is the recommendation of administration of enteral products and tetracyclines, quinolones and levothyroxine?

A

Tetracyclines, quinolones and levothyroxine will chelate with polyvalent cations, including calcium, magnesium and iron, which reduces drug bioavailability; separate from tube feeds

102
Q

What is the recommendation of administration of enteral products and Ciprofloxacin?

A

The oral suspension is not compatible with tube feeds because the oil-based suspension adheres to the tube. Immediate-release tablets are used instead; crush and mix with water, and flush the line with water before and after administration

103
Q

What is the recommendation of administration of enteral products and Phenytoin?

A

Levels are reduced when the drub binds to the feeding solution, leading to less free drug availability and subtherapeutic levels; separate tube feeds by 2 hours

NAPLEX Review (45 decks)

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