Chapter 1: Calculations Flashcards by mike ferenz

How many mL are in 1 quart

1 quart is equal to 2 pints which is equal to 32 oz (1 pint = 16 oz) and there are 30 mL per oz. So 32oz x 30mL = 960 mL

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How many grams in 1 pound?

454g = 1 lb

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How many mg in 1 grain

65mg = 1 grain

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How many quarts in 1 gallon? Convert 1 gallon into mL?

There are 4 quarts in 1 gallon

Each quart = 2 pints. So 4 quarts = 8 pints and since each pint contains 16 oz and there are 30ml in one ounce:
8 x 16 x 30 = 3,840 mL in 1 gallon

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How many ounces in 1 cup?

8 oz

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How many mcg are in 1 mg?

There are 1,000 mcg in 1 mg

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What % of ferrous sulfate contains elemental iron?

Ferrous sulfate (FeSO4) contains 20% elemental iron

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Convert aminophylline to theophylline?

Aminophylline to theophylline; multiply by 0.8

Theophylline must have better bioavailability if the conversion from aminophylline involves taking 80% of what was started with for proper theophylline dosing

Likewise, converting from theophylline to aminophylline would obviously require more aminophylline so the conversion requires dividing theophylline qty by 0.8

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Convert 0.04% to a ratio strength?

Ratio strengths are displayed as example 1:5000

0.04g/100g = 1part/xparts –> solving for x gives 2500 so 0.04% as a ratio strength = 1:2500

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What is the equation for specific gravity (SG)?

SG = g/mL

SG is the ratio of the density of a substance to the density of water. Water has a SG of 1 where 1mL of water = 1 g of water. Substances with SG greater than 1 are heavier than water whereas substances with a SG less than 1 are lighter than water.

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What is the formula you would use for dilution and concentration problems?

Ex. How many grams of petrolatum (diluent) should be added to 250g of a 20% ichthammol ointment to make a 7% ichthammol ointment?

Q1 x C1 = Q2 x C2

Ex. 250g x 20% = Xg x 7%
X = 714.3g - 250g (already present) = 464.3g of petrolatum required

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Osmolarity is the total number of particles in a given solution and is directly proportional to its osmotic pressure. Identify the number of dissociation particles from each of the following:

Dextrose
Mannitol
Potassium chloride (KCl)
Sodium chloride (NaCl)
Sodium acetate (NaC2H3O2)
Calcium chloride (CaCl2)
Sodium citrate (Na3C6H5O7)

Dextrose   1
Mannitol    1
Potassium chloride (KCl)              2
Sodium chloride (NaCl)                2
Sodium acetate (NaC2H3O2)     2
Calcium chloride (CaCl2)            3
Sodium citrate (Na3C6H5O7)     4

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What is the osmolarity calculation formula?

mOsmol/L =
[Wt of substance (g/L) / MW (g/mole)] x # of particles x 1000

Osmolarity is the measure of total number of particles (or solutes) per liter of solution. Solutes can either be ionic (such as NaCl, which dissociates into 2 solutes) or non-ionic, which does not dissociate (such as glucose and urea).

Examples:
KCl dissociates into 2 particles (K+ and Cl-)
CaCl dissociates into 3 particles (Ca+2 and Cl-)

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What is the E-value formula?

E = (58.5)(i) / (MW of drug)(1.8)

The “E value” also called sodium chloride equivalent, is the relationship between the amount of drug that produces a particular osmolarity and the amount of sodium chloride that produces the same osmolarity.

An important factor when doing E-value problems is understanding the dissociation factor (i). If the substance consists of only 1 ion, then use 1 for the i value. If it dissociates into 2 ions, add 0.8 to 1 = 1.8 for i value. If it dissociates into 3, add 0.8 to 1.8 = 2.6 and so on.

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What are moles measured in? Millimoles?

Moles are measured in g/MW: mols = g/MW

Millimoles measured in mg/MW: mmols = mg/MW

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Match the following with the correct description:

A. Milliosmoles
B. Millimoles
C. Milliequivalent

Mg of a solute equal to 1/1,000 of its gram equivalent weight, taking into account the valence of the ions
Molecular weight
Number of particles

Milliosmoles: Number of particles

Millimoles: Molecular weight

Milliequivalent: Mg of a solute equal to 1/1,000 of its gram equivalent weight, taking into account the valence of the ions

What is the equation for mEq?

mEq = (mg x valence)/MW

mEq = (mmol x valence) b/c mmol = mg/MW

State the IBW equations for male and female

Male: IBW = 50 + 2.3(inches > 5ft)
Female: IBW = 45.5 + 2.3(inches > 5ft)

State the adjusted body weight equation

AdjBW = IBW + 0.4(TBW - IBW)

Which (3) drugs should be dosed using IBW in a patient with normal weight?

aminophylline
theophylline
acyclovir

State whether the following drugs are dosed based on TBW, IBW, or AdjBW in OBESE patients:

Aminophylline
Theophylline
Vancomycin
UFH
LMWH
Aminoglycosides
Acyclovir

Aminophylline           IBW
Theophylline             IBW
Vancomycin              TBW
UFH                           TBW
LMWH                       TBW  
Aminoglycosides     ADjBW   
Acyclovir                   IBW

Explain which patient weight to use when calculating CrCl (i.e. If underweight, normal weight, or obese)?

Calculating CrCl:
If a patient is underweight use IBW, if patient is normal weight user actual body weight, and if patient is obese use AdjBW

The Harris-Benedict equation estimates basal energy expenditure baed on the resting state. Which of the following is this equation based on: (Select all that apply)

A. Fat
B. Protein
C. Carbohydrates
D. Fluids
E. None of the above, the Harris Benedict equation has nothing to do with nutritional requirements

The Harris-Benedict equation is used to calculate non-protein calories required to live or the basal metabolic rate. It does not include calories from eating and activity. It is calculated differently in males and females and is based on gender, weight, height, and age

How do you calculate the grams of nitrogen a patient is receiving from the amount of protein?

Nitrogen intake = grams of protein / 6.25

Nitrogen is released during protein catabolism and is mainly excreted as urea in urine. Nitrogen balance is the difference between the body’s nitrogen gains and losses. Grams of nitrogen are used as an expression of the amount of protein received by the patient. There is 1g of nitrogen for each 6.25 g of protein.

For PN, what is the usual distribution of non-protein calories (as dextrose) and fats (lipids)? i.e. what % do both typical represent for NON-protein calories

Dextrose: 70-85% Lipids: 15-30%

Why must the hang time be limited for IV fat emulsions used in PN?

Risk of infection

Which of the following statements regarding PN are correct? A. 10% lipid emulsions provide 1.1kcal/g B. Amino acids are not counted as an energy source in critically ill patients C. Total energy expenditure is based on dextrose and lipids D. Due to potential infection and thrombosis, PN is higher risk than enteral feeding E. 0.22 micron filters are the preferred size for filtering lipid emulsions

B, C, and D are correct Amino acids are used to build muscle and may not be counted as an energy source in critically ill patients because they are catabolic and medical team may want to provide adequate energy from carbohydrates and lipids in order to "spare" proteins to be used for muscle. TEE is based on non-protein calories (i.e. dextrose and lipids). Two factors that make PN more dangerous than enteral feeding are the risk for thrombosis and infection A and E are incorrect 10% lipid emulsions provide 1.1kcal/mL, not per g. Likewise, 20% provides 2 kcal/mL and 30% provides 3kcal/mL. 1.2 micron filters are commonly used for lipid emulsions. Lipid emulsions cannot be filtered through 0.22 micron filters.

Sodium can be added to PN as either sodium chloride or sodium acetate. Which type would be added to PN in an acidotic patient?

Sodium acetate would be the preferred choice since sodium acetate is converted to sodium bicarbonate

State the corrected Ca+2 equation?

Corrected Ca = Ca(serum) + 0.8(4 - albumin)

Low albumin will lead to... (Select all that apply) A. Falsely high serum calcium concentration B. Falsely low serum calcium concentration C. Serum calcium levels actually increase D. Serum calcium levels actually decrease E. Albumin level has no bearing on calcium levels

B. Falsely low serum calcium concentration In the body, calcium is either bound to albumin or is found in its free form (ionized). It's the ionized calcium that you are concerned because ionized calcium is the physiologically active form of calcium; calcium bound to albumin is inactive. Standard lab tests are measuring the total calcium, unless you get a special ionized calcium level. When albumin is low (nephrotic syndrome, compromised liver function, etc) you have a lower total calcium on lab tests due to less albumin. Total calcium = ionized calcium + calcium bound to albumin.

Calcium is important for which of the following: (Select all that apply) ``` A. Cardiac conduction B. Sleep/wake cycle C. Muscle contraction D. Bone homeostasis E. Energy ```

A, C, and D are correct Cardiac conduction, muscle contraction, and bone homeostasis are all roles of calcium in the body.

Phosphate and calcium need to be added to PN bags carefully or they can bind together and precipitate causing a PE. Which of the following can help reduce this risk? (Select all that apply) A. Do not exceed 45 mEq/L of calcium and phosphorous added together B. Add calcium first, then phosphorous at the end of PN preparation C. Use calcium gluconate rather than calcium chloride D. A higher pH of PN will reduce risk of precipitation E. Make sure to keep the PN refrigerated since temperature increases can increase risk of precipitation

A, C, and E are correct Calcium gluconate is the preferred calcium in PN because it is less reactive than calcium chloride. Temperature increases cause more calcium and phosphate to dissociate in solution and increase risk of precipitation B and D are incorrect Phosphate should be added to PN first (after dextrose and amino acids), then other PN components, then the solution should be agitated, THEN add calcium near the end. This ensures that when calcium is added, it is added to the largest volume of liquid. A lower, more acidic pH = less risk of precipitation.

The standard mix of trace elements in PN bags contains zinc, copper, chromium, and manganese. Which of these trace elements should be withheld in severe liver disease?

Copper and manganese

T/F: | Iron is often included in PN?

False

All of the following are advantages of EN over PN, EXCEPT: (Select all that apply) ``` A. Lower cost B. Higher risk of complications C. Higher incidence of hyperglycemia D. Prevents gut atrophy E. Less infections ```

B and C are the exceptions EN is better than PN b/c it costs less, by using the gut it prevents atrophy, and also has a LOWER risk of complications (less infections, LESS hyperglycemia, reduced risk of cholelithiasis and cholestasis)

Which of the following best represents the general rule for preventing drug/enteral feeding interactions, by holding feedings before/after the drug is administered? A. Hold feedings 6 hours before and 4 hours after B. Hold feedings 4 hours before and 6 hours after C. Hold feedings 1 hour before and 1 hour after D. Hold feedings 1 hour before and 2 hours after E. Hold feedings 2 hours before and 1 hour after

D. Hold feedings 1 hour before and 2 hours after the drug is administered. However, specific drugs may require a longer hold on feedings so as not to interact.

What does PEG tube stand for?

PEG tube is a percutaneous endoscopic gastrotomy tube that goes through the skin into the stomach. Also referred to as just "gastrotomy"