Clinical Calculations Test 1

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Includes Metric, Apothecary & Household systems, conversions & methods of calculation, Metric Conversions, Interpretation of Drug Levels, Insulin Syringe Preparations

Metric System: What are the basic units of measurement used for:
Length,Linear distance-

Length,Linear distance-Meter

Metric System: Prefix for Larger Units

Kilo-1,000 (one thousand)
Hecto-100 (one hundred)
Deka-10 (ten)

Metric System: Prefix for Smaller Units

Deci- 0.1 (one-tenth)
Centi- 0.01 (one hundredth)
Milli- 0.001 (one-thousandth)
Micro-0.000001 (one-millionth)
Nano- 0.000000001 (one-billionth)

Metric System: What do these abbreviations stand for?
Kg,g, mg, mcg, ng, kl, L, dL, mL, km, M, cm, mm

Kilogram, miliigram, microgram, nanogram, kiloliter, Liter, deciliter, milliliter, kilometer, meter, centimeter, millimeter

Metric System: What is the method for changing from a larger unit to a smaller unit?

Multiply by 10 for each unit increased, or move decimal point to right for each unit changed

Metric System: What is the method for changing from a smaller unit to a larger unit?

Divide by 10 for each unit increased or move the decimal place to the left for each unit changed

Convert 7.5 grams to milligrams

7.5 g = x mg
g=1, mg = 1/1,000 (change of -3^10)
So multiply by 10 3 times or move decimal RIGHT 3 places
7.5 g = 7,500 mg

Convert 7,500 mcg to milligrams

7,500 mcg = x mg
mcg = 1/1,000,000, mg = 1/1,000 (change of +3^10)
So divide by 10 3 times or move decimal to left 3 places
7,500 mcg = 7.5 mg

Apothecary: How many milligrams are in a grain?

60 mg = 1 gr

Household Units: drop (gtt), teaspoon (t), Tablespoon (T), Ounce (oz), Cup (c)
Solve for X:
1 gt = X minim
1 t = X drops
1 T = X t
1 oz = X T
1 C = X oz
1 med. size glass = X oz
1 measuring cup = X oz

1 gt = 1 minim
1 t = 60 drops
1 T = 3 t
1 oz = 2 T
1 C = 6-8 oz
1 med. size glass = 8 oz
1 measuring cup = 8 oz

Household Units Continued:
Solve for X:
2 glasses = X oz
9 t = X T
24 oz = X coffee cups

*2 glasses = 16 oz
1 gl = 8 oz so 2x8=16
*9 t = 3 T
3 t = 1 T so 9/3=3
*24 oz = 4 coffee cups
1 coffee cup = 6 oz so 4x6=24

Interpretation of Drug Labels:
Know how to label & describe:
1. Brand (Trade) Name
2. Generic Name
3. Drug form
4. Dosage
5. Manufacturer
6. Expiration Date
7. Lot Number

Look to Ch 3 in Clinical Calculations for examples or google "drug labels" and practice labeling. *Careful of solutions & suspensions that need to be reconstituted or diluted, the dosage/form may not be what it first appears*
1. Brand (Trade) Name is the "catchy" simplified name
2. Generic Name is "true" name
3. Form can be tablets, suspension, capsules, vials etc.
4. Dosage (may have to adjust depending on pt script)
5. Manufacturer (Name of company/brand)
6. Expiration date-self-explanatory
7. Lot # self explanatory (may not be on label in all cases)

Insulin Syringes: One important thing to remember about order of drawing medications into syringe is?

Always draw CLEAR before CLOUDY! (So clear will be closest to push handle and cloudy closest to needle)
Reg Ins = Clear, NPH= Cloudy

Dose Calculations: Fractional equations method, what is the formula?

Dose "on hand" H and the "form" F are compared to the "desired dose" D and the "unknown" that is needed x.
Fractions: H/F is equal to D/x
Cross multiply: Hx=FD
Divide both sides by H to get x by itself: x=FD/H

Dose Calculations: Ratio-Proportion Method, what is the formula?

Dose "on hand" H and the "form" F are compared to the "desired dose" D and the "unknown" that is needed x.
Proportion set up: H : F :: D : x
Multiply inner and outer terms: Hx=FD
Divide both sides by H to get x alone: x=FD/H
*Don't forget to cancel out like units on both denominator and numerator sides.

What is insulin administered in?

Insulin is prescribed and measured in USP UNITS
Often 100 Units per mL, syringes and insulins are color coded

What is the step x step method for mixing an insulin syringe?

1. Cleans rubber tops w/alcohol swab
2. Draw up units of air and inject in "NPH" insulin bottle. Do not allot needle to come into contact w/ insulin. (Units air = units of insulin needed)
3. Draw up units of air and inject into "Reg" Insulin bottle. Withdraw needed Units of "Reg" insulin as it is pulled first.
4. Withdraw units needed of "NPH" insulin
5. Administer immediately

Dosage Calculations:
If you need to administer 60 mEq and the drug comes 15 mEq/5mL what would you administer to the patient?

H:f :: D:x
15:5 :: 60:x
Multiply inner & outer: 15x=300
Divide both sides by 15, 300/15 = x
OR H/F=D/x
15/5 = 60/x
3x=60 x=20 mL

Dosage Calculations:
If you need to administer 500 mg of drug and the drug comes in a 250 mg/5ml solution. How many mL would you administer?


Dosage Calculations:
If you need to give patient 75 mg of medication and have 50 mg scored tablets, how many tablets would you give patient?

H:F :: D:x
50:1 :: 75:x
75/50 = 1.5 tablets

Algebraic Equations for Unit 1 dosage problems

H=have, D=desired, F=form, x=Answer
H:F :: D:x
D/H multiplied by F = x

Math Basics: Multiplying Fractions

1. Multiply the top numbers (the numerators).
2. Multiply the bottom numbers (the denominators).
3. Simplify the fraction if needed.
1 × 2 = 1 × 2 = 2 = 1
2 5 2 × 5 10 5
(In the case of a whole #, put the # over 1. i.e. 5= 5/1)

Math Basics: Dividing Fractions

1. Turn the second fraction (the one you want to divide by) upside-down (this is now a reciprocal).
2. Multiply the first fraction by that reciprocal
3. Simplify
1 ÷ 1 = 1 x 4 = 4 Simplified 4 = 1
8 4 8 x 1 8 8 2
(In the case of a whole #, Multiply the bottom # of the fraction by the whole # & simplify)

Math Basics: Multiplying Decimals

(Multiply without the decimal point, then re-insert it in the correct spot)
1. Multiply normally, ignoring the decimal points.
2.Then put the decimal point in the answer - it will have as many decimal places as the two original numbers combined.
Example: 0.25 x 0.2
25 x 2 = 50
0.25 = 2 spaces + 0.2 = 1 space/2+1=3 spaces
Final answer = 0.050

Math Basics: Division of Decimals

1. Use Division or Long Division (ignoring the decimal point)
Then put the decimal point in the same spot as the dividend (the number being divided)
7 )91
2. Put the decimal point in the answer directly above the decimal point in the dividend:
7 )9.1
The trick is to convert the number you are dividing by to a whole number first, by shifting the decimal point of both numbers to the right:
Now you are dividing by a whole number, and can continue as normal.
(Must shift the decimal point of both numbers the same number of places.)
Example: Divide 6.4 by 0.4
Move the decimal point so that you are dividing by a whole number:
6.4 64
0.4 4
6.4/0.4 is exactly the same as 64/4,
as you moved the decimal point of both numbers.
64 / 4 = 16

Math Basics: Addition/Subtraction Fractions

Addition & Subtraction:
1: Make sure the bottom numbers (the denominators) are the same
2: Add or Subtract the top numbers (the numerators)
3: Simplify the fraction

Correct or Incorrect?
A. 0.5%
B. 6.0 tablets
C. 100 cc IV drip

A. Correct. Use of 0 before decimal prevents confusion of thinking # is a whole (5%) rather than a decimal (0.5%).
B. Incorrect. The use of a 0 after the decimal can lead to mistakingly reading the # as x10 (60 tab instead of 6 tab).
C. Incorrect. "cc" can be mistaken for 00, u, or um when written poorly/hastily. Instead use mL (1cc = 1mL).
D. Incorrect. Use of 0 before the decimal is correct, unless there is already a 0 after the decimal. In this case the # may be read as negative 10-fold (.008 instead of .08).

Correct or Incorrect?
A. Indermal100mcg
B. 10 mL Depo Provera every 3 months
C. 100000 U Insulin

A. Incorrect. When no space is left between dosage and drug name the "l" at end of name may be mistaken as a "1" (1,100 mcg instead of 100mcg) Same for "a", "o", "c" and "0".
B. Correct. The space between the 10 and the mL ensure the "m" will not be mistaken for "0" or "00", therefor increasing the dosage (100mL read as 100ooL or 10000L).
C. Incorrect. Without proper commas in large #s, the numbers can easily be read or reported with fewer/more 0s (100000 U can be read 10,000 U).

I weigh 141 lbs (Shhh don't tell). How many kilograms do I weigh?

1 kg = 2.2 lbs
141/2.2 = 64.0909 or 64.1 kg
(Remember, we always weight less in kgs)

How many cm in an inch?
Inches in a cm?

2.54 cm = 1 in
1 cm = 0.394 in

Important Conversions:
1. How many mL in an oz?
2. How many mL in a Tablespoon (T, Tbsp) ?
3. How many mL in a teaspoon (t, tsp) ?
4. How many t in a T ?

1. 30 mL in 1 oz
2. 15 mL in a T
3. 5 mL in a t
4. 3 t in a T

Temperature Conversions:
1. How do you convert Fahrenheit (F) to Celsius (C)?
2. How do you convert C to F ?

1. F = (9/5 C) + 32
Multiply 9/5 by C & add 32 last
2. C = 5/9 (F - 32)
Subtract 32 & multiply F by 5/9 last
(Hint - Celsius = Smaller fraction = Subtract, Ssss sounds)

Temperature Conversions:
1. How many degrees F in 38 C ?
2. How many degrees C is 99 F ?

1. (9/5 38) + 32 =
9 x 38 = 342 = 68.4 + 32 = 100.4 F
5 1 5
2. (99 - 32) 5/9 =
99-32 = 67 5 x 67 = 335 = 37.2 C
9 1 9

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