Third Week: Med Calculations

Question 1

How Does the Nurse Give an Accurate Dose?

Answer 1

• dosage needs to be in the same unit of measure as the medication on hand
• convert to the unit of measure that you have on hand
• round to the nearest tenth

Question 2

Systems of Measurement

Answer 2

-Metric
-household
Special Systems of Measurement:
-Unit (insulin)
-International Units (vitamins)
-Milliequivalent (KCL)

Question 3

1 gm= ___mg=____mcg

Answer 3

1 gm = 1000 mg = 1,000,000 mcg

bigger-> smaller: move decimal to the right 3 places or multiply by 1000

Question 4

1 Liter =_____mL

Answer 4

1 Liter = 1000 mL

Question 5

1 kg = _____ gm

Answer 5

1 kg = 1000 gm

Question 6

2.5 cm = _____ inch

Answer 6

2.5 cm = 1 inch

Question 7

1 kg = ___ lbs

Answer 7

1 kg = 2.2 lbs

Question 8

30 gm = ___oz

Answer 8

30 gm = 1 oz

Question 9

1 tsp = ___ mL

Answer 9

1 tsp = 5 mL

Question 10

1 Tbls = ___mL

Answer 10

1 Tbls = 15 mL

Question 11

240 ml = ___fl oz = ___cups

Answer 11

240 mL = 8 fl oz = 1 cup

Question 12

1000 mL (1 L) = ____fl oz

Answer 12

1000 mL (1 L) = 32 fl oz

Question 13

Conversion Formulas: Larger —> Smaller Unit

Answer 13

• multiply by 1000 or

- move 3 decimal places to the right

Question 14

Conversion Formulas: Smaller —> Larger Unit

Answer 14

• divide by 1000 or

- move 3 decimal places to the left

Question 15

Converting with Proportions

Answer 15

• determine appropriate equivalent (conversion factor)
• set up proportion
• be consistent with format
• cross multiply
• remember “x” goes on the left side of the equation

Question 16

Calculating Conversions Using Proportions Example:
Oder: 90 mL = ___oz
On Hand: 30 mL = 1 oz

Answer 16

30mL = 90mL
——– ——–
1 oz x

30x = 90
—– —– = 3 oz
30 30

Question 17

Converting Digoxin Example

Digoxin 250 mcg = ___ mg?

Answer 17

Smaller to Larger

mg

Question 18

Example:

2 tsp = ____mL?

Answer 18

conversion factor : 1 tsp = 5 mL
1 tsp = 2 tsp
—— ——
5 ml x

1x=10ml
– —
1 1

x=10 ml

Question 19

When Calculating Dosages that have been converted to the same unit of measure you can use this formula:

Answer 19

Desired
———– x Quantity = amount of dose to be given
have

Question 20

Calculating Dosages by Weight

Answer 20

-some medications require daily weight for dosage calculations, others will use admission weight
-to convert lbs to kg, remember conversion factor:
2,2 lbs = 1 kg

weight in lbs

• —————– = weight in kg
  
  2. 2

Question 21

Calculating Dosages by Weight Example:
Order: Amoxicillin 25 mh/kg/day
Patient weight: 44 lbs

Answer 21

44lbs/ 2.2= 20 kg
-once you know your patients weight in kg we can figure out their total daily dose (TDD)
25mg x 20kg = 500 mg/day

Question 22

Calculating Divided Doses

Answer 22

once you have calculated the TDD, divide it by how many times per day the patient is to receive the medication

TDD/ # of doses = amount desired per dose

-order: Amoxicillin 500 mg/day in 2 divided doses
500mg/ 2 doses= 250 mg per dose

Question 23

Body Surface Area (BSA)

Answer 23

unit of measurement is m2 (meters squared)
-determined using a nomogram
-if need to calculate with nomogram you would need:
height, weight, draw straight line connecting height to weight –> intersection of line is patients BSA

Question 24

Calculating BSA

Answer 24

-multiply drug dose ordered by the patients BSA (m2)
ex:
order: generic drug 100 mg/ m2/ day
BSA: 1.97 m2

100mg x 197 = 197mg per day (TDD)