12446567 basic-computations-2-iv-ivf

Basic Computation/sPart II

IV Drugs & IVFChapter 4

Interpretation/Calculating Medication Dosages

Ratio – is the relationship of two quantities

1:10 , 1:2500 1/10 , 1/2500

Interpretation/Calculating Medication Dosages

RATIO

e.g For every 20 students there is 1 teacher. The ratio of teacher to students is 1 in 20 or 1:20 or 1/20

Proportion – formed by using two ratios that are equal

1 = 5 = 2 x 5 = 10 x 1 2 10 Cross products are equal to

10 = 10

½ is equal to 5/10

Interpretation/Calculating Medication Dosages

Proportion

Dose ¼ = 3/12

Cross products are 12 = 12

¼ = 3/12

Example:

The Md orders 20 mg IM of a drug for a patient. The drug is available in 10 ml vial that contains 50 mg of drug. How many ml will be needed to supply the dose of 20 mg?Given:

1. 10 ml vial 2. 50 mg of drug in 10 ml vial 3. 20 mg is the desired

Cont. Ratio 10ml = 1ml 50mg 5mg Ratio for the required dose x ml 20 mg

Proportion: 1ml = x ml 5mg 20 mg 5 x x = 1 x 20 5x = 20 x = 4ml ( 20 divided by 5 )

Example/s:.

1. Ampicillin oral susp. 250mg/5ml . How many ml would be measured into a medication syringe to obtain a dose of 75mg of ampicillin?

Example/s

2. Paracetamol 125mg/ 5ml. How many ml would be measured into a medication syringe to obtain 15 mg of Paracetamol?

Example/s

3. How many ml of Paracetamol IV should be given to obtain a dose of 15mg in a 15kg-man, if a vial contains 300mg/2ml of Paracetamol?

Example/s

4. A vial contains 250mg of tetracycline HCl in a total of 2 ml of solution. How many mg of tetracycline HCl are contained in 0.6 ml of this solution?

Conversion Between Systems of measurement

1000 g = 1 kg 1000 mg = 1 g 1000 ng = 1 mcg 1000 ml = 1 L 100 ml = 1 dL

Conversion Between Systems of measurement

Rule: 1 To convert a quantity in the metric

system to a large metric unit (mg to g) move the decimal point to the left

Smaller to larger =right to left

Example: 2mg = 0.002g

Conversion Between Systems of measurement

Rule: 2 To convert a quantity to a smaller

metric unit, move the decimal point to the right

Example: 2.4 l = 2400 ml

Examples

Convert 25 g to mg Convert 150 ml to liters

Apothecary System of weights

based upon the grain, which is the smallest unit in the system

Nitroglycerin 1/100gr, 1/150 gr Atropine sulfate 1/200gr. 1/150 gr Approximate equivalent

15 grains = 1 gram 1grain = 60 mg

Apothecary System of weights

Convert 15 milligrams to grains

1 grain = x grain 60 mg 15 mg 60 x = 15 x = 15/60 x = .25 grain

Example:

The physician orders 7 ½ grains of aminophylline po for a client. On hand are aminophylline tablets 500 mg. How many tablets are required for one dose?GIVEN:

1 gram = x gram 15 grain 7.5 grain 15 x = 7.5 x = 0.5 g (500mg)

Example:

How many mg of nitroglycerin are in one 1/150 grain tablet of the drug?

Given: 1 gram = x gram 15 grains 1/150 grains 15 x = 1/150 = .0067 x = 0.0004g = 0.4 mg

Calculation of Fractional Doses:

ratio and proportion

Example:

The Md orders 1,000,000 units of Pen G for a patient. The pen G on hand is available as a solution containing 250,000 units/ml

250,000 units = 1, 000,000 units

1 ml x ml 250,000x = 1,000,000

x = 4 ml

Example 1:

The physician orders 250 mcg of Vitamin B12 IM daily. The vitamin on hand is labeled 1,000mcg/ml. How many ml should be given to the patient?

Example 2:

A patient is to be given 25 mg Diphenhydramine po and is available as 12.5mg/5ml prep.. How many ml should be given?

Example 3:

A medication order calls for 750 mg calcium lactate to be given TID PO. On hand are tablets of calcium lactate 0.5 g. How many tablets should be given for each dose?

Calculation of Dosages Based on Weight

The physician orders thiabendazole chewable tablets for a 110 pound child. The recommended dosage is 20 mg/kg/dose. How many 500 mg tablets should be given to this patient for each dose.

Calculation of Dosages Based on Weight

Convert weight to kg 20 mg = x mg 1 kg 50 kg x = 1000 mg 500 mg = 1000mg 1 tab x tab x = 2 tablets per dose

Example:

The recommended dose of Meperidine is 6mg/kg/day for pain. It is given every 4 to 6 hours. How many ml of Demerol injection 50mg/ml should be administered to a 33 pound child as a single dose every 6 hours?

Cont.

Calculate the daily dose for a 33-pound child

6mg/ 1 kg (2.2lb) = x mg / 33 lb x = 90 mg Demerol / day

Cont.

Calculate the number of ml of demerol injection 50 mg/ml needed for the daily dose

50 mg/ 1 ml = 90 mg/ x ml

Cont.

Calculate the number of ml to be given every 6 hours

1.8 ml/ 24 h = x ml/ 6 h 24 x = 10.8 x = 0.45 ml

Calculations Involving Intravenous Administration

How long will it take to complete an IV infusion of 1.5 L of D5 W being administered at the rate of 45 drops /min? The IV set is calibrated to deliver 15 drops/ml.

Calculations Involving Intravenous Administration

Determine the number of ml/min being infused

Drop rate of IV set = 15 gtt/1ml = 45gtt/ x ml

15 x = 45

x = 3 ml/min

Calculations Involving Intravenous Administration

Calculate the number of ml/hour

3 ml/min. x 60 min/hr = 180/ hour

Calculations Involving Intravenous Administration

Calculate the number of hours required to administer the total volume of the solution. If 180 ml are delivered each hour, then how many hours are required to administer 1,500 ml?

180ml/hr = 1,500 ml/hr 180 x = 1,500 x = 8.3 hours or 8 hours 20 min.

Calculations Involving Piggyback IV Infusion

An IV piggyback of Cefazolin 500mg in 100ml/hour is ordered. The piggyback IV set is calibrated to deliver 10 gtts.ml. How many drops/min. should be administered?

Calculations Involving Piggyback IV Infusion

100 ml/ 60 min. = x ml/ min. 60 x = 100 x = 1.7 ml/ min. Flow rate: Drop rate 10 gtt/ min./ 1min. = x gtt/ 1.7 ml X = 17 gtt/ min.

Calculations Involving Piggyback IV Infusion

Daily fluid requirement 2000ml of electrolyte solution

administered 24 hours and that Cefazolin sodium 500 mg in 100 ml/hr is ordered QID. The number od ml/day and the times of the piggybank infusion must be subtracted from the daily fluid requirement.