Download BASIC IV MEDICATION RULES/FORMULAS Calculating IV Flow

BASIC IV MEDICATION RULES/FORMULAS
1) Calculating IV Flow Rates:
RULE:
Example #1:
Amount of infusion
Time in hours
Order: Infuse 3,000 mL over 24 hours
Amount of infusion
Time in hours
Example #2:
3,000 mL = 125 mL/hr
24 hours
Order: Infuse 400 mL over 6 hours
Amount of infusion
Time in hours
400 mL = 67 mL/hr
6 hours
However, when time to be infused is less than an hour:
RULE: Amount of infusion X 60 minutes
Length of time ordered
Example #1:
Order: Infuse 50 mL over 30 minutes
Amount of infusion
X 60 minutes
Length of time ordered
Example #2:
Order: Infuse 100 mL over 45 minutes
Amount of infusion
X 60 minutes
Length of time ordered
Example #3:
100 mL X 60 minutes = 133 mL/hr
45 min
Order: Infuse 100 mL over 30 min
Amount of infusion
X 60 minutes
Length of time ordered
Example #4:
50 mL X 60 minutes = 100 mL/hr
30 min
100 mL X 60 minutes = 200 mL/hr
30 min
Order: Infuse 200 mL over 100 minutes
Amount of infusion
X 60 minutes
Length of time ordered
200 mL X 60 minutes = 120 mL/hr
100 min
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2) Calculating IV Flow Rates in gtt/min:
RULE:
Example #1:
Amount of fluid to be infused X drop factor
Time in minutes
Order: Infuse 100 mL in one hour. Drop factor is 10.
Amount of fluid to be infused X drop factor
Time in minutes
Example #2:
17 gtt/min
Order: Infuse 50 mL in 20 minutes. Drop factor is 60.
Amount of fluid to be infused X drop factor
Time in minutes
Example #3:
100 mL X 10 gtt =
60 min
50 mL X 60 gtt =
20 min
150 gtt/min
Order: Infuse 1,000 mL in 8 hours. Drop factor is 20.
Amount of fluid to be infused X drop factor
Time in minutes
1,000 mL X 20 gtt =
480 min (8hr)
42 gtt/min
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3) Determining the Amount of Drug in a Specific Amount of Solution
RULE:
Example 1:
Dose desired X Vehicle = ?
Dose available
Order: 20 mEq of potassium chloride in 1,000 mL to be administered at a rate
of 2 mEq per hour.
Dose desired X Vehicle = ?
Dose available
2 mEq X 1,000 mL = 100 mL/hr
20 mEq
Therefore 100 mL of fluid would be needed to administer 2 mEq of potassium chloride per hour.
How many gtt/min would administer 2 mEq per hour if the drop factor is 15?
RULE:
Amount of fluid to be infused X drop factor
Time in minutes
100 mL X 15 gtt = 25 gtt/min
60 min
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Example 2:
A Heparin drip is prepared by pharmacy and contains 20,000 units of heparin in 500 mL of
0.9% NaCl. The order is to infuse @ 1,200units/hr. At what rate would you set the
pump to infuse the 1,200 units of heparin?
RULE: Dose desired X Vehicle = ?
Dose available
1,200 units X 500 mL = 30mL/hr (pump setting)
20,000 units
Example 3:
The aminophylline drip contains 1g (1,000mg) in 500 mL D5W. The pump is delivering
20 mL/hr. How much aminophylline is the patient receiving per hour?
RULE: Pump setting X Dose ordered = ?
Total IV fluid
20 mL X 1,000 mg = 40 mg/hr
500 mL
Example 4:
The heparin drip contains 20,000 units in 500 mL of 0.9% NaCl. The pump is delivering
30 mL/hr. How much heparin is the patient receiving per hour?
RULE: Pump setting X Dose ordered = ?
Total IV fluid
30 mL
500 mL
Example 5:
X 20,000 units = 1,200 units/hr
Patient is to have a heparin drip. Order is to start the infusion at 18 units/kg/hr. The
patient weighs 198 lbs. The pharmacy has prepared a bag with 20,000 units of heparin in
500 mL of D5W. At what rate do you set the pump?
#1. Calculate kg weight:
198 lbs  2.2 = 90 kgs
#2. Calculate hourly dose: (18 units) X (90 kgs) = 1,620 units/hr
RULE: Dose desired X Vehicle = ?
Dose available
1,620 units X
20,000 units
Setting the pump at 41 mL/hr will deliver 18 units/kg/hr.
500 mL = 40.5 or 41 mL/hr
4) IV Push Medications: Calculating a Safe Dose
Order:
Morphine Sulfate 15 mg IV push now. On hand is morphine sulfate 10mg/1mL.
Drug reference states to give the medication no faster than 2.5 mg/min.
a) How many mLs of morphine do you give?
RULE:
Dose desired
Dose available
Therefore: 15 mg
10 mg
X
Vehicle = ?
X 1 mL = 1.5 mL
(You will give 1.5 mL to deliver 15 mg of morphine)
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b) How many minutes will it take to give the morphine?
RULE: Dose desired
Safe dose
Therefore: 15 mg
2.5 mg
X 1 min =
X 1 min = 6 min
(It will take 6 min. to give 1.5 mL of morphine safely)
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c)
How many mL will you give each minute?
RULE: Volume to be infused
Time to infuse
Therefore:
1.5 mL = 0.25 mL/min
6 min
(You will push 0.25 mL of morphine every minute)
0.25 mL X 6 min = 1.5 mL total
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5) IV Piggyback Medications : Calculating a Safe Duration Time and Pump
Rate
Order: Vancomycin 1 gm (=1,000mg) IV q 12 hours
Drug Reference: Single dose properly diluted (concentration of no more than 5mg/mL) at a rate
not to exceed 10 mg/min or 60 min* whichever is longer. Pharmacy provides
Vancomycin 1 gm in 200 mL* 0.9% sodium chloride.
a) According to the reference, over what duration should this medication be administered?
RULE:
Dose desired
Safe dose
Therefore….. 1,000 mg
10 mg
X 1 minute = ?
X
1 min = 100 min (It will take 100 minutes to infuse the ABX safely)
*(100 minutes is longer than 60 minutes therefore use 100 minutes to give the drug)
b) What is the proper pump setting?
RULE:
Volume to be infused X 60 min (pump setting is per hour therefore use 60 min)
# of minutes of infusion
Therefore…. 200 mL* X 60 min = 120 mL/hr (Set the IV pump at 120 mL/hr to deliver
100 min
1,000gm of antibiotic safely)
*The pharmacy placed 1,000mg (1 gram) of the drug in 200 mL of IV solution. Why? The drug book said
the less concentration should be at least 5mg/mL. Therefore 5 mg X 200 mL = 1,000 mg. Pharmacy is
correct! Had they put it in anything than 200mL, the concentration would have be too strong/unsafe.
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6) Calculating Rate in mL/hr
Order: A solution of Trandate (labetalol) 100 mg in 100 mL of D5W is to infuse at a rate of 25mg/hr. To
infuse 25 mg/hr, how should the pump be set?
RULE:
Dose ordered in mg
X Total volume (mL) = ?
Total available in mg
25 mg X
100 mg
100 mL = 25 mL/hr
If you set the pump at 25 mL/hr, this will administer the ordered 25 mg/hr.
7) Calculating Advanced/Critical Drips
RULE: Hourly dose in mg X IV Fluid Total (Vehicle) = ?
Total dose in mg
Example:
Order is for Nipride (50 mg/250 mL) to infuse at 2 mcg/kg/min. Pt weighs 154 lbs.
#1. Calculate kg weight:
154 lbs  2.2 = 70 kg
#2. Calculate hourly dose: (2 mcg) X (70 kg) X (60 min) = 8,400 mcg/hr
#3. Convert mcg to mg:
8,400 mcg = 8.4 mg
8.4 mg X 250 mL = 42 mL/hr
50 mg
Setting the pump at 42 mL/hr will deliver 2 mcg/kg/min of Nipride