Advanced Calculations
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Transcript Advanced Calculations
Advanced Calculations
Nursing 201
Ms. Frasier
Summer 2014
Dimensional Analysis
Simple technique with a fancy name
Allows manipulation of units
Also referred as factor label
method or the unit factor
method
Less errors
The advantage of dimensional analysis
is only one equation is needed
Review
ml/hr
gtt/min
Infusion of IV fluids with an IV pump
Solve for mL/h
The formula: x mL/h = Total volume in milliliters
Total time in hours
On the left side of the equation, place what you are solving
𝑚𝑙
for.
X =
ℎ𝑟
On the right side of the equation, place the available
information related to the measurement that was placed
on the left side of the equation. 1000ml
8h
Answer 125mL/hr
Drops per minute (gtt/min)
Knowing the drop factor is the first step
The drop factor always appears on the IV package
Macrodrops are large and deliver 10, 15, 20 gtt/mL
Microdrops are small and deliver 60 gtt/mL
Drop factor = gtt/mL
Example: order: D5W to infuse at 100ml/hr. drop factor
10gtt/mL. at what rate in gtt/min should the IV be regulated?
1. You are calculating for gtt/min, so write gtt/min to the left of
the equation, (that is what you are looking for)
2. Extract the information that contains gtt/min from the
problem; drop factor is 10gtt/mL. add this factor into the
equation. X gtt = 10gtt
min
mL
The next fraction is written so that the denominator matches
the previous fraction (what you are looking for). Looking back
at problem we are to infuse 100mL in 1 hr. enter the 1hr as
60min since we are looking for gtt/min.
𝑥𝑔𝑡𝑡
𝑚𝑖𝑛
=
10𝑔𝑡𝑡 ×100𝑚𝐿
1𝑚𝐿 × 60𝑚𝑖𝑛
=
1000
60
= 16.6 =17𝑔𝑡𝑡/𝑚𝑖𝑛
Order: An IV medication of 50mL NS in 20 min. drop factor
(60gtt/mL). At what rate in gtt/min should the IV be
regulated?
You are calculating gtt/min, so write gtt/min to the left of the
equation, followed by equals sign, label x, since that is what
you are looking for: extract the information that contains gtt
from the problem. Drop factor 60gtts/mL. numerators match
up
𝑥𝑔𝑡𝑡
𝑚𝑖𝑛
₌
60𝑔𝑡𝑡
𝑚𝐿
×
50𝑚𝐿
20
=
3000
20
= 150𝑔𝑡𝑡/𝑚𝑖𝑛
Practice Problems
Calculate the flow rate in mL/hr using dimensional analysis
1. 1,800 mL of D5W in 24 hr by infusion pump _____________
2. 2,000 mL D5W in 24 hr by infusion pump _______________
3. 500 mL RL in 12 hr by infusion pump __________________
4. 100 mL 0.45% NS in 45 min by infusion pump ___________
5. 1,500 mL D5LR in 24 hr by infusion pump _______________
6. 750mL D5W in 16 hr by infusion pump ________________
7. 30 mL of Ancef in 0.9% NS in 20min by infusion pump _____
Answers
=
1800𝑚𝑙
24ℎ𝑟
= 75𝑚𝐿/ℎ𝑟
2. × ℎ𝑟 =
2000𝑚𝑙
24ℎ𝑟
= 83.3 = 83𝑚𝐿/ℎ𝑟
1. ×
𝑚𝐿
ℎ𝑟
𝑚𝑙
𝑚𝐿
3. 𝑥 ℎ𝑟 =
𝑚𝐿
4. × ℎ𝑟 =
5. ×
𝑚𝐿
ℎ𝑟
=
500𝑚𝐿
12ℎ𝑟
= 41.6 = 42𝑚𝑙/ℎ𝑟
100𝑚𝐿
45𝑚𝑖𝑛
1500𝑚𝐿
24ℎ𝑟
𝑚𝐿
750𝑚𝐿
16ℎ𝑟
𝑚𝑙
30𝑚𝐿
6. × ℎ𝑟 =
×
60𝑚𝑖𝑛
1ℎ𝑟
=
400
3
= 133mL/hr
= 62.5 = 63mL/hr
= 46.8 = 47 𝑚𝐿/ℎ𝑟
7. × ℎ𝑟 = 20𝑚𝑖𝑛 ×
60𝑚𝑖𝑛
1ℎ𝑟
=
90
1
= 90𝑚𝐿/ℎ𝑟
Practice Problems
Calculate the flow rate in gtt / min using dimensional analysis
1. Administer D5LR at 75mL/hr. the drop factor is 10gtt/mL
2. Administer D5NS at 30mL/hr. the drop factor is a microdrop
3. Administer RL at 125mL/hr. the drop factor is 15gtt/mL
4. Administer 1000 mL D5NS in 6 hrs. the drop factor is 15gtt/mL
5. An IV medication in 60mL of NS is to be given in 45 min. the
drop factor is a microdrop
6. 1000 mL of LR is to infuse in 16 hr. the drop factor is 15gtt/mL
7. Infuse 150mL of D5W in 2hr. The drop factor is 20gtt/mL
Answers
1. ×
𝑔𝑡𝑡
𝑚𝑖𝑛
×
75𝑚𝐿
ℎ𝑟
=
60
𝑚𝐿
×
30𝑚𝐿
ℎ𝑟
3. × 𝑚𝑖𝑛 =
15
𝑚𝐿
×
125𝑚𝑙
1ℎ𝑟
2. ×
𝑔𝑡𝑡
𝑚𝑖𝑛
=
10𝑔𝑡𝑡
𝑚𝐿
𝑔𝑡𝑡
𝑔𝑡𝑡
4. × 𝑚𝑖𝑛 =
×
×
×
1ℎ𝑟
60𝑚𝑖𝑛
1ℎ𝑟
60𝑚𝑖𝑛
=
=
60
2
750
60
=
= 12.5 =
13𝑔𝑡𝑡
𝑚𝑖𝑛
30𝑔𝑡𝑡
𝑚𝑖𝑛
1ℎ𝑟
1875
31𝑔𝑡𝑡
=
= 31.25 =
60
𝑚𝑖𝑛
60𝑚𝑖𝑛
15𝑔𝑡𝑡
1000𝑚𝐿
1ℎ𝑟
×
×
= step 1: calculate mL/hr
𝑚𝐿
6ℎ𝑟
60𝑚𝑖𝑛
15𝑔𝑡𝑡
167𝑚𝐿
1ℎ𝑟
2505
×
×
=
= 41.7 = 42𝑔𝑡𝑡/𝑚𝑖𝑛
𝑚𝐿
1ℎ𝑟
60𝑚𝑖𝑛
60
𝑔𝑡𝑡
60𝑔𝑡𝑡
𝑚𝐿
𝑔𝑡𝑡
15𝑔𝑡𝑡
1000𝑚𝐿
1ℎ𝑟
×
×
= 𝑠𝑡𝑒𝑝 1: 𝑐𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑒 𝑚𝐿/ℎ𝑟
𝑚𝐿
16ℎ𝑟
60𝑚𝑖𝑛
15𝑔𝑡𝑡
63𝑚𝐿
1ℎ𝑟
63
×
×
=
= 15.75 = 16𝑔𝑡𝑡/𝑚𝑖𝑛
𝑚𝑙
1ℎ𝑟
60𝑚𝑖𝑛
4
5. × 𝑚𝑖𝑛 =
6. × 𝑚𝑖𝑛 =
×
60𝑚𝐿
45𝑚𝑖𝑛
=
240
3
=
80𝑔𝑡𝑡
𝑚𝑖𝑛
Critical Care Calculations
Critically ill clients receive medications that are potent and
require close monitoring
Titrated medications are added to a specific volume of fluid
and rate adjusted to desired effect; when a solution is
titrated, the lowest dosage of the med is set first and ↑ or ↓
as necessary
The drugs that are titrated are potent antiarrhythmics,
vasopressor, and vasodilator medications
Infusion pumps are used for titration
Critical Care Calculations
• Volume
• mL / hr
• Dosage
•
•
•
•
•
•
•
•
mg / min
mg / hr
mcg / min
mcg / hr
mcg / kg / min
mg / kg / min
mcg / kg / hr
mg / kg / hr
• mg / min
• mg / hr
A client is receiving Pronestyl 60mL/hr. the solution available is
pronestyl 2g in 500mL D5W . Calculate the mg/hr and the mg/min
the client will receive.
𝑚𝑔
x
ℎ𝑟
×
=
𝑚𝑔
𝑚𝑖𝑛
1000𝑚𝑔
1𝑔
=
×
1000𝑚𝑔
1𝑔
2𝑔
500𝑚𝐿
×
×
2𝑔
500𝑚𝐿
60𝑚𝐿
1ℎ𝑟
×
=
60𝑚𝑙
60𝑚𝑖𝑛
240𝑚𝑔
1ℎ𝑟
=
= 240𝑚𝑔/ℎ𝑟
240𝑚𝑔
60
=4 mg/min
mcg / min
mcg / hr
Order: a patient with heart failure has nitroglycerin infusing at
3mL/h. the nitroglycerin concentration is 100mg in 500 mL of
D5W. At what rate, in micrograms per minute, is the
nitroglycerin infusing?
×
𝑚𝑐𝑔
𝑚𝑖𝑛
×
𝑚𝑐𝑔
ℎ𝑟
=
1000𝑚𝑐𝑔
1𝑚𝑔
×
100𝑚𝑔
500𝑚𝐿
=
1000𝑚𝑐𝑔
1𝑚𝑔
×
100𝑚𝑔
500𝑚𝐿
×
3𝑚𝐿
1ℎ𝑟
×
×
3𝑚𝐿
ℎ𝑟
1ℎ𝑟
60𝑚𝑖𝑛
=
=
600𝑚𝑐𝑔
ℎ𝑟
600
60
=
10𝑚𝑐𝑔
𝑚𝑖𝑛
• mcg/kg/min
• mcg/kg/hr
Order: 400 mg of dopamine is added to 250ml. Of 0.9% NS. The
order is to begin the infusion at 2mcg/kg/min. the patient’s weight
is 150lb. The nurse needs to calculate the rate, in milliliters per
hours, at which to set the IV pump.
1. Convert client’s weight to kilograms:
150lb ÷2.2 = 68.18𝑘𝑔 = 68.2𝑘𝑔
2. Now that you have the client’s weight in kg, determine the
dosage per min.
68.2kg x 2mcg/kg/min = 136.4mcg/min
𝑚𝑙
x
ℎ𝑟
=
250𝑚𝑙
400𝑚𝑔
×
1𝑚𝑔
1000𝑚𝑐𝑔
×
136.4𝑚𝑐𝑔
1𝑚𝑖𝑛
×
60𝑚𝑖𝑛
1ℎ𝑟
=
40,920
= 5 𝑚𝑙/ℎ𝑟
8000
Practice Problems
1. A client weighing 50kg is to receive a Dobutrex solution of
250mg in 500ml D5W ordered to titrate between 2.5 and 5
mcg/kg/min.
a. Determine the flow rate setting for a volumetric pump.
b. If the IV flow rate is being maintained at 25mL/hr after
several titrations, what is the dosage infusing per minute?
2. Order: Epinephrine at 30mL/hr. The solution available is 2mg
of epinephrine in 250mL D5W. Calculate the following:
a. mg/hr
b. mcg/hr
c. mcg/min
3. Aminophylline 0.25g is added to 500mL D5W to infuse at
20mL/hr. Calculate the following:
a. mg/hr
4. Order: 3mcg/kg/min of Nipride:
Available: 50mg of Nipride in 250mL D5W . Client’s weight is 60
kg.
a. Calculate the flow rate in mL/hr that will deliver this dosage.
5. A nitroglycerin drip is infusing at 3mL/hr. The solution
available is 50mg of nitroglycerin in 250mL D5W. Calculate the
following:
a. mcg/hr
b. mcg/min
Heparin IV
• HIGH ALERT MEDICATION
• Heparin is a potent anticoagulant that prevents clot formation
and blood coagulation
• Expressed in units (no “U” abbreviation)
• The therapeutic range for heparin is determined individually
by monitoring the client’s blood clotting value (APTT –
activated partial thromboplastin time)
• Heparin is considered to be more therapeutic when based on
weight in kg.
• May be given SQ or IV. Never IM.
• Should always be on a pump…will be ordered either ml/hr or
units/hr
• Remember heparin comes in many different strengths. Make
sure you have the correct one.
Examples
• mL/hr – units/hr
Order: 15 units/hour. On hand you have 40units in 250ml of NS.
How many ml/hr will you administer?
𝑚𝑙
ℎ𝑟
=
250𝑚𝑙
40𝑢𝑛𝑖𝑡𝑠
×
15𝑢𝑛𝑖𝑡𝑠
ℎ𝑟
=
3750
40
= 94 ml/hr
Order: D5W 1000ml containing 20,000 units of heparin to infuse
at 30mL/hr. calculate the dosage of heparin the client is to receive
per hour.
𝑢𝑛𝑖𝑡𝑠
ℎ𝑟
=
20,000𝑢𝑛𝑖𝑡𝑠
1000𝑚𝐿
×
30𝑚𝐿
ℎ𝑟
=
600000
1000
= 600 units per hour
Calculating heparin dosages based on weight
A client weighs 165 lb.
Order: heparin 25,000 units in 1000ml 0.9% sodium chloride.
Bolus with heparin at 80units/kg, then initiate drip at
18units/kg/hr. calculate the initial bolus dosage, then calculate
the infusion rate at ml/hr.
𝑥 𝑢𝑛𝑖𝑡𝑠
𝑚𝑙
ℎ𝑟
Or
=
=
80𝑢𝑛𝑖𝑡𝑠
𝑘𝑔
1000𝑚𝐿
25000𝑢𝑛𝑖𝑡𝑠
𝑚𝑙
ℎ𝑟
=
×
×
𝑜𝑛𝑒 𝑘𝑔
2.2𝑙𝑏
1350𝑢𝑛𝑖𝑡𝑠
ℎ𝑟
1000𝑚𝑙
25000𝑢𝑛𝑖𝑡𝑠
×
=
18𝑢𝑛𝑖𝑡𝑠
𝑘𝑔
x
165𝑙𝑏
1
1350
25
×
=
13200
= 6000 𝑢𝑛𝑖𝑡𝑠 𝐼𝑉 bolus
2.2
= 54ml/hr
75𝑘𝑔
ℎ𝑟
=
1350 𝑚𝑙
25𝑢𝑛𝑖𝑡𝑠
= 54𝑚𝐿/ℎ𝑟
A client weighs 176 lb. Heparin infusion 20,000 units in 1000mL
0.9% sodium chloride.
Order: bolus with heparin sodium at 80units/kg, then initiate
drip at 18units/kg/hr. Calculate the following:
a. ___________ bolus dosage
b. ___________ infusion rate (initial)
c. ___________ mL/hr
Answers: 6400 units, 1440units/hr, 72mL/hr
46. pg.519 Order: Heparin drip at 18units/kg.
Available: 25,000units of heparin in 1,000mL of D5W. The client
weighs 80 kg. At what rate will you set the infusion pump?
First determine units/kg the client should receive.
18x80 = 1440units then mL/hr
Answer: 58 mL/hr
47. Pg 519 A client weighs 200 lb.
Order: Administer a bolus of heparin sodium IV at 80units/kg. how
many units will you administer:
𝑢𝑛𝑖𝑡𝑠 = 80𝑢𝑛𝑖𝑡𝑠
𝑥
𝑘𝑔
×
1𝑘𝑔
2.2 𝑙𝑏
×
200𝑙𝑏
1
= 7,272 𝑢𝑛𝑖𝑡𝑠
48. pg. 520 A client weight 210 lb.
Order: Heparin IV infusion: heparin sodium 25,000 units in 1,000
mL of 0.9% NS. Order is give a bolus with heparin sodium
80units/kg, then initiate drip at 18units/kg/hr.
Calculate the following:
a. Heparin bolus dosage ____________________
b. Infusion rate for the IV (initial) _____________
c. At what rate will you set the infusion pump? ___________
• Practice! Practice! Practice!
• Review Heparin Weight Based Protocol