Download IV Dosage Calculations Tutorial

D
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CALCULATIONS
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Terms & Concepts
What is the IV flow rate?
The speed at which
intravenous fluid
infuses into the body
What are the tubing sizes?
10, 15, or 20 gtt/mL
(Macrodrip tubing)
60 gtt/mL (Microdrip
tubing)
What is the drop factor?
The number of drops
(abbreviated “gtt”)
required to deliver
1mL of fluid
What determines gtt/mL?
The size of the IV
administration set
(tubing)
How do you calculate the IV flow rate?
Using the IV flow rate formula
IV Flow Rate Formula
IV Flow Rate Formula is used when calculating an
infusion by gravity (without an IV pump).
Volume to be Infused (in mL) x Drop Factor = Flow Rate
Total Infusion Time (in minutes)
(in gtt/min)
Electronic Flow Rate Formula is used when
calculating an infusion by IV pump (electronic
infusion device, or EID).
Volume to be Infused (in mL) = Flow Rate
Total Infusion Time (in hours)
(in mL/h)
*Round all rates to the nearest whole number
Dosage Calculations
Complete necessary conversions (i.e. dosage
per weight, mass, volume, etc) prior to using
either of the two previous flow rate formulas.
Conversions may be calculated using:
• Ratio/Proportion
• Dimensional Analysis
• Whatever method you are most comfortable
with and use consistently/correctly
!
Order: Infuse 800mL of NS in 10 hours.
#1
• This is a straight-forward IV flow rate
calculation, in which no conversion is
required.
• We know we will be using the Electronic
Flow Rate Formula because we were not
given the tubing size or drop factor,
which would be required to calculate a
gravity flow rate.
800mL ÷ 10 hours =
• The correct formula is:
80mL/h
Volume to be Infused (in mL) = Flow Rate
Total Infusion Time (in hours)
(in mL/h)
Order: Infuse 150mL of D5W in 30 minutes
using an administration set with a drop #2
factor of 20gtt/mL.
• This is also a straight-forward IV flow rate
calculation, in which no conversion is
required.
• We know we will be using the IV Flow Rate
Formula because we were given the drop
factor.
• The correct formula is: 150mL x 20gtt/mL ÷ 30
minutes = 100gtt/min
Volume to be Infused (in mL) x Drop Factor = Flow Rate
Total Infusion Time (in minutes)
(in gtt/min)
Order: Infuse 100mL of LR by IV pump in 20
minutes.
#3
• We know we will be using the Electronic
Flow Rate Formula because we were
directed to use an IV pump, and because
we were not given the tubing size or drop
factor.
• Before using our flow rate formula, we must
complete the necessary conversion(s).
• To use our Electronic Flow Rate Formula, we
need the total volume to be infused in mL
(which we know), and the total infusion time
in hours (which we don’t know).
• We must convert minutes to hours using our
chosen dosage calculation method.
CONTINUED
Order: Infuse 100mL of LR by IV pump in 20
minutes.
• Our calculation method of choice is
ratio/proportion, which involves a 3-part
process: 1) Set up ratio, 2) Cross-multiply, 3)
Isolate X by dividing its value by itself
Step 1
20 min = X hour
60 min 1hour
Step 2
60(X) = 20(1) or 60X = 20
Step 3
60X = 20
60 60
so
X = 0.33
CONTINUED
Order: Infuse 100mL of LR by IV pump in 20
minutes.
• Now that we have converted minutes to
hours (20 minutes = 0.33 hours), we can
use our Electronic Flow Rate Formula to
solve our IV dosage calculation problem.
100mL ÷ 0.33 hours = 303mL/h
(The IV pump would be programmed for
303 mL per hour in order to infuse the
desired 100 mL in 20 minutes.)
Order: Infuse 200mL of D5W in 4 hours using a
Microdrip tubing.
• We know we will be using the IV Flow Rate
Formula because we were given a tubing
size (remember that a Microdrip
administration set delivers 60gtt/mL). #4
• Before using our flow rate formula, we must
complete the necessary conversion(s).
• To use our IV Flow Rate Formula, we need
the total volume to be infused in mL (which
we know), the drop factor (which we also
know), and the total infusion time in hours
(which we don’t know).
• We must convert hours to minutes using our
chosen dosage calculation method.
CONTINUED
Order: Infuse 200mL of D5W in 4 hours using
a Microdrip tubing.
• Complete the conversion calculation.
Step 1
4 hours = X minutes
1 hour 60 minutes
Step 2
1(X) = 4(60) or 1X = 240
Step 3
1X = 240
1
1
so
X = 240
CONTINUED
Order: Infuse 200mL of D5W in 4 hours using
a Microdrip tubing.
• Now that we have converted hours to
minutes (4 hours = 240 minutes), we can
use our IV Flow Rate Formula to solve our
IV dosage calculation problem.
200mL x 60gtt/mL ÷ 240 minutes =
50gtt/min
(The roller clamp on the IV tubing would
be manually regulated to deliver 50 drops
per minute.)
Reminders
When preparing to tackle any type of IV flow rate
calculation, be sure to determine what, if any,
conversions need to take place first.
Once you have completed all necessary
conversions, you are ready to calculate the IV
flow rate using one of the two IV flow rate
formulas we’ve discussed in this tutorial.
Remember, it is always best to be consistent with
the dosage calculation method you choose to
use when completing this type of problem.
Order: Give 500mg of dopamine in 250mL of D5W to
infuse at 20mg/h. Calculate the flow rate in mL/h.
*In order to know how many mL we need to infuse in 1
hour per the IV pump, we need to convert our dosage
needed (20mg) into its equivalence in mL.
*Set up ratio, and then cross-multiply:
500mg = 250mL
so
500X = 250(20)
20mg
X mL
*Isolate X and solve:
500X = 5000
500
500
so
X = 10mL
*There are 20mg of dopamine in 10mL of solution, so we
will program our IV pump at 10mL/h.
Your patient has an order to receive 800U of heparin per
hour by continuous intravenous infusion. If the
pharmacy mixes the IV bag to contain a total of
5,000U of heparin in 500mL of D5W, how many mL per
hour should the patient receive?
*In order to calculate mL/hour, we need to convert our
dosage needed (800U) into its equivalence in mL.
*Set up ratio, and then cross-multiply:
5000U = 500mL
so
5000X = 500(800)
800U
X mL
*Isolate X and solve:
5000X = 400,000
5000
5000
so
X = 80mL
*There are 800U of heparin in 80mL of solution, so we will
program our IV pump at 80mL/h.
Order: 21.7mg of dopamine in 105mL of D5W to be
infused at a rate of 9mg/h. Calculate the flow rate in
mL/h.
*In order to calculate mL/hour, we need to convert our
dosage needed (9mg) into its equivalence in mL.
*Set up ratio, and then cross-multiply:
21.7mg = 105mL
so
21.7X = 9(105)
9mg
X mL
*Isolate X and solve:
21.7X = 945
21.7 21.7
so
X = 43.55mL
*There are 9mg of dopamine in 43.55mL of solution, so
we will program our IV pump at 44mL/h.
Order: Aggrastat at 12.5mg in 250mL to be infused at a rate of
6 mcg/kg/hr in a patient who weighs 100kg. At what flow
rate will you set the IV pump?
*For problems that include a weight/mass, do that conversion
1st:
6mcg per kg = 6mcg x 100kg = 600mcg/hr
*Since our ordered dose is in mg, we need to convert mcg to
mg:
600mcg ÷ 1000 = 0.6mg/hr
*In order to calculate mL/hour, we need to convert our
dosage needed (0.6mg) into its equivalence in mL.
*Set up ratio, and then cross-multiply:
12.5mg = 250mL
so
12.5X = 0.6(250)
0.6mg
X mL
*Isolate X and solve:
12.5X = 150
so
X = 12mL
12.5
12.5
*There are 0.6mg of Aggrastat in 12mL of solution, so we will
program our IV pump at 12mL/h.
A 1000cc solution of D5NS with 20,000U of heparin is
infusing at 20mL/h. The IV set delivers 60gtt/mL. How
many units of heparin is the patient receiving each
hour?
*This is a reverse calculation, as we already know the
electronic flow rate (mL/h). We will use our dosage
calculation method to work through the problem.
*Set up ratio, and then cross-multiply:
20,000U = 1000mL so
1000X = 20(20,000)
XU
20mL
*Isolate X and solve:
1000X = 400,000
so
X = 400U
1000
1000
*There are 400U of heparin in 20mL of solution, which
means the patient is receiving 400U of heparin per
hour. The drop factor is simply a distracter, and is not
used in this problem.
The physician orders an IV infusion of D5W 1000mL to be
infused over the next 8 hours. The IV tubing you are
using delivers 15gtt/mL. What is the correct rate of
flow?
*In order to use the IV Flow Rate Formula, we need to
know time in minutes instead of hours, which is the only
conversion we will need to do to solve this problem.
*We can eliminate the extra steps of a time conversion
by incorporating it into our formula:
1000mL x 15gtt/mL = 15,000 = 31.25
8 h x 60 min
480
*Remember our “mL” labels are cancelled out during
the calculation process, and we must round all flow
rates, leaving us with 31gtt/min as the correct rate of
flow.
Your patient has an order to infuse 10mEq of KCl in
100mL of D5½NS over the next 30 minutes. The set
calibration is 10gtt/mL. What is the correct rate of flow?
*We will be using the IV Flow Rate Formula, and no
conversion calculation is needed:
100mL x 10gtt/mL = 1000 ÷ 30 = 33.33
30 min
*The correct rate of flow is 33gtt/min.
*Do not be confused by extra numbers, such as are used
in the name of a solution (i.e. D5W or ½NS). These
have no bearing on your dosage calculation.
*Be careful in determining which value(s) are pertinent in
solving your problem. In this example, the 10mEq of
KCl is not a necessary component in terms of
calculating the correct rate of flow, so ignore it!
The 0900 medications scheduled for your patient include
Keflex 1.5g in 50mL of a 5% dextrose solution.
According to the pharmacy, this preparation should
be administered in 30 minutes. The IV tubing on your
unit delivers 15gtt/mL. What is the correct rate of flow
in gtt/min?
*We will be using the IV Flow Rate Formula, and no
conversion calculation is needed:
50mL x 15gtt/mL = 750 ÷ 30 = 25
30 min
*The correct rate of flow is 25gtt/min.
*Again, remember the 5% dextrose is just describing the
type of solution, and the Keflex 1.5g does not have
anything to do with calculating the flow rate for this
problem.
On Wednesday afternoon, your patient returns from
surgery with an IV fluid order for 1000mL every 8 hours.
On Thursday morning at 0800, you note that 600mL of
a 1L bag has been infused. The physician orders the
remainder of the bag to infuse over the next 6 hours.
The IV tubing used by your unit delivers 10gtt/mL. What
is the correct rate of flow?
*There are 400mL remaining in the IV bag, which needs
to be infused in 6 hours.
*We need to know time in minutes instead of hours,
which can be incorporated into our IV Flow Rate
Formula calculation:
400mL x 10gtt/mL = 4000 ÷ 360 = 11.11
6 h x 60 min
*The correct rate of flow is 11gtt/min.
The physician orders 1.5L of Lactated Ringers solution to
be administered intravenously to your patient over the
next 12 hours. Calculate the rate of flow if the IV tubing
delivers 20gtt/mL.
*In order to utilize the IV Flow Rate Formula, we must
convert liters to milliliters and hours to minutes, both of
which can be completed as part of the formula
calculation:
(1.5L x 1000) x 20gtt/mL = 30,000 ÷ 720 = 41.67
12 h x 60 min
*The correct rate of flow is 42gtt/min.
Miscellaneous
Dosage
#1:
The physician orders 200mg of Rocephin
to be taken by a 15.4 lb infant every 8
hours. The medication label shows that
75-150 mg/kg/day is the appropriate
dosage range for this medication. Is the
order within the desired range?
Convert weight (lbs to kg):
15.4 lbs ÷ 2.2 = 7kg
Calculate minimum and maximum dosage:
75mg x 7kg = 525mg
(minimum daily therapeutic dose)
150mg x 7kg = 1050mg
(maximum daily therapeutic dose)
Determine if the order is within range:
200mg every 8 hours (or 200mg x 3 times
per day) = 600mg
Solve the problem:
Yes, 600mg/day of Rocephin is within the
desired daily range of 525mg and
1050mg for this patient.
#2:
Solumedrol 1.5mg/kg is ordered for a
child weighing 34 kg. This medication is
available as 125mg/2mL. How many mL
will you administer?
Calculate mg according to weight:
1.5mg/kg x 34 kg = 51mg
Convert mg to mL using your chosen dosage
calculation method:
125mg = 2mL so 125X = 51(2)
51 mg X mL
125X = 102
125
125
so X = .82mL
Solve the problem:
You will administer 0.82mL of Solumedrol
to this patient.
#3:
You are to infuse 800mL of Lactated
Ringers over 20 hours using an IV
administration set that delivers 20gtt/mL.
What is the drip rate?
Solve using the IV Flow Rate Formula:
800mL x 20gtt/mL = 16,000gtt = 13gtt/min
20 h x 60 min
1200 min
Calculate the mL/h of the following orders via
IV pump:
#4.
Administer 1500mL of 0.9 NS in 24 hours.
#5.
Administer 750mL of LR in 16 hours.
#6.
Administer 500mL of D5W in 12 hours.
#7.
Administer 2000mL of D5W in 24 hours.
Solve the previous calculations using the
Electronic Flow Rate Formula:
1500mL ÷ 24 hours = 63mL/h
750mL ÷ 16 hours = 47mL/h
500mL ÷ 12 hours = 42mL/h
2000mL ÷ 24 hours = 83mL/h
#8
Order: Administer 30mL of Ancef in 0.9 NS
over 20 minutes via intravenous infusion
pump.
Convert minutes to hours:
20 minutes = X hours so 60X = 20(1)
60 minutes 1 hour
60X = 20 so X = 0.33∞ hours
60
60
Solve using the Electronic Flow Rate Formula:
30mL ÷ 0.33∞ hours = 90mL/h
#9
Order: Administer 100mL of ½NS in 45
minutes.
Convert minutes to hours:
45 minutes = X hours so 60X = 45(1)
60 minutes 1 hour
60X = 45 so X = 0.75 hours
60
60
Solve using the Electronic Flow Rate Formula:
100mL ÷ 0.75 hours = 133mL/h
#10 Order: Administer 150mL of D5W in 30
minutes.
Convert minutes to hours:
30 minutes = X hours so 60X = 30(1)
60 minutes 1 hour
60X = 30 so X = 0.5 hours
60
60
Solve using the Electronic Flow Rate Formula:
150mL ÷ 0.5 hours = 300mL/h
#11 Your patient is to receive 2000mL of D5W
with a flow rate of 160mL/h. How long will
this order take to infuse?
Solve using your chosen dosage calculation
formula:
2000mL = X hours so 160X = 2000(1)
160mL
1 hour
160X = 2000 so X = 12.5 hours
160
160
*It will take 12 ½ hours to infuse 2000mL of D5W
to your patient under this order.
#12 Your patient has been prescribed 1L of NS.
The IV pump is set at 150mL/h. How long
will this order take to infuse?
Solve using your chosen dosage calculation
formula:
1L x 1000 = 1000mL
1000mL = X hours so 150X = 1000(1)
150mL
1 hour
150X = 1000 so X = 6.7 hours
150
150
*It will take just under 7 hours to infuse 1000mL
of NS to your patient under this order.
#13 The physician orders D5W IV at 125mL/h.
The infusion set is calibrated for a drop
factor of 10gtt/mL. Calculate the IV flow
rate in gtt/min.
Solve using the IV Flow Rate Formula:
125mL x 10gtt/mL = 1250gtt = 21gtt/min
1 h x 60 min
60 min
#14 Order: 150mL Lactated Ringers solution to
infuse in 30 minutes. The drop factor is
15gtt/mL.
Solve using the IV Flow Rate Formula:
150mL x 15gtt/mL = 75gtt/min
30 min
#15 Order: Cefazolin 0.5g in 100mL D5W IV
piggyback to run over 30 minutes. The
drop factor is 20gtt/mL. What is the drip
rate?
Solve using the IV Flow Rate Formula:
100mL x 20gtt/mL = 67gtt/min
30 min
#16 Order: Ampicillan 500mg IV in 100mL of
NS to infuse over 45 minutes. How will you
program the infusion pump?
Convert minutes to hours:
45 minutes = X hours so 60X = 45(1)
60 minutes 1 hour
60X = 45 so X = 0.75 hours
60
60
Solve using the Electronic Flow Rate Formula:
100mL ÷ 0.75 hours = 133mL/h
#17 Order: Bactrim 500mg IV in 50mL D5½NS
in 30 minutes by IV pump. What is the
mL/h?
Convert minutes to hours:
30 minutes = X hours so 60X = 30(1)
60 minutes 1 hour
60X = 30 so X = 0.5 hours
60
60
Solve using the Electronic Flow Rate Formula:
50mL ÷ 0.5 hours = 100mL/h
#18 Order: NS 1800mL IV to infuse in 15 hours
by infusion pump. Calculate the flow rate.
Solve using the Electronic Flow Rate Formula:
1800mL ÷ 15 hours = 120mL/h
#19 You receive a physician’s order for D5W
250mL IV over the next 2 hours by infusion
pump. What is the mL/h?
Solve using the Electronic Flow Rate Formula:
250mL ÷ 2 hours = 125mL/h
#20 You receive an order for D5W 500mL with
heparin 25,000U IV at 850U per hour.
Calculate the flow rate in mL/h.
Convert U/h to mL/h to solve this problem:
25,000U = 500mL so 25,000X = 850(500)
850U
X mL
25,000X = 425,000 so X = 17mL/h
25,000
25,000
*The flow rate is 17mL/h.
#21 You receive an order for D5W 1000mL IV
to infuse at 50mL/h to begin at 0600. At
what time will this IV be complete?
Solve using your chosen dosage calculation
formula:
1000mL = X hours so 50X = 1000(1)
50mL
1 hour
50X = 1000 so X = 20 hours
50
50
*This IV will be complete at 0200 the following
morning.
#22 You receive an order for LR solution
1000mL IV to run at 125mL/h. How long will
this IV last?
Solve using your chosen dosage calculation
formula:
1000mL = X hours so 125X = 1000(1)
125mL
1 hour
125X = 1000 so X = 8 hours
125
125
*This IV will last for 8 hours.
#23 Order: Dobutamine 250mg in 250mL D5W
per IV to infuse at 5mcg/kg/min. The
client’s weight is 80 kg. Calculate the flow
rate using an infusion pump.
Calculate mcg according to weight:
5mcg/kg x 80 kg = 400mcg/min
Convert mcg/min to mg/min:
400mcg ÷ 1000 = 0.4mg/min
Convert mg/min to mg/hour:
0.4mg x 60 minutes = 24mg/h
Convert mg to mL based on dosage on hand:
250mg = 250mL so 250X = 24(250)
24mg
X mL
250X = 6000 so X = 24mL
250
250
Solve using the Electronic Flow Rate Formula:
24mL/h via IV pump
#24 Order: Lidocaine 2g in 500mL D5W IV to
run at 4 mg/min. What is the flow rate per
IV pump?
Convert g to mg:
2g x 1000 = 2000mg
Convert mg/min to mL/min based on dosage
on hand:
2000mg = 500mL so 2000X = 4(500)
4mg
X mL
2000X = 2000
2000
2000
so X = 1mL/min
Convert mL/min to mL/h to solve the problem:
1mL x 60 minutes = 60mL/h
#25 Order: Ancef 1g in 100mL D5W IV
piggyback to be infused over 45 minutes.
You are using a Microdrip tubing. What is
the flow rate in gtt/min?
Solve using the IV Flow Rate Formula:
100mL x 60gtt/mL = 133gtt/min
45 min
#26 Order: 50mL Zofran solution IV piggyback
to infuse over 30 minutes. The drop factor
is 60gtt/mL. What is the flow rate in
gtt/min?
Solve using the IV Flow Rate Formula:
50mL x 60gtt/mL = 100gtt/min
30 min
#27 Order: 1000mL D5W IV q 24 hours. The
drop factor is 60gtt/mL. What is the flow
rate in gtt/min?
Convert hours to minutes and solve using the IV
Flow Rate Formula:
1000mL x 60gtt/mL = 60,000 = 42gtt/min
24 hours x 60 minutes 1440
#28 A dose strength of gr ¼ of an IV push
medication is ordered. The available
dosage is 15mg/mL. How many mL will
you administer?
Convert gr to mg:
1grain = 60mg so 1X = ¼(60)
¼ grain X mg
1X = 15 so X = 15mg
1
1
Solve the problem:
15mg = 1mL, so you will administer 1mL.
#29 You have an order for epinephrine to be
infused at 30mL/h. The solution available
is 2mg of epinephrine in 250mL D5W.
Calculate the mcg/min.
Convert mL/h to mg/h based on dosage on
hand:
2mg = 250mL so 250X = 2(30)
X mg 30mL
250X = 60 so X = 0.24mg/h
250 250
Convert mg/h to mcg/h:
0.24mg x 1000 = 240mcg/h
Convert mcg/h to mcg/min to solve the
problem:
240mcg ÷ 60 minutes = 4mcg/min
#30 Aminophyline 0.25g is added to 500mL
D5W to infuse in 8 hours. Calculate the
mg/h.
Use the Electronic Flow Rate Formula to
determine mL/h:
500mL ÷ 8h = 62.5mL/h
Convert mL/h to g/h based on dosage on
hand:
0.25g = 500mL so 500X = 0.25(62.5)
X g 62.5mL
500X = 15.6
500
500
so X = 0.03g/h
Convert g/h to mg/h to solve the problem:
0.03g x 1000 = 30mg/h
#31 You receive an order to infuse 500mL ½NS
with 30,000U heparin at 600U/h. The drop
factor is 60gtt/mL. What is the gtt/min?
Convert U/h to mL/h per on dosage on hand:
30,000U = 500mL so 30,000X = 500(600)
600U
X mL
30,000X = 300,000
30,000
30,000
so X = 10mL/h
Convert hours to minutes and solve using the IV
Flow Rate Formula:
10mL x 60gtt/mL = 10gtt/min
1 hour x 60 minutes
#32 A patient is to receive Pitocin at
15microgtt/min. The solution contains 10U
Pitocin in 1000mL D5W. Calculate the
number of units of Pitocin the patient is
receiving per hour.
Convert mgtt/min to mgtt/h:
15mgtt x 60 minutes = 900mgtt/h
Convert mgtt/h to mL/h (*remember Microdrip
tubing delivers 60 drops in 1mL):
60mgtt = 1mL so 60X = 900(1)
900mgtt X mL
60X = 900
60
60
so
X = 15mL/h
*Continued on next slide
Convert mL/h to U/h:
10U = 1000mL so
XU
15mL
1000X = 150
1000 1000
so
1000X = 10(15)
X = 0.15U
Solve the problem:
The patient is receiving 0.15U/hour of
Pitocin.
#33 You have an order for 3 mcg/kg/min of
Nipride. You have available 50mg of
Nipride in 250mL D5W. The client’s weight
is 60 kg. Calculate the flow rate in mL/h
that will deliver the correct dose.
Calculate mcg according to weight:
3mcg/kg x 60 kg = 180mcg/min
Convert mcg/min to mg/min:
180mcg ÷ 1000 = 0.18mg/min
Convert mg/min to mg/hour:
0.18mg x 60 minutes = 10.8mg/h
Convert mg to mL based on dosage on hand:
50mg = 250mL so 50X = 10.8(250)
10.8mg X mL
50X = 2700 so X = 54mL
50
50
Solve using the Electronic Flow Rate Formula:
54mL/h via IV pump
#34 A 50mg nitroglycerin drip in 250mL D5W is
infusing at 3mL/h. Calculate the mcg/min
of nitroglycerin this patient is receiving.
Convert mL/h to mg/h based on dosage on
hand:
50mg = 250mL so 250X = 50(3)
X mg
3mL
250X = 150
250
250
so X = 0.6mg/h
Convert mg/h to mcg/h:
0.6mg x 1000 = 600mcg/h
Convert mcg/h to mcg/min to solve the
problem:
600mcg ÷ 60 minutes = 10mcg/min
#35 A dose strength of 0.3g of a medication
has been ordered to infuse over 20
minutes. The available dosage is 0.4g in
1.5mL of solution. Calculate the mL/h.
Convert g to mL based on dosage on hand:
0.4g = 1.5mL so 0.4X = 0.3(1.5)
0.3g
X mL
0.4X = 0.45 so X = 1.125mL
0.4
0.4
Convert minutes to hours:
20 minutes = X hours so 60X = 20(1)
60 minutes 1 hour
60X = 20 so X = 0.33∞ hours
60 60
Use the Electronic Flow Rate Formula to solve:
1.125mL ÷ 0.33∞ hours = 3mL/h