Download CHAPTER 16 IV Flow Rate Calculation

144
SECTION 6 INTRAVENOUS CALCULATIONS
CHAPTER 16
IV Flow Rate Calculation
Objectives
The learner will:
1.
identify the calibrations in gtt/mL on IV administration sets.
2.
calculate flow rates using dimensional analysis.
3.
calculate flow rates using the formula and division factor methods.
4.
recalculate flow rates to correct off-schedule infusions.
Suggested Review Questions
1.
What information is needed to calculate the infusion rate of IV fluids in drops/minute?
2.
What is the correct format for writing the equation when using dimensional analysis to
calculate IV flow rates?
3.
What is a formula that can be used to calculate IV flow rates?
4.
Explain the division factor method for calculating IV flow rates.
5.
Explain the purpose and formula for recalculating the rate of IV fluids infusing via gravity
when they become off-schedule.
Answers to Review Questions
1.
Infusion rates in drops/minute (gtt/min) are usually calculated when fluids are infusing by
gravity. The essential information needed to calculate the gtt/min rate is
a.
the tubing drop factor, the number of gtt/mL
b.
the prescribed infusion rate in mL/hr
© 2010 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.
CHAPTER 16 IV FLOW RATE CALCULATION
2.
145
The format for constructing the DA equation to calculate IV flow rates in gtt/min is
gtt/min =
tubing drop factor (gtt)
amount of fluid to be infused (mL)
1 hr
×
×
1 mL
time (in hr)
min
Therefore, if 75 mL of IV fluid were to infuse each hour and the drop factor is 15 gtt/mL,
the equation would be
1
gtt
15 gtt
75 mL
1 hr
= 18.75 = 19 gtt/min
=
×
×
min
1 mL
1 hr
60 min
4
The DA equation can be simplified by substituting 60 minutes for the 1 hr entry. Thus, the
equation would be
tubing drop factor (gtt)
amount of fluid to be infused (mL)
×
1 mL
time in minutes
gtt/min =
And if 75 mL of IV fluid were to infuse each hour and the drop factor is 15 gtt/mL, the
equation would be
1
gtt
15 gtt
75 mL
= 18.75 = 19 gtt/min
=
×
min
1 mL
60 min
4
3.
A formula that can be used to calculate IV flow rates (or drops per minute) is
gtt
volume × set calibration
=
min
time in minutes
This formula is especially useful when the time for the infusion is 60 minutes or less.
4.
To calculate IV infusion rates when the order is expressed in mL/hr and gtt/min the
division factor method can also be used. The division factor method is obtained by
dividing 60 by the drop factor of the IV administration set. Once the division factor is
known, it can be used to calculate the gtt/min by simply dividing the mL/hr ordered by the
division factor. For example, the division factor for IV tubing with a drop factor of 15 is 4
(60/15 = 4); if IV fluids are ordered at 75 mL/hr, the gtt/min are determined by dividing 75
by 4 = 18.75 or 19 gtt/min. Once the division factor has been determined for each of the
commonly used IV administration sets, it is remembered and used to quickly calculate the
© 2010 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.
146
SECTION 6 INTRAVENOUS CALCULATIONS
gtt/min for IV fluids ordered as mL/hr. The division factor for each of the commonly used
IV administration sets is
10 gtt/mL – division factor is 6
15 gtt/mL – division factor is 4
20 gtt/mL – division factor is 3
60 gtt/mL – division factor is 1
5.
The rate of all continuous IV infusions should be counted by the nurse at least once each
hour, as changes in the fluid gravity pressure and position of the extremity where the IV
catheter is placed can alter the established IV infusion rate. The nurse needs to monitor the
IV so that the fluid does not infuse too quickly or too slowly. When assessing an IV
infusion that has become off-schedule, the remaining volume of fluid and time of infusion
are determined. IV rates that are found to be too fast are slowed down. IV rates that are too
slow are recalculated to the original ordered rate. Sometimes, the IV rate may be increased
so that the infusion can be completed within the ordered time frame; however, careful
assessment of the patient and consideration of the type of fluid infusing (i.e., does it
contain a medication) is done to determine if increasing the infusion rate above the ordered
rate has the potential to harm the patient. Always follow the hospital policy related to
increasing infusion rates.
The formula for recalculating IV infusion rates is the same for increasing and
decreasing the IV rate. The remaining infusion time and volume are used to determine the
number of mL/hour that should infuse to complete the infusion within the ordered time
frame. The mL/hour is then divided by the division factor to determine the adjusted
infusion rate. The two step formula is
(1) Volume remaining ÷ time remaining = mL/hr to infuse
(2) mL/hr to infuse ÷ division factor = gtt/min
© 2010 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.
CHAPTER 16 IV FLOW RATE CALCULATION
147
Name ____________________________________________ Date ____________________
Chapter 16: IV Flow Rate Calculation
Additional Practice Problems
Calculate the IV flow rate in gtt/min for the following IV solutions and medications. Round
answers to the nearest whole number (or drop).
1.
An IV piggyback of piperacillin diluted in 50 mL of 0.9% NaCl is to infuse in 20 minutes.
The set calibration is 20 gtt/mL.
___________
2.
1000 mL of lactated Ringer’s is to infuse over 12 hr. The set calibration is 15 gtt/mL.
___________
3.
An IV piggyback of gentamicin diluted in 100 mL of 5% dextrose in water is to infuse in
1 hr. The set calibration is 10 gtt/mL.
___________
4.
Your patient is to receive 1000 mL of D5 0.45% NaCl over 24 hr. The set calibration is
60 gtt/mL.
___________
5.
Your patient is to receive 1500 mL of 0.9% NaCl over 10 hours. The set calibration is
10 gtt/mL.
___________
6.
An IV piggyback of 500 mg imipenem-cilastatin sodium diluted in 50 mL D5W is to
infuse over 30 minutes. The set calibration is 15 gtt/mL.
___________
© 2010 Cengage Learning. All Rights Reserved. Permission to reproduce granted for classroom use only.
148
7.
SECTION 6 INTRAVENOUS CALCULATIONS
10 mL of IV medication are to infuse in 15 minutes. A microdrip infusion set is used.
___________
8.
An IV piggyback of 200 mg ciprofloxacin hydrochloride diluted in 100 mL of 0.9% NaCl
is to infuse over 45 minutes. The set calibration is 20 gtt/mL.
___________
9.
An order for 125 mL of D5 0.9% NaCl per hour is written. The set calibration is
15 gtt/mL.
___________
10.
A child is to receive 500 mL of D5W over the next 12 hours. A microdrip infusion set is
used.
___________
Recalculate the flow for the infusions below to complete on schedule. Calculate the gtt/min
and round answers to the nearest whole number (or drop).
11.
An IV of 1000 mL was scheduled to infuse in 8 hours. After 3 hours, you note that 600 mL
have infused. The set calibration is 10 gtt/mL.
___________
12.
An IV of 500 mL was started at 8:00 AM to infuse over 5 hours. At 10:00 AM you note
that 125 mL have infused. The set calibration is 15 gtt/mL.
___________
13.
An IV of 1000 mL was infusing at 100 mL/hr. After 300 mL had infused, the order was
written to complete the infusion within the next 4 hours. Set calibration is 20 gtt/mL.
___________
14.
A 250 mL bag of IV fluid was to infuse in 2 hours. After 1 hour you note that 150 mL
have infused. Set calibration is 10 gtt/mL.
___________
© 2010 Cengage Learning. All Rights Reserved. Permission to reproduce granted for classroom use only.
CHAPTER 16 IV FLOW RATE CALCULATION
15.
149
A volume of 400 mL of fluid was to infuse over 5 hours. After 2 hours you note that
200 mL already infused. Set calibration is 15 gtt/mL.
___________
16.
125 mL of IV fluid are to infuse over 3 hours. After 1 hour you note that only 25 mL have
infused. Set calibration is 60 gtt/mL.
___________
17.
An IV of 1000 mL is ordered to infuse over 6 hours. After 3 hours, you note that 750 mL
have already infused. Set calibration is 20 gtt/mL.
___________
18.
750 mL of IV fluid are to infuse over 3 hours. After 1 hr and 30 minutes you note that
400 mL have infused. Set calibration is 10 gtt/mL.
___________
19.
An IV of 250 mL of solution is infusing at 25 mL/hour. After 3 hours you note that
125 mL of solution have infused. Set calibration is 60 gtt/mL.
___________
20.
800 mL has inused from a 1000 mL IV bag in 5 hours. The drip rate had been set so that
the infusion would be complete in 10 hours. Set calibration is 15 gtt/mL.
___________
© 2010 Cengage Learning. All Rights Reserved. Permission to reproduce granted for classroom use only.
150
SECTION 6 INTRAVENOUS CALCULATIONS
Solutions to Additional Practice Problems
Calculate the IV flow rate in gtt/min for the following IV solutions and medications. Round
answers to the nearest whole number (or drop).
1.
Since the infusion time is less than 60 minutes, the formula method is used.
Answer = 50 gtt/min.
1
50 mL × 20 gtt/ mL
= 50 gtt/min
gtt/min =
20 min
1
2.
The infusion time is greater than 1 hr, so dimensional analysis is used.
Answer = 21 gtt/min.
1
gtt
15 gtt
1000 mL
1 hr
1000
=
×
×
=
= 20.8 = 21 gtt/min
min
48
12 hr
60 min
1 mL
4
3.
The infusion time is 1 hr. Either the formula or dimensional analysis method can be used.
Answer = 17 gtt/min.
Formula method:
1
100 mL × 10 gtt/ mL
100
gtt/min =
=
= 16.6 = 17 gtt/min
6
60 min
6
Dimensional analysis:
1
gtt
10 gtt
100 mL
1 hr
100
=
×
×
=
= 16.6 = 17 gtt/min
min
6
1 mL
1 hr
60 min
6
4.
The infusion time is greater than 1 hr, so dimensional analysis is used.
Answer = 42 gtt/min.
1
gtt
60 gtt
1000 mL
1 hr
1000
=
×
×
=
= 41.6 = 42 gtt/min
min
24
24 hr
60 min
1 mL
1
© 2010 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.
CHAPTER 16 IV FLOW RATE CALCULATION
5.
151
The infusion time is greater than 1 hr, so dimensional analysis is used.
Answer = 25 gtt/min.
1
gtt
10 gtt
1500 mL
1 hr
1500
=
×
×
=
= 25 gtt/min
min
60 min
60
10 hr
1 mL
1
6.
Since the infusion time is less than 60 minutes, the formula method is used.
Answer = 25 gtt/min.
1
50 mL × 15 gtt/ mL
50
gtt/min =
=
= 25 gtt/min
2
30 min
2
7.
Since the infusion time is less than 60 minutes, the formula method is used.
Answer = 40 gtt/min.
4
gtt/min =
10 mL × 60 gtt/ mL
= 40 gtt/min
15 min
1
8.
Since the infusion time is less than 60 minutes, the formula method is used.
Answer = 44 gtt/min.
gtt/min =
9.
2000
100 mL × 20 gtt/ mL
=
= 44.4 = 44 gtt/min
45 min
45
The infusion time is 1 hr. Either the formula or dimensional analysis method can be used.
Answer = 31 gtt/min.
Formula method:
1
125 mL × 15 gtt/ mL
125
gtt/min =
=
= 31.2 = 31 gtt/min
4
60 min
4
Dimensional analysis:
1
gtt
15 gtt
125 mL
1 hr
125
×
×
=
=
= 31.2 = 31 gtt/min
min
4
1 hr
60 min
1 mL
4
© 2010 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.
152
10.
SECTION 6 INTRAVENOUS CALCULATIONS
The infusion time is greater than 1 hr, so dimensional analysis is used.
Answer = 42 gtt/min.
1
gtt
60 gtt
500 mL
1 hr
500
×
×
=
=
= 41.6 = 42 gtt/min
min
12
12 hr
60 min
1 mL
1
Recalculate the flow for the infusions below to complete on schedule. Calculate the gtt/min
and round answers to the nearest whole number (or drop). [Note: recalculation is
computed based on mL/hr; therefore, the formula method has been used in the calculations
below.]
11.
Time remaining:
8 hr – 3 hr = 5 hr
Volume remaining: 1000 mL − 600 mL = 400 mL
400 mL ÷ 5 hr = 80 mL/hr
1
80
80 mL × 10 gtt/ mL
=
= 13.3 = 13 gtt/min
6
60 min
6
12.
Time remaining:
5 hr − 2 hr = 3 hr
Volume remaining: 500 mL − 125 mL = 375 mL
375 mL ÷ 3 hr = 125 mL/hr
1
125
125 mL × 15 gtt/ mL
=
= 31.2 = 31 gtt/min
4
60 min
4
13.
Time remaining:
4 hr
Volume remaining: 1000 mL − 300 mL = 700 mL
700 mL ÷ 4 hr = 175 mL/hr
1
175 mL × 20 gtt/ mL
175
=
= 58.3 = 58 gtt/min
3
60 min
3
© 2010 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.
CHAPTER 16 IV FLOW RATE CALCULATION
14.
Time remaining:
2 hr − 1 hr = 1 hr
Volume remaining: 250 mL − 150 mL = 100 mL
100 mL ÷ 1 hr = 100 mL/hr
1
100
100 mL × 10 gtt/ mL
=
= 16.6 = 17 gtt/min
6
60 min
6
15.
Time remaining:
5 hr − 2 hr = 3 hr
Volume remaining: 400 mL − 200 mL = 200 mL
200 mL ÷ 3 hr = 66.6 mL/hr
1
66.6
66.6 mL × 15 gtt/ mL
=
= 16.6 = 17 gtt/min
4
60 min
4
16.
Time remaining:
3 hr − 1 hr = 2 hr
Volume remaining: 125 mL − 25 mL = 100 mL
100 mL ÷ 2 hr = 50 mL/hr
1
50 mL × 60 gtt/ mL
= 50 gtt/min
60 min
1
17.
Time remaining:
6 hr − 3 hr = 3 hr
Volume remaining: 1000 mL − 750 mL = 250 mL
250 mL ÷ 3 hr = 83.3 mL/hr
1
83.3
83.3 mL × 20 gtt/ mL
=
= 27.7 = 28 gtt/min
3
60 min
3
© 2010 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.
153
154
18.
SECTION 6 INTRAVENOUS CALCULATIONS
Time remaining:
3 hr − 1.5 hr = 1.5 hr
Volume remaining: 750 mL − 400 mL = 350 mL
350 mL ÷ 1.5 hr = 233.3 mL/hr
1
233.3
233.3 mL × 10 gtt/ mL
=
= 38.8 = 39 gtt/min
6
60 min
6
19.
If 250 mL are infusing at 25 mL/hr, the entire infusion would take 10 hr.
Time remaining:
10 hr − 3 hr = 7 hr
Volume remaining: 250 mL − 125 mL = 125 mL
125 mL ÷ 7 hr = 17.85 (rounded to nearest 10th) = 17.9 mL/hr
1
17.9 mL × 60 gtt/ mL
= 17.9 = 18 gtt/min
60 min
1
20.
Time remaining:
10 hr − 5 hr = 5 hr
Volume remaining: 1000 mL − 800 mL = 200 mL
200 mL ÷ 5 hr = 40 mL/hr
1
40 mL × 15 gtt/ mL
40
=
= 10 gtt/min
4
60 min
4
© 2010 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.