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Calculating
drip rate:
- Drip
rate is the number of drops per minute to
be infused (gtt/min).
- Drip
factor of the tubing is found on the manufacturer's packaging.
(expressed as gtt/ml)
- If
the problem states microdrops (microgtts), then the drip factor of
the tubing is 60 gtt/ml.
Formula:
total
# of milliliters (volume)
total # of minutes (time)
|
x |
drip
factor |
=
gtt/min
|
Example:
The
physician orders IV fluids to hydrate a client. The order is written
as "D5NS 4 Liters over 24 hours." Looking at the
package indicates the drip factor of the tubing is 15 gtt/ml.
What is the drip rate?
Critical
information:
- Volume
= 4000 ml
- Time
= 24 hours
- Drip
factor of tubing = 15 gtt/ml.
Tip:
- How
many minutes is the ordered time period?
- 24
(hr) x 60 (minutes) = 1440 minutes
4000
ml
1440 minutes
|
X |
15
gtt
1 ml |
| 4000
x 15 |
= |
60000 |
| 60000
/ 1440 |
= |
41.66 |
| Answer:
41.66 gtt/min or 42 (if your instructor wants you to "round"). |
Example:
Order:
Run current IV fluids at 175 ml/hr for 2 hours.
Critical
information:
- Volume
= 175 ml
- Time
= 1 hr
- (What
is the drip factor of the tubing? Assume 15 gtt/ml unless otherwise
indicated. Exception would be: If on infusion pump or problem
states microgtts, use 60 gtt/ml)
Extraneous
information for calculating:
- 2 hours
(but important in carrying out the order).
175
ml
60 min
|
x |
15
gtt
1 ml |
| 175
x 15 |
= |
2625 |
| 2625
/ 60 |
= |
43.75 |
| Answer:
43.75 gtt/min or 44 (if your instructor wants you to "round"). |
method when you know the ordered ml/hr:
| 15
gtt/ml: divide the ml/hr by 4 |
| 10
gtt/ml (typically blood products): divide ml/hr by 6 |
| 20
gtt/ml: divide ml/hr by 3 |
method
| 175
/ 4 |
= |
43.75
gtt/min |
| 175
/ 6 |
= |
29.16
gtt/min |
| 175
/ 3 |
= |
58.33
gtt/min |
(Most
nurses can calculate this way "in their head" at the bedside.)
Sometimes
the nurse will need to administer an intravenous med at a prescribed concentration.
Example:
The
client's K+ is 2.0 mEq/dl and the physician orders a potassium
bolus of 40 mEq of KCl in 200 ml of NS to be delivered at a rate of
10 mEq/hr. What is the drip rate in microdrops? (Ideal,
deliver on a pump.)
Critical
information:
- How
many ml is needed to provide 10 mEq?
- Flow
rate = 10 mEq
- Drip
factor = 60 gtt/ml
Tip:
Tip:
- You
could have canceled out the 60s.
|
50
ml
60
min
|
x |
60
gtt
1 ml |
|
x
|
=
|
50 |
- This
technique can be used to calculate drip rate of many continuos infusions
of IV meds.
|
| |
(Baxter IV Pump)
|
Calculating
flow rate:
- Flow
rate refers to number of ml of fluid to be infused over one hour (ml/hr).
Formula:
| total
# of milliliters (volume)
total
# of hours
|
= |
X
ml/hr |
Example:
Order:
500 ml NS bolus over 3 hours
Critical
information:
- Volume
= 500 ml
- Time
= 3 hours
500
ml
3 hrs |
= |
?
|
or |
500
ml
3 hrs
|
= |
x
ml 1 hr |
| 500
/ 3 |
= |
166.67 |
3x |
= |
500 |
| Answer:
166.67 ml/hr or 167 (if your instructor wants you to "round"). |
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Calculating
time if given the flow rate:
- The
nurse needs to know how long a volume of fluid in the IV bag at the
current flow rate will last, i.e.., When will a new bag need to be
hung?
Formula:
|
Volume
Flow
rate
|
= |
(Infusion)
time |
Example:
The
nurse makes rounds and notes that the current IV bag contains approximately
450 ml. The IV flow rate is 150 ml/hr. How long will it be before
the nurse must hang a new bag?
Critical
information:
- Volume
= 450 ml
- Flow
rate = 150 ml/hr
450
ml
150 ml/hr
|
= |
. |
| 450
/ 150 |
= |
3
hr |
Calculating
time if given the drip rate:
Sometimes
exam problems provide you with the volume to be given and the drip rate
of the IV and you must calculate how long (time) it will take to infuse.
Critical
information for calculation:
- Must
be given volume to be infused
- Must
be given drip rate (gtt/min)
- Must
know drip factor (gtt/ml)
- Time
is constant (1 hr = 60 minutes)
Formula:
|
drip
rate
|
|
volume
|
|
drip
factor
|
|
time
constant
|
|
time
|
1 min
x gtt
|
x
|
(ml)
|
x
|
x
gtt
1 ml
|
x
|
1
hr
60 min
|
=
|
x
hr
|
Example:
Order:
Administer 1000 cc at 50 gtt/min.
Critical
information:
- Volume
= 1000 ml
- Drip
rate = 50 gtt/min
- Known
= time constant (1 hr = 60 min)
- Missing
= drip factor of tubing (You would use what is available or standard
protocol for the unit you are working in. Assume 15 gtt/ml unless
otherwise indicated.)
1
min
50gtt/min
|
x
|
1000
ml
|
x
|
15
gtt
1 ml
|
x
|
1
hr
60 min
|
=
|
x
hr
|
1
x 1000 x 15 x 1
50 x 1 x 60
|
= |
15000
3000
|
=
|
TIP:
- You
can use the principle of reducing to minimize the number you will
have to deal with.
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Administering
fluids/medications via an infusion pump
- How
do I use the pump to deliver the right dose?
- Each
brand of infusion pump has specific tubing, filling volumes, filters
and other accessories.
A problem
indicates that a medication or fluid is to be given via an infusion pump.
Even though the problem may state the tubing that is specific to the particular
pump has a "drip factor of 15 gtts/ml or 20 gtts/ml", it will still be
delivered the equivalent to 60 gtts/ml if it is placed on the pump.
Remember when the physician orders x ml/hr or you calculate
x ml per hour, that is essentially what you dial into the
IV pump.
Example:
John
is to receive Cleocin 150 mg IV q 8 hours. The nurse dilutes the
medication to a total volume of 30 ml and plans to deliver it via an
infusion pump over thirty minutes. What would be the flow rate?
Critical
information:
- Volume
= 30 ml
- Use
of an infusion pump (equivalent of drip factor of tubing) = 60 gtts/ml
- Time
= 30 minutes
Extraneous
information for calculation:
- Cleocin
150 mg IV q 8 hours.
Calculate:
|
30
(cc)
|
x
|
60
(gtt / ml)
30 ( min)
|
|
30
|
x
|
2
|
| flow
rate |
=
|
60
|
|
Numbers
to be dialed into the pump = 60
|
Hint:
Use the principle of reducing fractions to reduce 60/30 to 2.
Note
this is 30 multiplied by 2, not 30x which then is set up as the divisor.
Example:
The
doctor writes an order for D5 NS to run at 90 cc/hr.
The packaging for the IV tubing indicates that the drip factor of the
tubing is 15 gtt/cc. Hospital policy states that all fluids are
placed on a pump. How will the nurse set the infusion pump?
Critical
information:
- Doctor's
order of 90 ml/hr
- Use
of an infusion pump.
Extraneous
information for calculation:
- Drip
factor of the tubing.
|
Answer:
Set the pump for 90.
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10/2003
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