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Intravenous (IV) infusions
Intravenous (IV) infusions
When a patient needs a steady supply of fluids or medications, we use an infusion pump. Most pumps are programmed in milliliters per hour... or ml/hr. There are pumps that use syringes or cassettes, but most use bags of fluids/medications and tubing. For the first section of this lesson, we will go over programming and timing of infusions.
Orders are given to infuse a set amount over a defined time period- 500 ml normal saline in 2 hours. Or given as a rate per hour- lactated ringers 125 ml/hr.
It is important to know how to set the pump rate and when to expect that a new bag will need to be hung.
These calculations will help you in mastering this
The physician orders a rate, but how long will the bag last?
The physician orders a rate, but how long will the bag last?
In this case, we know the rate to set the pump to. We will also know the volume of the bag once it is supplied by pharmacy. With these two numbers, we can know how long the bag will last.
Volume/Rate = Time of Infusion (use hours as the unit, if needed convert from minutes to hours before using this formula)
Example: Order is for normal saline (NS) at 125 ml/hr. Supplied is NS 1,000 ml bag.
Volume is 1,000 ml
Rate is 125 ml/hr
1,000/125 = 8 hours
Example: Order for Lactated Ringers (LR) at 75 ml/hr. Supplied is LR 1,000 ml bag.
Volume is 1,000 ml
Rate is 75 ml/hr
1,000/75 = 13.333 hours
Example: Heparin 5,000 units per hour is ordered. Supplied is 500 ml of heparin 100 units per ml.
Volume is 500 ml
Rate is... uh oh. We need to do a calculation first... our typical formula- 5,000 units/100 units x 1 ml = 50 ml/hr
500/50 = 10 hours
The physician orders a volume and a set time, what do we set the pump to?
The physician orders a volume and a set time, what do we set the pump to?
Volume/Time = Rate (use hours as the unit, if needed convert from minutes to hours before using this formula)
Example: Physician orders a NS bolus of 1,000 ml to be given over 2 hours. What is the pump set to?
Volume = 1,000 ml
Time = 2 hours
1,000/2 = 500 ml/hr
Example: Total Parenteral Nutrition is to run over 24 hours. The bag is 1,500 ml in volume. What do we set the pump to?
Volume = 1,500 ml
Time = 24 hours
1,500/24 = 62.5 ml/hr (note, round to nearest whole only if your hospital or school requires. Many, but not all pumps can be programmed to the tenths)
Example: Order for Acetaminophen 1 g IV over 15 minutes. Supplied is Acetaminophen 1 g in 100 ml IV solution.
Volume is 100 ml
Rate is... uh oh, we need to change to hours. 15 minutes/60 minutes = 0.25 hour
100/0.25 = 400 ml/hr
When will I need to hang a new bag?
When will I need to hang a new bag?
Using the formula of Volume/Rate = Time, we can plug the result into the 24 hour clock to be ready to hang a new bag so it doesn't run dry
Example: 1 l bag of NS hung at 0600 with a rate of 125 ml/hr. When will a new bag need to be hung?
Volume is 1 l or... 1,000 ml
Rate is 125 ml/hr
1,000/125 = 8 hours
0600 + 8 = 1400... or 2 pm (but we should get used to using 24 hour time- 1400 is the answer
Example: A new 1,000 ml bag of LR is hung at 2000 at a rate of 75 ml/hr. What time will a new bag need to be hung?
Volume is 1,000 ml
Rate is 75 ml/hr
1,000/75 = 13.3333 hours- in this case we can convert the .33 to minutes- 0.33 x 60 = 20 minutes, so 13 hours 20 minutes
2000 + 13 hours 20 minutes = 33 hours 20 minutes... now subtract 24 hours and move the remaining hours to the next day
33 hours 20 minutes - 24 hours = 9 hours and 20 minutes... or 0920 the next day
Example: A new bag of 5% dextrose in water (D5) is hung at 1800. The rate is set to 150 ml/hr and the bag has a volume of 1 l. When will the bag run dry?
Volume = 1 l... or 1,000 ml
Rate = 150 ml/hr
1,000/150 = 6.667 hours- again let's change the .667 to minutes- 0.667 x 60 = 40 minutes... so 6 hours 40 minutes
1800 + 6 hours 40 minutes = 24 hours 40 minutes... now subtract 24 hours and carry the remainder to the next day
24 hours 40 minutes - 24 hours = 40 minutes... or 0040 the next day
Drop Factors
Drop Factors
When the pump fails or you just don't have a pump, drop factors come to the rescue. IV tubing sets have a drip chamber and a carefully manufactured outlet that releases a set amount of volume per drop. By knowing the drop factor, or drops per ml, we can then count how many drops fall per minute and... like magic we have a flow rate that is measurable and adjustable, but not very accurate. Always use a pump for critical medications
Look at the tubing label for the drop factor
Look at the tubing label for the drop factor
Most tubing is 10, 15, 20. or 60 drops per ml (or gtt/ml). It takes that many visible drops into the drip chamber to equal 1 ml. If the tubing has a drop factor of 10 drops/ml, then it takes 10 drops to equal 1 ml.
To enable timing of the drops, we calculate it as drops/minute so we can count over a period of a minute or fraction of a minute and make adjustments as needed.
The formula is:
Volume / Time in minutes x Drop Factor = drops per minute (gtt/min)
Example: Order for NS at 125 ml/hr. No pump is available. The tubing has a drop factor of 20. how many drops per minute will the nurse set the tubing to?
Volume = 125 ml
Time is every hour... or 60 minutes
Drop factor = 20
125/60 x 20 = 41.6667 drops/min... round this to whole numbers because we can't count fractions of a drop. 42 drops/min or gtt/min
Example: Order for Vancomycin 1 g in 250 ml to be infused over 90 minutes. No pump is available. The tubing has a drop factor of 10 gtt/ml. What will the nurse set the infusion set to in drops per minute?
Volume = 250 ml
Time = 90 minutes
Drop Factor = 10
250/90 x 10 = 28 drops/min after rounding
There is a shortcut with drop factors
There is a shortcut with drop factors
Warning- this shortcut only works with drips going every 60 minutes.
Take your drop factor and divide by 60, then multiply that by the ml/hr rate.
Example: NS at 120 ml/hr. Drop factor is 20 gtt/ml. 20/60 x 120 = 40 gtt/min
Example: LR at 150 ml/hr. Drop factor is 60 gtt/ml. 60/60 x 150 = 150 gtt/min
You can use this to check your work, but again, it won't work on the problem above where we plugged 90 minutes into the equation.
Okay, time for some practice problems!
Order for D5 0.45 NS at 125 ml/hr. Available are 1,000 ml bags. How many bags will be needed every 24 hours?
3 bags IV
Volume = 1,000 ml
Rate = 125 ml/hr
1,000/125 = 8 hours... 24 divided by 8 = 3 bags needed in 24 hours
LR is ordered to be given as a 500 ml bolus over 1.5 hours to increase blood pressure. What will the nurse set the pump to?
333 ml/hr IV
Volume = 500 ml
Time = 1.5 hour
500/1.5 = 333.33 ml/hr... we can just round to whole number, but you could probably set the pump to 333.3 ml/hr
The night shift nurse hung a bag of 0.45% NS at 2100. The rate was set to 100 ml/hr. The bags are 1 l each. When will the next bag need to be hung?
0700 next day IV
Volume = 1 l or 1,000 ml
Rate = 100 ml/hr
1,000/100 = 10 hours
2100 + 10 = 31... 31 - 24 = 7 hours... or 0700 next day
The order is for Acetaminophen 1 g infused in 15 minutes. There is no pump. The bag supplied by pharmacy is acetaminophen 1 g in 100 ml. The tubing has a drop factor of 10. What will the nurse set the tubing drop rate to?
67 gtt/min IV
Volume = 100 ml
Time = 15 minutes
Drop Factor = 10
100/15 x 10 = 67 drops/min after rounding
Physician orders a bolus of 500 ml NS is 30 minutes. What will the nurse set the pump rate to?
1,000 ml/hr IV *not may pumps can be programmed to 1,000 ml/hr. 999 ml/hr is often the max limit. A wise experienced nurse might answer 999 ml/hr. Rates higher than 999 ml/hr will likely need two pumps or infused manually
Volume = 500 ml
Time = 30 minutes... or 0.5 hour
500/0.5 = 1,000 ml/hr
At 0630, the nurse hung a 1 l bag of LR at 40 ml/hr. Infusion bags can only be hung for 24 hours before being replaced per infection prevention guidelines. When will a new bag need to be hung?
0630 next day IV
Volume = 1 l or 1,000 ml
Rate = 40 ml/hr
1.000/40 = 25 hours
Since the bag can't hang for more than 24 hours, it must be changed at 0630 the next day even if it is not empty
The physician orders the NS to be reduced from 125 ml/hr to 60 ml/hr. There is 600 ml left in the bag at the time the rate is changed. In how many hours will a new bag need to be hung?
10 hours IV
Volume = 600 ml
Rate = 60 ml/hr
600/60 = 10 hours
Using the image above, what would the nurse set the gtt/min to for an infusion of LR at 120 ml/hr?
30 gtt/min IV
Volume = 120 ml
Time = 60 minutes
Drop Factor = 15
120/60 x 15 = 30 gtt/min
Using image above, what would the nurse set the gtt/min to? Order is for ceftriaxone 1 g IV. Supplied is ceftriaxone 1 g in 50 ml sterile water to be infused over 30 minutes.
33 gtt/min IV
Volume = 50 ml
Time = 30 minutes
Drop Factor = 20
50/30 x 20 = 33 gtt/min after rounding
Using image above, what would the nurse set the drip rate to? Order is for NS at 75 ml/hr.
75 gtt/min IV
Volume = 75 ml
Time = 60 minutes
Drop Factor = 60
75/60 x 60 = 75 gtt/min
Still going strong! Next is IV drips and pushes and how to time them correctly
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