IV Flow Rates and Duration
IV Solutions may be administered using a gravity flow administration set. Each tubing will be packaged with a drop factor printed on the package, that tells how many drops (gtt) are in each mL. Click on each picture to enlarge it. When finished, click on "Back" to return to page.
Dimensional analysis can be used to calculate flow rate; when finding flow rate in drops per minute, the starting factor is Gtt per mL, which will be printed on the tubing box.
Order: 1 L Normal Saline at 75 mL/ hour
Tubing label: 15 gtt/ mL
|Gtt =||15 gtt||75 mL||1 hour||= ? gtt|
|Min||1 mL||1 hour||60 min||1 min|
Gtt = 15 gtt X 75 X 1 = 1125 = 18.75 gtt/min = 19 gtt/min Min 1 1 60 min 60
There are also electronic infusion pumps to regulate IV flow rate. The tubing has a cassette that fits into the pump which is set to deliver the IV in mL per hour. The following picture is a PLUM infuser. Click on the picture to enlarge it; to return to page, click on the "Back" icon.
Dimensional analysis can be used to calculate the flow rate in mL per hour as follows:
Order: 1 L D5W to run over 8 hours using an infusion pump.
mL = 1000 mL = mL/ hr = 125 mL/hr hour 8 hours
Sometimes the IV order, especially for a small volume medication will include the time to administer the medication in minutes. In this case, the starting factor is still mL per hour, since that is what the infusion pump delivers.
Order: Give 1 g Kefzol over 20 minutes
Supply: 1 g Kefzol in 50 mL D5W
mL = 50 mL 1 g 60 min = ? mL hour 1 g 20 min 1 hour 1 hour
mL = 50 mL X 1 X 60 = 150 mL/ hr hour 1 20 1 hour
It is often useful for the nurse to know when the current IV bag will finish, to anticipate getting the next bag ready.
For example: There is 400 mL left in the IV bag at 0900 hrs. It is infusing at 20 gtt/min. The drop factor is 10 gtt/mL. At what time will the next bag be needed?
Hours = 1 hour 1 min 10 gtt 400 mL = ? hours 60 min 20 gtt 1 mL
Hours = 1 hour X 1 X 10 X 400 = 3.33 hours 60 20 1
Multiply the decimal hours (0.33) by 60 to get that back into minutes:
0.33 * 60 = 19.8 = 20 minutes
Thus, the infusion time is 3 hours and 20 minutes. Since it was 0900 hours at the beginning, adding 3 hours and 20 min will make the ending time 1220 hrs.
Flow rate calculations follow in Quiz 5
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