Calculating parenteral doses: large volume

CHAPTER 6 Calculating parenteral doses


large volume





Intravenous infusions









Gravity-assisted infusion


An infusion may be set up which simply allows the fluid to travel from the bag through the administration set to the cannula or by central venous access under the influence of gravity. With this type of infusion, the rate of fluid can be controlled in three ways. These are the:





To calculate how to set the infusion at the prescribed rate, you need to know the amount to be infused and the length of time the infusion is to take. The next step is to work out how much will be infused in 1 hour. This is done by dividing the total volume by the time the infusion is to take:



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For example, 500 mL of a clear fluid is to be transfused over 4 hours:



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The prescribed rate is 125 mL/h.


In order that the infusion can be regulated, however, the nurse needs to know how many drops per minute at which to set the infusion. In this instance, a clear solution is in use and therefore the appropriate administration set would be one set at 20 drops/mL.


To calculate the rate of flow in drops per minute, which the nurse will be able to count using a watch:


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The infusion can be controlled at 42 drops per minute.


Some prescription sheets provide a ready reckoner to assist the nurse in calculating the rate of flow and should be used where provided.


Since other variables come into play, such as the positioning of the patient which may increase the flow rate, this method is not wholly reliable, and so to limit the risks associated with the infusion of large volumes of fluid, the maximum size of bag used is often limited to 500 mL.



Jun 18, 2016 | Posted by in MIDWIFERY | Comments Off on Calculating parenteral doses: large volume

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