4 Intravenous infusion

This chapter deals with the arithmetic of flow rates and drip rates for intravenous (IV) infusion.

The fluid being infused passes from a flask (or similar container) into a giving set (administration set), which has a drip chamber. The giving set may be free-hanging or attached to a volumetric infusion pump.

If the giving set is free-hanging, the nurse needs to calculate the drops per minute to be infused. The nurse can then manipulate the roller clamp on the giving set to ensure the drip rate is correct.

By contrast, if the giving set is connected to an infusion pump, then the nurse only needs to calculate the number of millilitres per hour to be infused and set the pump accordingly.

Note: There may be a burette between the flask and the giving set. The use of a burette will depend on institution policy and the type of infusion.

Skills covered in this chapter include:

• calculating the volume of fluid delivered to a patient over a given time

• infusion pump settings

• rates of flow in mL/hr

• rates of flow in drops/min.

24-hour time will be used in some exercises.

There are two main types of giving sets in general use – these break down fluid into a drop factor of either 20 or 60 drops per mL. A drip chamber that delivers 60 drops per mL (or has a drop factor of 60 drops/mL) is also known as a microdrip. Another giving set with a drop factor of 15 drops/mL is used occasionally.

Important: If in any doubt about the answer to a calculation, then ask a supervisor to check your working.

Refer to Inside front cover page for explanations of abbreviations.

Calculating time for an infusion

Example 2

A teenager is to receive 750 mL of Hartmann’s solution. An infusion pump is set at 60 mL/hr. How long will it take to give the solution?

Exercise 4A

1 An intravenous line has been inserted in a patient. Fluid is being delivered at a rate of 42 mL/hr. How much fluid will the patient receive in a 2 hr b 8 hr c 12 hr?

2 A male patient is receiving Hartmann’s solution at a rate of 125 mL/hr. How much solution will he receive over a 3 hr b 5 hr c 2 hr?

3 A girl is to be given dextrose 5% via an infusion pump. If the pump is set at 60 mL/hr, how much dextrose 5% will she receive in a

c 12 hr?

4 A female patient is to receive 500 mL of normal saline. The drip rate is adjusted to deliver 25 mL/hr. How long will the fluid last?

5 A young man is to be given one litre of dextrose 4% in

normal saline. The infusion pump is set at a rate of 80 mL/hr. What time will it take to give the litre of solution?

6 Half a litre of normal saline with 2 g potassium chloride is to be given to a patient IV. How long will this take if the infusion pump is set at 75 mL/hr?

7 A patient is to receive 100 mL of normal saline IV. If the infusion pump is set to deliver 150 mL/hr, how long will the infusion take?

Check your answers on page 150.

Calculating rates of flow in millilitres per hour (mL/hr) given the time in hours

In order to do this type of calculation you will need to remember this formula:

Note: The volume must be in millilitres (mL).

Example

A patient is to receive half a litre of fluid IV over 6 hours using an infusion pump. At how many millilitres per hour should the pump be set? The pump does not have a decimal setting so calculate the answer to the nearest whole number.

Exercise 4B

Calculate the required flow rate of a volumetric infusion pump for each of the following infusions. Give answers in mL/hr to the nearest whole number.

1 One litre of normal saline is to be administered over 8 hours.

2 A patient is to receive 500 mL of dextrose 5% over 12 hours.

3 500 mL of Hartmann’s solution is to be given to a teenager over 7 hours.

4 Over the next 15 hours, a female patient is to receive 2 L of dextrose 4% in

normal saline.

5 A teenager is to receive one litre of normal saline over 6 hours.

6 A woman is to be given 500 mL of dextrose 5% over 8 hours.

7 Over a period of 16 hours, a patient is to receive one litre of dextrose 4% in

normal saline.

8 A patient is to be given one litre of normal saline over 24 hours.

9 Over the next 9 hours, a patient is to receive half a litre of dextrose 4% in

normal saline. At what flow rate should the volumetric infusion pump be set?

10 One litre of Hartmann’s solution is to be given over 12 hours. Calculate the required flow rate for the volumetric infusion pump.

Check your answers on page 150.

Calculating rates of flow in millilitres per hour (mL/hr) given the time in minutes

Example

75 mL of fluid in a burette needs to be infused over 20 minutes. Calculate the flow rate required in mL/hr.

Exercise 4C

Each of the following medications has been added to a burette. Calculate the required pump setting in mL/hr for the given infusion time. Give answers to the nearest whole number.

	Medication	Infusion time
1	40 mL of fluid containing 600 mg of penicillin	20 minutes
2	120 mL of fluid containing 500 mg of vancomycin	50 minutes
3	100 mL of fluid containing 1 g of flucloxacillin	30 minutes
4	50 mL of fluid containing 0.5 g of potassium chloride	half an hour
5	60 mL of fluid containing 75 mg of ranitidine	35 minutes
6	80 mL of fluid containing 80 mg of gentamicin	45 minutes
7	75 mL of fluid containing 75 mg of gentamicin	40 minutes
8	70 mL of fluid containing 1.2 g of penicillin	25 minutes
9	80 mL of fluid containing 750 mg of flucloxacillin	half an hour
10	100 mL of fluid containing metronidazole 500 mg	half an hour