IV Flow Rates

Intravenous fluid must be given at a specific rate, neither too fast nor too slow. The specific rate may be measured as ml/hour, L/hour or drops/min. To control or adjust the flow rate only drops per minute are used.

The burette contains a needle or plastic dropper which dispenses a fixed  number of drops per ml (the drop factor). A number of different drop factors are available (determined by the length and diameter of the needle).

Common drop factors are:
10 drops/ml (blood set), 15 drops / ml (regular set), 60 drops / ml (microdrop).

Determining the number of drops / minute needed to complete an infusion:

To determine the flow rate in drops / minute we need to know:

  1. The drop factor of the given set (drops / ml)
  2. The volume to be infused (ml)
  3. The time prescribed (minutes)

The formula for working out flow rates is:

 volume (ml) x drop factor (drops/ml)   = drops /  minute

time (min)

Example
1500 ml IV Saline is ordered over 12 hours. Using a drop factor of 15 drops/ml  how many drops per minute need to be delivered?

 1500 (ml) x 15 (drops/ml)  = 31 drops /  minute

12 x 60 time (min)

Determining the time needed to complete an infusion:

With just a minor variation to the formula given above we can work out when an infusion is due to finish if provided with:

  1. The drop factor of the given set (drops / ml)
  2. The volume to be infused (ml)
  3. The rate of the infusion (drops / minute)

The formula is:

 Volume (ml) x drop factor (drops/ml)

 = time to completion (minutes)

Rate (drops / minute)

Example

600 mls of saline remains in a bag which is being infused at a rate of 15 drops per minute via a giving set with a drop factor of 10 drops / ml. How long will the infusion take to complete at that rate?

Place the values in the formula:

 600 (ml) x 10 (drops/ml)

 = 400 minutes

15 (drops / minute)

= 6 hours and 40 minute

Other Calculations
Metric Conversions Body Mass Index Tablet Dosages Fluid Dosages IV Flow Rates Dosage by Weight