To calculate drops per minute (DPM) for an IV infusion, use the following formula:
Drops per minute=Volume (mL)×Drop factor (drops/mL)Time (minutes)\text{Drops per minute}=\frac{\text{Volume (mL)}\times \text{Drop factor (drops/mL)}}{\text{Time (minutes)}}Drops per minute=Time (minutes)Volume (mL)×Drop factor (drops/mL)
Explanation:
- Volume is the total amount of fluid to be infused, measured in milliliters (mL).
- Drop factor is the number of drops per milliliter, which depends on the IV tubing used and is usually printed on the IV set package (common values are 10, 15, 20, or 60 drops/mL).
- Time is the duration over which the volume is to be infused, measured in minutes.
Example:
If you have 500 mL of fluid to be infused over 60 minutes with a drop factor of 15 drops/mL, the drops per minute are calculated as:
500×1560=125 drops per minute\frac{500\times 15}{60}=125\text{ drops per minute}60500×15=125 drops per minute
Alternative formula if infusion rate is given in mL per hour:
Drops per minute=Infusion rate (mL/hr)×Drop factor60\text{Drops per minute}=\frac{\text{Infusion rate (mL/hr)}\times \text{Drop factor}}{60}Drops per minute=60Infusion rate (mL/hr)×Drop factor
For example, if the infusion rate is 100 mL/hr and the drop factor is 10 drops/mL:
100×1060=16.6 drops per minute\frac{100\times 10}{60}=16.6\text{ drops per minute}60100×10=16.6 drops per minute
Notes:
- Macrodrip tubing typically has a drop factor of 10-20 drops/mL and is used for larger volumes.
- Microdrip tubing has a drop factor of 60 drops/mL and is used for precise, smaller volumes, such as in pediatrics.
- Adjust the flow rate by counting drops per minute and using the roller clamp to regulate the drip rate accordingly
This method allows accurate manual control of IV fluid administration when electronic pumps are not available.
