Calculating an IV rate depends on whether you need the rate in mL/hr or gtts/min (drops per minute). Both calculations require knowing the total volume of fluid, the infusion time, and, for gtts/min, the drop factor of the IV tubing.
Calculating IV Rate in mL/hr (Milliliters per Hour)
This calculation is straightforward and doesn't require the drop factor.
Formula:
(Total volume in mL) / (Total time in hours) = IV rate in mL/hr
Example:
- You need to administer 1000 mL of saline over 8 hours.
- 1000 mL / 8 hours = 125 mL/hr
The IV rate should be set to 125 mL/hr.
Calculating IV Rate in gtts/min (Drops per Minute)
This method accounts for the variability in the size of the drops delivered by different IV tubing. The drop factor is printed on the IV tubing packaging.
Formula:
(Total volume in mL) / (Total time in minutes) * (Drop factor in gtts/mL) = IV rate in gtts/min
Example:
- Administer 500 mL of D5W over 4 hours (240 minutes).
- The IV tubing has a drop factor of 15 gtts/mL.
- (500 mL / 240 min) * 15 gtts/mL ≈ 31 gtts/min
The IV rate should be adjusted to approximately 31 drops per minute. Note that in practice, you might round the final number to a whole number.
Important Considerations:
- Always double-check your calculations.
- Use the correct units (mL, hours, minutes, gtts/mL).
- Always follow your institution's guidelines and protocols for IV administration.
Many online calculators are available to assist with IV rate calculations, such as the one provided by MDCalc (https://www.mdcalc.com/calc/10290/iv-drip-rate-calculator). These calculators can reduce the risk of errors. However, always independently verify the calculation to ensure accuracy.
