Infusion by gravity drip…

This week, I posted on Twitter an article I saw in the American Nurse Today about “Calculating IV drip rates with confidence”. For an infusion nurse, calculations of drip rates and drug concentration is a given with the nature of my job. I didn’t realize that some nurses don’t calculate rates or don’t even know how. Often, the calculation is left up to the pharmacists and/or the nurses rely solely on the infusion pumps. With the emphasis on patient safety, and as the article stated, I strongly believe, we as  licensed professionals should double check by calculating the rates.

While it is strongly  recommended to use an electronic infusion pump, infusion by gravity drip can be carried out safely depending on the medication/solution to be infused, the age and acuity of the patient, and the healthcare setting. If you are faced with a situation where you need to infuse by gravity drip, remember the following steps:

  • Identify the drop factor of the IV administration set (tubing) you are using. You can find this information on the label of the tubing package.  Macrodrip sets are either 10, 15 or 20 drops to deliver 1 ml of fluid.
  • Use this formula to calculate gravity flow rates:
    • Drops/min:        ml/hr divided by 60 min/hr x drop factor

  • Examples:

A. IV fluid of 1000ml to infuse for 8 hours using tubing with drop factor of 15.

  • 1000ml for 8 hours = 125ml/hr.
  • 125ml/hr divided by 60 min/hr = 2.08ml/min
  • 2.08ml/min X 15 drop factor = 31.2 drops/min

B. IV fluid of 1000ml to infuse for 8 hours using tubing with drop factor of 10.

  • 1000ml for 8 hours = 125ml/hr.
  • 125ml/hr divided by 60 min/hr = 2.08ml/min
  • 2.08ml/min X 10 drop factor = 20.8 drops/min

C. IV fluid of 1000ml to infuse for 8 hours using tubing with drop factor of 20.

  • 1000ml for 8 hours = 125ml/hr.
  • 125ml/hr divided by 60 min/hr = 2.08ml/min
  • 2.08ml/min X 20 drop factor = 41.6 drops/min

Regardless of what flow control device is used, remember that the flow control devices should be considered an enhancement to patient care and doesn’t replace the nurse’s responsibility to monitor the infusion of the prescribed therapy.

Oh, by the way, in case you have forgotten, when infusing by gravity, you do need to count the drops/minute – for a full minute and adjust the flow using the roller clamp till you have regulated to the desired rate.  :)

If you are enticed to use  “flow regulators” (like dial-a-flow), remember, those are still gravity drip infusion and you will need to count the drip rate even if you set the dial to the correct number to ensure accuracy.

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