Common Conversions & Abbreviations
Common Conversions
- 1 kg = 1000 g = 2.2 lbs
- 1 lb = 454 g
- 1 L = 1000 mL = 1000 cc
- 1 g = 1000 mg
- 1mg = 1000 mcg
- 1 hr = 60 min
Common Abbreviations
| Drop / Drops gtt / gtts | Unit / Unit no abbreviation | Intravenous IV |
| Liter L | Solution sol, soln | Intravenous Push IVP |
| Mililiter mL | Amount amt | Intravenous Piggyback IVPB |
| Gram g | Dilute dil | Intramuscular IM |
| Microgram mcg | Mix M | Injection inj |
| Kilogram kg | Liquid liq | Hypodermic hypo |
| Pound lb | Quantity Qty | Infusion inf |
| Cubic Centimeter cc | Weight wt | Hour h, hr |
| Miliequivalent mEq | Volume vol | Minute min |
| Ounce oz | Temperature temp | With / Without c / s |
IV Calculation & Definitions
Drop/Gtt
Noted as a common abbreviation in infusion documentation, a drop (gtt) is a unit of measure used for continous medication administration. I can help clinicians ensure that patients are receiving the correct amount of medication at an appropriate rate.
IV Drop factor
The IV drop factor refers to the number of drops in 1 mL of a solution. This is a predetermined that can be found on the IV tubing packages (i.e. microdrip and macrodrip tubing). Microdrip and macrodrip refer to the diameter of the needle where the drop enters the drip chamber, and both have specific purposes.
Microdrip Tubing
Microdrip tubing is used to produce small drip sizes. Typically used with potent medications or for populations with a narrow tolerance range (e.g. pediatric patients), microdrip tubing helps clinicians administer the appropriate amount of a medication without causing bloating or discomfort for the patient. The drip factor for a microdrip is typically estimated at 60 ggt/mL.
Macrodrip Tubing
Macrodrip is the more standard kind of IV tubing. It produces bigger drops to infuse large amounts of fluid or infuse medications quicker. When using macrodrip tubing, it is important to monitor the patient for dehydration as the drop rate and fluid intake may be too low. This kind of tubing is typically available at 10, 15, or 20 ggt/mL.
Infusion Rate
The infusion rate is the volume of liquid that will be infused over a certain amount of time. To calculate this, you will need to know the total volume that you will be infusing and the total time that the infusion will take place. Depending on the units of measurement provided, you may need to convert your calculation to mililiters per hour.
Infusion Rate Formula:
Infusion Rate = volume to infuse in mL / time of the infusion in hrs.
Example: You have 50 mL of a solution to infuse over 30 minutes
Infusion Rate = (50 mL / 30 min) * (60 min/hr)
Infusion Rate = 100 mL/hr
IV Drip Rate
The IV drip rate is the measurement of the drops that fall into the drip chamber in a minute. It can be used to calculate the volume of liquid or medication a patient will receive in a certain amount of time.
The drip of rate is determined using the drop factor of tubing, the total volume needing to be infused, and the total time for the infusion. It is important to remember to round to the nearest whole number at the end of your calculations, as you cannot administer part of a drop.
IV Drip Rate Formula
Drip Rate = (volume to infuse in mL / time of infusion in min) x drop factor
Example: you have 100 mL of a solution to infuse over 90 minutes. The predetermined drop factor of the macrodrip tubing you are using is 15 ggt/mL.
Drip Rate = (100 mL / 90 min) x 15 ggt/mL
Drip Rate = 1500 ggt / 90 min
Drip Rate = 16.66 ggt/min = 17 ggt/min
There is also a simplified formula for calculating the IV drip rate that requires the infusion rate and simple division depending on the drop rate. For this method, you divide the infusion rate (mL/hr) by a predetermined number associated with the drop factor of the tubing.
Example: Using the same example from above, you have 100 mL of a solution to infuse over 90 minutes. The predetermined drop factor of the macrodrip tubing you are using is 15 ggt/mL.
Drip Rate = ((100 mL / 90 min) x (60 min/hr) / 4
Drip Rate = (100 x 60) / (90 x 4)
Drip Rate = 16.66 = 17 ggt/min
Infusion Conversions
As mention above, there are a few common conversions involved in infusion therapy that clinicians may find beneficial to memorize, but there may be instances when a conversion needs to be manually calculated. To this, determine the unit that is currently being measured, the drug concentration, and the desired unit. For example:
To find mcg/min when the infusion rate (mL/hr) and the drug concentration (mg/mL):
mcg/min = (mg/mL) x (1000 mcg / 1 mg) x (mL/hr) x (1 hr / 60 min)
Example: A patient is being infused with 50 mg / 500 mL NaCl solutions at a rate of 8 mL/hr. What dose (mcg/min) is the patient receiving?
mcg/min = (50 mg / 500 mL) x (1000 mcg / 1 mg) x (8 mL/hr) x (1 hr / 60 min)
mcg/min = 400000 mcg / 30000 min = 13.3 mcg/min
Example: A patient is being infused with 800 mg / 250 mL D5W solution at a rate of 16 mL/hr. The patient weights 188 lbs. Calculate the weight-based rate.
mcg/kg/min = ((800 mg / 250 mL) x (1000 mcg/mg) x (16 mL/hr) x (1 hr / 60 min) / (188 lbs x (454 g/lb) x (kg /1000 g))
mcg/kg/min = (128000000 mcg / 15000 min) / (85352 / 1000 kg)
mcg/kg/min = 9.99 mcg/kg/min = 10 mcg/kg/min
Universal Formula
The universal formula, or the desired over have method, is a comprehensive formula that uses the following components to calculate the dose: the medication dosage prescribed (the desired amount: D), the dose on the medication container (the amount on hand: H), and the form and amount of the medication supplied (the volume: V).
Formula:
Dose = (desired amount / amount on hand) x volume OR dose = (D/H)V
Example: You need to administer 75 mg of a medication. The drug concentration available from the pharmacy is 15 mg/mL. How many mL will you need to administer a 75 mg dose?
Dose = (75 mg / 15 mg) x 1 mL.
Dose = 5 mL
Dimensional Analysis (DA), or the Factor Label Method
Lastly, the dimensional analysis method, or factor label method, uses the conversion factors between systems of measurement that we've been using, but does not require memorizing specific formulas. Because of its formula flexibility, this method can be used for all dosage calculations.
There are four steps to using dimensional analysis:
- Determine the unit of measure needed and place this label in the left side of the equation.
- Place the information with the same unit of measure as the preceding denominator in the numerator on the right side of the equation (canceling out unwanted labels).
- Repeat step two until all unwanted labels have been eliminated.
- Solve to determine the correctly labeled answer. Do not round until you have the final answer.
Example: A patient is being infused with 30 mg/250 mL NaCl solution at a rate of 8 mL/hr. What does (mcg/min) is the patient receiving?
mcg/min =
mcg/min = (30 mg / 250 mL) x (1000 mcg/mg)
mcg/min = (30 mg / 250 mL) x (1000 mcg/mg) x (8 mL/hr)
mcg/min = (30 mg / 250 mL) x (1000 mcg/mg) x (8 mL/hr) x ( 1 hr / 60 min)
mcg/min = 16 mcg/min
OR
mcg/min =
mcg/min = (30 mg / 250 mL) x (1000 mcg/mg)
mcg/min = 120 mcg/mL
mcg/min = (120 mcg/mL) x (8 mL/hr) = 960 mcg/hr
mcg/min = (960 mcg/hr) x (1 hr / 60 min)
mcg/min = 16 mcg/min
The importance of Appropriate Calculations
While there are many more abbreviations and IV calculations needed in the field of infusion, some being medication-specific, these are a few of the most commonly used formulas by clinicians.
According to a study conducted by the National Center for Biotechnology Information, miscalculations are one of the leading contributors to medication errors in intravenous and subcutaneous medications administration for in-hospital treatment.
Need quick and reliable infusion calculations?
Infusion Calculator is a powerful app designed for healthcare professionals to perform fluid-related calculations with easy and accuracy.
Key features:
- Calculating infusion rate based on weight, total drug amount, volume, and dose
- Determining total drug in fluid using patient weight, dose, volume, and rate
- Estimating infusion time based on volume and rate
- Calculating infusion rate from volume and time
Easily switch between units in the app settings to match your clinical needs.
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Disclaimer: this article should not be taken as official infusion calculation training. Individuals looking to enter the field of infusion or those searching for official training should consult educational resources established by a certified clinic board.
References:
https://handbook.bcehs.ca/drug-monographs/medication-infusions/infusion-drip-rate-formula/
https://www.kmedhealth.com/critical-factors-affecting-flow-rate-of-intravenous-therapy/
https://www.mometrix.com/academy/calculations-of-drip-rates/?nab=1