IV FLOW RATES

INTRODUCTION The pharmacy staff is responsible for calculating the flow rate of a medication to be administered intravenously. This rate is expressed in terms of how many milliliters per hour or drops per minute a patient should receive. It can also be expressed in terms of how much IV fluid should be prepared per shift or per day. Often referred to as the infusion rate or rate of infusion.

Volume of fluid or amount of drug to be infused DURATION OF THERAPY The duration of therapy may be calculated using the following formula: Duration of therapy = Volume of fluid or amount of drug to be infused Flow rate *Flow rate = ml/hr *When calculating the duration of therapy, always round your answer down to the whole hour.

EXAMPLE PROBLEM DURATION OF THERAPY A 1 L IV is running at 125 mL/hour. How often will you send up a new bag? X hours = 1000 mL 125 mL/hour = 8 hours

ANOTHER EXAMPLE PROBLEM DURATION OF THERAPY If an IV is running at 150 mL/hour and three 1 L bags are sent to the floor, how long will these bags last? X hours = the time the 3 bags will last X hours = 3000 mL 150 mL/hour = 20 hours

Volume of fluid or amount of drug to be infused FLOW RATE When an order specifies a volume or amount of drug to be given over a specific period of time, the flow rate (mL/hr) can be calculated using the following formula: Flow rate = Volume of fluid or amount of drug to be infused Duration of therapy

EXAMPLE PROBLEM #1 FLOW RATE The following order is sent to the IV room: Medication: Solu-Cortef 300 mg Fluid volume: 300 mL Time of infusion: 4 hours What volume of fluid is given per hour, and what amount of drug is given per hour?

TO SOLVE PROBLEM……. FIRST: Determine the volume of fluid given per hour. 300 mL / 4 hours = 75 mL/hour SECOND: Calculate the amount of drug given per hour. 300 mg / 4 hours = 75 mg/hour

EXAMPLE PROBLEM #2 FLOW RATE The following order is sent to the IV room. Medication: Cefazolin 500 mg Fluid volume: 50 mL Time of infusion: ½ hour What volume of fluid is given per hour, and what amount of drug is given per hour?

TO SOLVE PROBLEM……. FIRST: Determine the volume of fluid given per hour. 50 mL / 0.5 hours = 100 mL/hour SECOND: Calculate the amount of drug given per hour. 500 mg / 0.5 hours = 1000 mg/hour

EXAMPLE PROBLEM #3 FLOW RATE A 500ml IV bag is administered over 4 hours. What is the flow rate? TO SOLVE: mL/hr = 500mL/4hr X = 500/4 = 125 X = 125mL/hr

EXAMPLE PROBLEM #4 FLOW RATE Run KCL 10MEQ in D5W 1000 ml at 80 mL/hour. How many mL/min would this run? FIRST: determine what is pertinent information to solve the problem TO SOLVE: mL/1 min = 80 mL/60 min X = 80/60 X = 1.33 mL/min

DROP SETS Pharmacy staff and the nursing staff are responsible for calculating the rate of administration for IV fluids in a drops per minute rate (expressed gtt/min). The abbreviation gtt comes from the Latin word guttae, which means “drops.” An IV set is identified by the number of drops it takes to make 1 mL. This calibration is referred to as a drop set or drip set.

DROP SETS IV sets are designed to administer medication at different rates. The most common sets are: 10, or 10 gtt/mL 15, or 15 gtt/mL 20, or 20 gtt/mL 60, or 60 gtt/mL (AKA mini drip set)

DROP SETS The drop sizes for the 10,15, and 20 calibrations produce macrodrops. The 60 calibration produces microdrops. The 60 gtt/mL is called a mini-drip set.

Pharmacy Calculations, Fourth Edition INFUSION RATES The infusion rate, measured in drops per minute, is calculated as follows : x gtt/min = Flow Rate x Drop size 60min/1hr Flow Rate = ml/hr Drop size = gtt/ml (Round down to a whole drop when a drop per minute calculation results in a partial drop) Equation appears on page 189 © Paradigm Publishing, Inc.

EXAMPLE PROBLEM #1 INFUSION RATE Pharmacy Calculations, Fourth Edition EXAMPLE PROBLEM #1 INFUSION RATE If an IV is running at 60 mL/hr, what is the rate in drops per minute using a 15 drop set? x gtt/min = (60 mL/1 hour) x (15 gtt/mL) 60 min/hour = 15 gtt/min Example 7.3.1, pages 189 and 190 © Paradigm Publishing, Inc.

EXAMPLE PROBLEM #2 INFUSION RATE You have D5W infusing at 80ml/hr. What is the infusion rate in gtt/min if there are 30gtts/ml? x gtt/min = (80 mL/1 hour) x (30 gtt/mL) = 40 gtt/min 60 min/hour