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.
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 PROBLEMDURATION 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 PROBLEMDURATION 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
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 #1FLOW 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 #2FLOW 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 #3FLOW 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 #4FLOW 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.
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)
EXAMPLE PROBLEM #1INFUSION 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 PROBLEM #2INFUSION 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