IV FLOW RATESIV FLOW RATES

INTRODUCTIONINTRODUCTION• 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 THERAPYDURATION 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 PROBLEMEXAMPLE PROBLEMDURATION OF THERAPYDURATION 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 PROBLEMANOTHER EXAMPLE PROBLEMDURATION OF THERAPYDURATION 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 RATEFLOW RATEWhen 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 #1EXAMPLE PROBLEM #1FLOW RATEFLOW 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…….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 #2EXAMPLE PROBLEM #2FLOW RATEFLOW 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…….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 #3EXAMPLE PROBLEM #3FLOW RATEFLOW 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 #4EXAMPLE PROBLEM #4FLOW RATEFLOW RATE

DROP SETSDROP 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.

14

DROP SETSDROP 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 SETSDROP 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 RATESINFUSION RATESThe 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 #1EXAMPLE PROBLEM #1INFUSION RATEINFUSION 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 #2EXAMPLE PROBLEM #2INFUSION RATEINFUSION 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