Intravenous TherapyIntravenous TherapyIV Calculations (Math)IV Calculations (Math)

Sasha A. Rarang, RN, MSNSasha A. Rarang, RN, MSN

Basic Infusion Time FormulaBasic Infusion Time Formula

Infusion Time = Infusion Time = total volume to infusetotal volume to infuse ml/hr being infusedml/hr being infused

““How longHow long will it take for a particular amount of solution to be will it take for a particular amount of solution to be completed?”completed?”

Ex: Calculate the infusion time for an IV solution of 500 ml D5W that is Ex: Calculate the infusion time for an IV solution of 500 ml D5W that is currently infusing at 50 ml/hr?currently infusing at 50 ml/hr?

500 ml500 ml = 10 hrs = 10 hrs 50 ml/hr50 ml/hr

OR by ratio OR by ratio 50 ml50 ml = = 500 ml500 ml (cross multiply & solve for x) (cross multiply & solve for x)1 hr1 hr x x

50x = 50050x = 500 x = 10 hrsx = 10 hrs

Basic Infusion Time FormulaBasic Infusion Time Formula

Time can also be expressed in hours & minutesTime can also be expressed in hours & minutes Multiply the partial portion (after the decimal point) Multiply the partial portion (after the decimal point)

of the hour by 60 to obtain the time to the nearest of the hour by 60 to obtain the time to the nearest minuteminute

Ex: Ex: 500 ml500 ml = 6.66 hr = 6.66 hr

75 ml/hr75 ml/hr

.66 x 60 min = 39.6 minutes or 40 minutes.66 x 60 min = 39.6 minutes or 40 minutes

Therefore the TOTAL time is 6.66 hrs or 6 hrs & 40 minutesTherefore the TOTAL time is 6.66 hrs or 6 hrs & 40 minutes

Flow RatesFlow Rates

Refers to an amount of solution over a Refers to an amount of solution over a period of timeperiod of time

Can be expressed as gtt’s/min or ml’s/hrCan be expressed as gtt’s/min or ml’s/hr– For our purposes, whenever we discuss For our purposes, whenever we discuss

regulating an IV by the regulating an IV by the roller clamp or by roller clamp or by gravitygravity, we will use the flow rate of , we will use the flow rate of gtt’s/min.gtt’s/min.

– When trying to figure out the flow rate using an When trying to figure out the flow rate using an IV pumpIV pump or regulating the IV using a machine, or regulating the IV using a machine, we will use the flow rate of we will use the flow rate of cc’s/hrcc’s/hr

Flow RatesFlow Rates

Flow rate via gravity or by the roller clampFlow rate via gravity or by the roller clamp Refer to your handout “IV Calculation Refer to your handout “IV Calculation

Worksheet”Worksheet” Vital information needed: microdrip or Vital information needed: microdrip or

macrodrip; drop factormacrodrip; drop factor

IV Drug AmountsIV Drug Amounts ““How much medication is the patient receiving?” How much medication is the patient receiving?” ““What is the flow rate to insure proper delivery of the amount of medication ordered?”What is the flow rate to insure proper delivery of the amount of medication ordered?”

DD x Q x QHH

Ex: An IV of 1000 ml of D5W containing 40,000 U of Heparin is ordered to infuse at 30 ml/hr. Ex: An IV of 1000 ml of D5W containing 40,000 U of Heparin is ordered to infuse at 30 ml/hr. Calculate the dosage of Heparin the pt is receiving (How many units/hr of Heparin)Calculate the dosage of Heparin the pt is receiving (How many units/hr of Heparin)

30ml/hr30ml/hr x 40,000 u = 1200 u/hr x 40,000 u = 1200 u/hr1000 ml1000 ml

OR by ratio OR by ratio 40,000 u40,000 u = = x x u u (cross multiply & solve for (cross multiply & solve for xx)) 1,000 ml 30 ml1,000 ml 30 ml

1,0001,000xx = 1200000 = 1200000 xx = 1200 u/hr = 1200 u/hr

IV Drug AmountsIV Drug Amounts Ex: Morphine Sulfate IV drip concentration 50 mg in 100 cc D5W. MD orders 2mg of Ex: Morphine Sulfate IV drip concentration 50 mg in 100 cc D5W. MD orders 2mg of

Morphine per hour. What will the flow rate be to insure delivery of 2 mg/hr? ( How many Morphine per hour. What will the flow rate be to insure delivery of 2 mg/hr? ( How many cc’s per hr?)cc’s per hr?)

2mg/hr2mg/hr x 100 cc = 4 cc/hr x 100 cc = 4 cc/hr

50 mg50 mg

Or by ratio Or by ratio 50 mg50 mg = = 2 mg 2 mg (cross multiply & solve for (cross multiply & solve for xx))

100 cc 100 cc xx cc cc

50 50 xx = 200 = 200

x x = 4 cc/hr = 4 cc/hr