Intravenous Therapy IV Calculations (Math) Sasha A. Rarang, RN, MSN

Basic Infusion Time Formula  Infusion Time = total volume to infuse ml/hr being infused ml/hr being infused “How long will it take for a particular amount of solution to be completed?” Ex: Calculate the infusion time for an IV solution of 500 ml D5W that is currently infusing at 50 ml/hr? 500 ml = 10 hrs 50 ml/hr OR by ratio 50 ml = 500 ml (cross multiply & solve for x) 1 hr x 50x = 500 x = 10 hrs x = 10 hrs

Basic Infusion Time Formula  Time can also be expressed in hours & minutes  Multiply the partial portion (after the decimal point) of the hour by 60 to obtain the time to the nearest minute  Ex: 500 ml = 6.66 hr 75 ml/hr 75 ml/hr.66 x 60 min = 39.6 minutes or 40 minutes Therefore the TOTAL time is 6.66 hrs or 6 hrs & 40 minutes

Flow Rates  Refers to an amount of solution over a period of time  Can be expressed as gtt’s/min or ml’s/hr –For our purposes, whenever we discuss regulating an IV by the roller clamp or by gravity, we will use the flow rate of gtt’s/min. –When trying to figure out the flow rate using an IV pump or regulating the IV using a machine, we will use the flow rate of cc’s/hr

Flow Rates  Flow rate via gravity or by the roller clamp  Refer to your handout “IV Calculation Worksheet”  Vital information needed: microdrip or macrodrip; drop factor

IV Drug Amounts  “How much medication is the patient receiving?”  “What is the flow rate to insure proper delivery of the amount of medication ordered?” D x Q H 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) 30ml/hr x 40,000 u = 1200 u/hr 1000 ml OR by ratio 40,000 u = x u (cross multiply & solve for x) 1,000 ml 30 ml 1,000 ml 30 ml 1,000x = ,000x = x = 1200 u/hr x = 1200 u/hr

IV Drug Amounts  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 cc’s per hr?) 2mg/hr x 100 cc = 4 cc/hr 2mg/hr x 100 cc = 4 cc/hr 50 mg 50 mg Or by ratio 50 mg = 2 mg (cross multiply & solve for x) 100 cc x cc 100 cc x cc 50 x = x = 200 x = 4 cc/hr x = 4 cc/hr