Intravenous Therapy IV Calculation (Math)

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Intravenous TherapyIV Calculation (Math)

• Sasha A. Rarang, RN, MSN

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Basic Infusion Time Formula

• Infusion Time total volume to infuse
• 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

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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
• .66 x 60 min 39.6 minutes or 40 minutes
• Therefore the TOTAL time is 6.66 hrs or 6 hrs
  40 minutes

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Flow Rates

• Refers to an amount of solution over a period of
  time
• Can be expressed as gtts/min or mls/hr
• For our purposes, whenever we discuss regulating
  an IV by the roller clamp or by gravity, we will
  use the flow rate of gtts/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 ccs/hr

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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

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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
• 1,000x 1200000
• x 1200 u/hr

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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 ccs per hr?)
• 2mg/hr x 100 cc 4 cc/hr
• 50 mg
• Or by ratio 50 mg 2 mg
  (cross multiply solve for x)
• 100 cc x cc
• 50 x 200
• x 4
  cc/hr