Lecture Math for the pharmacy technician: Concepts and calculations: Chapter 8 – Lynn M. Egler, Kathryn A. Booth

Chapter 8, Intravenous calculations, presents information and calculations unique to administering intravenous (IV) medications. After introducing IV solutions, attention is turned to calculating fl ow rates. Students also learn calculations for intermittent IV infusions, infusion times, and infusion volumes.

Math for the Pharmacy Technician:  Concepts and Calculations

Chapter 8:  Intravenous 

Calculations

Calculations 

Egler • Booth

Intravenous Calculations

  Calculate medications for intermittent IV  infusions. 

Introduction

 Intravenous (IV) fluids are solutions 

including medication that are delivered  directly into the bloodstream via a vein

 Blood is also delivered by IV

 IV fluids have a rapid effect

 Are necessary during emergencies or 

other critical care situations

Therapeutic Fluids

• Deliver medication to 

the patient

 D 5 LR

 5% D/LR 

 D5%LR

Lactated Ringer’s Ringer’s Lactate

Half Normal Saline Solution (0.45% NaCl)

(0.9% NaCl)

2

1

IV Concentrations

 5% Dextrose

It contains 5 g of dextrose per 100 mL.

 Normal saline is 0.9% saline

It contains 900 mg, or 0.9 g, of sodium chloride per

100 mL.

 ½ Normal saline is 0.45% saline

It contains 450 mg, or 0.45 g, of sodium chloride per

100 mL.

IV Concentrations  (con’t)

 Isotonic

 They have no effect on the fluid balance of the

surrounding cells or tissues.

 Fluid moves across the cell membrane into

surrounding cells and tissues.

 This movement restores the proper fluid level in cells and tissues of patients who are dehydrated.

 Hypotonic

 Hypertonic

IV Concentrations (con’t)

 These solutions draw fluids from cells and

tissues across the cell membrane into the bloodstream.

 They are helpful for patients with severe fluid shifts such as those caused by burns.

Example: 3% saline

IV Concentrations

Patients with   normal   electrolyte levels are 

likely to receive   isotonic   solutions   

 Patients with   high   electrolyte levels will 

receive   hypotonic   solutions.

 Patients with   low   electrolyte levels   will 

receive   hypertonic   solutions.

Calculating Flow Rates         for  Manual Regulation

F = the flow rate in milliliters/hour

C = the calibration factor of the tubing in drops per mL

60 = number of minutes in an hour

60

FxC f

Review and Practice

Total time to infuse the solution is 

13 hours and 20 minutes

Find the total time to infuse.

Ordered: 1000 mL NS to infuse at a rate of

75 mL/h

Review and Practice

T = 6 hours = total time to infuse the 750 mL

Find the total time to infuse.

Ordered: 750 mL LR to infuse at a rate of

125 mL/hr started at 11 p.m.

solution ordered.

Calculating Infusion Completion Time    (con’t)

Since each day is only 24 hours long, 

when the sum is greater than 2400 

(midnight), you must start a new day by  subtracting 2400.  

This will determine the time of completion, 

which will be the next calendar day.

Review and Practice

V=175 mL or the volume that  will infuse over 5 hours

Find the total volume infused in 5 hours if the infusion rate is 35 mL/h.

Review and Practice

V = 2400 mL = the volume that  will infuse over 12 hours

Find the total volume infused in 12 hours if the infusion rate is 200 mL/h.

 Uses shorter tubing

 IVPB bags are smaller: 50,100, or 150 mL

Intermittent Peripheral Infusion  Devices

Intermittent Peripheral Infusion  Devices  (con’t)

already inserted catheter for IV access, flushed  with heparin. 

 Calculate amount to administer and the 

flow rate.

Results can be fatal if the wrong

medication or dosage is given