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

Math for the Pharmacy Technician: 
Concepts and Calculations
Egler • Booth

Chapter 8: Intravenous 

Calculations 
Calculations

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Intravenous Calculations

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Learning Objectives
When you have successfully completed Chapter 8, you will have 
mastered skills to be able to:

Identify the components and 

concentrations of IV solutions.
Calculate IV flow rates. 
Calculate infusion time based on 
volume and flow rate.

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Learning Objectives (con’t)
Calculate infusion completion time based 

on flow rate.
Calculate volume based on infusion time 
and flow rate. 
 Calculate medications for intermittent IV 
infusions. 

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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

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IV Solutions­Functions





Replacement fluids
Maintenance fluids
KVO (Keep Vein Open) fluids
Therapeutic fluids

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IV Replacement Fluids


Replace electrolytes and fluids lost 
due to hemorrhage, vomiting, or 
diarrhea
Examples:


Whole blood



Nutrient solutions



Fluids to treat dehydration
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IV Maintenance Fluids


Maintain normal electrolyte 
and fluid balance
Example:
– Normal

saline given
during and after
surgery

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IV KVO Fluids
 To keep the vein open (KVO or TKO)
Example:
 5% dextrose in water

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Therapeutic Fluids

•

Deliver medication to 
the patient

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IV Labels

Solutions are labeled with
 The name of the components
 The exact amount of the 
components

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IV Labels 
IV Labels (con’t)


In abbreviations for IV solutions:

 Letters identify the component
 Numbers identify the 
concentration

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IV Labels 
IV Labels (con’t)
Example:

An order for 5% dextrose in Lactated 
Ringer’s solution might be 
abbreviated in any of the following 
ways:
 D5LR
 D5LR
 5% D/LR 

 D5%LR
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Common Abbreviations
D
W, H20
S
NS, NSS

Dextrose

RL
LR

Ringer’s Lactate

Water
Saline
Normal Saline
(0.9% NaCl)

Lactated Ringer’s

1
2 NS

Half Normal Saline Solution
(0.45% NaCl)
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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.

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IV Concentrations (con’t)

Isotonic

They have no effect on the fluid balance of the
surrounding cells or tissues.
Examples: D5W, NS, LR

Hypotonic
 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.
Examples: 0.45% NS, 0.33% NaCI
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IV Concentrations 
IV Concentrations (con’t)

Hypertonic

 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

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IV Concentrations 
IV Concentrations (con’t)
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.

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Compatibility



Additives

 Medications, electrolytes, and nutrients 



combined with IV solutions
Common additives: potassium chloride, 
vitamins B and C, and antibiotics
Come prepackaged in the solution or 
may need to be mixed

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Compatibility 

Compatibility (con’t)
Before combining any medications, 
electrolytes, or nutrients with an IV 
solution, be sure the components are 
compatible.

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Incompatible Combinations
Examples









Ampicillin   +   5% dextrose in water
Cefotaxime sodium   +    Sodium bicarbonate
Diazepam   +    Potassium chloride
Dopamine HCl   +   Sodium bicarbonate
Penicillin   
+    Heparin

Penicillin   
+    Vitamin B complex
Sodium bicarbonate   +   Lactated Ringer’s
Tetracycline HCl   +   Calcium chloride

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Calculating Flow Rates
To calculate flow rates in milliliter per hour, 
identify the following:
V (volume) is expressed in milliliters
T (time) must be expressed in hours (convert the units
when necessary using calculation methods)
F (flow rate) will be rounded to the nearest tenth

F

V Use the formula method or dimensional analysis to 
determine the flow rate in milliliters per hour.
T
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Review and Practice
 Find the flow rate.

• Ordered: 500 mg ampicillin in 100 mL NS to
infuse over 30 minutes

Flow rate = 200 mL/h

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Calculating Flow Rates         for 
Manual Regulation
To determine the flow rate (f) in drops per 
minute:
1.
Change the flow rate mL/h (F) to 
gtt(drops)/min (f) using the formula    

f

FxC
60

where
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
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Review and Practice

• Find the flow rate in drops per minute that is

equal to 35 mL/hour using 60 gtt (Drops) /mL
microdrop tubing.
Flow rate = 35 gtt/min

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