1. Veterinary Practice Laboratory Unit 1
Chapter 4
The Metric System and Lab Calculations
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2. Got Math?
Veterinary technicians require knowledge and skill at performing a variety of calculations in the clinical laboratory. Reagent solutions may need to be prepared or diluted, samples must be measured and sometimes diluted, and results must be calculated. All of these mathematical operations require that the veterinary technician have a thorough understanding of the metric system, as well as a strong background in basic algebra
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3. Numbers Abstract Concrete No unit designations
Specific unit value (e.g., grams)
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4. Metric System Most commonly used system in veterinary medicine
Based on the powers of 10
Decimal system
Three basic units
Weight (grams)
Volume (liters)
Length (meters)
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5. Powers of Ten Use of prefixes to indicate powers of ten Centi 10-2
Milli 10-3
Micro
Deca
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6. General Rules
Any number without a number to the left of the decimal point must have a 0 in that place
Not .12
But 0.12
Avoid tragic mistakes in dosages
Do not add zeros after the decimal numbers
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7. International System of Units
Derived form the French Le Système International d’Unités
Abbreviated SI
SI units are designated for seven different types of measurement: length, mass, time, electric current, temperature, luminosity, and quantity
In the veterinary clinical laboratory, the SI units of importance are those for mass, temperature, and quantity
The SI unit of mass is the kilogram, temperature is reported in kelvin, and quantity as moles
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8. Dilutions Ratios Amount of one item relative to the amount of another
1:10 dilution of a patient sample combines 10 microliters of sample with 90 microliters of distilled water
Results then are multiplied by 10 to yield the correct value
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9. Serial Dilutions
Needed when performing immunologic tests or preparing manual calibration curves on instruments
Example
Bilirubin contains 20 mg/dL and is diluted 1:5, 1:10, and 1:15; the resulting concentrations of each dilution are 4 mg/dL, 2 mg/dL, and 1 mg/dL, respectively
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10. Scientific Notation Easy way to handle very large numbers
Uses the powers of 10
100 = 0
101 = 10
102 =10 × 10 = 100
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11. Steps to Convert to Exponential Form
1. Move the decimal point so that the first term is more than 1 and less than The second term is a power of 10 that is equal to the number of times that the decimal point was moved 3. The sign (+ or −) determines the direction in which to move the decimal. The use of + means that the decimal point was moved to the left; the use of − means moved to the right Example: 6,097,000 = × 106
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12. pH and Logarithms Used to manipulate very large or small numbers pH
A substance with a pH of 6 has an H+ concentration of 10-6
Tidbit – Richter scale also uses logarithms
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13. Temperature Conversions
Celsius is most commonly used in veterinary medicine
However, some test kits may refer to Fahrenheit or Kelvin systems for storage, etc.
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14. Points of Equivalence Absolute zero K = ‒273° C = ‒459.4° F
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15. Calculations F = 9/5(C + 40) – 40 C = 5/9 (F + 40) – 40 or
What is the correct conversion to Fahrenheit of 37° C?
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16. Summary Math is a must!! Metric system Powers of 10
International system of units
Dilutions
pH and logarithms
Temperature conversions
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