The document discusses the pre-analytical phase of laboratory medicine. It describes the proper procedure for blood collection, including identifying the vein, cleaning the area, inserting the needle at a 15-30 degree angle, and releasing the tourniquet within one minute of drawing blood. It also discusses effects of factors like age, sex, diet, drugs, exercise and diagnostic procedures on blood samples and potential issues like hemolysis, lipemia, and effects of anticoagulants on electrolyte measurements. Proper collection techniques and use of dry heparinized tubes are recommended to avoid interference in test results.

1. Laboratory Medicine

2. Pre-analytical phase
Procedure of blood collection –
•A blood sample is taken by a
phlebotomy in a laboratory
•Blood samples are taken in the arm,
hand and finger(in some cases)
•Collection takes place from the
median cubital vein

3. The first step to the collection is to:
• Ask the patient to state and spell his/her
name
• Give you his/her birth date
• Check these against the requisition
• Put the gloves

4. The second step
• Identify the Vein
• Put a tourniquet on patients arm
• Clean the vein area with alcohol swab and allow
to air dry for 30 seconds
• Insert the needle at a 15 to 30-degree angle
• If properly inserted, blood should flash into
the tube or syringe

5. • Remove the proper volume of blood
• Release the tourniquet within one minute
• Remove the needle from the patient's arm
• Press down on the vessel with cotton

6. The third step
• Dispose of contaminated materials and needles in the
hospital approved containers
• Shake the tubes 3-4 times
• Wright the name of patient on the tubes
• Stand the tubes 5 minutes before centrifuging
• Put the tubes in the centrifuge
• Deliver blood specimens to the laboratory

8. Effects of pre-analytical phase
• Age
• Sex
• Diet
• Drugs
• Exercise
• Diagnostic procedures(endoscopy)
• Pregnancy
• Timing of collection
• Hemolysis, lipemia, jaundice
• anti-coagulants

9. Hemolysis
May easily occur during blood sampling:
• very intense aspiration of blood
• too hard mixing of sample
• too long time putting a tourniquet
• transferring blood from the syringe to the
tube with needle
• cooling down the sample on <0°C

10. potassium measurement will be highly
affected by hemolysis.

11. lipemia occurs when patient don’t fast 12
ours before sampling

12. Hemolysis, lipemia, jaundice

13. Anti-coagulants
when taking blood gases
and electrolytes
• Heparin binds all positive ions in blood, especially
calcium ions
• Dilution with liquid heparin cozies decreased results of
electrolytes
• Therefore dry heparin is recommended
That’s why:
• Exclusive use of preheparinized syringes are
recommended for electrolyte measurements on a
blood gas analyzer

14. Sampling from catheters
should avoid
• dilution or contamination by flush solution(0.9
% NaCl)
• it is important to remove an adequate amount
of fluid (also called the discard volume,
consisting of flush solution and blood) before
sampling to avoid interference and dilution
from/by the flush solution on the electrolyte,
pH, and blood gas parameters.