Lab Flashcards
How much of the body does blood make up?
7-10% of bodyweight
What is blood made up of?
A fluid part - plasma
A solid part - Erythrocytes, Leucocytes and Thrombocytes
What materials are needed for collecting a blood sample?
Needle - 19-23G, 3/4inch, depends on patient size
Syringe - 1-5ml, sterile and tested plunger
Sample Tubes - labelled with patient details
Swab soaked in chlorhexidine solution
Clean dry swab and bandage material
Gloves
Clippers - clean and tested, various sizes
Assistant/ restrainer
Potentially a tourniquet
Where are the blood collection points in dogs, cats and rabbits?
Jugular, cephalic, lateral saphenous
*in rabbits also have marginal ear vein
What size needle is used for parenteral injection?
21-26
What are things you should not do when collecting blood that can damage/clot blood?
Do not draw back forcefully on plunger - can collapse the vein and damage blood
Always transfer to collecting tube ASAP - to prevent contamination and clotting
Always expel the blood gently into the tube and remove the needle prior to doing this - to avoid cell damage
Always collect enough blood to fill to the required level on the collection tube
What is serum?
The fluid compartment of blood that clotting factors have been removed from i.e. no solid
What would you collect serum in?
A brown plain tube, or a clear serum gel tube WITHOUT anticoagulant
What is different about serum samples?
The blood is allowed to clot. In brown tubes it will clot at room temp after about 2 hours. In serum gel tube, use centrifuge to spin down and the gel forms a layer between the serum and the blood.
How can serum be stored? Short and long term?
In fridge for a few days between 2-8 degrees. Or in freezer lower than -20. Both will need to be brought up to room temp and gently mixed before testing
What do sample tubes for unclotted samples contain?
Anticoagulant
How can plasma be stored?
Short term in fridge for a few days at 2-8 degrees
Long term in freezer at less than -20 degrees
What is a pink tube? What is it used for?
Ethylene Diamine Tetra-acetic Acid (EDTA)
Minimal change in morphology of blood cells
Used in blood smears and cell counts
don’t use for reptiles or avian species
What is an orange tube? What is it used for?
Lithium Heparin
Salts in the tube bind with and prevent clots
Used for biochemical tests and hormone tests
What is a yellow tube? What is it used for?
Sodium Fluoride or Potassium Oxalate
Must be used for blood glucose as it stops the oxidation of glucose
What is Haemolysis?
Rupture of RBCs causing haemoglobin to be released staining the plasma or serum red/pink
What causes Haemolysis?
Cell trauma due to vigorous agitation Extremely rapid collection Adding to a hypotonic solution Leaving plasma unseparated in transit Needle too fine Didn't remove needle when decanting blood
What would cause a sample to clot?
If there is insufficient anticoagulant for the volume of blood
Too long to take or test sample
What is Lipaemia?
Fat globules in serum or plasma
Appears cloudy
What causes lipaemia?
Recently fed Liver disease (hyperlipidaemia - fats not metabolised)
What is and what causes an icteric sample?
High levels of bilirubin
Indicates liver disease
normal for horses and cattle
What is a haematology test?
A total Blood Cell Count
What makes up a haematology test?
- Quantitative
- PCV, Total white cell count etc.. - Qualitative
- Blood smear examination for changes in cell shape and structure
What does PCV measure?
The percentage of red blood cells in a blood sample
What would an increased PCV indicate?
Dehydration (as plasma levels reduced)
or Endotoxic shock or splenic issues
What would a decreased PCV indicate?
Decrease in RBCs = anaemia or haemorrhage
What is the normal PCV for a dog and cat?
Dog : 37-55%
Cat: 24-45%
What is used to hold a sample for PCV?
Haematocrit tube
What is used to read a PCV?
Hawksley microhaematocrit reader
What would you use a blood smear for?
To examine RBC or WBC shape, size and colour.
Can identify abnormalities of the cells
Total WBC count (per litre of blood)
Differential WBC count (percentage of each type of WBC compared to 100 WBCs)
What are the 3 Romanowsky stains?
Giemsa
Leishmans
Diff-Quick
How would you perform a giemsa stain?
Dip the slide in methanol for 3m to ‘fix’ the slide
Dilute 1 part giemsa stain to 9 parts water
Flood the slide with this and leave for 15-30m
Wash off excess stain with buffer solution
Drain and air dry at room temp
How would you perform a Leishman’s stain?
Flood slide with Leishman’s stain and leave for 1-2m
Add twice the volume of Leishmans stain into the buffer solution and mix by rocking
Allow the newly diluted stain to act for 15 minutes - metallic scum will appear
Wash gently with buffer until slide is salmon pink
Drain and dry at room temperature
How would you perform a DiffQuick stain?
Use 1. Methanol (blue) 2. Eosin (red) 3. Methylene Blue ( purple)
Prepare a deep pot of each solution
Dip the dried blood smear into the blue for 5x1s, shale off the excess. Repeat for the red and then the purple.
Carefully rinse of excess stain with distilled water
Air dry
How long does normal blood take to clot?
Within about 1-2 minutes normally
What tests are used to test clotting time?
Thrombocyte counts
Buccal mucosa bleeding times (small incision made in inner lip and blotting paper used to press again and time until bleeding stops counted)
Activated Clotting Time (1ml of whole blood placed into small glass tube. Kept at 37 degrees. Time recorded from aspiration to clotting)
What is a Quantitative Buffy Coat and how does it work?
It is used to count cells
Separates RBCs, granulocytes, monocytes and platelets into layers. The cell count is based on the width of the layers.
How does a coulter counter work?
Counts blood cells by measuring electrical resistance as they pass through an aperture
What must be carried out regularly on in-house analysers?
Quality control
What does a haematology analyser do?
Counts the number and type of RBCs and WBCs
What does an electrolyte analyser do?
Measures the levels of essential electrolytes
Describe the appearance of
- erythrocyte
- Proerythroblast
- Normoblast
- Reticulocyte
- Bi concave disc with no nucleus. Stains pink
- 1st stage of RBC production. Large with large nucleus. Stains blue.
- Smaller and the nucleus is beginning to be extruded
- Has small pieces of blue stain in cytoplasm. No nucleus
What are the 3 forms of WBC?
- Polymorphonuclear granulocytes (PMNL)
- Monocytes
- Lymphocytes
What are the PMNL?
Neutrophils, eosinophils and basophils
What is the function of neutrophils?
Found in the bloodstream at acute stages of inflammation. Can indicate skin infection.
Phagocyte
What does a neutrophil look like?
The cytoplasm stains grey/blue. The nucleus and granules stain purple/violet.
Granules are little dots in the cytoplasm
What is the function of an eosinophil?
Kill endoparasites - response to parasite reaction
Contains a toxic-based proteins
What does an eosinophil look like?
Bilobed nucleus stained purple. With granules stained orange/red
What is the function of Basophils?
Release histamines in response to allergens and inflammatory response. (the granules contain histamine and heparin). Seen in animals with chronic tissue damage or myeloid leukaemia
What do basophils look like?
Similar in size to neutrophil. Kidney bean shaped nucleus. Cytoplasm is a mass of purple granules
What is the function of monocytes?
What do they look like?
Phagocytosis
Repair damaged blood vessels - attach to damaged areas and ‘plug’ the leak
Involved in producing fibrin for clotting.
There are no granules in the cytoplasm.
What is the function of lymphocytes?
Cellular immune response
Involved in antibody production, recognition of foreign substances.
T lymphocytes are produced in the Thymus and B lymphocytes are produced in the bone marrow
What abnormalities can occur in the size of RBC?
Can be larger than usual - a macrocyte
Smaller than normal - a microcyte
Great variation in cell sizes - anisocytosis
What are the abnormalities in shape of RBCs
- Crenation
- spikey appearance caused by damage to cell
- seen in auto-immune HA - Schistocyte
- RBC fragments - Spherocyte
- spherical RBC - Rouleaux
- normal shape but the cells are stacked
What are the abnormalities in colour of RBCs?
- Hypochromasia
- pale due to low haemoglobin - Polychromasia
- larger blue cells seen in regenerative anaemia
What are the abnormal inclusions seen in RBCs?
- Heinz bodies
- Blue granular at edge of cell. Due to denatured Hb - Howell-Jolly bodies
- Basophillic nuclear remnants seen in young RBCs
- Seen in splenectomy and RA - Babesia
- parasite - detected using a Romanowsky stain - Mycoplasma haemofelis
- parasite causing feline anaemia
What is the immature form of RBC?
- Reticulocytes
- immature RBC. Anuclear. Have stainable cytoplasmic RNA
Describe the process for carrying out a PCV
- Wear gloves
- Gently invert the EDTA sample
- Insert a plain capillary tube into the blood sample and fill to 3/4 full
- Remove from sample and wipe clean
- Seal with cristaseal sealing compound
- The tube is placed into the centrifuge with the clay plug against the outside rim and balanced
- Sample should be spun at 10,000 for 5 minutes or PCV setting on centrifuge
- Once spun, the PCV reading is determined through the use of a Hawskley micro-haematocrit reader as a %