Lab 5 RBC Flashcards
What will happen when there is a problem with RBCs?
Tissue hypoxia
What are the most important parameters for detecting pathological processes?
RBC count
Haemoglobin concentration/function
How can Hgb be measured?
Drabkin method (Spectrophotometry)
Potassium ferricyanide added to whole blood
RBCs hemolyzed, Fe3+ is formed from Fe2+
Cyanmethemoglobin is the orange coloured end product, measired at 540 nm
What is normal Hgb content in the blood?
18-20 mmol/l or 120-180 g/l
In case of intravascular hemolysis, what change in Hgb conc is expected?
No change
Upward shift in oxygen dissociation curve
Oxygen binding capacity increased by: hypothermia low 2-3 DPG conc (stimulates O2 release) alkalosis CO (cherry colour)
Downward shift in oxygen dissociation curve
Oxygen binding capacity decreased by: decreased affinity hyperthermia high 2-3 DPG conc acidosis
2,3-DPG
Diphosphoglycerate
Prod by RBC during glycolysis
Promotes release of O2, binds to deoxygenated Hgb near respiring tissue to ensure tissues that need O2 get it
SAT %
Oxygen saturation
The percentage of oxygenated Hgb molecules compared to the whole amount of Hgb molecules in one unit of blood
Arterial: 95-99%
Venous: 80-90%
Methemoglobin
Hemoglobin containing Fe3+ (ferric) oxidized form
Cannot take up oxygen
Reduced back to Hgb by methemoglobin-reductase enzyme
What can cause severe oxidative damage to RBCs?
Nitrites, free radicals, paracetamol, onion
Leads to methemoglobinaemia
What are some symptoms of methemoglobinaemia?
Dark brown colour of blood
Deeply cyanotic mucous membranes
Who has Hgb that are most sensitive to oxidative damage?
Cats and newborns of any species
How can you treat severe methemoglobinaemia?
Blood transfusions and antioxidants
How can we give a rough estimation of Hgb?
Suspecting normal mean Hgb conc of RBC (MCHC)
PCV / 3 x 1000 = Hgb g/l
Give some causes of increased Hgb concentration
relative polycythaemia: dehydration
absolute polycythaemia: RBC leukemia, high altitude, greyhound, llama
Give some causes of decreased Hgb concentration
relative oligocythaemia: hyperhydration
absolute oligocythaemia: anaemia
What species have Hgb conc affected by age?
Swine
Younger have lower Hgb conc than older swine
Give some reasons for intravascular hemolysis
DIC
Thrombocytopenic purpura
Hemolytic uremic syndrome
Mechanical stress
Give some reasons for extravascular hemolysis
Hypersplenism
Inherited: sickle cell anemia, spherocytosis
Give methods to measure RBC count
Bürker chamber (lol)
Estimation
Automatic cell counter
What sample is used for Bürker chamber and what dilution?
EDTA whole blood
200x dilution
How is RBC count estimated?
If we suspect a normal average RBC volume (MCV)
Ht / 5 x 100 = RBC count x 10^12/l
RBC count by automatic cell counter
Size dependent: electric impedance
40-100 fl
histogram is provided from the results
What can we expect to see on the ACC histogram during immunohemolytic anaemia?
RBCs form aggregates, they are not counted
Normal RBC count
4.5-8 x 10^12/l (teraliter)
Histogram expected during non-regenerative anemia
Low RBC count
narrow RDW
Histogram expected during regenerative anemia
Low RBC count
BUT wide RDW and larger cells (reticulocytes)
Histogram expected during microcytic anemia
Low RBC count
“left shift” small cells
Histogram expected during macrocytic anemia
Low RBC count
“right shift” larger cells
MCH
Mean corpuscular hemoglobin Average Hgb content of RBCs HGB/RBC count Normal: 20 pg PER CELL (but young can be higher) Hypo/hyperchromasia
MCV
Mean corpuscular volume Indicates average size of RBCs PCV/RBC count Normal: 60-70 fl Micro/macrocythaemia
What species and ages do you see differences in size of RBCs?
Fe/Eq smaller RBCs Young RBCs are bigger Newborns have bigger RBCs Akita inu: small RBCs Poodle: large RBCs
Causes of microcytosis
Chronic blood loss
Fe, Cu, B6 deficiency
Portosystemic shunt
Causes of macrocytosis
Polycythaemia absoluta vera
B12, Cobalt, folic acid deficiency
MCHC
Gives a ratio: sees if the RBCs are large or small too
MCH/MCV
Normal: 300-350 g/l
Hypo/hyperchromic
Decreased MCHC
Hypochromasia
Newborns
Regenerative anaemias
Iron deficiency anaemias (also Cu/B6)
Increased MCHC
Hyperchromasia Acute erythroleukemia (polycythaemia vera) B12, folic acid and cobalt deficiency Immunohemolytic anaemia (spherocytosis) Lead poisoning Splenectomy
What changes in derived parameters are seen during regenerative anaemias?
Increased MCV, decreased MCHC
Macrocytosis, hypochromic (inc reticulocytes)
What changes in derived parameters are seen during non-regenerative anaemias?
Normocytic, normochromic
Normal or decreased MCH
What changes in derived parameters are seen during non-Fe/Cu/B6 deficiency anaemias, liver failure or portosystemic shunt?
Microcytic, hypochromic
Decreased Hgb synthesis
What is pyridoxine needed for in blood production?
Porphyrine production (Hgb)
What is copper needed for in blood production
Iron oxidation (ceruloplasmin)
What changes in derived parameters are seen in Akita inus?
Microcytic normochromic
What changes in derived parameters are seen during
FeLV infection, B12, Co, Folic acid deficiency, erythroleukemia and poodle macrocytosis?
Macrocytic normochromic
RDW
Red cell Distribution Width
Range of average size of RBCs
Derived from the histogram at 20% of the peak
High RDW = high variation in size (positive)
Short = non-regenerative process
PDW
Platelet Distribution Width
How can you differentiate RBCs from reticulocytes in a blood smear?
Basophil punctuates stained by brylliant-cresil blue stain
The punctuates are rRNA remnants
Large punctuates: young reticulocyte
Species differences reticulocytes
Cats: punctuated form more common (older)
Eq/Ru: no reticulocytes are found in blood, only in bone marrow
What are nucleated RBCs called?
Normoblast
Cannot carry blood
Can reticulocytes perform the same tasks as RBCs?
Yes, they can carry oxygen
What blood sample and what stain is used for reticulocyte count?
EDTA fresh whole blood
Brylliant-cresil stain
The cells have to be alive: 2-3 hrs needed in room temp for the reticulocytes to take up the stain
When and why should the reticulocyte count/percentage be corrected?
When the animal is sick
Correlated to the RBC count or the PCV
Because mature RBCs are more sensitive to damage than young RBCs and reticulocytes
