ANSC- lecture 17- Hematocrit

Hematocrit

• what is it?

• what else can it be called?

Measure of the proportion of red blood cells in the total volume of blood

• Hematocrit can also be referred to as packed cell volume (PCV)

Hematocrit ranges

•Sheep – 30% to 60%

•Goats – 24% to 45%

•Cattle – 24% to 50%

•Pigs – 30% to 50%

Equation for hematocrit

hematocrit= height of RBC/ height of all components in blood x 100%

factors affecting hematocrit (9)

• what can you do to get ref values

•Age

•Older = higher HCT

•Health

•Diseases

•Nutritional deficiencies

•Reproductive status

•Late pregnancy = lower HCT

•Environmental conditions

•Altitude

•Sex

•Males have higher hematocrit vs females

Using a population’s or herd’s hematocrit will help establish reference values

Low hematocrit means..

Anemia- decrease in RBC concentration or production

•Nutritional deficiencies

•Minerals & vitamins needed for RBC production and/or to carry gases

•Iron, copper, or vitamin B12 (aka cobalamin) needed for RBC production

•Iron needed for both RBC production and to carry O₂

•Internal or external parasites (blood sucking)

•Haemonchus contortus (barber pole worm)

•Stable flies (blood sucking flies)

•A lot of ticks, fleas, lice, mosquitoes can cause a low HCT

•Disease

•Anaplasmosis- caused by bacteria (Anaplasma marginale) that infects RBCs, so body destroys infected RBCs leading to hemolytic anemia

•Spread by ticks and flies

•Can also be spread when blood from infected animal enters another animal

•Contaminated needle re-used or contaminated instruments

•Blood loss

•Hemorrhaging -blood loss from a broken/damaged blood vessel [Internal bleeding]

•Severe trauma or injury

hemolysis

Hemolysis = breakdown or destruction of RBC

hemolytic anemia

Hemolytic anemia = anemia caused by RBC destruction

high hematocrit means

Increase in HCT can be caused by:

•Dehydration- reduced fluid intake or excessive fluid loss

•Less fluids in blood à     concentration of RBC à     hematocrit

•Diarrhea à fluid loss

•Excessive urination (polyuria) à fluid loss

•High altitudes- living at high altitudes increases RBC to compensate for low oxygen levels {typically normal}

•Not normal and rare - Polycythemia (aka erythrocytosis)- blood disorder where there is an increase in red blood cells that can be caused by chronic hypoxia

where does RBC production occur?

RBC production occurs in bone marrow

hypoxia

Low oxygen levels in the blood = hypoxia

measuring hematocrit

•Use blood collected with anticoagulants

•Plasma tubes (EDTA & Heparin) Why?

•Use capillary tube

•Small tube that will collect blood by moving the tube back and forth at an angle until the desired amount enters

•Use clay to seal after blood is in tube or can use self seal tubes

•Spin capillary tube with centrifuge

•Measure the % RBC with hematocrit reader or use centrifuge with built in reader