Hematology

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Hematology

• AVS 435 Equine Exercise Physiology

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• Blood serves a number of functions
• Removal of waste products
• Communication (endocrine)
• Thermoregulation
• Delivery of substrates to tissues
• Fuel
• Oxygen
• Key element in O2 transport is RBC

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• Components of whole blood
• Add anticoagulant, spin in centrifuge layers
• Aqueous portion (plasma or serum)
• Normally straw-colored in horses
• Water, glucose, FFAs, electrolytes, endocrine
• Dissolved proteins total proteins
• Albumin osmotic pressure gradients
• Immunoglobulins antibodies
• Fibrinogen (in plasma only)

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• Components of whole blood
• Cellular components
• Buffy coat WBCs
• RBC red blood cells

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• Blood collection
• Venous or arterial collection
• Venous easier to locate, less likely to keep
  bleeding after puncture than arterial
• Virtually no differences between venous and
  arterial samples in chemistry or hematology
• Chemistry enzymes, electrolytes, dissolved
  proteins (albumin, globulins)
• Hematology red blood cells, white blood cells,
  platelets

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• Vacutainers /- anticoagulant
• No anticoagulant clot serum
• Anticoagulant
• Potassium EDTA
• Lithium heparin
• Sodium citrate

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• Blood collection
• Improper handling of sample skewed results
• Storage gt 2-3 hours at RT, or 1-2 days
  refrigerated
• Ongoing metabolism in RBCs
• Decreased glucose, elevated potassium

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• Hemolysis (destruction of RBCs) can be caused by
• Too small needle (lt 21 gauge)
• Too much vacuum during collection
• Shaking sample instead of gently rolling or
  inverting
• True hemolytic disease viral, autoimmune,
  parasitic, oxidative damage, plant/heavy metal
  toxins, neoplasia

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• Hematocrit
• Packed cell volume PCV
• Measurement ofproportion of RBCsrelative to
  total blood volume, expressed as
• Packed refers to centrifugation

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• Hematocrit
• Normal resting equinePCV 32-45
• 32 in humans/dogs would anemia
• Horses have tremendousability to manipulate
  circulating RBCs as needed, at rest and during
  exercise

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• Why does increasing RBCs matter?
• RBCs package hemoglobin (Hb)
• Increasing RBCs in circulation, increase amount
  of oxygen delivery to tissues

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• Spleen is storage reservoir for RBCs
• Comparatively larger in horses than other species
• .2 1.1 of body mass in horses
• 500 kg horse 1 - 5.5 kg
• Dogs, humans 0.3
• Splenic contraction ejects sequestered RBCs
  into circulation
• Neurogenic endocrine control
• Flight or fight - norepinephrine
• Can increase PCV to 65

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• Also increase O2 delivery by increasing blood
  volume
• Correlated with increased performance in both
  humans and horses
• Equine BV 7 12 of body mass
• Increases with conditioning
• 500 kg gt 50 kg gt 50 liters blood
• Important to know for fluid therapy

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• Blood volume is increased initially by moving
  plasma from interstitial space to vascular space
• Interstitial between tissue spaces

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• Increasing volume of oxygen consumed (Fick
  principle again)
• VO2 CO (O2 arterial O2 venous),
• Where VO2 is Volume O2 in ml/kg/min
• Oxygen uptake
• CO is cardiac output (HR x SV)
• Can we increase HRmax? SV?
• Can we increase amount of O2 carried in
  circulating blood?

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• 99.6 of oxygen is carried to tissues by
  hemoglobin
• Packaged in RBCs
• Cannot increase the amount of Hb carried per RBC
• Must increase s of RBCs in circulation
• Human PVC 40-45
• Cannot sequester in spleen

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• How to increase RBCs?
• Induced erythrocythemia in humans
• Homologous transfusions
• Self or same blood type
• Good way to spread disease in humans
• Limitations in storage
• Correlation between increases in PCV and VO2max
  gt performance

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• Horses do this via splenic contraction
• As PCVs approach 70, can be fatal
• Function of increased viscosity

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• Use of erythropoietin
• Endocrine product normally produced by kidneys to
  stimulate production of RBCs in bone marrow
• Renal failure, decreased EPO
• Anemia
• Amgen Epogen
• Recombinant DNA
• Replaces naturally-occurring EPO

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• Illegal use in human athletes
• Increase PCV by 30
• Increased endurance performance 10-19
• PCV gt 55 in humans increased viscosity, MAP
• Stroke, heart attack, death

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• Illegal use in horses
• Increases PCV 13 (75-80?)
• Increases VO2max 15
• Increases in speed at VO2max
• Viscosity sudden death?
• Horses presented at Univ of Missouri
• Txed with EPO
• Anemic / PCV lt 20 why?

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• T1/2 3-4 days, but affect on RBC production lasts
  for weeks
• Increase in performance may be present long after
  illegal substance can be measured in blood

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• Shifts in circulation at rest vs exercise

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• How would prolonged exercise affect
• Renal function?
• GI motility?