Haematologic Adaptation Flashcards
What is the maximal hematocrit seen in TB & greyhounds during maximal exercise?
TB - 65%
Greyhound - 66%
Explain the main differences of a greyhound to other dogs in terms of body proportions
- 1/3 increase in body wt
- more blood mass
- less skin weight
- reduced liver size
- heart is significantly larger (near double in size)
- Adipose tissue decreased compared to body weight
- Fat is reduced
How does the PCV of greyhounds differ from other dogs? Why?
- Greyhound PCV is 1/3rd higher than other breeds
- Adaptation for increased oxygen delivery to muscle
Explain greyhounds and their increased RBC mass
- increased 44% due to same increase in blood vol
- increase 33% due to same increased HCT
- increased 20% due to splenic contraction during racing
- total increase about 100% during racing
- corresponds to 100% increase in VO2 max –> maximal oxygen consumption
What is unique about Greyhound MCV?
- 93% of greyhounds have MCV in upper half of reference interval
- Attributable to increased RBC turnover & putatively increased reticulocytes
What is unique about greyhound MCHC?
- It is 7% higher than other breeds
What is unique about blood viscosity in greyhounds?
- blood viscosity is higher than other breeds
- High HCT = high viscosity
- HCT accts for >90% of blood viscosity
What is unique about greyhound WBCs?
- lower neuts & lymphocytes
- 43% decrease compared to other breeds
Explain why greyhounds are good blood donors
- Ideal blood donors
- 60-70% are universal blood donors (neg for DEA 1:1, pos for DEA 3)
- large dogs
- big neck veins, thin skin
- high HCT
- gentle, patient, easy to handle
Explain hemostasis in greyhounds
- Tendency towards bleeding
- 10-15% greyhounds bleed spontaneously or after minimally invasive Sx
- Often have delayed post-op bleeding
- Cause of <8% fatality
How would you test a greyhound for a tendency to have delayed bleeding?
- TEG assessment of clotting - Decrease clot strength & viscoelasticity, delayed kinetics of clot formation
Why do greyhounds have a putative mechanism of bleeding?
Compensatory adaptation to higher viscosity
Greyhound platelet counts are about…
27% lower than other breeds
What are Greyhound features in hematology?
- Marked increase in HCT, Hb, RBC
- mild increase MCHC, MCV, MCH
- mild decrease WBC, Platelets
- mod increase in viscosity
- mod increase in vol
- mod eosinophil vacuolation
- Ideal blood donors
How does resting metabolic capacity correlate w/ body weight?
Bigger size = lower metabolic rate (basal)
Smaller size = higher metabolic rate (basal)
Greyhounds have higher metabolic rate compared w/ size
Explain mammalian body weight vs VO2max
- Athletic species have maximal metabolic rate that can be attributed to body wt
- Athletes have higher VO2 b/c of sport adaptations
Explain how athleticism (VO2max) comes from muscle capillary RBC vol
- More RBCs = more oxygen consumption
Explain equine hematologic adaptations for enhanced delivery of Oxygen (Hb) to tissues
- high circulating RBC/L
- high blood vol < 12% body wt, 50-100% > cold-blooded
- large splenic reserve, increase Hct 65%
- Hb packaging –> smaller RBCs vs cold-blooded; adaptation to increased/finer capillarisation & increased SA; more capillaries in skin for better delivery
What is unique about athletic horse breeds and their spleens?
Atheletic horse breeds have bigger spleens which allow for more blood storage for times of aerobic need of endurance athletes
What are the main qualitative features of a mammalian spleen?
- circulation (closed, open, both)
- nature of venousvessels in splenic cords (venules or sinuses)
What are the main quantitative features of the mammalian spleen?
Red vs white pulp
Huge splenic stores of mature erythrocytes in the horse can be used for…
Athleticism and to compensate for hemorrhage
The equine spleen is categorised as extreme storage-type. Why?
- High muscularity for contraction to release
- High red pulp proportion for storage & large size for both.
