Haematologic Adaptation

Question 1

What is the maximal hematocrit seen in TB & greyhounds during maximal exercise?

Answer 1

TB - 65%
Greyhound - 66%

Question 2

Explain the main differences of a greyhound to other dogs in terms of body proportions

Answer 2

• 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

Question 3

How does the PCV of greyhounds differ from other dogs? Why?

Answer 3

• Greyhound PCV is 1/3rd higher than other breeds
• Adaptation for increased oxygen delivery to muscle

Question 4

Explain greyhounds and their increased RBC mass

Answer 4

• 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

Question 5

What is unique about Greyhound MCV?

Answer 5

• 93% of greyhounds have MCV in upper half of reference interval
• Attributable to increased RBC turnover & putatively increased reticulocytes

Question 6

What is unique about greyhound MCHC?

Answer 6

• It is 7% higher than other breeds

Question 7

What is unique about blood viscosity in greyhounds?

Answer 7

• blood viscosity is higher than other breeds
• High HCT = high viscosity
• HCT accts for >90% of blood viscosity

Question 8

What is unique about greyhound WBCs?

Answer 8

• lower neuts & lymphocytes
• 43% decrease compared to other breeds

Question 9

Explain why greyhounds are good blood donors

Answer 9

• 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

Question 10

Explain hemostasis in greyhounds

Answer 10

• Tendency towards bleeding
• 10-15% greyhounds bleed spontaneously or after minimally invasive Sx
• Often have delayed post-op bleeding
• Cause of <8% fatality

Question 11

How would you test a greyhound for a tendency to have delayed bleeding?

Answer 11

• TEG assessment of clotting - Decrease clot strength & viscoelasticity, delayed kinetics of clot formation

Question 12

Why do greyhounds have a putative mechanism of bleeding?

Answer 12

Compensatory adaptation to higher viscosity

Question 13

Greyhound platelet counts are about…

Answer 13

27% lower than other breeds

Question 14

What are Greyhound features in hematology?

Answer 14

• 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

Question 15

How does resting metabolic capacity correlate w/ body weight?

Answer 15

Bigger size = lower metabolic rate (basal)
Smaller size = higher metabolic rate (basal)
Greyhounds have higher metabolic rate compared w/ size

Question 16

Explain mammalian body weight vs VO2max

Answer 16

• Athletic species have maximal metabolic rate that can be attributed to body wt
• Athletes have higher VO2 b/c of sport adaptations

Question 17

Explain how athleticism (VO2max) comes from muscle capillary RBC vol

Answer 17

• More RBCs = more oxygen consumption

Question 18

Explain equine hematologic adaptations for enhanced delivery of Oxygen (Hb) to tissues

Answer 18

• 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

Question 19

What is unique about athletic horse breeds and their spleens?

Answer 19

Atheletic horse breeds have bigger spleens which allow for more blood storage for times of aerobic need of endurance athletes

Question 20

What are the main qualitative features of a mammalian spleen?

Answer 20

• circulation (closed, open, both)
• nature of venousvessels in splenic cords (venules or sinuses)

Question 21

What are the main quantitative features of the mammalian spleen?

Answer 21

Red vs white pulp

Question 22

Huge splenic stores of mature erythrocytes in the horse can be used for…

Answer 22

Athleticism and to compensate for hemorrhage

Question 23

The equine spleen is categorised as extreme storage-type. Why?

Answer 23

• High muscularity for contraction to release
• High red pulp proportion for storage & large size for both.