Approach to polycythaemia Flashcards
What is polycythaemia also known as?
Erythrocytosis
More accurate name
What is polycythaemia/erythrocytosis?
Increased haematocrit, due to either:
Increased RBC count
Increased RBC size
Decreased plasma volume
How could you distinguish erythrocytosis of the mucous membranes and endotoxaemia (sepsis - also shows red mucous membranes)?
Would have neutrophilia and pyrexia with sepsis
What are the 2 types of erythrocytosis?
Relative erythrocytosis
Absolute erythrocytosis
What is relative erythrocytosis? What are the 2 causes?
Relative increase of red cell mass due to:
Decreased plasma volume
RBC redistribution
What is absolute erythrocytosis? What are the causes of primary and secondary erythrocytosis?
An actual increase in red cell mass due to:
Bone marrow disorder (primary)
Increased erythropoietin (secondary)
Relative erythrocytosis can be due to decreased plasma volume. What can cause decreased plasma volume?
Dehydration
Acute GI disease
Hyperthermia
How does dehydration alter total protein and albumin?
Causes increased protein and albumin
Relative erythrocytosis can be due to RBC redistribution. Give an example of when RBCs can be redistributed and which species this occurs in
Splenic contraction
Horses
Unlikely in dogs
When may splenic contraction occur?
With exercise
With excitement or fear
How does splenic contraction alter PCV?
Causes moderate to mild increased PCV
RBCs released from spleen into blood
What are the clinical consequences of splenic contraction?
None as transient
May have stress leukogram
How can relative erythrocytosis be treated?
Replacement of fluids/electrolytes
Treat underlying cause
What causes secondary absolute erythrocytosis?
Increased erythropoietin
What causes primary absolute erythrocytosis?
Bone marrow disorders
e.g. chronic myeloproliferative disorder, chronic erythroid leukaemia
What are the 2 types of secondary absolute erythrocytosis?
Appropriate - due to generalised hypoxia/hypoxaemia
Inappropriate - without generalised hypoxia/hypoxaemia
What is appropriate secondary absolute erythrocytosis?
An increase in RBCs
Due to increased erythropoietin
Due to generalised hypoxia
Give examples of what can cause appropriate secondary absolute erythrocytosis (generalised hypoxia)
Altitude sickness
Severe heart/lung disease
Hypoventilation
What is inappropriate secondary absolute erythrocytosis?
Increased RBCs
Due to increased erythropoietin
NOT due to generalised hypoxia
How does inappropriate secondary absolute erythrocytosis affect oxygen levels?
Doesn’t - normal sautéed O2 and PO2
Give examples of what can cause inappropriate secondary absolute erythrocytosis
Tumours/lesions causing localised renal hypoxia
Or tumours producing erythropoietin
Rare
How can absolute erythrocytosis be treated?
Phlebotomy - remove XS blood (care not to make hypovolaemiac- calculate amount)
Or chemotherapy
Why is erythrocytosis a problem?
Increased workload on heart
Affects flow, risk of thrombosis
Hyperviscosity syndrome - sluggish flow, increased congestion
