Makindo Medical Notes.com

About

• High Hb may be due to
  • Increased red cell mass: True Polycythaemia
  • A lack of plasma: Apparent Polycythaemia

Causes

• Primary proliferative polycythaemia (polycythaemia vera, PV)
• Hypoxic state: raised Hb serves a purpose:
  • Chronic lung disease
  • Smoking
  • Cyanotic heart disease
• Inappropriately high level of erythropoietin production
  • Renal cell carcinoma
  • Uterine tumour s
  • Cerebellar haemangioblastoma
  • Relative/apparent polycythaemia:
• Reduced plasma
  • Dehydration, obesity, hypertension, diuretics, smoking

Clinical

• Hyperviscosity symptoms
• Confusion, Altered vision, vascular insufficiency

Investigations

• Repeat FBC to confirm. Check for high haematocrit.
• U&E: Check renal function.
• Uric acid: raised in some types of polycythaemia.
• Blood film: look for elevated platelets and WCC and exclude a leukaemia
• Check for JAK2 mutation (see Remember box).
• Bone marrow (see Remember box).
• Erythropoietin levels (normal or low in PV).
• Blood gases or oximetry confirm COPD or lung disease
• CXR: emphysema
• Abdominal/pelvic USS exclude uterine and renal tumour s
• Bone marrow : gives additional information.
• Erythropoietin levels raised.

Management

• Secondary polycythaemia due to lung disease: Reduce Hb by venesection (removal of 400–500 mL blood) every 2 days. Target PCV is reduced to <0.5 and in females to <0.45. Treat any underlying cause.
• Polycythaemia vera: Venesect 400–500 mL weekly. Control marrow activity with hydroxycarbamide. Use targeted therapy with JAK1 and JAK2 agonists in patients who don’t respond to first-line therapy.