Haemoglobin

Haemoglobin A (HbA)

  • Main type of Hb in adult blood
  • Comprised of 2 alpha and 2 beta chains

Haemoglobin A2 (HbA2)

  • 1.5 to 3% of adult blood
  • 2 delta chains instead of 2 beta chains

Fetal haemoglobin (HbF)

  • Main type of Hb during intrauterine development
  • Levels reduce during infancy to around 0.5% in adult venous blood

Carboxyhaemoglobin (COHb)

  • Hb affinity for CO more than 200 times greater than for oxygen – this means it displaces oxygen and is only slowly released
  • Normal range in non-smokers is < 1.5% adult venous blood
  • In smokers levels up to 5% adult venous blood

Methaemoglobin (MetHb)

  • Formed when the iron within haemoglobin is oxidied to the ferric state (FE3+)
  • Not able to participate in respiratory function as it cannot bind oxygen
  • Normal levels < 1% adult venous blood

Oxyhaemoglobin (OxyHb)

  • In adult venous blood this is usually around 70%

Free Hb

  • Can be used as a measure of haemolysis
  • Normal levels in adult venous blood < 0.00004%
  • Levels can be impacted by phlebotomy technique

Useful sources

  1. Goljan, EF. (2014) Rapid Review: PathologyPhiladelphia: Elsevier Saunders.
  2. Rhoades, RA and Bell, DR. (2009) Medical Physiology: Principles for Clinical MedicinePhiladelphia: Wolters Kluwers.
  3. Hammond, E and McIndoe, A. (1997) QBase Anaesthesia: Volume 1, MCQs for the Anaesthesia Primary: MCQs for the Primary FRCA v. 1. London: Greenwich Medical Media.
  4. Na, N, et al. (2005) Serum free hemoglobin concentrations in healthy individuals are related to haptoglobin type. Clinical Chemistry, 51(9), 1754-1755.

What’s Next?

Oxygen dissociation curve

Haemoglobinopathies

Test Me

Link to questions on this topic

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