Cyanosis

Last Updated on by FRCEM Intermediate

CENTRAL CAUSES

  • decreased arterial oxygen saturation
    -> decreased FiO2 (altitude)
    -> lung disease (COPD)
    -> V/Q mismatch (PE)
    -> right to left shunt (cyanotic congenital heart disease)
  • polycythaemia
  • haemoglobin abnormalities (methaemoglobinaemia, sulphaemoglobinaemia)

PERIPHERAL CAUSES

  • all causes of central cyanosis cause peripheral cyanosis
  • exposure to cold
  • reduced cardiac output (cardiogenic shock, LVF)
  • arterial or venous obstruction

CAUSES OF CYANOTIC CONGENITAL HEART DISEASE

5 Ts

  • Tetralogy of Fallot (TOF)
  • Transposition of the Great Arteries (TGA) — PA and aorta are reversed
  • Truncus Arteriosus — both RV and LV flow into one artery
  • Tricuspid Atresia — leads to shunt through patent PFO, RV is non-functional)
  • Total Anomalous Pulmonary Venous Connection (TAPVC) — APO results from obstructed pulmonary venous drainage, PGE1 doesn’t work for this

Other

  • Pulmonary atresia (absent connection between RV and PA) is also a rare cause of cyanotic congenital heart disease)
  • Eisenmenger’s syndrome (an acyanotic lesion causing left-to-right shunt can lead to pulmonary hypertension if untreated, the raised PA pressures ultimately cause shunt reversal and cyanosis)

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