cyanosis

Introduction

Bluish discoloration of the skin & mucous membranes that occurs when the capillary content of reduced hemoglobin is > 5 g/dL.

Etiology

• central cyanosis
  • severe hypoxia (pO2 < 55 mm Hg)
  • mild hypoxia with
    • polycythemia (red cyanosis)
    • shock
    • hemoglobin with low affinity for oxygen
  • decreased atmospheric pressure (high altitude)
  • impaired pulmonary function
    • alveolar hypoventilation
    • ventilation-perfusion mismatch
    • impaired oxygen diffusion
  • anatomic shunt
    • congenital heart defect
    • pulmonary arteriovenous fistula
    • multiple small intrapulmonary shunts
• pseudocyanosis
  • methemoglobinemia
  • sulfhemoglobinemia
  • argyria (from silver nitrate)
  • hemochromatosis
  • carboxyhemoglobin causes cherry red flush, not cyanosis
• peripheral cyanosis
  • reduced cardiac output
  • cold exposure
  • redistribution of blood flow from extremities
  • arterial obstruction
  • venous obstruction
• anemia does not cause cyanosis

Pathology

• unsaturation of arterial hemoglobin
• high tissue extraction of oxygen
• decreased perfusion

Clinical manifestations

• bluish discoloration of the skin & mucous membranes
• clubbing of fingers may be present in patients with pulmonary disease or congenital heart disease
• massage or warming of cyanotic extremity with resolve peripheral, but NOT central cyanosis

More general terms

• sign/symptom

More specific terms

• acrocyanosis
• lower extremity cyanosis