Search
cyanosis
Bluish discoloration of the skin & mucous membranes that occurs when the capillary content of reduced hemoglobin is > 5 g/dL.
Etiology:
1) central cyanosis
a) severe hypoxia (pO2 < 55 mm Hg)
b) mild hypoxia with
- polycythemia (red cyanosis)
- shock
- hemoglobin with low affinity for oxygen
c) decreased atmospheric pressure (high altitude)
d) impaired pulmonary function
- alveolar hypoventilation
- ventilation-perfusion mismatch
- impaired oxygen diffusion
e) anatomic shunt
- congenital heart defect
- pulmonary arteriovenous fistula
- multiple small intrapulmonary shunts
2) pseudocyanosis
- methemoglobinemia
- sulfhemoglobinemia
- argyria (from silver nitrate)
- hemochromatosis
- carboxyhemoglobin causes cherry red flush, not cyanosis
3) peripheral cyanosis
- reduced cardiac output
- cold exposure
- redistribution of blood flow from extremities
- arterial obstruction
- venous obstruction
4) anemia does not cause cyanosis
Pathology:
1) unsaturation of arterial hemoglobin
2) high tissue extraction of oxygen
3) decreased perfusion
Clinical manifestations:
1) bluish discoloration of the skin & mucous membranes
2) clubbing of fingers may be present in patients with pulmonary disease or congenital heart disease
3) massage or warming of cyanotic extremity with resolve peripheral, but NOT central cyanosis
Specific
acrocyanosis
lower extremity cyanosis
General
sign/symptom
References
- Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed)
Lippincott-Raven, Philadelphia, 1998, pg 720
- Harrison's Principles of Internal Medicine, 13th ed.
Isselbacher et al (eds), McGraw-Hill Inc. NY,
1994, pg 182
- Harrison's Principles of Internal Medicine, 14th ed.
Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 209