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Chapter 035. Hypoxia and Cyanosis (Part 5)

PERIPHERAL CYANOSIS Probably the most common cause of peripheral cyanosis is the normal vasoconstriction resulting from exposure to cold air or water. When cardiac output is reduced, cutaneous vasoconstriction occurs as a compensatory mechanism so that blood is diverted from the skin to more vital areas such as the central nervous system and heart, and cyanosis of the extremities may result even though the arterial blood is normally saturated. Arterial obstruction to an extremity, as with an embolus, or arteriolar constriction, as in cold-induced vasospasm (Raynaud's phenomenon, Chap. 243), generally results in pallor and coldness, and there may be associated. | Chapter 035. Hypoxia and Cyanosis Part 5 PERIPHERAL CYANOSIS Probably the most common cause of peripheral cyanosis is the normal vasoconstriction resulting from exposure to cold air or water. When cardiac output is reduced cutaneous vasoconstriction occurs as a compensatory mechanism so that blood is diverted from the skin to more vital areas such as the central nervous system and heart and cyanosis of the extremities may result even though the arterial blood is normally saturated. Arterial obstruction to an extremity as with an embolus or arteriolar constriction as in cold-induced vasospasm Raynaud s phenomenon Chap. 243 generally results in pallor and coldness and there may be associated cyanosis. Venous obstruction as in thrombophlebitis dilates the subpapillary venous plexuses and thereby intensifies cyanosis. Approach to the Patient Cyanosis Certain features are important in arriving at the cause of cyanosis 1. It is important to ascertain the time of onset of cyanosis. Cyanosis present since birth or infancy is usually due to congenital heart disease. 2. Central and peripheral cyanosis must be differentiated. Evidence of disorders of the respiratory or cardiovascular systems are helpful. Massage or gentle warming of a cyanotic extremity will increase peripheral blood flow and abolish peripheral but not central cyanosis. 3. The presence or absence of clubbing of the digits see below should be ascertained. The combination of cyanosis and clubbing is frequent in patients with congenital heart disease and right-to-left shunting and is seen occasionally in patients with pulmonary disease such as lung abscess or pulmonary arteriovenous fistulae. In contrast peripheral cyanosis or acutely developing central cyanosis is not associated with clubbed digits. 4. PaO2 and SaO2 should be determined and in patients with cyanosis in whom the mechanism is obscure spectroscopic examination of the blood performed to look for abnormal types of hemoglobin critical in the .