Cyanosis By Mayada Aly Moussa MD Lecturer of
Cyanosis By Mayada Aly Moussa, MD Lecturer of Internal medicine and Haematology Alexandria Faculty of Medicine
Definition Bluish discoloration of the skin and mucous membrane that results from: • when the absolute level of reduced hemoglobin (Deoxyhemoglobin) in the capillary bed exceeds 5 g/DL. (Normal reduced Hb 1 -2 gm/d. L or • Increased concentration of abnormal Hemoglobine derivatives (eg. Methemoglobinemia, sulphaemoglobinemia) in the superficial blood vessels.
Central cyanosis • Pathologic condition caused by reduced arterial oxygen saturation (SO 2) less than 85% • Involves highly vascularized tissues, such as the lips, tongue and mucous membranes, through which blood flow is brisk and the arteriovenous difference is minimal • Cardiac output typically is normal, and patients have warm extremities.
Causes of central cyanosis • Alveolar hypoventilation; COPD, massive fibrosis • Diffusion impairment • Ventilation-perfusion mismatch • Congenital heart disease; Right-to-left shunting at the intracardiac, great vessel, or intrapulmonary level • High altitude • Hemoglobinopathy (including methemoglobinemia , sulphaemoglobinemia) that limits oxygen transport
Peripheral cyanosis • Normal systemic arterial oxygen saturation and increased oxygen extraction from peripheral blood • The increased extraction of oxygen results from sluggish movement of blood through the capillary circulation; stagnation of blood in peripheral circulation • Affects the skin of distal extremities (not the mucous membrane, not the tongue).
Causes of peripheral cyanosis • • • Low cardiac output; shock Congestive heart failure Vasoconstriction ; Cold exposure Arterial or venous thrombosis Raynaud’s disease
Mixed type • All the causes of central cyanosis may lead to peripheral cyanosis.
Diagnostic clinical features of central cyanosis not present in peripheral cyanosis
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