TY - CHAP M1 - Book, Section TI - Chapter 49. Approach to the Cyanotic Infant A1 - Steinhorn, Robin H. A2 - Rudolph, Colin D. A2 - Rudolph, Abraham M. A2 - Lister, George E. A2 - First, Lewis R. A2 - Gershon, Anne A. PY - 2011 T2 - Rudolph's Pediatrics, 22e AB - Cyanosis, or bluish discoloration of the skin, is derived from the Greek word kuaneos, meaning dark blue. Cyanosis is caused by the presence of deoxygenated hemoglobin in the blood vessels that is most visible on the surface of the skin and mucosa. In general, cyanosis occurs because (1) the binding of oxygen to hemoglobin is abnormal so that blood does not carry much oxygen despite having a normal partial pressure of oxygen, or PO2 (eg, methemoglobin or carboxyhemoglobin); (2) the perfusion of the skin is poor, such that the venous and capillary blood are very deoxygenated even though the arterial blood may be well oxygenated (eg, cold environment or circulatory shock); or (3) the arterial, and therefore the capillary and venous blood, is poorly oxygenated (eg, a right-to-left shunt with congenital cardiac disease, parenchymal pulmonary disease, or hypoventilation). Cyanosis tends to become apparent when there is about 3 to 5 g/dl of deoxygenated hemoglobin, but detection varies widely depending on lighting, observer differences, and pigmentation of the skin, among other factors. The oxygen binding capacity of the fetal hemoglobin in the newborn also alters the degree of desaturation at a given PaO2. For example, at a PaO2 45, the saturation of adult hemoglobin would fall below 80%, typically creating a cyanotic appearance but fetal hemoglobin saturation would remain in the mid 80s, which may not be associated with overt cyanosis (see eFig. 49.1). There is urgency to determine the cause of the cyanosis because of the high risk of tissue injury or death posed by poor oxygenation and in order to guide important interventions to improve tissue oxygenation. Although a specific diagnosis may not necessarily be determined at the bedside without special studies, the underlying nature of the disturbance usually can be derived with common clinical tools and the physical examination. SN - PB - The McGraw-Hill Companies CY - New York, NY Y2 - 2024/03/29 UR - accesspediatrics.mhmedical.com/content.aspx?aid=6734833 ER -