is congenital heart disease Although most newborns with cyanotic congenital heart disease are recognized in utero or while in the newborn nursery, on occasion, such a newborn will initially present to the emergency department (ED) in the first few days or weeks of life with cyanosis One condition particularly prone to such late presentation is tetralogy of Fallot with pulmonary atresia When the ductus closes, profound cyanosis ensues Rarely, an infant with mild tetralogy of Fallot (or “pink tet”) may present with intermittent cyanosis during a “tet” or “hypercyanotic” spell These self-limited episodes are caused by increased right-to-left shunting and decrease in pulmonary blood flow The causes of cyanotic congenital heart disease are listed in Table 21.1 (II,A) TABLE 21.3 LIFE-THREATENING CAUSES OF CYANOSIS I Respiratory A Decreased inspired O2 concentration B Upper airway obstruction/disruption C Chest wall immobility D Tension pneumothorax E Massive hemothorax F Lung disease leading to hypoxemia II Vascular A Cardiac Cyanotic congenital defects Congestive heart failure Cardiogenic shock B Pulmonary Pulmonary edema Primary pulmonary hypertension of the newborn Pulmonary embolism Pulmonary hemorrhage C Peripheral Septic shock III Other A Neurologic conditions leading to hypoxemia B Severe methemoglobinemia Cyanosis may also be caused by pulmonary congestion from cardiac failure or left-to-right shunt lesions leading to increased pulmonary blood flow and diminished diffusion of O2 across the blood–gas barrier (see Chapter 86 Cardiac Emergencies ) Several pulmonary vascular abnormalities can also lead to cyanosis These include primary pulmonary hypertension of the newborn or pulmonary hypertension from other causes When pulmonary pressures are high, blood is shunted away from the lungs and the child becomes hypoxemic Pulmonary embolism and pulmonary hemorrhage, although rare in children, also impair lung perfusion and must be considered Low perfusion states may lead to local or peripheral cyanosis, particularly of the hands, feet, and lips Moderate cold exposure, for example, can result in local blueness Patients in septic or cardiogenic shock may have perfusion-related cyanosis as a result of pump failure Poor perfusion can also result from hyperviscous states such as polycythemia or leukemia Acrocyanosis, or blueness of the hands and feet with preserved pinkness centrally, is seen commonly in newborns and is related to variable perfusion in the extremities It is seen in wellappearing babies and resolves within the first few days of life Neurologic conditions can also lead to Hb deoxygenation and cyanosis Patients who hypoventilate because of central nervous system (CNS) depression, whether from primary CNS lesions or drugs/toxins that depress the respiratory center, are often centrally cyanotic at presentation to the ED Episodic blue spells in infants and young children who are otherwise well may be caused by breath holding, especially when associated with a sudden insult such as fear, pain, frustration, or anger (see Chapter 126 Behavioral and Psychiatric Emergencies ) Cyanosis may be noted as part of the picture in an infant with a brief resolved unexplained event (BRUE) Seizures are often associated with cyanosis from inadequate respiration during the convulsion A variety of neuromuscular diseases that affect chest wall or diaphragmatic function may ultimately lead to hypoventilation With respect to the Hb molecule itself, methemoglobinemia is an unusual but important reason for presentation to the pediatric ED Methemoglobinemia can be either congenital or acquired Congenital methemoglobinemia is caused by either Hb variants designated M hemoglobins or deficiency of NADH-dependent methemoglobin reductase The more common acquired form occurs when red blood cells are exposed to oxidant chemicals or drugs Methemoglobinemia has also been associated with diarrheal illnesses in children Young infants are particularly susceptible to the development of methemoglobinemia as a result of immature enzyme systems required to reduce Hb Even at low levels, skin discoloration is prominent, often with intense or “slate gray” cyanosis from the presence of methemoglobin beneath the skin (see Chapter 93 Hematologic Emergencies ) Other conditions leading to a blue appearance of the skin may be confused with cyanosis A rare but perplexing presentation is that of the well-appearing child with unusually localized cyanosis, which can be related to blue dye of clothing Slate blue discoloration of the face, neck, and arms has been noted in patients on chronic amiodarone therapy Certain pigmentary lesions such as Mongolian spots (also known as slate gray nevi) can be confused with cyanosis, especially when uncharacteristically large or in unusual locations Adolescents will occasionally tattoo areas of the body that may be misinterpreted as local cyanosis EVALUATION AND DECISION A careful yet rapid history and physical examination are critical in the care of the cyanotic patient because timely correction may be lifesaving Many historical features can help narrow the differential diagnosis and lead to prompt evaluation and treatment The onset and pattern, location, quality, temporal nature, and presence of palliative or provocative features should be explored Age of the patient with respect to onset of cyanosis, whether at birth, shortly after birth, or acquired later, is critical In newborns, congenital cardiac and respiratory diseases are the most common causes of cyanosis Special attention must also be paid to known pre-existing heart or lung disease that may predispose to the acute onset of cyanosis History of exposure to environmental conditions or toxins, such as cold, trauma, smoke inhalation, confinement to an airtight space, drugs, or chemicals, is crucial Known patient or family history of methemoglobinemia may lead directly to the cause of cyanosis A history of sudden pain or fear with crying or seizure occurrence should be sought The physical examination must include a complete general examination, with special attention paid to the vital signs, oxygen saturation, and cardiovascular and pulmonary systems A key physical examination feature is the presence or absence of respiratory distress In general, children with respiratory distress are likely to have respiratory dysfunction, and careful examination of the airway, breathing, and circulation should be rapidly initiated A temperature should be obtained Presence of cough, “sniffing position,” stridor, retractions, or fever should be determined Lung examination may reveal adventitious (e.g., wheezing or rales) or diminished breath sounds Presence of a cardiac murmur often suggests cardiac disease Careful attention to the peripheral circulation, including pulses and capillary refill is also helpful A rapid neurologic examination should be performed FIGURE 21.1 Evaluation of cyanosis EKG, electrocardiogram; CNS, central nervous system Location of cyanosis helps determine its cause Cyanosis may be either central or peripheral in location Central cyanosis is noted in the mucous membranes, tongue, trunk, and upper extremities It is most often the result of decreased PaO2 but can also result from severe methemoglobinemia or polycythemia If the cyanosis is peripheral only (hands, feet, lips), moderate cold exposure, newborn acrocyanosis ( e-Figs 21.1 and 21.2 ), shock states, or mild methemoglobinemia may be the cause Local blue discoloration of a single extremity corresponds to compromise of distal circulation or autonomic tone as seen in traumatic vascular lesions or complex regional pain syndrome Cyanosis and swelling of just the head may be seen with superior vena cava syndrome In addition, a local blue hue to the skin may also be a result of simple phenomena such as pigmentary lesions or blue clothing dye If blue coloring appears on an alcohol swab wiped across the discolored area of skin, dye is responsible ( eFig 21.3 ) Differential cyanosis of the lower body versus the upper body may indicate high pulmonary vascular resistance with right-to-left shunting via the ductus arteriosus Transposition of the great arteries with pulmonary-to-aortic ... Hb molecule itself, methemoglobinemia is an unusual but important reason for presentation to the pediatric ED Methemoglobinemia can be either congenital or acquired Congenital methemoglobinemia