INTRODUCTION — Cyanosis is a bluish discoloration of the tissues that results when the absolute level of deoxygenated hemoglobin in the capillary bed exceeds 3 g/dL [1-3]. Cyanosis is a common clinical finding in newborn infants. Neonatal cyanosis, particularly central cyanosis, can be associated with significant and potentially life-threatening diseases, including pulmonary, cardiac, metabolic, neurologic, infectious, and hematologic disorders (table 1).
The etiology and evaluation of cyanosis in newborn infants will be reviewed here. Other related topics include:
PERIPHERAL VERSUS CENTRAL CYANOSIS
●Acrocyanosis – Acrocyanosis is often seen in healthy newborns and refers to peripheral cyanosis around the mouth and the extremities (hands and feet) (picture 1). It is a benign condition caused by vasomotor changes resulting from the transition from fetal to extrauterine life. These vascular changes often result in peripheral vasoconstriction and increased tissue oxygen extraction . (See "Physiologic transition from intrauterine to extrauterine life", section on 'Circulatory changes'.)
Acrocyanosis is differentiated from pathologic causes of peripheral cyanosis (eg, septic shock) by its clinical course. It occurs in otherwise healthy infants immediately after delivery and does not persist beyond 24 to 48 hours after birth.
●Peripheral cyanosis – In peripheral cyanosis, the concentration of deoxygenated hemoglobin on the venous side of the capillary bed is increased due to increased tissue oxygen extraction, whereas the systemic arterial oxygen saturation is normal. Peripheral cyanosis may be associated with peripheral vasoconstriction. It typically affects the distal extremities and sometimes the circumoral or periorbital areas . The extremities may be cool or clammy. In neonates with isolated peripheral cyanosis, the mucus membranes remain pink, which differentiates it from central cyanosis. It can be a benign (eg, acrocyanosis) or pathologic finding. Causes include cold exposure, sepsis, shock, venous obstruction, and polycythemia. Some of these causes may be associated with both central cyanosis and peripheral vasoconstriction. (See 'Causes of peripheral cyanosis' below.)
●Central cyanosis – Central cyanosis refers to reduced oxygen saturation in the arterial circulation. Newborn infants normally have central cyanosis until up to 5 to 10 minutes after birth, as the oxygen saturation rises to 85 to 95 percent by 10 minutes of age . Persistent central cyanosis is always pathologic and should be evaluated and treated promptly.
Mechanisms — Neonatal central cyanosis is most commonly due to hypoxia due to one or more of the following mechanisms:
●Alveolar hypoventilation – Although the primary effect of alveolar hypoventilation is hypercarbia (eg, recurrent apnea), decreased ventilation of the lung can cause hypoxemia and cyanosis. Causes of hypoventilation include central nervous system depression (eg, perinatal asphyxia), airway obstruction (choanal atresia), or neuromuscular disorders (eg, spinal muscular atrophy type 1).
●Ventilation-perfusion mismatch – Normally, areas of decreased ventilation are matched with decreased blood flow. Alterations of this relationship can cause hypoxemia and cyanosis (eg, neonatal pneumonia, pneumothorax).
●Right-to-left shunt – In right-to-left shunting, systemic venous blood bypasses ventilated alveoli and returns to the left side of the heart without being oxygenated, resulting in cyanosis. The site of shunting can be intracardiac (eg, cyanotic congenital heart disease [CCHD]), through the ductus arteriosus (eg, persistent pulmonary hypertension), or intrapulmonary (eg, perfusion of non-ventilated areas of the lung). (See "Cardiac causes of cyanosis in the newborn" and "Persistent pulmonary hypertension of the newborn (PPHN): Clinical features and diagnosis".)
●Diffusion impairment – Oxygen molecules must diffuse from the alveoli to the pulmonary capillaries to oxygenate hemoglobin. Interference with alveolar-arterial diffusion (eg, pulmonary edema) results in reduced oxygen saturation.
In addition, reduced arterial oxygen saturation can be caused by hemoglobinopathies that inadequately transport oxygen or polycythemia.
The etiology of persistent central cyanosis varies from a wide range of disorders that include cardiac, metabolic, neurologic, infectious, hematologic, and parenchymal and non-parenchymal pulmonary disorders (table 1). (See 'Causes of central cyanosis' below.)
Factors that affect cyanosis detection — The following factors can affect the detection of cyanosis:
●Hemoglobin concentration – The total hemoglobin concentration affects the level of oxygen saturation at which cyanosis is perceptible. This is because the perception of cyanosis depends upon the absolute concentration of deoxygenated hemoglobin, not the ratio of deoxygenated to oxygenated hemoglobin. Cyanosis is visually perceptible when deoxygenated hemoglobin exceeds 3 g/dL, which generally corresponds to an oxygen saturation level <85 percent in a neonate with a hemoglobin concentration of 15 g/dL (figure 1). In patients with polycythemia, cyanosis can be detected at higher oxygen saturations; whereas an anemic patient may not have perceptible cyanosis despite significant hypoxemia. For example, in a patient with a hemoglobin concentration of 8 g/dL, cyanosis is not perceptible until the oxygen saturation falls below 63 percent.
●Fetal hemoglobin – Fetal hemoglobin, the predominant form of hemoglobin in newborn erythrocytes, binds oxygen more avidly than adult hemoglobin, which aids in fetal uptake of oxygen from the placenta but results in less oxygen delivery to the tissues. The oxygen dissociation curve for fetal versus adult hemoglobin is shifted to the left, so that for a given level of arterial oxygen tension (PaO2), the arterial oxygen saturation (SaO2) is higher in newborns than older infants or adults (figure 2) . So for a given level of SaO2, there is a lower PaO2 value in newborns compared with older patients. As examples, when SaO2 is 50 percent, PaO2 is 20 mmHg in newborns and 27 mmHg in older patients; at SaO2 of 80 percent, PaO2 is 35 mmHg in newborns and 45 mmHg in older patients .
As a result, cyanosis is detected at a lower PaO2 in newborns who have predominantly fetal hemoglobin compared with older patients. This observation should prompt the measurement of PaO2 (eg, arterial blood gas) when evaluating a cyanotic newborn as the PaO2 provides more complete data than SaO2. (See 'Arterial blood gas' below.)
●Skin pigmentation – Cyanosis is often less apparent in patients with darker skin pigmentation. For this reason, examination should include the nail beds, tongue, and mucous membranes, which are less affected by pigmentation.
●Other factors – Other physiologic factors common in sick newborns affect the oxygen dissociation curve (figure 2).
•Factors that increase the affinity of hemoglobin for oxygen include alkalosis, hyperventilation (low PCO2), cold temperature, and low levels of 2,3 diphosphoglycerate . In these conditions, the oxygen dissociation curve is shifted to the left, which decreases the concentration of deoxygenated hemoglobin at a given PaO2 and lowers the PaO2 at which cyanosis first appears.
•In contrast, acidosis, fever, or increased concentration of adult hemoglobin shifts the curve to the right, thereby lowering oxygen affinity. As a result, at a given PaO2, these conditions increase oxygen delivery to the tissues resulting in a greater concentration of deoxygenated hemoglobin, and promote the appearance of cyanosis at a higher PaO2.
CAUSES OF PERIPHERAL CYANOSIS — Peripheral cyanosis is due to increased oxygen extraction that generally results from sluggish movement of blood through the capillary circulation. Causes include:
●Cold exposure and benign acrocyanosis (see 'Peripheral versus central cyanosis' above)
●Sepsis (see "Clinical features, evaluation, and diagnosis of sepsis in term and late preterm neonates" and "Clinical features and diagnosis of bacterial sepsis in preterm infants <34 weeks gestation")
●Elevated venous pressure or venous obstruction (eg, venous thrombosis) (see "Neonatal thrombosis: Clinical features and diagnosis")
●Polycythemia (see "Neonatal polycythemia")
CAUSES OF CENTRAL CYANOSIS — Causes of central cyanosis in the newborn can be categorized based on their primary pathophysiology (hypoventilation, ventilation/perfusion mismatch, diffusion impairment, right-to-left shunting and hematologic disorders) (table 1). (See 'Pathophysiology' above.)
Hypoventilatory disorders — Hypoventilation resulting in hypoxemia may be due to airway abnormalities, and neurologic or metabolic disorders.
Airway abnormalities — Most airway abnormalities will present shortly after birth; cyanosis due to the following conditions is generally a result of alveolar hypoventilation secondary to airway obstruction .
●Choanal atresia – While choanal atresia is usually unilateral, bilateral atresia will present immediately after birth (picture 2A-B) and should be suspected in an infant who develops respiratory distress and cyanosis while in a quiet state but becomes pink while crying. The diagnosis is suspected by the inability to pass a suction catheter through the nose into the oropharynx, and computed tomography will confirm the diagnosis (image 1). Placement of an oral airway should relieve the obstruction until definitive surgical therapy can be performed. Severe choanal stenosis also may present with respiratory distress and cyanosis . (See "Congenital anomalies of the nose", section on 'Choanal atresia'.)
●Micrognathia or retrognathia – Micrognathia or retrognathia that is severe enough to be symptomatic is readily apparent on physical examination. Airway obstruction is caused by the posterior tongue obstructing the retropharyngeal airway while the infant is supine. Generally, obstruction is relieved by placing the infant prone, but an oral airway may be necessary. Although some infants may require tracheotomy, surgical mandibular distraction may be performed in the newborn period and avoid the need for a tracheotomy . (See "Congenital anomalies of the jaw, mouth, oral cavity, and pharynx", section on 'Micrognathia' and "Syndromes with craniofacial abnormalities", section on 'Pierre Robin sequence'.)
●Laryngeal and tracheal abnormalities – Laryngeal and tracheal abnormalities include congenital laryngomalacia, vocal cord paralysis, tracheal stenosis, and vascular rings that cause external compression of the trachea. These conditions may all present soon after birth with airway obstruction, stridor, and cyanosis . Stridor and cyanosis is especially evident while the neonate is crying because the increased negative thoracic pressure causes greater airway obstruction. (See "Congenital anomalies of the larynx", section on 'Laryngomalacia' and "Congenital anomalies of the intrathoracic airways and tracheoesophageal fistula", section on 'Congenital tracheal stenosis' and "Vascular rings and slings".)
Neurologic disorders — Neurologic dysfunction, such as hypoxic ischemic encephalopathy, intracranial hemorrhage, or seizures may cause hypoventilation and apnea resulting in hypoxemia and cyanosis. (See "Clinical features, diagnosis, and treatment of neonatal encephalopathy" and "Germinal matrix and intraventricular hemorrhage (GMH-IVH) in the newborn: Risk factors, clinical features, screening, and diagnosis".)
Metabolic disorders — Metabolic disorders such as severe hypoglycemia may be complicated by apnea leading to intermittent episodes of hypoxemia and cyanosis. (See "Pathogenesis, screening, and diagnosis of neonatal hypoglycemia", section on 'Clinical presentation' and "Inborn errors of metabolism: Epidemiology, pathogenesis, and clinical features", section on 'Clinical manifestations'.)
Ventilation-perfusion mismatch — Pulmonary disease resulting in ventilation-perfusion mismatch is the most common cause of neonatal cyanosis. Newborn infants who present with cyanosis from lung disease will almost always have some degree of respiratory distress.
Specific causes associated with ventilation-perfusion mismatch, which are discussed in detail separately, include the following:
●Respiratory distress syndrome (RDS) (see "Respiratory distress syndrome (RDS) in the newborn: Clinical features and diagnosis")
●Transient tachypnea of the newborn (see "Transient tachypnea of the newborn")
●Meconium aspiration syndrome (see "Meconium aspiration syndrome: Pathophysiology, clinical manifestations, and diagnosis")
●Neonatal pneumonia (see "Neonatal pneumonia")
●Air leak syndromes (see "Pulmonary air leak in the newborn")
●Congenital abnormalities of the lung and diaphragm, including congenital diaphragmatic hernia and cystic adenomatoid malformation (see "Congenital diaphragmatic hernia in the neonate" and "Congenital pulmonary airway malformation")
Impaired alveolar-arterial diffusion — Pulmonary edema is the major cause of impaired alveolar-arterial diffusion that results in neonatal cyanosis. Pulmonary edema may be associated with both pulmonary and nonpulmonary disease. Examples of nonpulmonary causes of pulmonary edema include:
●Sepsis – In the early stages of sepsis, tachypnea is often a finding due to increased respiratory drive resulting in respiratory alkalosis in response to sepsis-related metabolic acidosis. In the later stages of sepsis, capillary leak may result in pulmonary edema with impaired alveolar-arterial diffusion and ventilation-perfusion mismatch. (See "Clinical features, evaluation, and diagnosis of sepsis in term and late preterm neonates", section on 'Clinical manifestations'.)
●Arteriovenous or venous malformations – Very large arteriovenous or venous malformations (eg, Vein of Galen malformation) may cause high-output cardiac failure and pulmonary edema resulting in respiratory distress and cyanosis. (See "Causes and pathophysiology of high-output heart failure", section on 'Causes and their mechanisms'.)
●Heart failure in patients with cyanotic congenital heart disease (CCHD). (See "Cardiac causes of cyanosis in the newborn", section on 'Left-sided obstructive lesions'.)
Disorders with right to left shunting — Conditions that result in right to left shunting of deoxygenated blood to the systemic circulation include intracardiac lesions and persistent pulmonary hypertension. Intrapulmonary lesions resulting in impaired ventilation/perfusion of affected alveoli also causes right to left shunting. (See 'Pulmonary disorders' above.)
Cyanotic congenital heart disease — Whenever a newborn presents with cyanosis, especially if respiratory distress is not present, CCHD should always be considered as a potential etiology. Neonates with CCHD may also develop pulmonary edema due to heart failure resulting in impaired alveolar-arterial diffusion, which contributes to cyanosis. The causes, evaluation, and initial management of CCHD are discussed separately. (See "Cardiac causes of cyanosis in the newborn" and "Diagnosis and initial management of cyanotic heart disease in the newborn".)
Persistent pulmonary hypertension of the newborn — Persistent pulmonary hypertension of the newborn (PPHN) is a condition in which the normal circulatory transition from fetal to newborn circulation fails to occur. In newborns with PPHN, the pulmonary vascular resistance remains abnormally elevated after birth, and right to left shunting of blood persists through the fetal circulatory channels (ductus arteriosus and foramen ovale). This shunting leads to severe hypoxemia and cyanosis. PPHN is most frequently associated with parenchymal lung disease, including meconium aspiration syndrome, neonatal pneumonia, and RDS. As a result, the majority of infants with PPHN will present with respiratory distress and cyanosis. However, idiopathic PPHN may also occur unaccompanied by underlying parenchymal lung disease. PPHN including its pathophysiology, clinical features, diagnosis, and management is discussed separately. (See "Persistent pulmonary hypertension of the newborn (PPHN): Clinical features and diagnosis" and "Persistent pulmonary hypertension of the newborn (PPHN): Management and outcome".)
Hemoglobinopathies — Hemoglobinopathies that inadequately transport oxygen can result in cyanosis. These disorders include methemoglobinemia (a genetic disorder in which the iron of heme is oxidized to the ferric state, which is unable to bind oxygen) and other rare variants of hemoglobin with low oxygen affinity. (See "Hemoglobin variants that alter hemoglobin-oxygen affinity" and "Hemoglobin variants that alter hemoglobin-oxygen affinity", section on 'Low oxygen affinity hemoglobin variants: Cyanosis'.)
Polycythemia — Neonatal polycythemia, usually defined as a hematocrit >65 percent or a hemoglobin concentration >22 g/dL, occurs in approximately 1 to 5 percent of births. It is observed more frequently in infants of diabetic mothers, with delayed clamping or stripping of the umbilical cord, chronic fetal hypoxia, and fetal growth restriction. (See "Neonatal polycythemia".)
Polycythemia can cause cyanosis by one of the two following mechanisms.
●Polycythemic infants may appear cyanotic with a normal oxygen saturation and PO2 because of their elevated hemoglobin concentration. However, cyanosis is unlikely to occur in infants with arterial oxygen saturation above 90 percent (figure 1).
●Polycythemia with associated hyperviscosity may interfere with pulmonary perfusion and result in PPHN . (See 'Persistent pulmonary hypertension of the newborn' above.)
RAPID ASSESSMENT AND STABILIZATION — Newborns with persistent central cyanosis after birth should be promptly evaluated and supportive measures should be provided to stabilize the neonate. Neonates who appear cyanotic with respiratory distress and/or poor perfusion warrant prompt initiation of respiratory support, measurement of pulse oximetry, and further cardiorespiratory support while targeting specific etiologies based upon the evaluation.
Additional details of neonatal resuscitation, cardiorespiratory support, and other interventions are provided in separate topic reviews:
●(See "Neonatal shock: Management".)
CONFIRMING HYPOXEMIA (PULSE OXIMETRY) — Measuring the peripheral oxygen saturation (SpO2) by pulse oximetry confirms the presence of clinically significant hypoxemia. (See "Respiratory support, oxygen delivery, and oxygen monitoring in the newborn", section on 'Pulse oximetry'.)
The SpO2 should be measured in both preductal (right hand) and postductal (either foot) locations. A difference of ≥4 percent between the pre- and postductal SpO2 suggests either congenital heart disease (eg, critical aortic stenosis or coarctation of the aorta) or persistent pulmonary hypertension of the newborn (PPHN). However, in infants with PPHN, if right-to-left shunting is predominantly through the foramen ovale rather than the ductus, pre- and postductal saturations may not be different. These cases are difficult to differentiate from cyanotic heart disease. (See "Persistent pulmonary hypertension of the newborn (PPHN): Clinical features and diagnosis", section on 'Pre- and postductal oxygen saturation' and "Identifying newborns with critical congenital heart disease".)
In many birthing centers, all newborns undergo routine pulse oximetry screening prior to discharge from the birth hospitalization. This is discussed separately. (See "Newborn screening for critical congenital heart disease using pulse oximetry".)
EVALUATION — The goals of evaluation are to determine the underlying cause of cyanosis so that intervention can be focused on correcting or addressing the consequences of the specific disorder. Evaluation of the cyanotic infant should systematically assess the infant for airway, pulmonary, cardiovascular, or other causes.
Neonates who are critically ill require immediate cardiorespiratory support to ensure sufficient organ/tissue perfusion and oxygenation. (See 'Rapid assessment and stabilization' above.)
In the stable cyanotic neonate or after stabilizing the critically ill infant, the evaluation is focused on differentiating amongst the possible causes of cyanosis.
History — The history may provide clues to the underlying etiology of neonatal cyanosis and should include a complete assessment of the following:
●Pregnancy and labor – Maternal diabetes may be associated with cyanotic heart disease, neonatal polycythemia, and hypoglycemia. Other important pregnancy and labor historical factors include the following:
•Polyhydramnios is associated with fetal airway, esophageal, and neurological conditions.
•Oligohydramnios is associated with renal defects and pulmonary hypoplasia. (See "Evaluation of congenital anomalies of the kidney and urinary tract (CAKUT)", section on 'Amniotic fluid'.)
•Prolonged rupture of the fetal membranes and peripartum maternal fever may be associated with neonatal sepsis. (See "Clinical features, evaluation, and diagnosis of sepsis in term and late preterm neonates", section on 'Maternal risk factors'.)
•Meconium staining of the amniotic fluid is associated with meconium aspiration syndrome and pulmonary hypertension of the newborn (PPHN). (See "Meconium aspiration syndrome: Pathophysiology, clinical manifestations, and diagnosis", section on 'Pulmonary findings' and "Persistent pulmonary hypertension of the newborn (PPHN): Clinical features and diagnosis", section on 'Clinical manifestations'.)
●Family risk factors including a history of cyanotic congenital heart disease (CHD) (table 2) or underlying hemoglobinopathy. (See "Identifying newborns with critical congenital heart disease", section on 'Risk factors'.)
Physical examination — The physical examination is central to determining the cause of cyanosis. In particular, signs of respiratory distress (eg, tachypnea, inter- and subcostal retractions, nasal flaring, and audible grunting) are suggestive of pulmonary disease, whereas abnormal cardiac findings (eg, abnormal heart rate and sounds, and pathologic murmurs) indicate a cardiac etiology .
However, some cardiac lesions may have a prominent component of respiratory distress (eg, obstructed total anomalous pulmonary venous return and left-sided obstructive disease); thus, its presence does not rule out congenital heart disease. As a result, both CHD and sepsis should be considered as the underlying diagnosis in any critically ill infant who presents with respiratory distress, cyanosis, poor perfusion and/or shock. Left-sided obstructive lesions in which ductal closure has severely affected systemic blood flow may be indistinguishable from severe sepsis on physical exam and usually requires echocardiographic confirmation of the diagnosis. (See 'Echocardiography' below.)
Respiratory assessment includes:
●Respiratory rate – The respiratory rate should be counted for a full minute to account for variations in rate and rhythm. A normal early rate in the newborn period is 40 to 60 breaths per minute. Neurologic or metabolic causes of cyanosis are usually associated with slow or irregular respirations or intermittent apnea, whereas pulmonary and cardiac disorders are associated with tachypnea.
●Chest wall movement – Neonates with respiratory disorders or airway obstruction may have intercostal, subcostal, or subxiphoid retractions in the highly compliant newborn chest wall.
●Other signs of neonatal respiratory disease include grunting, nasal flaring, and increased use of accessory respiratory muscles.
●Airway assessment – Signs of airway abnormalities include noisy breathing or stridor that may be indicative of laryngomalacia.
Cardiac examination includes:
●Assessment of heart rate, pulses, and perfusion
●Cardiac auscultation to detect any abnormality in the second heart sound or the presence of a heart murmur
●Four-extremity blood pressure (BP) to assist in detection of severe coarctation of the aorta or interrupted aortic arch lesions (see "Clinical manifestations and diagnosis of coarctation of the aorta", section on 'Neonates')
Cardiac findings suggestive of critical CHD are summarized in the table (table 3) and described in detail separately. (See "Identifying newborns with critical congenital heart disease", section on 'Physical examination'.)
Arterial blood gas — Measurement of the peripheral oxygen saturation (SpO2) by pulse oximetry is generally sufficient to confirm hypoxemia and asses the severity. However, direct measurement of the arterial oxygen tension (PaO2) with an arterial blood gas (ABG) provides a more accurate assessment of hypoxemia. ABG analysis is generally warranted in neonates with severe hypoxemia or if the pulse oximetry tracing is unreliable (eg, due to poor perfusion). Clinicians should be aware that the pain associated with an arterial puncture may cause agitation in the newborn, and a resultant decrease in the PaO2. (See "Respiratory support, oxygen delivery, and oxygen monitoring in the newborn", section on 'Arterial blood gas measurement'.)
Other parameters on the ABG include the arterial carbon dioxide tension (PaCO2) and measurements of acid-base status (pH, base excess, calculated bicarbonate level). An elevated PaCO2 suggests pulmonary disease. Metabolic acidosis generally indicates poor perfusion, which may be due to inadequate cardiac output or distributive shock. Many blood gas analyzers can also measure a lactate level, which provides additional information about perfusion and oxygen delivery to the tissues.
In methemoglobinemia, which is a rare cause of neonatal cyanosis, the oxygen saturation will be low, but the measured PaO2 will be normal, which would not be the case in other causes of cyanosis. (See "Methemoglobinemia".)
It is no longer routine practice to perform hyperoxia testing (ie, measuring the PaO2 with and without 100 percent oxygen). The hyperoxia test was used in the past to distinguish cyanotic CHD from pulmonary disorders. In the contemporary era, it is generally preferred to proceed directly to echocardiography if there is suspicion of cardiac disease. This is because echocardiography is readily available in most institutions, and it is far more accurate for distinguishing between CHD versus noncardiac causes of cyanosis. In addition, it is well recognized that there are potential harmful effects of exposing neonates to 100 percent oxygen, especially preterm neonates. The hyperoxia test should only be used if reliable echocardiography is not immediately available. The hyperoxia test and its interpretation are discussed in detail separately. (See "Diagnosis and initial management of cyanotic heart disease in the newborn", section on 'Hyperoxia test'.)
Other blood tests — Other laboratory studies include:
●Complete blood count (CBC) – This will identify neonates with polycythemia. (See "Neonatal polycythemia", section on 'Laboratory testing'.)
The CBC is generally not useful for establishing or excluding the diagnosis of neonatal sepsis, as discussed separately. (See "Clinical features, evaluation, and diagnosis of sepsis in term and late preterm neonates", section on 'Complete blood count'.)
●Blood glucose – Cyanosis due to apnea and poor perfusion can be seen in neonates with severe hypoglycemia. (See "Pathogenesis, screening, and diagnosis of neonatal hypoglycemia", section on 'Clinical presentation'.)
●Blood culture – Blood culture should be performed in all neonates with clinically significant cyanosis as sepsis is an important potential cause. (See "Clinical features, evaluation, and diagnosis of sepsis in term and late preterm neonates", section on 'Blood culture'.)
Chest radiograph — Chest radiography should be performed in all neonates with clinically significant hypoxemia. The chest radiograph will identify pulmonary disease. It can also demonstrate findings that may suggest CHD; however, the chest radiograph may be normal in some types of CHD.
●Pulmonary disease – In most neonatal pulmonary disorders, the lung fields will be abnormal. Examples include (see "Overview of neonatal respiratory distress and disorders of transition", section on 'Chest imaging'):
•Transient tachypnea of the newborn (TTN) (image 2) (see "Transient tachypnea of the newborn", section on 'Radiographic features')
•Respiratory distress syndrome (RDS) (image 3) (see "Respiratory distress syndrome (RDS) in the newborn: Clinical features and diagnosis", section on 'Chest imaging')
•Pneumonia (see "Neonatal pneumonia", section on 'Diagnostic imaging')
•Meconium aspiration syndrome (image 4) (see "Meconium aspiration syndrome: Pathophysiology, clinical manifestations, and diagnosis", section on 'Diagnosis')
•Congenital lobar emphysema (image 6) and congenital pulmonary airway malformation (image 7) (see "Radiographic appearance of developmental anomalies of the lung" and "Congenital lobar emphysema" and "Congenital pulmonary airway malformation")
●Cardiac disease – Findings suggestive of cardiac disease include (table 3) (see "Diagnosis and initial management of cyanotic heart disease in the newborn", section on 'Chest radiograph'):
•The situs of the heart, stomach, and liver - Abnormal configurations (eg, dextrocardia, right aortic arch, situs inversus) strongly suggest cardiac disease.
•Cardiac size and shape – These may also be abnormal in specific CHD lesions, such as Tetralogy of Fallot ("boot-shaped" heart) (image 8) and transposition of the great arteries ("egg-on-a-string"-shaped heart).
•Pulmonary vascular markings – Increased or decreased pulmonary vascular markings may be seen in cyanotic cardiac lesions (table 3). Decreased pulmonary vascular markings may also be seen in idiopathic pulmonary hypertension of the newborn. (See "Persistent pulmonary hypertension of the newborn (PPHN): Clinical features and diagnosis", section on 'Chest radiograph'.)
Echocardiography — Echocardiography generally differentiates between cardiac and non-cardiac causes of neonatal cyanosis. It should be performed in infants in the following clinical setting:
●Cyanosis out of proportion to lung pathology on chest radiography
●Persistent cyanosis despite supplemental oxygen and/or positive pressure ventilation
●Findings on physical exam and/or chest radiography suggestive of heart disease (table 3)
●Poor perfusion or shock
SUMMARY AND RECOMMENDATIONS
●Definition – Cyanosis is a bluish discoloration of the tissues that is perceptible when the absolute level of deoxygenated hemoglobin in the capillary bed exceeds 3 g/dL. It is a common clinical finding in newborn infants. (See 'Introduction' above.)
Factors that affect the detection of cyanosis include hemoglobin concentration, the presence of fetal hemoglobin, skin pigmentation, and other physiologic factors that affect the oxygen dissociation curve (eg, acid-base status, temperature of the infant, and levels of 2,3 diphosphoglycerate) (figure 2). (See 'Factors that affect cyanosis detection' above.)
●Peripheral versus central cyanosis
•Peripheral cyanosis – Peripheral cyanosis typically affects the distal extremities and sometimes the circumoral or periorbital areas. It can be a benign (eg, acrocyanosis (picture 1)) or pathologic finding. Causes include cold exposure, sepsis, shock, venous obstruction, and polycythemia. Some of these causes may be associated with both peripheral and central cyanosis. (See 'Causes of peripheral cyanosis' above.)
•Central cyanosis – Central cyanosis refers to reduced oxygen saturation in the arterial circulation. Newborn infants normally have central cyanosis until up to 5 to 10 minutes after birth. Persistent central cyanosis is pathologic and should be evaluated and addressed promptly. (See 'Causes of central cyanosis' above and 'Rapid assessment and stabilization' above.)
●Causes – Neonatal cyanosis can be associated with significant and sometimes life-threatening diseases due to cardiac, pulmonary, metabolic, neurological, infectious, and hematologic disorders (table 1). (See 'Causes of central cyanosis' above.)
●Evaluation – Infants with persistent cyanosis after birth should be promptly evaluated and treated as they are at-risk for potentially life-threatening consequences. The goals of the evaluation are to assess the severity of illness and to determine the underlying cause of cyanosis so that treatment can focus on correcting or managing the specific disorder. (See 'Evaluation' above.)
•Initial stabilization – Neonates who appear cyanotic with respiratory distress and/or poor perfusion warrant prompt initiation of respiratory support and further cardiopulmonary interventions, targeting specific etiologies based upon the evaluation. (See 'Rapid assessment and stabilization' above and "Neonatal resuscitation in the delivery room" and "Respiratory support, oxygen delivery, and oxygen monitoring in the newborn".)
•Pulse oximetry – Measuring the peripheral oxygen saturation (SpO2) confirms the presence of clinically significant hypoxemia. The SpO2 should be measured in both preductal (right hand) and postductal (either foot) locations. (See 'Confirming hypoxemia (pulse oximetry)' above and "Respiratory support, oxygen delivery, and oxygen monitoring in the newborn", section on 'Pulse oximetry'.)
•History – The history may identify maternal or perinatal conditions, or family history that provides clues to the underlying cause. (See 'History' above.)
•Examination – Physical examination findings may point to an underlying cause. For example, signs of respiratory distress (tachypnea, retractions, nasal flaring, grunting) suggest likely pulmonary disease, whereas abnormal cardiac findings (abnormal heart sounds, pathologic murmurs) suggest a cardiac etiology. (See 'Physical examination' above and "Identifying newborns with critical congenital heart disease", section on 'Physical examination'.)
•Diagnostic tests – Tests that are helpful in assessing the severity of hypoxemia and differentiating among the various underlying causes of hypoxemia include (see 'Diagnostic tests' above):
-Arterial blood gas (see 'Arterial blood gas' above)
-Complete blood count (see 'Other blood tests' above)
-Blood glucose (see 'Other blood tests' above)
-Chest radiograph (see 'Chest radiograph' above)
-Echocardiography (see 'Echocardiography' above)
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