Cyanosis becomes visible when there is >3–5 g/dL of deoxygenated hemoglobin/dL. The degree of cyanosis depends on both oxygen saturation and hemoglobin concentration. Cyanosis can be a sign of severe cardiac, respiratory, or neurologic compromise. The most common etiology of cyanosis in a newborn infant is respiratory. Cyanosis can also be caused by a reduced blood oxygen–carrying capacity secondary to an abnormal form of hemoglobin, such as methemoglobinemia. Cyanosis may not be apparent in a severely anemic infant or may be difficult to see in a darkly pigmented newborn. The causes of cyanosis can be classified as arising from respiratory, cardiac, central nervous system (CNS), or other disorders.
Respiratory diseases. Include primary pulmonary diseases, airway obstruction, and extrinsic compression of the lungs and congenital defects. Pulmonary diseases are the most common cause of cyanosis in the newborn.
Primary pulmonary diseases. Respiratory distress syndrome (RDS), TTN, aspiration syndromes, pneumonia, bronchopulmonary dysplasia/chronic lung disease (BPD/CLD), pulmonary interstitial emphysema (PIE), pulmonary hemorrhage.
Airway obstruction. Mucous plug, Pierre Robin syndrome, choanal atresia, vocal cord paralysis, macroglossia, atelectasis, and others.
External compression of the lungs. Any air leak syndrome, pleural effusion, and others.
Congenital defects. Congenital diaphragmatic hernia, pulmonary hypoplasia, cystic adenomatoid malformation, lobar emphysema, and others.
Infections. Sepsis is the second most common cause of cyanosis in infants. Sepsis causes increased oxygen utilization, which results in cyanosis. Meningitis can also present with cyanosis.
Hypotension and shock. This can be secondary to sepsis, cardiogenic, neurogenic, or hypovolemic, and all can present with cyanosis. (See Chapter 65.)
Cardiac diseases. The majority of congenital heart diseases that present in the first couple of weeks of life are ductal-dependent cardiac lesions.
All cyanotic heart diseases which include the 5 T's. Transposition of the great arteries is the most common cyanotic congenital heart disease in newborns.
Transposition of the great arteries.
Total anomalous pulmonary venous return.
Tricuspid atresia.
Tetralogy of Fallot.
Truncus arteriosus.
Sixth T (“tons of others”/”terrible T's”) includes all the others: severe pulmonic stenosis, double outlet right ventricle, pulmonary atresia with intact ventricular septum/or with ventricular septal defect (VSD), variations on single ventricle, Ebstein anomaly of the tricuspid valve, hypoplastic heart syndrome with intact foramen ovale (no mixing at the atrial level), and others.
Persistent pulmonary hypertension of the newborn (PPHN). In PPHN, infants do not transition from fetal to newborn circulation. Pulmonary hypertension causes right-to-left shunting of blood, a decrease in pulmonary blood flow, and cyanosis.
Severe congestive heart failure. This can occur from cardiomyopathies (infant of diabetic mother [IDM], inborn errors of metabolism, genetic or neuromuscular disease), myocarditis (bacterial or viral), congenital cardiac disease, sepsis, perinatal asphyxia, and sustained tachyarrhythmias.
Pneumopericardium or pericardial effusion.
Other congenital anomalies such as those associated with cardiac malformations: Turner syndrome, Noonan syndrome, etc. Pulmonary arteriovenous malformation is a rare cause of cyanosis in the newborn.
Central nervous system diseases. CNS disorders can cause apnea, seizures, and decreased respiratory effort.
Infectious. Bacterial or viral CNS infection (meningitis, encephalitis).
Seizures. Infection, metabolic, CNS injury, genetic syndrome, congenital disorder, primary seizure disorder.
Hypoxic ischemic encephalopathy (HIE).
Hemorrhage. Periventricular/intraventricular hemorrhage, subdural hemorrhage, subarachnoid hemorrhage, intracerebellar hemorrhage, infarction.
Congenital disorders. Congenital hydrocephalus, spinal muscle atrophy, congenital central hypoventilation syndrome.
Drug toxicity (opioid toxicity).
Neuromuscular disorders. Werdnig-Hoffman disease, Pompe disease, Barth syndrome, Duchenne or Becker muscular dystrophy, limb-girdle muscular dystrophy, congenital myopathy, neonatal myasthenia gravis, phrenic nerve injury, and congenital myotonic dystrophy.
Hematologic disorders. A hemoglobin disorder can interfere with the transport of oxygen and cause cyanosis.
Methemoglobinemia (normal arterial O2). Because the arterial blood is brown in color, it gives off a bluish hue in the skin of Caucasian people. It can be congenital (familial) or secondary to a toxin (medications such as eutectic mixture of lidocaine and prilocaine [EMLA], sulfonamides, others) or environmental substances.
Polycythemia/hyperviscosity syndrome (normal arterial O2). Infants with this can present with peripheral cyanosis, tachypnea, congestive heart failure (CHF), and cardiomegaly. Cyanosis is detectable at a higher value of Sao2. Polycythemia can cause pulmonary hypertension.
Severe anemia from hemorrhage or bleeding disorders.
Metabolic abnormalities can present with apnea and cyanosis
Drug withdrawal.
Hypoglycemia, hypermagnesemia, severe metabolic acidosis.
Inborn errors of metabolism.
Rarely abnormalities of calcium, potassium, and phosphorus can cause hypoxia and cyanosis. Calcium and potassium abnormalities can cause cardiac arrhythmias.
Other disorders
Apnea and bradycardia
Hypothermia
Hypoadrenalism/hypopituitarism
Abdominal distension with elevation of the diaphragm
Respiratory depression secondary to maternal medications (eg, magnesium sulfate and narcotics) or sedation
Pseudocyanosis. Caused by fluorescent lighting.