Cardiac causes of cyanosis and shock typically present in the first 2 weeks of life and present in the critically ill neonate. The differential diagnosis, however, is broad at this age, and, in addition to congenital heart disease, the clinician should consider infection (sepsis, pneumonia), metabolic disease (see Chapter 79) and nonaccidental trauma. For the neonate presenting with cyanosis, the hyperoxia test helps to differentiate respiratory disease from cyanotic congenital heart disease (although imperfectly). When placed on 100% oxygen, the infant with cyanotic congenital heart disease will fail to demonstrate an increase in Pao2, while those with respiratory causes will often respond with an improvement in pulse oximetry.
Acral cyanosis (blue discoloration of the distal extremities) can be normal in the neonate, but central cyanosis (including the mucus membranes of the mouth) is the cardinal feature of cyanotic congenital heart disease. Appreciation of cyanosis in dark-skinned neonates may be difficult, and an accurate set of vital signs including pulse oximetry and 4-extremity blood pressures is essential. Cyanosis associated with a heart murmur strongly suggests congenital heart disease, but the absence of a murmur does not exclude a structural heart lesion. The cyanotic infant may be tachypnic, as well, though the increased respiratory rate in cyanotic heart disease is often effortless and shallow unless associated with congestive heart failure, which is rare in the first weeks of life.
Shock with or without cyanosis, especially during the first 2 weeks of life, should alert the clinician to the possibility of ductal-dependent congenital heart disease in which systemic (shock) or pulmonary (cyanosis) blood flow depends on patency of the fetal ductus arteriosis. Shock in the neonate is recognized by inspection of the patient's skin for pallor (or, more often, an “ashen grey” appearance), mottling, and cyanosis, and assessment of the mental status appropriate for age. Mental status changes include apathy, irritability, or frank lethargy. Tachycardia and tachypnea may be the initial signs of impending cardiovascular collapse. Distal pulses should be assessed for quality, amplitude, and duration, and a differential between preductal (right brachial) and postductal (femoral) pulses or blood pressure is classic for ductal-dependent lesions such as coarctation of the aorta.
Diagnosis and Differential
The workup for congenital heart disease begins with chest radiograph and electrocardiogram (ECG) with pediatric analysis. Chest radiographs are assessed for heart size, shape, and pulmonary blood flow. An abnormal right position of the aortic arch may be a clue to the diagnosis of congenital cardiac lesion. Increased pulmonary vascularity may be seen with significant left-to-right shunting or left-sided failure. Decreased pulmonary blood flow is seen with right-sided outflow lesions such as pulmonic stenosis. Cyanotic heart lesions often demonstrate right axis deviation and right ventricular hypertrophy on ECG while left outflow obstruction (eg, coarctation of the aorta) may show left ventricular hypertrophy. Echocardiography is generally required to define the diagnosis.
The differential diagnosis for cyanosis or shock due to congenital heart disease typically includes cyanotic lesions: transposition of the great vessels, tetralogy of Fallot, and other forms of right ventricular outflow tract obstruction or abnormalities of right heart formation. Acyanotic lesions that can present with shock include severe coarctation of the aorta, critical aortic stenosis, and hypoplastic left ventricle. It should be noted that cyanosis may accompany shock of any cause.
Transposition of the great vessels represents the most common cyanotic defect presenting in the first week of life. This entity is easily missed due to the absence of cardiomegaly or murmur (unless there is a coexistent ventricular septal defect [VSD]). Symptoms (before shock) include central cyanosis, increase respiratory rate, and/or feeding difficulty. There is usually a loud and single S2. Chest radiographs may show an “egg on a string” shaped heart with a narrow mediastinum and increased pulmonary vascular markings. ECG may show right-axis deviation and right ventricular hypertrophy.
Tetralogy of Fallot is the most common cyanotic congenital heart disease overall, and can present with cyanosis later in infancy or childhood. Physical examination reveals a holosystolic murmur of ventricular septal defect, a diamond-shape murmur of pulmonary stenosis, and cyanosis. Cyanotic spells in the toddler may be relieved by squatting. Chest radiograph may show a boot-shape heart with decreased pulmonary vascular markings or a right-sided aortic arch. The ECG often demonstrates right ventricular hypertrophy and right axis deviation.
Hypercyanotic episodes, or “tet spells,” may bring children with tetralogy of Fallot to the ED in dramatic fashion. Symptoms include paroxysmal dyspnea, labored respirations, increased cyanosis, and syncope. Episodes frequently follow exertion due to feeding, crying, or straining with stools and last from minutes to hours.
Left ventricular outflow obstruction syndromes may present with shock, with or without cyanosis. Several congenital lesions fall into this category, but in all these disorders, systemic blood flow is dependent on a large contribution of shunted blood through a patent ductus arteriosus. When the ductus closes, infants present with decreased or absent perfusion, pallor or an ashen appearance, hypotension, tachypnea, and severe lactic acidosis. Diminished lower extremity pulses and BP, particularly compared to right brachial pulse and BP, is classic for coarctation of the aorta.
Emergency Department Care and Disposition
Cyanosis and respiratory distress are first managed with high-flow oxygen, cardiac and oxygen monitoring, and a stable intravenous or intraosseous line. Caveat: Neonates tolerate low oxygen saturations well due to oxygen-avid fetal hemoglobin; oxygen is a potent pulmonary vasodilator and may lead to “pulmonary steal” of systemic blood flow, worsening systemic shock in ductal-dependent systemic blood flow such as coarctation of the aorta. Treatment with prostaglandins (see below) is critical in these instances.
For severe shock in infants suspected of having shunt-dependent lesions, prostaglandin E1 should be given in an attempt to reopen the ductus. Treatment begins with 0.05 to 0.1 microgram/kilogram/min; this may be increased to 0.2 microgram/kilogram/min if there is no improvement. Side effects include fever, skin flushing, diarrhea, and periodic apnea.
Immediate consultation should be obtained with a pediatric cardiologist and, if the patient is in shock, a pediatric intensivist.
Management of hypercyanotic spells consists of positioning the patient in the knee-to-chest position and administration of morphine sulfate 0.2 milligram/kilogram SC, IM, or IO. Resistant cases should prompt immediate consultation with a pediatric cardiologist for consideration of phenylephrine for hypotension or propranolol for tachycardia.
Noncardiac causes of symptoms should be considered and treated appropriately, including a fluid challenge of 10 to 20 mL/kg of normal saline solution, and empiric administration of antibiotics as indicated. Fluids should be administered more judiciously to neonates with congenital heart disease, typically in 10 mL/kg boluses.
Epinephrine is the initial drug of choice for hypotension. An infusion is started at 0.05 to 0.5 microgram/kilogram/min and titrated to the desired blood pressure.
By definition, these children are critically ill and require admission, usually to the neonatal or pediatric intensive care unit.