Cyanotic Newborn (Case 38)

Chapter 79 Cyanotic Newborn (Case 38)

Ganga Krishnamurthy, MD

Case

A newborn infant is noted to be cyanotic soon after birth.

Differential Diagnosis

Cyanotic congenital heart defect	Primary pulmonary disease
Neuromuscular condition associated with cyanosis	Persistent pulmonary hypertension of the newborn (PPHN)

Speaking Intelligently

The first step in evaluating a cyanotic infant is to distinguish between central cyanosis and peripheral cyanosis. Cyanosis is defined as a bluish discoloration of the skin and mucous membranes and is indicative of the presence of at least 3 to 5 g/dL of reduced hemoglobin in the circulation. A newborn infant often appears blue at birth. However, as the lungs assume the responsibility of becoming the organ of gas exchange following delivery, newborn infants who have undergone a normal transition will rapidly become pink. Although peripheral cyanosis occurs as a result of peripheral vasoconstriction and sluggish blood flow, central cyanosis is more ominous. If cyanosis is present without apparent respiratory distress, the likelihood of underlying cardiac disease is high on the differential and should lead to a prompt assessment of preductal and postductal saturation evaluations, four-extremity blood pressure measurement, chest radiograph study, electrocardiogram (ECG), arterial blood gas estimation, and echocardiography, all of which should guide the practitioner to an accurate diagnosis. Prostaglandin therapy may need to be started promptly if a ductal-dependent lesion is suspected.

Patient Care

Physical Examination

• Vital signs, including temperature, heart rate, respiratory rate, and four-extremity blood pressure recordings should be taken. Infants with serious underlying congenital heart defects often have a normal heart rate and blood pressure.

• Preductal (right arm) and postductal (leg) oxygen saturation indicate arterial supply before and after the ductus arteriosus, respectively. Hence, a pulse-oximetry probe placed on the right hand will indicate the saturation of blood flowing through the arterial distribution of the right subclavian artery, a preductal blood vessel. A differential greater than 15% between preductal and postductal saturation may indicate persistent pulmonary hypertension.

• Physical examination should distinguish central from peripheral cyanosis. Infants with a good cardiac output status will be warm and well perfused with good distal pulses and warm extremities. A polycythemic infant may appear “ruddy” and may have peripheral cyanosis because of sluggish peripheral blood flow.

• The presence of any phenotypic abnormalities suggestive of an underlying genetic disorder should be noted.

• Infants with an underlying pulmonary cause will have an increase in work of breathing.

• Precordial activity, heart sounds and the presence of a murmur should be noted. A normal precordial and auscultatory examination does not exclude serious underlying heart disease.

Clinical Entities: Medical Knowledge

Cyanotic Congenital Heart Defect
Pϕ	Cyanosis in the clinical setting of congenital heart disease is due to admixture of desaturated and saturated blood or, alternatively, decreased pulmonary blood flow. Examples of cyanotic congenital heart defects include truncus arteriosus, transposition of the great arteries, tetralogy of Fallot with pulmonary stenosis, critical pulmonary stenosis, pulmonary atresia with intact ventricular septum, tricuspid atresia, and total anomalous pulmonary venous connection.
TP	Cyanosis associated with congenital heart disease is not usually accompanied by increase in the work of breathing, an important distinguishing characteristic from respiratory causes. For those lesions in which pulmonary blood flow is dependent on the patent ductus arteriosus, cyanosis may only become evident or worsen as the ductus arteriosus closes and pulmonary blood flow becomes compromised.
Dx	Accurate diagnosis may follow careful clinical examination, interpretation of the hyperoxia test, EKG, and chest radiograph and is generally confirmed by echocardiography. Infants with a cyanotic heart defect will have an abnormal hyperoxia test (i.e., the PaO₂ does not increase significantly after administration of 100% oxygen) because the hypoxia is due to right-to-left shunting and not to abnormal oxygenation in the lungs. The presence of cyanosis, an ejection systolic murmur in the pulmonary area, oligemic lung fields, and normal rightward axis on ECG leads to the likely diagnosis of critical pulmonary stenosis. The typical presentation of transposition of the great arteries is a cyanotic infant without a murmur, with a postductal saturation that is much higher than the preductal saturation, and a narrow superior mediastinal shadow on radiography.
Tx	Urgent consultation with a pediatric cardiologist is the first step. Most lesions, including transposition of the great arteries and total anomalous pulmonary venous return, will need surgical intervention in the newborn period. Transcatheter intervention is the first line of treatment in infants with critical pulmonary stenosis. Some lesions such as tetralogy of Fallot without significant obstruction to pulmonary blood flow may not need surgery in the newborn period but will require surgical intervention later on in infancy. See Nelson Essentials 144.

Primary Pulmonary Disease
Pϕ	Newborn infants with primary pulmonary disease such as GBS pneumonia, meconium aspiration syndrome, respiratory distress syndrome, intrapleural collection of air or fluid, or airway anomalies may present with cyanosis. Cyanosis is due to defective oxygenation secondary to primary lung disease.
TP	Cyanosis secondary to a pulmonary etiology is usually accompanied by an increase in work of breathing. Auscultation may reveal abnormal air entry and adventitious sounds.
Dx	Diagnosis can be made by careful review of maternal and infant history, physical examination, and chest radiograph. CBC may reveal leukocytosis and bandemia in infants with pneumonia. ABG with significant hypoxia and hypercarbia suggests significant impairment of oxygenation and minute ventilation.
Tx	Defects in oxygenation or minute ventilation may be ameliorated or corrected by respiratory interventions, including oxygen, noninvasive ventilation (continuous positive airway pressure [CPAP]), or endotracheal intubation and mechanical ventilation. Antibiotic therapy is often needed. Surfactant replacement is required if the underlying defect is associated with surfactant deficiency. See Nelson Essentials 136.

Persistent Pulmonary Hypertension of the Newborn
Pϕ	Pulmonary vascular resistance is high during fetal life and rapidly decreases after birth. Failure to follow this normal transition is called persistent pulmonary hypertension of the newborn (PPHN). It is anatomically described as persistence of fetal circulation due to failure of the closure of the foramen ovale and persistence of the patent ductus arteriosus.
TP	The manifesting features may be reflective of the underlying etiology of PPHN. These infants have differential cyanosis with postductal arterial saturations significantly lower than the preductal saturation.
Dx	Chest radiograph, history, and physical examination may help in differentiating the etiology of PPHN. Echocardiography provides evidence to support and quantify the degree of pulmonary hypertension.
Tx	Defects in oxygenation and minute ventilation may be corrected by respiratory interventions. These include placement on conventional or high-frequency oscillatory mechanical ventilation to provide oxygen as well as adjunctive therapy such as inhaled nitric oxide. Both oxygen and nitric oxide are pulmonary vasodilators. Antibiotic therapy is often needed. Placement on extracorporeal membrane oxygenation (ECMO) may be required if adequate oxygenation cannot be achieved with conventional therapy. See Nelson Essentials 61.

Neuromuscular Condition Associated With Cyanosis
Pϕ	Infants who fail to achieve adequate ventilation will present with cyanosis. Infants with neuromuscular abnormalities such as spinal muscular atrophy type I or nemaline myopathy may present in the newborn period. The cyanosis is secondary to inadequate respiratory effort as a result of profound hypotonia.
TP	Severe neurologic or neuromuscular lesions may manifest in the newborn period with hypotonia. There may be an antecedent maternal history of poor fetal movements, persistent breech presentation, or polyhydramnios.
Dx	Additional testing is required to elucidate the etiology. Tests include serum creatine phosphokinase (CPK), serum and cerebrospinal fluid lactate and pyruvate, electromyography, nerve conduction velocity tests, and muscle biopsy. Genetic tests for triplet repeat sequence, fragile X, and other inherited abnormalities may be indicated. Neurologic examination of the mother may assist in the diagnosis of muscular dystrophy.
Tx	Attention must first be placed on securing the airway if needed and monitoring the adequacy of breathing. Endotracheal intubation and placement on mechanical ventilation may be needed. Further treatment is based on the underlying diagnosis and in many cases may be only supportive. See Nelson Essentials 182.

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Tags: Pediatrics A Competency-Based Companion

Jul 18, 2016 | Posted by admin in PEDIATRICS | Comments Off

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