576 SECTION V Pediatric Critical Care Pulmonary In all cases, surgical resection is indicated 98 The prognosis for infants who have a bronchogenic cyst, whether mediastinal or pulmonary, is good 99 Pu[.]
576 S E C T I O N V Pediatric Critical Care: Pulmonary In all cases, surgical resection is indicated.98 The prognosis for infants who have a bronchogenic cyst, whether mediastinal or pulmonary, is good.99 Pulmonary Parenchymal Cysts Pulmonary parenchymal cysts may represent a disorder of bronchial growth, although they may alternatively be acquired Like adenomatoid malformations and bronchogenic cysts, congenital cysts arise early in fetal life Pulmonary parenchymal cysts are thought to develop when completion of the terminal bronchioles and development of the alveoli occur Pulmonary cysts are typically thin walled, singular, multilocular, and located in the periphery Unlike bronchogenic cysts, some communication usually exists between the pulmonary cyst and the tracheobronchial tree; thus approximately 75% fill with air Like adenomatoid malformations, pulmonary cysts contain mostly elastic tissue and little or no cartilage Although pulmonary cysts are generally small (1–2 cm in diameter), they can expand dramatically and are much more likely to cause respiratory insufficiency than are bronchogenic cysts As in adenomatoid malformations, an absence of cartilaginous support leads to trapping of air However, unlike adenomatoid malformations, pulmonary cysts are rarely associated with other anomalies Rupture of a peripheral cyst can result in a pneumothorax Rarely, multiple cysts occur, which may extensively involve both lungs These cases are generally fatal within the perinatal period Chest radiographs typically reveal thin-walled, round cysts with an air density Often, faint strands of lung tissue can be seen within the cysts A large pulmonary cyst may be confused with congenital lobar emphysema In this circumstance, a CT scan can easily distinguish the cystic nature of the former condition Cysts are identified prenatally in 70% of cases using high-resolution ultrasonography Reports of spontaneous resolution of pulmonary cysts have been infrequent As with other cystic lesions of the lung, surgical resection of the affected lobe is usually indicated Pulmonary Sequestrations Like bronchogenic cysts, pulmonary sequestrations result from an abnormal budding of the foregut, which retains its embryonic systemic arterial connections Thus a sequestration is a mass of nonfunctioning, ectopic pulmonary tissue that has its own (systemic) blood supply Sequestrations not communicate with the trachea-bronchial tree.100 There are two types of pulmonary sequestrations, which are histologically similar Extralobar sequestrations are surrounded by a separate pleura, whereas intralobar sequestrations are surrounded by lung tissue and have no separate pleural covering Extralobar sequestrations account for about 25% of cases, are more common (90%) on the left side, more common in males (80%), and usually located in a subpulmonic location Extralobar sequestrations are commonly associated (50%–60%) with other anomalies, including direct esophageal communication, bronchial atresia, colonic duplication, CPAM, pulmonary hypoplasia, and diaphragmatic hernia Most cases of extralobar sequestration become apparent during infancy Presentations range from fetal hydrops with massive pleural effusions or pulmonary hypoplasia to recurrent lower respiratory infections (particularly if a GI communication is present) Intralobar sequestrations are the more common type (75%) They are usually left sided (65%–70%) and typically occur in the lower lobes Unlike extralobar sequestrations, they are rarely associated with other anomalies Most cases are asymptomatic and are discovered on chest radiographs obtained for other reasons Symptomatic cases typically present in late childhood with recurrent infections Distinguishing between extralobar and intralobar sequestrations on chest radiographs may be difficult Both lesions can appear as either solid or cystic structures, although extralobar lesions are more often solid and intralobar lesions are more often cystic Delineation of the vascular supply to the sequestration is important to differentiate extralobar sequestrations from CPAMs and to guide surgical management Magnetic resonance imaging has replaced arteriography for obtaining this information Some authors recommend a study of the GI tract, particularly if communication with the sequestration is suspected As with other cystic lesions of the lung, surgical removal is indicated and may be done thoracoscopically Whereas extralobar sequestrations can be removed en bloc because of their separate pleural covering, intralobar sequestrations require lobectomy Partial success with a nonsurgical approach using transumbilical artery embolization during the newborn period has been reported Congenital Lobar Emphysema Congenital lobar emphysema is an unusual disorder characterized by progressive lobar overdistention of the lung as a consequence of developmental disruptions.89,101,102 In fewer than 25% of cases, clinical and radiographic findings are typical of a ball-valve type of obstruction More commonly, the cause for air trapping remains uncertain Intrinsic bronchial obstruction may result from a deficiency of cartilaginous support or an intraluminal mass, such as a mucous plug Extrinsic bronchial obstruction usually results from an underlying cardiovascular abnormality, such as a vascular sling or, rarely, a PDA An intrathoracic mass, such as an enlarged lymph node or a bronchogenic cyst, also can cause extrinsic obstruction Congenital lobar emphysema is more common in male infants102 and typically occurs in the upper lobes or the right middle lobe Fewer than 1% of cases occur in the lower lobes Up to 20% of cases show bilateral involvement Associated cardiovascular anomalies are common Rib cage anomalies and aplasia/dysplasia of the kidneys have been reported in a small percentage of cases In most infants with congenital lobar emphysema, the condition presents within the first month of life, and about one-third of infants exhibit respiratory signs within hours of birth Respiratory compromise is directly related to the degree of overinflation Typically, infants have mild to moderate tachypnea, asymmetric inflation of the chest, and cyanosis A chest radiograph reveals the overinflated lobe with ipsilateral atelectasis and flattening of the hemidiaphragm; mediastinal shift away from the affected side may be observed A CT scan may help to identify the cause of obstruction, if one is present Lobectomy is the definitive treatment and may be performed thoracoscopically Surgery is limited to symptomatic cases Favorable outcomes are reported in asymptomatic or minimally symptomatic cases in which surgery was not performed.103 Pulmonary Agenesis and Aplasia Pulmonary agenesis and aplasia are rare, highly lethal disorders with similar underlying causes that differ from causes of pulmonary hypoplasia Pulmonary agenesis and aplasia result from an arrested development of the embryonic lung The earlier in CHAPTER 51 Neonatal Pulmonary Disease development arrest occurs, the more severe the defect In pulmonary agenesis, the bronchial tree, pulmonary parenchyma, or pulmonary vasculature does not develop In pulmonary aplasia, there is a rudimentary bronchial pouch The resulting lesions may involve one lobe or the entire lung Focal or bilateral defects are rare Pulmonary agenesis or aplasia may be associated with other nonpulmonary anomalies, including microphthalmia/anophthalmia, cleft palate, cardiac defects, congenital diaphragmatic hernia/ eventration, and limb abnormalities Abnormal blood flow in the dorsal aortic arch during the 4th week of gestation has been hypothesized to cause pulmonary agenesis The contralateral lung may develop as many as two-fold more alveoli in response to pulmonary aplasia/agenesis The clinical presentation is variable If the defect is focal and isolated, the infant may have normal respirations, though mild respiratory distress may be present A chest radiograph reveals unilateral lung or lobar collapse with a shift of mediastinal structures, which leads to a suspicion of bronchial or bronchiolar obstruction Misdiagnosis may subject the infant to unnecessary risks of bronchoscopy despite CT being readily available for diagnosis Associated anomalies of the cardiovascular, GI, genitourinary, central nervous, and musculoskeletal systems have all been described If the defect is isolated to a single lobe, surgical resection will reduce respiratory signs and lower the risk for infection If the defect is extensive but the fetus is potentially viable, an ex utero intrapartum procedure may be attempted Prognosis depends on the degree of pulmonary involvement, whether there have been recurrent pulmonary infections, and the presence of associated anomalies Bilateral defects are invariably lethal If the defect is focal, the remaining normal lung undergoes compensatory hypertrophy Nevertheless, mortality exceeds 50%, generally because of the presence of associated malformations Right-sided defects have a poorer prognosis than left-sided lesions, partly because of a higher association with other anomalies and partly because of an increased risk for disseminating infection Right-sided lesions also may produce a more severe mediastinal shift, distorting the trachea and great vessels Repeated lower respiratory infections can result in progressive pulmonary debilitation and increase the risk of death Congenital Defects of the Lymphatics Congenital chylothorax is thought to result from a failure of peripheral and central lymphatic channels to fuse or, perhaps, from a rupture of inadequately fused channels at birth The congenital condition has a different course and prognosis from postoperatively acquired chylothorax Most affected infants show respiratory signs within hours from birth and may require mechanical ventilation Congenital chylothorax may be associated with chromosomal abnormalities or other malformations Familial cases are especially common in babies with associated congenital pulmonary lymphangiectasis with bilateral chylothoraces Progressive respiratory compromise develops as fluid accumulates in the hemithorax Pleural drainage is both diagnostic and therapeutic Initially, the lymphocyte-rich fluid is clear, but it becomes opaque when milk feedings are introduced Nutritional support is critical because of a loss of protein in the chylous drainage Most cases spontaneously resolve in to weeks Occasionally, a several-day course of a somatostatin analog, which reduces chyle flow, or surgical closure of the thoracic duct is indicated.104 Whether congenital or postoperative, common chylothorax 577 complications include nosocomial infection, hemodynamic disturbance, and protein loss In the congenital form, time to resolution is significantly affected by additional underlying problems Pulmonary lymphangiectasia is a rare condition that can be a primary or due to secondary dilation of pulmonary lymphatics from obstructed pulmonary venous flow Primary lymphangiectasia can be isolated, termed congenital pulmonary lymphangiectasia, or it can be part of a generalized condition that includes intestinal lymphangiectasia, in which pulmonary involvement is less severe Congenital pulmonary lymphangiectasia may result from the failure of connective tissue elements to regress during fetal lung development In some cases, a hereditary pattern has been suggested Affected infants usually show respiratory signs soon after birth However, some infants may remain symptom free for several weeks Affected infants are usually born at term and may have a normal examination except for mild tachypnea They may be more severely affected with cyanosis or frankly hydropic Preterm infants may be mistaken as having surfactant-deficient RDS Radiographs generally reveal streaky reticular densities as a result of engorged lymphatics and, occasionally, a finer, ground-glass appearance may be confused with surfactant deficiency Nonpulmonary Causes of Respiratory Distress Many nonpulmonary disorders may present with respiratory distress in the neonate (Box 51.1) Conditions that affect the control or mechanics of breathing, patency, or integrity of the upper airway; perfusion to and from the lung; or acid–base balance can present with increased respiratory effort or signs of respiratory insufficiency (i.e., respiratory acidosis or hypoxemia) • BOX 51.1 Nonpulmonary Conditions That Cause Respiratory Distress in the Newborn Airway Obstruction/Patency Choanal stenosis/atresia Mandibular hypoplasia/micrognathia Laryngomalacia Laryngeal web/stenosis Vocal cord injury Airway vascular tumors/malformations Tracheoesophageal fistula Vascular compression Interference With Respiratory Mechanics Neuromuscular disorders Phrenic nerve injury Eventration of the diaphragm Pleural effusion Chest wall anomalies Perfusion Abnormalities Persistent pulmonary hypertension of the newborn Hyperviscosity Congenital heart disease Disorders of Acid-Base Balance Sepsis 578 S E C T I O N V Pediatric Critical Care: Pulmonary The clinical and radiographic picture may or may not be consistent with an underlying pulmonary pathologic condition However, nonpulmonary causes should be considered, particularly if an infant does not respond to conventional treatments In many nonpulmonary conditions, a delay in diagnosis can lead to progressive injury and death Choanal Atresia/Stenosis Choanal obstruction resulting from a failure of bony or membranous regression is the most common supralaryngeal congenital defect It occurs in approximately in 4000 live births Choanal atresia is often associated with defects in other organs or with syndromes that include other craniofacial anomalies, especially CHARGE syndrome (coloboma of the eye, heart anomaly, choanal atresia, retardation, and genital and ear anomalies) Choanal atresia is usually unilateral, typically on the right side; a 2:1 excess of choanal atresia has been reported in girls Unilateral choanal atresia occurs more frequently in isolated cases, whereas bilateral choanal atresia should prompt further evaluation for other congenital anomalies Clinical presentation depends on the degree of obstruction Bilateral choanal atresia or severe bilateral stenosis becomes evident in the newborn period, whereas unilateral cases or mild stenosis may not present for weeks, months, or years Infants who have respiratory signs typically are distressed during times of sleep or feeding, when nasal breathing predominates Clinical presentation in infants with unilateral obstruction or mild stenosis may occur only when the nares become obstructed, as during the passage of a nasogastric tube or inflammation in an upper respiratory infection With occlusion of the patent nares, an infant may suddenly decompensate with signs of severe respiratory distress Infants in severe distress may require elective intubation if an oral airway proves insufficient or cannot be easily maintained Direct visualization of the obstruction is best performed by an otolaryngologist using a fiberoptic scope A cranial CT scan can determine the presence and thickness of the bony plate within the nasal cavity, which is an important surgical consideration A high degree of suspicion is key to diagnosing and properly treating this disorder; if true bilateral choanal atresia is present, associated anomalies must be excluded Laryngomalacia Laryngomalacia is the most common cause of stridor in the neonate It is a dynamic lesion resulting in collapse of the supraglottic structures during inspiration, leading to airway obstruction Infants have an omega-shaped epiglottis (curled onto itself ) Similar to infants with mandibular hypoplasia, infants with laryngomalacia tend to have more respiratory insufficiency in the supine position because it allows the relatively unsupported anterior tissue to drop into the hypopharynx, causing obstruction Affected infants may have stridor during periods of crying or distress Rarely, the lesion may cause sufficient hypoxemia or hypoventilation to interfere with normal growth and development Treatment includes prone positioning, and resolution is common by age to years Vocal Cord Paralysis Vocal cord paralysis may be unilateral or bilateral Unilateral cord paralysis usually presents with a weak or sometimes hoarse cry Obstructive signs, such as stridor or retractions, are less severe and less common The infant may also cough or choke while feeding because of an inability to prevent aspiration while swallowing Common causes are stretch injury during delivery or recurrent laryngeal nerve injury during ductus ligation Consequently, left-sided paralysis or paresis is most common Respiratory signs from unilateral cord paralysis usually improve over several weeks or months without intervention but may take years to resolve Bilateral cord paralysis is a more serious problem and is often the result of an intracranial pathologic condition, such as Chiari malformation, intracranial hemorrhage, or hypoxic-ischemic encephalopathy These infants may have near total airway obstruction and moderate to severe stridor Many will require tracheostomy to maintain a stable and patent airway Airway Vascular Tumors/Malformations Hemangiomas are the most common vascular tumors of the airway They occur in isolation or as part of the PHACE syndrome (posterior fossa malformations, hemangioma, arterial anomalies, coarctation of the aorta/cardiac defects, and eye anomalies) Congenital hemangiomas located just below the level of the vocal cords are another relatively uncommon cause of stridor in neonates, with or without expiratory wheeze Hemangiomas often enlarge as the newborn grows and can threaten the airway Positional changes tend to have little effect on the severity of respiratory signs Superficial capillary hemangiomas on the skin of the neck are often present, suggesting the diagnosis Propranolol has had a beneficial role in the involution of hemangiomas The availability of laser surgical ablation has markedly reduced the need for tracheostomy in children with subglottic hemangioma Tracheobronchomalacia Tracheobronchomalacia is characterized by abnormally compliant airway cartilage, leading to intermittent airway collapse during normal respiration Specific classification depends on the area(s) involved (e.g., tracheomalacia, tracheobronchomalacia, and bronchomalacia) Infants may be mildly or severely affected depending on the extent of involvement and the capacity of surrounding supporting tissues to maintain airway patency Affected infants generally have respiratory signs in the newborn period, but presentation may be delayed for days or weeks if the defect is mild In these milder cases, infants may remain free from respiratory distress until intercurrent infection leads to increased airway secretions and increased work of breathing Signs are expiratory wheezing and respiratory distress, including tachypnea and retractions, for which the infant may receive a mistaken diagnosis of reactive airway disease Paradoxically, the use of bronchodilators may actually worsen the condition A chest radiograph may show hyperinflation Definitive diagnosis is made by direct visualization, typically with flexible tracheobronchoscopy Treatment is supportive, as airway compromise generally lessens as the infant grows However, more severe cases may require stenting with CPAP or even surgical plication Tracheostomy alone may not be helpful if the affected area extends beyond the proximal trachea A high association with other congenital anomalies, including vascular rings or tracheoesophageal fistula, also should be considered A history of recurrent coughing or choking should prompt further investigation CHAPTER 51 Neonatal Pulmonary Disease Tracheoesophageal Fistula Esophageal atresia with tracheoesophageal fistula (TEF) occurs in approximately in 4500 live births, making it one of the most common congenital malformations Usually isolated, it can be associated with other anomalies, including complex syndromes and malformation sequences such as VATER (vertebral defects, anal atresia, TEF, esophageal atresia, and renal anomalies), VACTERL (VATER plus cardiac and upper limb defects), and CHARGE In the absence of a recognized syndrome, TEF may also be associated with isolated cardiac defects, present in up to 50% of cases Whether as part of a syndrome or an isolated anomaly, TEF usually is associated with esophageal atresia; in 5% to 7% of cases, there is no associated esophageal atresia (H-type TEF) TEF and associated esophageal atresia and TEF as part of a more general disorder invariably present in the immediate newborn period Infants with an isolated H-type fistula may remain clinically silent for many weeks or even months Although relatively rare (approximately in 100,000 live births), an H-type fistula must be suspected in any infant who coughs during feedings and has recurrent pneumonitis The diagnosis of an H-type fistula can be difficult but is best discovered by a cine esophagram In cases in which this study is inconclusive, bronchoscopy may be necessary Successful repair and preservation of pulmonary function depends on early diagnosis Vascular Compression Vascular compression of the trachea or main stem bronchus can result from incomplete regression of the embryonic branchial arch arteries during fetal development The most common anomaly is a vascular “ring” consisting of a double aortic arch in which the vessel completely encircles the trachea and esophagus Other variants include an ectopic aortic arch (passing behind the esophagus) or an aberrant origin of the right brachiocephalic artery Vascular rings cause inspiratory stridor and expiratory wheezing, neither of which change appreciably with the infant’s position Intermittent worsening of signs is sometimes seen during feeding as milk passes through the esophagus, further compressing the trachea Additionally, feeding difficulty may occur because of esophageal compression When a previously undiagnosed infant first presents with these upper airway signs, the infant may be misdiagnosed as having tracheomalacia, bronchomalacia, or tracheobronchomalacia until further imaging confirms the vascular abnormality The presence of an abnormally shaped mediastinum on a chest film often provides a clue to diagnosis Endoscopy may identify tracheal or esophageal compression An echocardiogram may define the vascular anomaly Occasionally, cardiac catheterization may be indicated Decisions regarding surgical correction of this defect depend on the relative compromise of the trachea and esophagus Phrenic Nerve Paralysis Stretch injury to the cervical nerve roots C3 to C5 during delivery can lead to temporary paralysis of the hemidiaphragm, and avulsion of the nerve roots can lead to permanent injury without intervention Phrenic nerve paralysis occurs more commonly on the right Brachial plexus injury or Horner syndrome is present in 70% to 80% of cases, and clavicular fracture is common Infants 579 who are at highest risk are those with birthweights greater than kg, shoulder dystocia, or difficult breech presentations Diminished ventilation is present on the affected side and the infant may be tachypneic or even be cyanotic if severely compromised The chest radiograph will show varying degrees of atelectasis, a raised hemidiaphragm on the affected side, and the heart and mediastinum shifted toward the contralateral side Ultrasound will demonstrate that the paralyzed diaphragm elevates during inspiration and descends on expiration (paradoxical movement) Treatment is supportive in most cases because function usually will spontaneously return in several weeks When there is nerve avulsion or permanent dysfunction, surgical plication may be necessary Eventration of the Diaphragm The diaphragm consists of three layers: a muscular layer sandwiched between the pleural and peritoneal layers Eventration of the diaphragm occurs when all or part of the diaphragmatic muscle is replaced by fibroelastic tissue It is a rare disorder that results in a nonfunctioning diaphragm having highly elastic fibrous tissue Partial defects are more common and usually occur on the right side However, complete defects are more common on the left side and often are associated with other organ anomalies Normal abdominal pressure permits the viscera to easily push the affected diaphragm upward into the hemithorax In utero, this phenomenon may lead to pulmonary hypoplasia (although this is usually mild) whereas, occurring after birth, eventration can cause respiratory compromise by affecting lung expansion Radiographic and ultrasound findings are similar to those of a paralyzed diaphragm, but a history of birth trauma or associated injuries is usually absent With large defects, the appearance of bowel in the thoracic cavity on a chest radiograph may be mistaken for a diaphragmatic hernia However, close inspection should reveal the thin, overlying diaphragmatic pleura Treatment is supportive; defects that remain symptomatic beyond the neonatal period may require plication Pleural Effusion Collection of fluid within the pleural cavity, if excessive, can result in significant respiratory distress Pleural effusions in the neonate may result from inflammation, fluid transudation, or frank leakage from disrupted vessels (either vascular or lymphatic) Small pleural effusions normally are present during the first hours of life as fetal lung liquid resorbs from the airspaces, but a large pleural effusion or persistence beyond the first day of life is abnormal and may be associated with pneumonia Large effusions can result in significant respiratory compromise Although initial management is similar regardless of cause, successful long-term management depends on accurately identifying the source of the pleural effusion Congenital Anomalies of the Chest Wall Thoracic cage abnormalities represent a group of uncommon but frequently overlooked causes of respiratory distress in the neonate They may be structural or functional in nature The structural abnormality may be limited to the sternum or may involve the entire thoracic cage Sternal deformities include pectus excavatum, which is a relatively common but usually benign condition; complete separation of the sternum often accompanies ectopia cordis and usually is lethal Generalized structural abnormalities invariably involve some degree of thoracic restriction and pulmonary 580 S E C T I O N V Pediatric Critical Care: Pulmonary hypoplasia Many of these abnormalities are themselves lethal or are part of a more generalized lethal disorder Some conditions, however, such as achondroplasia and Ellis-van Creveld syndrome, are compatible with normal life Functional anomalies result from dysfunctional chest wall musculature Like structural defects, they may be restricted to the thoracic cage However, more often they are part of a systemic disorder, such as congenital muscular dystrophy, glycogen storage disease, or myasthenia gravis Severe congenital kyphoscoliosis does not itself usually cause neonatal respiratory problems but may augment mild respiratory illness from another cause Most infants with thoracic cage abnormalities are readily recognized in the immediate newborn period, although a relatively protuberant abdomen may distract the clinician from the primary problem Infants with restrictive thoracic cages (either structural or functional) will have tachypnea and retractions The radiograph shows a narrow, elongated thoracic cage with high clavicles and depressed hemidiaphragms Treatment is supportive; in the absence of severe pulmonary hypoplasia or an underlying lethal disorder, infants may relatively well, despite requiring initial mechanical ventilation Persistent Pulmonary Hypertension of the Neonate The organ of gas exchange for the fetus is the placenta, not the lung Placental blood flow is high and pulmonary blood flow is minimal To achieve intrauterine gas exchange, blood returning to the right side of the heart is directed to the systemic (and, thereby, placental) circulation This blood flow path occurs via two fetal right-to-left shunts—namely, the foramen ovale, which shunts blood from the right to left atrium, and the ductus arteriosus, which shunts blood from the pulmonary artery to the descending aorta Due to these shunts, less than 10% of the combined fetal ventricular output goes to the lungs At birth, dramatic lung changes must occur for the fetus to undergo a successful transition from placental to pulmonary gas exchange Liquid is removed from the potential airspaces (see earlier discussion on retained fetal lung liquid), and blood flow course is redirected After inflation of the lungs with air, a dramatic increase in oxygen tension within the lungs leads to vasodilation The resultant drop in pulmonary vascular resistance leads to a 10-fold increase in pulmonary blood flow, which causes left atrial pressure to exceed right atrial pressure, allowing the one-way flap across the foramen ovale to close Flow across the ductus arteriosus reverses and, combined with increased blood oxygen tension, leads to gradual ductal closure over the first few hours of life In the syndrome of persistent pulmonary hypertension of the newborn (PPHN), this transition of the pulmonary circulation fails to occur normally Pulmonary vascular resistance and pulmonary arterial pressure remain high and blood flow continues largely to bypass the lungs as in fetal life (this is why the term persistent fetal circulation has been used although, in a strict sense, it is inaccurate because there is no longer a placental/umbilical circulation) PPHN should be suspected if the degree of hypoxemia is out of proportion to pulmonary disease PPHN is associated with many neonatal disorders, including RDS, meconium aspiration, air leak syndromes, perinatal asphyxia, congenital sepsis, and structural lung disorders, such as pulmonary hypoplasia or alveolar-capillary dysplasia PPHN can also be idiopathic Infants with PPHN may be affected moderately or severely, depending on the extent of shunting PPHN can be a self-limited disease, running a course over several days In more severe cases, severe hypoxemia can lead to significant morbidity and mortality PPHN mortality previously has been as high as 50% to 60% but has improved significantly since the introduction of new treatment modalities, including HFV, inhaled nitric oxide, and ECMO Because nitric oxide increases cyclic guanosine monophosphate levels, selective phosphodiesterase inhibitors such as sildenafil are sometimes used in infants who have a prolonged course of PPHN or in whom pulmonary arterial hypertension develops after the newborn period, either idiopathic or as a result of underlying cardiorespiratory disease The long-term benefits and risks of sildenafil are unknown Hyperviscosity Syndrome Neonates with polycythemia (i.e., a central hematocrit 65%) are at risk for abnormally high blood viscosity, which interferes with regional tissue perfusion Polycythemia may occur in several situations, including twin-twin transfusion, maternal-fetal transfusion, prolonged delayed cord clamping, home delivery, maternal diabetes, small-for-gestational-age infants, postmature infants, and infants with Down syndrome or Beckwith-Wiedemann syndrome Signs generally relate to the degree of hyperviscosity and range from tachypnea to apnea, listlessness to irritability, hypoglycemia, and jitteriness to seizures Hyperviscosity syndrome generally presents during the first hours of life Affected infants are at risk for thrombotic injury; partial blood volume exchange is a therapeutic option Congenital Heart Disease In the neonate, significant congenital heart disease (CHD) typically presents as cyanosis with minimal or no respiratory distress or cardiorespiratory failure CHD in which pulmonary blood flow is either excessive or nonrestrictive often presents with respiratory distress Infants with D-transposition of the great arteries with an intact ventricular septum may be visibly cyanotic but appear to be comfortable Cyanotic heart disease should be suspected in these infants, even if a murmur is absent, particularly if the infant has persistent low oxygen saturation or is hypoxemic in 100% oxygen Conditions with left ventricular outflow tract obstruction or a large ventricular septal defect (VSD) often present without cyanosis but have pallor, systemic hypotension, marked respiratory distress, and often a loud murmur Chest radiographs may show cardiomegaly or pulmonary vascular congestion Simple left-toright shunt lesions—including a small VSD, atrial septal defect, atrioventricular septal defect, and PDA—do not often present with severe pulmonary edema or distress during the neonatal period because a relatively high pulmonary vascular resistance can restrict pulmonary blood flow In contrast, PDA in preterm infants can present with pulmonary edema and respiratory distress In the mixed types of CHD, there is an overlap in presentation Infants may be cyanotic as well as display signs of respiratory conditions such as tachypnea and retractions This type of presentation, common with hypoplastic left heart syndrome and obstructed total anomalous pulmonary venous return (TAPVR), may initially be confused with sepsis, pneumonia, meconium aspiration, or even RDS TAPVR deserves particular mention because it is not detected in utero and sometimes may be missed postnatally, even on repeated echocardiograms In fact, TAPVR with pulmonary venous obstruction is a surgically correctable ... presence and thickness of the bony plate within the nasal cavity, which is an important surgical consideration A high degree of suspicion is key to diagnosing and properly treating this disorder;... easily push the affected diaphragm upward into the hemithorax In utero, this phenomenon may lead to pulmonary hypoplasia (although this is usually mild) whereas, occurring after birth, eventration... the thin, overlying diaphragmatic pleura Treatment is supportive; defects that remain symptomatic beyond the neonatal period may require plication Pleural Effusion Collection of fluid within