RESPIRATORY DISTRESS IN THE FULL TERM NEONATE

C H R I S T Y L . C U M M I N G S , M D

OBJECTIVES

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Informal case-based learning Differentiate between cardiac and respiratory causes of cyanosis Describe the primary parenchymal diseases that can cause respiratory distress in the term neonate Describe the primary developmental lung abnormalities that can cause respiratory distress in the term (or near-term) neonate

RULE OUT CARDIAC DISEASE

• • • Pulse Oximetry Test • Determines whether formal hyperoxia test is useful • • Cyanosis without marked respiratory distress and O 2 sat < 85% in room air and 100% oxygen suggests intracardiac shunt If O 2 sat increases to > 85% on 100% oxygen, a full hyperoxia test should be performed Hyperoxia Test • Obtain baseline right radial (preductal) arterial blood gas measurement with baby breathing room air and 100% O 2 • A Pa O2 > 300 mm Hg on 100% O2 is normal, 150-300 mm Hg suggests pulmonary disease, and 50 -150 mm Hg suggests cardiac disease (or severe pulmonary hypertension) ECHO

HINTS ON CHEST RADIOGRAPH

• • • RDS • Mostly premies, but seen in term (rare) and near-term • Reticular granular pattern and air bronchograms MAS • Patchy areas of atelectasis due to complete airway obstruction, interspersed with areas of air trapping due to partial obstruction and a one-way valve phenomenon • White out, and/or air leak syndrome Neonatal pneumonia • • Classical patchy infiltrates, but the findings also may be indistinguishable from RDS Pleural effusion supports diagnosis of PNA, seen 67%

HINTS ON CHEST RADIOGRAPH

• • • TTN • • Diffuse parenchymal infiltrates, a “wet silhouette” around heart, or accumulation of fluid in various intralobar spaces (fissure) Indicate increased pulmonary interstitial, alveolar, or pleural water content CHD • Cardiac enlargement, unusual silhouette (snowman, boot) Congenital lymphangiectasia • Lungs may appear normal, overinflated or exhibit a coarse interstitial infiltrate due to distended, abnormal lymphatics • Effusion (chylous)

POSSIBLE DIAGNOSIS RELATED TO RADIOGRAPHIC FEATURES

CASE

• • 1 hour old FT baby boy with tachypnea (RR 70s) born via C/S, GBS neg PE: • • Moderate retractions O2 sat 88% on RA • O2 sat 100% on 100%

TRANSIENT TACHYPNEA OF THE NEWBORN (TTN)

• • • • • • Relatively benign, self-limited disease 11:1000 births, M>F Increased risk: • M, C/S, perinatal asphyxia, cord prolapse, IDM, maternal asthma or anesthesia during labor Tachypnea (>60bpm) shortly after birth, lasts 1-5d Unclear etiology: • • Delayed resorption of fetal lung fluid related to elevated CVP, delayed clearance of pulmonary liquid by lymphatics Mild asphyxia resulting in mild pulmonary capillary leak and to myocardial dysfunction with elevated filling pressure Almost never requires mechanical ventilation

RESORPTION OF ALVEOLAR FLUID AT BIRTH: CELLULAR MECHANISMS

CASE

• 1 hour old FT baby boy born via NSVD who required PPV in DR, increasing WOB, retractions, required intubation

RDS IN TERM INFANT: SP-B DEFICIENCY

• • • • • • Congenital abnormalities of surfactant proteins • Most common is deficiency of surfactant protein B (SP-B) • Autosomal recessive, frame-shift mutation chromosome 2, Severe respiratory distress after birth CXR identical to RDS Continued distress despite mechanical ventilation, oxygen, repeated surfactant, corticosteroids Prognosis is poor, most die within 1-6 months Only effective therapy (although neither available for nor consented to by all) is lung transplantation

CASE

• • 1 hour old FT baby girl born via NSVD, meconium, who emerged limp, was suctioned below cords x1 Now with grunting, retractions, desats, requiring intubation

MECONIUM ASPIRATION SYNDROME

• • Incidence: • 13% of all live births complicated by meconium-stained amniotic fluid, and of these, 4% to 5% develop MAS Mechanism • Direct toxicity of the meconium  • Inactivation of surfactant • Activation of complement • • • chemical pneumonitis Vasoconstriction Partial/complete airway obstruction by thick meconium Secondary pulmonary hypertension

MECONIUM ASPIRATION SYNDROME

• Management • NRP guidelines, endotracheal suction below cords if limp • Intubation, mechanical ventilation • • Surfactant • RCTs shown that surfactant reduces need for ECMO iNO • • Since the approval of iNO by the US FDA in 2001, there has been a steady decrease in the use of ECMO for neonates with MAS HFOV +/ • Reduction in complications from air-leak syndromes (PTX)

CASE

• • • FT baby girl born via NSVD, GBS+, treated with PCN x1 2 hours PTD Increased WOB, desats Requires PPV

PNEUMONIA

• • • • Early onset <7d, late onset >7d In utero • Rubella, CMV, HSV, mumps, adenovirus, Toxo, T. pallidum, M. tuberculosis, Listeria monocytogenes, VZV, HIV During delivery/perinatally • GBS, Escherichia coli, Klebsiella sp, Chlamydia trachomatis Postnatally • Respiratory viruses (adenovirus, RSV), gram-positive bacteria(groups A, B, and G streptococci or S. aureus), and gram-negative enteric bacteria (Klebsiella sp, Proteus sp, Pseudomonas aeruginosa, flavobacteria, Serratia marcescens, and E coli)

PULMONARY CAUSES FOR RESPIRATORY DISTRESS

• • • • • • • Parenchymal conditions: Transient tachypnea of the newborn Meconium aspiration syndrome, other aspirations Respiratory distress syndrome Pneumonia Pulmonary edema Pulmonary hemorrhage Pulmonary lymphangiectasia

CASE

• • • FT baby boy born via repeat C/S with increased WOB, retractions Requires intubation Transillumination neg

CONGENITAL LOBAR EMPHYSEMA

• • • • • • • • Accounts for 50% of structural lesions causing respiratory distress in the newborn M:F 2:1, associated anomalies 14-40% (often CHD) Air trapping and overdistention of segments and lobes of the lungs Prenatal diagnosis via high-res U/S, MRI or CT Clinical signs/sx include respiratory distress, mediastinal shift, wheezing Upper lobes afftected 90% time Symptomatic lesions need surgical resection Asymptomatic lesions may be watched carefully

CASE

• • • • FT baby girl born via repeat C/S Respiratory distress Intubated • CXR appears ok, but on close inspection reveals small dense mass LLL CT with contrast shown

PULMONARY SEQUESTRATION

• • • • Abnormal lung tissue with no connection to normal tracheobronchial tree Receives arterial blood supply from systemic circulation, usually branch of the aorta Mutation in Homeobox gene Hoxb-5, crucial for normal airway branching/development Intralobar vs extralobar

PULMONARY SEQUESTRATION

• • • Intralobar – lesion within lobe without separate pleura • • • • 3x more common than extralobar May be acquired (recurrent infection due to lack of pleura) Lower lobe (95%), and in 55% of cases is on the left side M=F Extralobar - discrete mass of pulmonary parenchyma outside pleural investment of lung • • • In 66% of the cases, left side, proximal to esophagus and between lower lobe and diaphragm M:F 3-4:1 >65% associated with anomalies (CDH, TAPVR, CHD, CCAM) Resection for both types necessary

CASE

• 1 day old FT female born via NSVD, GBS neg, with respiratory distress

CCAM/CPAM

• • • Multicystic mass of dilated bronchiolarlike spaces that proliferate at the expense of alveoli Large lesions may obstruct venous return to heart, causing fetal hydrops Abnormal signaling/conjugation between developing terminal bronchioles and alveolar mesenchyme • Mesenchymal & plt-derived GF

CCAM/CPAM

• • • • M=F, usually affects right side one lobe Solid lesions worse prognosis than large cysts • • • • Type 1 (75%) – small # of large cysts, 2-10cm, mucin Type 2 - small cysts (<2cm), assoc anomalies, poor outcomes Type 3 – microscopic cysts, rare, appears solid on gross exam (Type 4 – acinar epithelium) Surgical resection for all types 100% survival with surgery (without hydrops fetalis)

CASE

• • FT baby boy delivered via repeat C/S, prenatal L:H ratio 0.8 and + liver Intubated immediately

CONGENITAL DIAPHRAGMATIC HERNIA (CDH)

 • Herniation of intestinal contents into thoracic cavity  Results in pulmonary hypoplasia leading to respiratory distress 95% occur through posterior foramen of Bochdalek (lies posteriorly and lateral to spine); of these, 80% are on left side      1 : 4,000 births Signs/symptoms:  Cyanosis, severe respiratory distress, scaphoid abdomen Usually seen during routine prenatal U/S  L:H ratio, presence of liver or other organs in chest Post delivery xray reveals intestinal loops in chest cavity Immediate intubation and gastric decompression is essential to higher survival rates  Intubation should be performed by most experienced team member

CONGENITAL DIAPHRAGMATIC HERNIA

PULMONARY CAUSES FOR RESPIRATORY DISTRESS

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Developmental abnormalities:

Lobar emphysema Pulmonary sequestration Cystic adenomatoid malformation Congenital diaphragmatic hernia Tracheoesophageal fistula Pulmonary hypoplasia

CASE

• • 3 hour old FT baby girl with respiratory distress while eating, improves with crying. CXR WNL.

ENT consulted, CT ordered

CHOANAL ATRESIA

• • • • • • • Congenital anomaly, back of the nasal passage (choana) is blocked, usually by abnormal bony or soft tissue formed during fetal development 0.82 cases per 10,000 individuals, F>>M Unilateral (R) and 2:1, B/L CHARGE syndrome 6% with chromosomal anomalies Cyanosis • • Worse with feeds or pacifier Improves with crying Surgical correction, stent, revisions

CHOANAL ATRESIA: CHARGE

• • • • • • C – Coloboma of the eye, CNS anomalies H - Heart defects A - Atresia of the choanae R - Retardation of growth and/or development G - Genital and/or urinary defects (Hypogonadism) E - Ear anomalies and/or deafness

CASE

• • • • FT baby boy with respiratory distress, hoarse cry Intubated for worsening respiratory status CXR WNL ENT consulted

LARYNGEAL WEB

• • • • • Incomplete recanalization of the laryngotracheal tube during 3 rd month of gestation (atresia – stenosis) Most commonly at level of vocal folds anteriorly Sx: Mild dysphonia to significant airway obstruction • 30% associated airway anomalies (subglottic stenosis), 22q11 Diagnosis – rigid laryngoscopy/bronchoscophy Management • Ranges from observation to emergent tracheotomy • • • Lysis endoscopically using cold knife or laser Endoscopic suturing of the cut edges or placement of a keel may prevent restenosis in these cases Thicker webs may require laryngofissure approach, with postoperative stenting of the airway

PULMONARY CAUSES FOR RESPIRATORY DISTRESS

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Airway abnormalities:

Choanal atresia/stenosis Laryngeal web Laryngotracheomalacia or bronchomalacia Subglottic stenosis

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CASE

RIB CAGE ABNORMALITIES JEUNE SYNDROME

• • • • • Asphyxiated Thoracic Displasia (Jeune syndrome) Autosomal recessive Clinical signs/sx: • • • • Bone dysplasia – rhizomelic brachymelia Thoracic anomalies – bell shaped rib cage, short ribs Renal and hepatic malformations Pulmonary hypoplasia Radiologic changes often seen by 16-18wk gestation Usually death in the newborn period from severe pulmonary hypoplasia

CASE

• • FT baby girl born via NSVD, worsening respiratory distress, increasing O2 Required intubation and intervention

PNEUMOTHORAX/MEDIASTINUM

• • • • • Air collection: pleura and chest cavity or mediastinum Neonatal pneumomediastium 2.5:1000 live births Assoc with mechanical ventilation, PNA, RDS, mec Often asymptomatic May require intervention

CASE

• 3 day old FT baby boy born via NSVD, worsening respiratory distress

CHYLOTHORAX

• • • • • • Pleural effusion from lymphatic fluid (chyle) Leakage from thoracic duct or branch M:F is 2:1and R>L side 50% occur within 24hr of life, 70% by 1 st week of life Composition: milky, chylomicrons, TGs, lymphs Treatment: • Thoracentesis, CT to allow drainage • • • D/c FFAs in diet; formula high in medium chain TGs (Portagen) bypasses lymphatic system via direct absorption into blood stream Surgical ligation of thoracic duct Chemical or surgical pleurodesis • Octreotide for several weeks

PULMONARY CAUSES FOR RESPIRATORY DISTRESS

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Mechanical abnormalities:

Rib cage anomalies (eg, Jeune syndrome) Pneumothorax Pneumomediastinum Pleural effusion Chylothorax

References:

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