Ch. 30 Full-Term Male Infant with Respiratory Distress

Question 1

Differential Diagnosis of surgical causes of NRDS (6)

Answer 1

1. Choanal atresia
2. Congenital diaphragmatic hernia (CDH)
3. Cystic lesions:
   
   1. Congenital cystic adenomatoid malformation (CCAM)
   2. Bronchopulmonary sequestration
   3. Congenital lobar emphysema (CLE)
4. Esophageal atresia +/- TEF
5. Mediastinal lesions:
   
   1. Bronchogenic cysts
   2. Mediastinal masses
6. Pneumothorax

Question 2

Choanal atresia

Distinguishing feature

Answer 2

NGT cannot be placed

Back of nasal passage (choana) blocked by abnormal bony or soft tissue because of failure of recanalization of nasal fossa during fetal development

Question 3

Congenital Diaphragmatic Hernia (CDH)

Distinguishing Feature

Answer 3

Loops of intestine (left) or liver (right) above the diaphragm on CXR

Question 4

Cystic Lesions:

Distinguishing Feature:

Answer 4

Congenital cystic adenomatoid malformation (CCAM)

Bronchopulmonary sequestration

Congenital lobar emphysema (CLE)

Cystic lesion seen on CXR

Question 5

Esophageal atresia +/- tracheoesophageal fistula (TEF)

Distinguishing Feature:

Answer 5

Scaphoid abdomen, excessive salivation, +/- stomach bubble, +/- vomiting

Question 6

Mediastinal lesions:

Distinguishing Feature

Answer 6

Bronchogenic cysts

Mediastinal masses

Diagnosed incidentally or patient develops infected cyst, 2ndary mass effects if large enough

Question 7

Pneumothorax

Distinguishing Feature

Answer 7

Decreased breath sounds on affected side with collapsed lung in CXR

Question 8

Full-Term Male Infant with Respiratory Distress

Most likely dx:

How to confirm:

Answer 8

CDH: Constellation of severe respiratory distress, absent breath sounds, scaphoid abdomen (abdominal contents have herniated into chest)

Confirm: CXR

Question 9

Most common causes of NRDS

Answer 9

NOT surgical

1. Benign, transient tachypnea of newborn (40% cases) due to residual pulmonary fluid which remains in lung tissue after delivery
   
   1. ​Sx: few hours to multiple days
2. Meconium aspiration syndrome
3. Persistant pulmonary HTN
4. Pneumonia

In premies, most common cause: hyaline membrane disease or respiratory distress syndrome due to decrease in surfactant production by type II alveolar cells

Question 10

History and Physical:

What is the significant of Supracostal Retractions and Grunting?

Answer 10

Indicate severe respiratory distress and should alert clinician to impending cardiorespiratory collapse

INTUBATE and place on MECHANICAL VENTILATION!

Question 11

History and Physical:

What does the absence of breath sounds in a newborn signify?

Answer 11

• Abnormal lung development –> pulmonary agenesis or bronchial atresia
• Pneumothorax/
• Space-occupying lesion as in CCAM, CDH, teratoma, bronchopulmonary sequestration, bronchogenic cyst

Question 12

History and Physical:

Why is the heartbeat displaced?

Answer 12

Space-occupying lesion has enough volume to shift mediastinum towards contralateral side

Barrel-shaped chest = associated finding

Question 13

Why is the absence of prenatal care important?

Answer 13

Possibility of malformation b/c CDH typically diagnosed in utero

Majority of CDH diagnosed prenatally by U/S or in some cases, MRI: CDH can be successfully dx as early as 15 weeks gestation (most diagnosed by 24 wks)

Findings:

bowel loops seen in thoracic cavity or shift of heart and mediastinum towards contralateral side

Question 14

Etiology:

CDH

Answer 14

Failure of septum transversum to completely divide pleural and coelomic cavities during fetal development

Fusion of diaphragmatic precursor usually completed posteriorly by 12th week of gestation

Herniation of intra-abdominal contents occurs during critical period of lung development when pulmonary arteries and bronchi are branching –> pulmonary hypoplasia

Question 15

Are there different types of CDH?

Answer 15

85% left side, 10% right side, <5% bilaterally

Posterolateral defect (Bochdalek hernia) = most common variant

Less common variants:

• Morgagni hernias
• Diaphragmatic eventration (thinning of intact diaphragm due to incomplete muscularization)
• Diaphragmatic agenesis (complete absence of hemidiaphragm)

Question 16

What are the changes that occur during childbirth that allow neonate to transition to breathing air?

Answer 16

In utero:

• Two fetal shunts
  
  • Blood entering RA shunted through foramen ovale into LA away from RV
  • Blood pumped into pulmonary arteries from RV shunted away from pulmonary arterial tree into systemic circulation through ductus arteriosus (connects main pulmonary artery to aortic arch)

When newborn takes first breath of air:

• Pulmonary vascular bed transitions from high resistance to low resistance system –> increase in P in LA relative to RA (blood flow reverses across foramen ovale –> closure)
• Inc. in oxygen concentration in blood –> local decrease in prostaglandins –> closure of ductus arteriosus

Question 17

Neonate’s transition to breathing air compromised by CDH.

Why?

Answer 17

Two fold:

1. Pulmonary hypoplasia mainly on ipsilateral side
   
   1. Medistinum shift –> compression of contralateral lung
   2. Decreased gas exchange and CO₂ retention
2. Pulmonary hypertension –> high R that does not reverse with infant’s first breath –> decreased blood flow and hypoxia

Result: Hypoxemia, acidosis, pulmonary vasoconstriction –> worsen pulmonary HTN

Question 18

Associated anomalies with CDH:

Answer 18

50-60% of affected infants have isolated CDH.

Associated anomalies:

1. Malrotation/nonrotation (60-100%)
2. CV: VSD/ASD/Hypoplastic L heart (63%)
3. GU: Undescended or ectopic testes/Horseshoe kidney (18-23%)
4. Limb: Polydactyly/Syndactyly (10-16%)
5. CNS: Neural tube defects/hydrocephalus (10-14%)
6. Xsomal abnormalities: Trisomy 13, 18, 21 (10%)

Question 19

Workup:

Best Initial Diagnostic Test

Answer 19

1. If unstable: INTUBATE
2. If stable: place NGT/OGT
   
   1. NGT does NOT pass –> choanal atresia
3. CXR
   
   1. NGT curled in upper esophagus –> esophageal atresia +/- TEF (depending on gas in abdomen)
   2. NGT in stomach
      
      1. –> stomach/bowel or liver in thorax –> CDH
      2. –> cystic lung lesions

• Atelectasis or consolidation on CXR –> meconium aspiration syndrome/pneumonia

Question 20

Prognosis: What are the factors affecting prognosis?

Answer 20

Overall mortality improved since development of ECMO and surgical repair (current survival rates: 60-80%)

Mortality directly related to degree of pulmonary hypoplasia and pulmonary HTN + presence of congenital anomalies

Question 21

Mgmt:

What is the most important step in clinical mgmt?

Answer 21

IMMEDIATE INTUBATION!!!

OGT placed to low continuous suction to decompress stomach and proximal small bowel –> alleviate pressure on lungs

Question 22

Mgmt:

How to manage persistent hypoxemia on mechanical ventilation?

Answer 22

1. Increase FiO2 to 100% while maintaining PEEP at physiologic levels (3-5 cm H2O) to ensure adequate opening of alveoli while minimizing barotrauma
2. Inhaled NO may improve pulm HTN
3. ECMO to stabilize and support unstable patients

DON’T OVER VENTILATE –> may increase barotrauma and worsen lung fxn

• Acceptable parameters:
  
  • Permissive hypercapnia (PCO2 < 60 mmHg)
  • Pre-ductal O2 sat (80-95%) or PaO2 around 60 mmHg

Question 23

Mgmt:

What is the timing of surgical repair?

Answer 23

The goal in CDH mgmt is supporting lung fxn b/c survival is directly related to degree of pulm hypoplasia and pulm HTN

Repairing diaphragm will NOT improve pulm fxn… so pts with mild pulm symptoms may undergo surgical repair 48-72 hrs… for most pts, need to await lung maturation first… most cases, TIME will improve lung fxn

(Don’t forgot to evaluate for other anomalies prior to surgery**)