Newborn Vital Signs - Interpretation

Differential Diagnosis (Most to Least Common)

1. Transient Tachypnea of the Newborn (TTN) - Most Common

• Caused by delayed clearance of fetal lung fluid
• Classic in: late preterm, C-section delivery (no labor), maternal sedation
• Features: grunting, tachypnea, nasal flaring, mild intercostal retractions, mild cyanosis
• CXR: perihilar streaking, fluid in fissures, good aeration/hyperinflation
• Resolves in 24-48 hours
• Treatment: supplemental O2 to keep SpO2 >90%, IV fluids, supportive care

2. Respiratory Distress Syndrome (RDS) / Surfactant Deficiency

• More common in premature infants (<34 weeks)
• Caused by lack of surfactant
• Features: severe retractions, grunting, cyanosis, worsening over first hours
• CXR: ground-glass appearance, air bronchograms, low lung volumes, indistinct cardiac border
• Treatment: surfactant replacement, CPAP or mechanical ventilation

3. Meconium Aspiration Syndrome (MAS)

• Meconium-stained amniotic fluid + respiratory distress after birth
• Causes airway obstruction, chemical pneumonitis
• CXR: bilateral patchy infiltrates, hyperinflation
• Can cause persistent pulmonary hypertension (PPHN)

4. Neonatal Pneumonia / Sepsis

• Group B Streptococcus (GBS) is the most common cause
• Risk factors: prolonged rupture of membranes, maternal fever, chorioamnionitis
• Features: temperature instability, poor feeding, lethargy
• CXR: may look identical to RDS or TTN
• Treatment: IV antibiotics (ampicillin + gentamicin)

5. Congenital Heart Disease (CHD) - Critical CHD

• Cyanotic CHDs (Tetralogy of Fallot, Transposition of Great Arteries, etc.)
• Key clue: hypoxia not improving with supplemental O2 (hyperoxia test: PaO2 <150 mmHg after 100% O2 = cardiac cause likely)
• May have murmur, abnormal pulses, hepatomegaly
• Echocardiogram is diagnostic

6. Persistent Pulmonary Hypertension of the Newborn (PPHN)

• Failure of normal pulmonary vascular resistance drop at birth
• Often secondary to MAS, sepsis, or asphyxia
• Features: severe hypoxia, labile oxygenation
• Treatment: iNO (inhaled nitric oxide), ECMO in severe cases

7. Pneumothorax

• Spontaneous or after resuscitation/PPV
• Sudden respiratory deterioration, unequal breath sounds
• CXR or transillumination is diagnostic
• Treatment: needle decompression or chest tube

8. Upper Airway Obstruction

• Choanal atresia: neonates are obligate nose breathers - obstruction causes distress that improves with crying (mouth breathing)
• Pierre Robin sequence: micrognathia, glossoptosis
• Key test: pass NG tube through each nostril

9. Diaphragmatic Hernia (CDH)

• Bowel sounds in the chest, scaphoid abdomen
• Usually diagnosed antenatally on ultrasound
• CXR: bowel loops in chest, mediastinal shift

Immediate Workup

1. CXR - first and most important step
2. Blood glucose - hypoglycemia is common and worsens respiratory effort
3. CBC, blood culture, CRP - rule out sepsis
4. Pulse oximetry - pre and post ductal (right hand + foot)
5. Hyperoxia test - to distinguish cardiac vs. pulmonary cause
6. ABG - assess ventilation and acid-base status
7. Echo - if cardiac cause suspected

Quick Summary

RR 80 + SpO2 94% in a newborn = respiratory distress. The most likely cause is TTN, but you must actively rule out RDS, sepsis, CHD, and MAS based on history, physical exam, and CXR.

• Creasy & Resnik's Maternal-Fetal Medicine, p. 1784
• Tintinalli's Emergency Medicine, Chapter 128