Central cyanosis in a neonate = duct-dependent cardiac lesion until proven otherwise. The hyperoxia test (PaO₂ on 100% O₂ < 100 mmHg) suggests cardiac > pulmonary etiology. Start prostaglandin E1 if cardiac suspected — apnea is an expected side effect.
🚩 Red-flag clues (must not miss)
- •Failed hyperoxia test (PaO₂ < 100 mmHg on 100% FiO₂) = cardiac
- •Differential cyanosis (upper > lower SpO₂ or vice versa) = ductal-dependent lesion
- •Sudden Tet spell (squatting/knees-to-chest helps) = Tetralogy of Fallot
- •Seizure-like spell + cyanosis in newborn = consider HSV, sepsis, hypoglycemia, IEM
Exam
- Pre- and post-ductal SpO₂ (right hand vs foot) — Δ ≥ 3% suggests CCHD
- Cardiac murmur, gallop, hepatomegaly
- Femoral pulses (absent → coarctation)
- Work of breathing — cardiac cyanosis often without distress
Labs
- VBG/ABG with PaO₂ on RA then on 100% FiO₂
- Glucose, lactate, CBC, CRP, blood culture
Imaging
- CXR (heart size, pulm vasc)
- Echocardiogram (definitive)
- ECG
Differential & next step
| Diagnosis | Clue | Next step |
|---|---|---|
| Tetralogy of Fallot — Tet spell | Hypercyanotic spell, RVOT murmur ↓ during spell | Knees-to-chest, O₂, morphine, fluid bolus, β-blocker, phenylephrine |
| Transposition of great arteries (TGA) | Profound cyanosis day 1, single S2 | PGE1; balloon atrial septostomy |
| Hypoplastic left heart (HLHS) | Shock when PDA closes day 2–7 | PGE1, intubate, norepinephrine, surgery |
| Total anomalous pulm venous return (TAPVR) | Cyanosis + pulmonary edema + 'snowman' CXR | Surgical, do NOT give PGE1 if obstructed |
| Persistent pulm HTN of newborn (PPHN) | Differential cyanosis, term/post-term | iNO, ventilation, sildenafil |
| Sepsis / pneumonia | Fever or hypothermia, work of breathing | Sepsis bundle |
| Methemoglobinemia | SpO₂ low but PaO₂ normal, chocolate blood | Methylene blue 1–2 mg/kg IV |
| Breath-holding spell (older infant) | Triggered by crying/anger, brief | Reassurance; check Hgb (iron deficiency) |
Medications & dosing
| Drug | Dose | Notes |
|---|---|---|
| Prostaglandin E1 (alprostadil) | Start 0.05 mcg/kg/min IV; titrate 0.01–0.1 | Maintains ductal patency. Side effects: APNEA (intubate), hypotension, fever |
| Methylene blue (methemoglobinemia) | 1–2 mg/kg IV over 5 min | Avoid if G6PD deficiency |
| Morphine (Tet spell) | 0.1–0.2 mg/kg IV/IM | |
| Phenylephrine (Tet spell) | 5–20 mcg/kg IV bolus | Increases SVR → reverses R-to-L shunt |
Management / next steps
- ABCs, continuous SpO₂ pre/post-ductal
- Hyperoxia test if cardiac suspected
- PGE1 infusion if duct-dependent suspected
- Echo + pediatric cardiology consult; transfer to CICU
Source: https://fprmed.com/fprmedcom/Pages/Pedi/Neonate_Cyanosis_Blue_Spells.html
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