💙 Cyanosis · Cardiac vs Pulmonary · Neonatal & Pediatric Tool

Schwartz Clinical Handbook — Chapter 24 · Hyperoxia test · Differential cyanosis · TGA · Tetralogy · PPHN · Methemoglobinemia

Select age, timing, pre‑/post‑ductal saturations, respiratory signs, murmur, and response to oxygen → differentiate congenital heart disease (ductal‑dependent, mixing) from primary lung disease or methemoglobinemia.
⚠️ Emergency: PGE1 infusion if ductal‑dependent CHD suspected; hyperoxia test to guide referral.

📋 Step 1 — Cyanosis features & exam
📌 Diagnostic impressions
📖 Schwartz Ch 24

Select timing (newborn vs older), differential saturations, respiratory distress, murmur, and hyperoxia test (PaO₂) → system distinguishes CHD (TGA, TOF, hypoplastic left heart) from lung disease, PPHN, methemoglobinemia, and guides PGE1, echo, or methylene blue.

✔️ Pre‑ductal SaO₂ > post‑ductal → ductal‑dependent systemic flow (CoA, IAA).
✔️ Hyperoxia test: PaO₂ <100 mmHg → CHD; >200 → lung disease.
✔️ Chocolate brown blood → methemoglobinemia.
✔️ Tet spell: cyanosis relieved by knee‑chest position.
📘 Schwartz pearls (Chapter 24)
• PGE1 (0.05‑0.1 mcg/kg/min) maintains ductus — lifesaving in ductal‑dependent lesions.
• Hyperoxia test: PaO₂ after 10 min on 100% FiO₂ — <100 → cardiac.
• Differential cyanosis: lower extremity saturations lower → coarctation / interrupted arch.
• Reverse differential → TGA with PPHN.