A 6-month-old girl from Delhi with known tetralogy of Fallot (diagnosed on antenatal ultrasound) presents to the emergency department with acute onset of severe cyanosis, rapid and labored breathing, and altered sensorium. The mother reports the baby was playing normally 2 hours ago. On examination, the infant is deeply cyanosed (SpO2 65%), tachypneic (RR 60/min), and unresponsive to commands. The heart rate is 180/min. Chest X-ray shows a 'boot-shaped' heart. There is no evidence of infection or metabolic derangement. What is the most appropriate immediate management?

Explanation

## Hypercyanotic Spell in TOF — Emergency Management **Key Point:** This is a **hypercyanotic spell** (also called "Tet spell") — an acute, life-threatening episode of severe cyanosis and altered mental status due to acute increase in right-to-left shunting. Recognition and immediate medical management are critical. ## Pathophysiology of Hypercyanotic Spell ```mermaid flowchart TD A[Increased RV contractility<br/>or decreased SVR]:::outcome --> B[Increased R→L shunt]:::outcome B --> C[Severe hypoxemia]:::outcome C --> D[Metabolic acidosis]:::outcome D --> E[Further RV irritability]:::outcome E --> B F[Crying, exertion, fever]:::action --> A ``` **Mnemonic:** **CRASH** — **C**yanosis, **R**apid deterioration, **A**ltered sensorium, **S**evere hypoxemia, **H**yperirritability of RV ## Immediate Management Algorithm ```mermaid flowchart TD A[Hypercyanotic spell suspected]:::outcome --> B[Position: Knee-chest]:::action B --> C[Oxygen: 100%]:::action C --> D[IV access]:::action D --> E[Morphine 0.1 mg/kg IV]:::action E --> F[Propranolol 0.1 mg/kg IV]:::action F --> G{Response in 15 min?}:::decision G -->|Yes| H[Continue observation<br/>Admit for monitoring]:::outcome G -->|No| I[Sodium bicarbonate<br/>Prepare for surgery]:::urgent ``` ## Step-by-Step Management ### 1. **Position & Oxygen** - **Knee-chest position** (squatting): Increases systemic vascular resistance, reduces R→L shunt, improves pulmonary blood flow - **100% oxygen**: Increases PaO~2~, reduces hypoxic pulmonary vasoconstriction - **Keep infant calm**: Avoid unnecessary handling; crying worsens spell ### 2. **Pharmacological Therapy** | Drug | Dose | Mechanism | Onset | | --- | --- | --- | --- | | **Morphine** | 0.1 mg/kg IV | Reduces RV contractility, sedates, reduces anxiety | 5–10 min | | **Propranolol** | 0.1 mg/kg IV | Beta-blocker; reduces RVOT obstruction, decreases RV irritability | 5–15 min | | **Sodium bicarbonate** | 1 mEq/kg IV | Corrects acidosis, reduces RV irritability | 5 min | **High-Yield:** Morphine is often given FIRST because it: - Reduces RV contractility (decreases shunt) - Causes sedation and reduces anxiety (prevents further crying/exertion) - Has rapid onset **Clinical Pearl:** Propranolol is the definitive agent but takes 5–15 minutes; morphine bridges the gap and provides symptomatic relief. ### 3. **Supportive Measures** - Maintain IV access - Monitor SpO~2~, heart rate, blood pressure - Avoid diuretics (reduce preload, worsen shunt) - Maintain hydration - Correct any metabolic acidosis with sodium bicarbonate if spell persists ### 4. **When to Escalate** - If spell persists >15–20 minutes despite medical therapy → prepare for emergency surgery - Recurrent spells despite propranolol → urgent surgical repair **Key Point:** Medical management resolves 80–90% of spells. Surgery is reserved for refractory cases or recurrent spells.