A 3-year-old boy from rural Maharashtra is brought to the pediatric clinic with a 6-month history of progressive dyspnea on exertion and squatting posture during play. On examination, he is cyanotic with clubbing of fingers. His oxygen saturation is 78% on room air. Cardiac auscultation reveals a single loud S2 and a systolic ejection murmur at the left upper sternal border. Chest X-ray shows a boot-shaped heart with reduced pulmonary vascular markings. Echocardiography confirms a large VSD, right ventricular outflow tract obstruction, right ventricular hypertrophy, and an overriding aorta. What is the most appropriate immediate management to relieve his acute cyanotic spell?

Explanation

## Acute Cyanotic Spell Management in Tetralogy of Fallot **Key Point:** Acute cyanotic spells (Tet spells) in TOF are caused by transient increase in right-to-left shunting due to increased right ventricular outflow tract obstruction. Immediate symptomatic relief is the priority. ### Pathophysiology of Tet Spell During a spell, infundibular spasm increases RVOT obstruction, worsening right-to-left shunting and systemic desaturation. The cycle is self-perpetuating: hypoxia → acidosis → increased catecholamines → more infundibular spasm. ### Acute Management Strategy **Knee-chest position** (or squatting, which the patient already does instinctively): - Increases systemic vascular resistance - Decreases right-to-left shunt magnitude - Improves pulmonary blood flow **Supplemental oxygen:** - Corrects hypoxemia - Reduces hypoxic pulmonary vasoconstriction **Morphine (0.1 mg/kg IV/IM):** - Relieves infundibular spasm - Reduces catecholamine surge - Sedates the child (reduces agitation and oxygen demand) **Additional agents if spell persists:** - Beta-blockers (propranolol) to reduce contractility and HR - Sodium bicarbonate for metabolic acidosis - Phenylephrine (alpha-agonist) to increase SVR if hypotensive ### Why This Patient Needs Immediate Intervention He is actively cyanotic (SpO₂ 78%) with classic TOF anatomy on echo. Spells can progress to loss of consciousness and death if untreated. **High-Yield:** The mnemonic for acute Tet spell management is **MOPS**: - **M**orphine - **O**xygen - **P**osture (knee-chest) - **S**odium bicarbonate (if acidotic) **Clinical Pearl:** Squatting is the child's own compensatory mechanism — it increases SVR and temporarily relieves the spell. This is why TOF children instinctively adopt this posture during play. ### Definitive Management Surgical repair (primary repair or staged approach with Blalock-Taussig shunt if very young) is definitive but NOT the immediate management of an acute spell. Long-term beta-blocker therapy (propranolol) reduces spell frequency and severity. [cite:Park 26e Ch 11]