💙 Chapter 49: Cyanotic Spells (Hypercyanotic/Tet Spells)

Tetralogy of Fallot · Infundibular Spasm · Knee-Chest Position · Morphine · Propranolol · PGE1 for Ductal-Dependent Lesions

💙 Cyanotic Spells: Life-Threatening Hypercyanotic Episodes in Tetralogy of Fallot

📊 Definition & Epidemiology
Cyanotic (hypercyanotic/Tet) spells are potentially life-threatening events with significant desaturation and irritability due to acute decrease in pulmonary blood flow. Peak incidence 2-3 months. Most common in TOF, also tricuspid atresia with PS, pulmonary atresia.
🩸 Pathophysiology
Infundibular spasm + decreased SVR → increased right-to-left shunt through VSD → worsening cyanosis → hyperpnoea → more hypoxia → vicious cycle. Triggers: crying, feeding, defecation, fever, early morning, agitation, hypotension.
🚨 Clinical Features
Fussy, inconsolable infant → progressive cyanosis → hyperpnoea → limpness → seizures/stroke/death if untreated. Older child squats spontaneously (increases SVR).
💊 Immediate Management (Sequential)
1. Knee-chest position (increases SVR)
2. 100% oxygen
3. Morphine 0.05-0.1 mg/kg IV (decreases infundibular spasm, sedation)
4. Fluid bolus 10-20 mL/kg (corrects hypovolaemia, increases preload)
5. Sodium bicarbonate 1-2 mEq/kg (if acidosis)
6. Beta-blocker (esmolol or propranolol) — decreases infundibular spasm
7. Phenylephrine or noradrenaline (if refractory, increases SVR)
⚙️ Refractory Spell
Intubate and ventilate. Emergency surgical palliation (BT shunt) or ECMO if available. Chronic prevention: oral propranolol 0.5-1.5 mg/kg/dose TID.
📋 Differential Diagnosis
Breath-holding spells, seizures, pneumonia, pulmonary embolism, ductal-dependent lesions (respond to PGE1, not knee-chest).
📌 Pathophysiology Cycle: Trigger (crying) → catecholamine surge → infundibular spasm (increased RVOT obstruction) + decreased SVR (secondary to hyperpnoea/acidosis) → increased R→L shunt through VSD → worsening cyanosis → hyperpnoea → more hypoxia/acidosis → further decreased SVR. BREAK THE CYCLE by increasing SVR (knee-chest, phenylephrine) and relieving infundibular spasm (morphine, beta-blockers).

🩺 Step-by-Step: Management of Cyanotic Spell (Hypercyanotic/Tet Spell)

1
Recognise the spell
Infant with known TOF or cyanotic CHD becomes fussy, inconsolable, then progressively cyanotic with hyperpnoea (deep, rapid breathing). Pulse oximetry shows sudden drop in SpO2.
2
Immediate positioning — Knee-chest position
Place infant in knee-chest position (legs flexed against chest, or over parent's shoulder). This increases systemic vascular resistance (SVR) by compressing abdominal aorta, reducing right-to-left shunt.
3
Administer 100% oxygen
While oxygen has limited direct effect (problem is reduced pulmonary blood flow, not lung disease), it helps maintain alveolar oxygenation.
4
Morphine 0.05-0.1 mg/kg IV
Morphine reduces infundibular spasm, decreases hyperpnoea (central respiratory depression), and provides sedation. May cause apnoea — prepare to bag.
5
Fluid bolus 10-20 mL/kg isotonic crystalloid
Corrects hypovolaemia (increases preload and cardiac output) and improves systemic perfusion. Often helps break the spell.
6
Sodium bicarbonate 1-2 mEq/kg (if acidosis)
If spell prolonged with metabolic acidosis, bicarbonate helps correct pH and may improve pulmonary blood flow.
7
Beta-blocker (esmolol or propranolol)
Esmolol 500 mcg/kg load then 50-200 mcg/kg/min infusion. Reduces infundibular spasm by decreasing catecholamine effect. Propranolol 0.01-0.05 mg/kg IV if esmolol unavailable.
8
Increase SVR with vasoconstrictor (refractory spells)
Phenylephrine 2-10 mcg/kg bolus or infusion 1-5 mcg/kg/min. Noradrenaline 0.05-0.1 mcg/kg/min. Ketamine 1-2 mg/kg also increases SVR.
9
Refractory spell → intubation, paralysis, emergency surgery/ECMO
Intubation with sedation/paralysis breaks the cycle. Emergency BT shunt or ECMO if medical therapy fails and patient decompensates.