Clinical scenario: TOF / Cyanosis / emergency
A 16-month-old boy with unrepaired Tetralogy of Fallot develops sudden deep cyanosis while crying. He is placed in the knee-chest position and receives high-flow oxygen, but there is no improvement after several minutes. He remains tachypneic and irritable with an oxygen saturation of 60%.
What is the most appropriate next step?
A. Furosemide
B. Morphine
C. Prostaglandin E₁
D. Sodium bicarbonate
E. Sodium nitroprusside
Correct answer & Explanation:
Correct Answer: B. Intravenous morphine
Explanation: Tet spell / management
This child is experiencing a hypercyanotic (“Tet”) spell, a life-threatening complication of unrepaired Tetralogy of Fallot caused by a sudden increase in right-to-left shunting across the ventricular septal defect due to dynamic right ventricular outflow tract obstruction.
Initial management includes:
- Knee–chest position
- High-flow oxygen
- Intravenous (or subcutaneous) morphine
- Intravenous fluids if hypovolemic
- Vasoconstrictors such as phenylephrine if the spell persists
- β-blockers (e.g., propranolol or esmolol) when indicated
Morphine reduces catecholamine release, decreases hyperpnea, and relieves infundibular spasm, helping reduce the right-to-left shunt.
Why the other options are incorrect
A. Intravenous furosemide
Not indicated. Tet spells are not caused by fluid overload, and diuresis may worsen right ventricular filling.
B. Intravenous morphine
Correct. After knee–chest positioning and oxygen, morphine is an established first-line medication to terminate a hypercyanotic spell.
C. Intravenous sodium bicarbonate
May be considered only if significant metabolic acidosis persists despite initial treatment. It is not the next immediate intervention.
D. Prostaglandin E₁ infusion
Useful in duct-dependent cyanotic heart disease or selected critically ill young infants, but it is not routine treatment for a Tet spell in a 15-month-old with classic Tetralogy of Fallot.
E. Urgent endotracheal intubation
Reserved for refractory spells with respiratory failure or failure of medical management, not as the immediate next step after initial stabilization.
Learning Point
The acute management sequence for a hypercyanotic spell is:
- Knee–chest position
- High-flow oxygen
- Morphine
- Intravenous fluids (if needed)
- Phenylephrine and/or a β-blocker if the spell persists
- Intubation and urgent surgical/interventional management for refractory cases
