Synopsis
Recognise tetralogy anatomy and age-dependent cyanosis, treat a hypercyanotic spell in the correct physiological sequence with complete weight-based rescue regimens, and anticipate repair and lifelong complications.
- Tetralogy consists of a VSD, overriding aorta, right-ventricular outflow tract obstruction and secondary right-ventricular hypertrophy; one developmental malalignment creates the first three and pressure load creates hypertrophy.
- Severity is governed mainly by outflow obstruction. Mild obstruction permits left-to-right flow and little cyanosis; severe obstruction drives venous blood through the VSD into the aorta.
- A hypercyanotic spell is sudden dynamic reduction in pulmonary flow with increased right-to-left shunting, often during crying, feeding, defecation, fever or dehydration.
- Recognise deeper cyanosis or pallor, rapid deep breathing, irritability, limpness or syncope and a softer or absent outflow murmur; do not wait for a numeric saturation threshold.
- Immediate sequence: call help, minimise distress, high-flow oxygen as tolerated and knees-to-chest to raise systemic resistance and venous return.
- If persistent, obtain IV or IO access and give morphine 50 micrograms/kg IV, repeat once after 3 minutes if required; without IV access use intranasal fentanyl 1–2 micrograms/kg or IM morphine 100 micrograms/kg under the emergency pathway.
- Give 0.9% sodium chloride 10 mL/kg and repeat only after reassessment when dehydration or low preload contributes; provide respiratory support if opioid or spell physiology depresses breathing.
- Refractory spells need paediatric cardiology and critical-care direction for IV propranolol 100 micrograms/kg or esmolol 600 micrograms/kg, and phenylephrine infusion starting 500 nanograms/kg/min within the guideline range.
- Echocardiography confirms anatomy and severity; ECG and chest radiography support baseline assessment, while blood count identifies anaemia or harmful hyperviscosity.
- Definitive treatment is surgical repair, usually closing the VSD and relieving outflow obstruction; timing depends on anatomy, saturation, growth and spells, with palliation when complete repair is not immediately feasible.
- Every repaired child needs congenital cardiac surveillance for pulmonary regurgitation, residual obstruction or VSD, right-ventricular dilatation, aortic root disease and atrial or ventricular arrhythmia.
Key red flags
A spell with reduced consciousness, limpness, seizure, persistent severe cyanosis, bradycardia or shock is immediately life-threatening and requires resuscitation-team and intensive-care support.
The obstruction murmur becoming shorter or absent during worsening cyanosis indicates falling pulmonary flow, not improvement.
A first suspected spell needs hospital assessment even if colour recovers, because the diagnosis, trigger, anaemia, hydration and need for earlier repair require review.
Fever, dehydration, feeding, crying, defecation, tachypnoea or procedures can precipitate dynamic outflow obstruction and should be corrected alongside rescue measures.
Cyanosis from birth or profound neonatal hypoxaemia may represent severe pulmonary obstruction or pulmonary atresia with duct-dependent flow and needs neonatal cardiac transfer.
After repair, syncope, sustained palpitations, exertional decline, heart-failure signs or haemoptysis suggests arrhythmia, pulmonary regurgitation, ventricular dysfunction or another late complication rather than a simple infant spell.
Investigation priorities
Recognise the emergency and begin treatment without waiting for imaging.
Management branches
A child with susceptible anatomy develops sudden deeper cyanosis, hyperpnoea or reduced responsiveness.
- Call emergency help, minimise handling and keep the child calm with the caregiver.
- Give high-flow oxygen as tolerated and position knees firmly against the chest.
- Attach continuous ECG and saturation monitoring and obtain IV or IO access without prolonging distress.