Hypercyanotic (tet) spell

Paediatric emergency management · Cardiology · Emergency

Paroxysm of worsening cyanosis, hyperpnoea and irritability in a child with Tetralogy of Fallot, from an increased right-to-left shunt. Keep the child calm — handling worsens it.

Stepwise management

Knee-to-chest position (or let the child squat) to raise systemic vascular resistance.
High-flow oxygen; calm, quiet environment; minimal handling.

Morphine0.1 mg/kg IM/SC or slow IV to reduce hyperpnoea and settle the child

Fluid bolus10–20 mL/kg isotonic fluid to improve preload

If persisting

Correct metabolic acidosis with sodium bicarbonate.
Raise SVR with phenylephrine (or noradrenaline).
Relieve infundibular spasm with a beta-blocker (esmolol or propranolol).
Refractory — anaesthesia, paralysis and urgent cardiology/surgical input.

Common questions

What is the first step in hypercyanotic (tet) spell?

Paroxysm of worsening cyanosis, hyperpnoea and irritability in a child with Tetralogy of Fallot, from an increased right-to-left shunt. Keep the child calm — handling worsens it.

What drug doses are used in hypercyanotic (tet) spell?

Morphine: 0.1 mg/kg IM/SC or slow IV to reduce hyperpnoea and settle the child. Fluid bolus: 10–20 mL/kg isotonic fluid to improve preload.

About this page

Compiled from standard paediatric references. Verify against a current formulary and your local protocol.

Spotted something wrong? Report an error on this page — corrections from clinicians are welcome and are reviewed before any change is published.

Last reviewed 2026-08-12.