Hypercyanotic attack


This is a life threatening paediatric cardiac emergency.

It usually occurs in infants with a peak incidence between 4 and 6 months.

A severe episode may lead to limpness, seizures, cerebrovascular accident or even death.

Spells may be brief (1-2 minutes) and self-correct or may progress to a severe, life-threatening episode.

Prompt recognition by parents and medical staff is important.

The attack is often early in the morning with no apparent reason.

It may be precipitated following a bath, by prolonged crying, defaecation, dehydration, febrile illness or induction of anaesthesia.

Causes of hypercyanotic attack

Congenital heart disease e.g. Tetralogy of Fallot, pulmonary stenosis, double outlet right ventricle, tricuspid atresia, Eisenmenger syndrome

Symptoms of hypercyanotic attack

The following are the symptoms of Hypercyanotic attack

  1. Irritability and prolonged crying
  2. Deep rapid breathing
  3. Increased severity of cyanosis

Signs of hypercyanotic attack

  1. Tachycardia
  2. Systolic murmur
  3. Coma
  4. Convulsions
  5. Hemiparesis


  • FBC
  • Chest X-ray
  • ECG
  • Echocardiography

Treatment for hypercyanotic attack


The following are the treatment objectives of hypercyanotic attack

  1. To recognise the problem early
  2. To reverse obstruction
  3. To correct metabolic derangement in severe hypoxia
  4. To prevent complications and death from severe hypoxia

Non-pharmacological treatment

  • Hold in knee chest position (teach parents)
    • The above actions increase peripheral vascular resistance and help to reduce cyanosis.

Pharmacological treatment

A. All children with hypercyanotic attack

Evidence Rating: [C]

Oxygen (100%), by face mask or nasal prongs,

  • 2 L/minute (monitoring oxygen saturation if possible) -to all patients to reduce hypoxia


0.9% Normal Saline or Ringers’ Lactate, IV,

  • 10 ml/kg, over 30 minutes then assess response


Morphine sulphate, slow IV (preferred), or IM, if IV line not accessible,

  • 100-200 micrograms/kg stat.

B. For patients with poor response to above measures


Propranolol, oral,


  • 1 month-12 years: 500 microgram/kg 8 hourly (max. 5 mg/kg daily)
  • Neonates: 500 microgram/kg 8 hourly (max. 2 mg/kg 8 hourly)

C. To correct acidosis in cyanotic patients with no improvement after 10 minutes of above treatment,


Sodium Bicarbonate, IV,

For all age groups

  • 1-2 mmol/kg


Emergency surgical shunt may be required

D. Maintenance treatment to prevent recurrent attacks pending surgery

Propranolol, oral,


  • 1 month-12 years: 0.25-1 mg/kg 6-8 hourly (max. 5 mg/kg daily)
  • Neonates: 0.25-1 mg/kg 8-12 hourly (max. 2 mg/kg 8 hourly)

Propranolol, slow IV with ECG monitoring


  • 1 month-12 years: 15-20 microgram/kg 6-8 hourly (max. 200 microgram/kg) repeated every 6-8 hours if necessary
  • Neonates: 15-20 microgram/kg (max. 100 microgram/kg) repeated every 12 hours if necessary

Referral Criteria

Hypercyanotic attack is an indication for early surgery.

Refer urgently to a paediatric specialist or cardiothoracic surgeon

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