8.2 Supraventricular Tachycardia

Question 1

You are asked to review a 2-year-old child in recovery who is agitated
and distressed after an elective myringotomy/grommets.

What is your differential diagnosis and management plan?

Answer 1

• Full history and examination
• Full set of observations
• Ensure parents/carers are present

Differential diagnosis

• Patient factors:
  separation anxiety, requiring feeding/water or nappy
  change, unfamiliar environment/people
• Anaesthetic factors:
  Inadequate analgesia, hypoxia, hypothermia,
  inadequate ventilation, sore throat
• Surgical factors:
  displacement of myringotomy tube
• Unrelated medical problem

Management
* Ensure parent/carer present to reassure and comfort.
* Assess ABC.
* Give analgesia/antiemetic as indicated.
* Ensure well oxygenated, not hypercarbic or hypothermic.
* Allow to feed if appropriate. Check and change nappy.
* Ask surgeons to review.
* Reassess as required.

Question 2

What does the ECG in Figure 8.3 show?

Answer 2

The ECG shows a narrow complex tachycardia, rate ∼ 300 bpm

Question 3

You are told the child is not decompensating (no evidence of shock) as yet.

How do you manage?

Answer 3

Question 4

How many joules would you shock with in this case?

Answer 4

Energy is calculated according to weight.

Formula for weight in children of 1–5 years:

Weight (in kgs) = (2 × age in years) + 8

In this case: Weight = (2 × 2) + 8 = 12 kg

Therefore, energy for shocks is as follows:
1 J/kg = 12 J; 2 J/kg = 24 J (rounded to nearest J on defibrillator)

Question 5

What is the dose of adenosine in this child?

Answer 5

Weight 12 kg based on formula above

• Start dose 100 mcg/kg = 1200 mcg
• Then 200 mcg/kg after 2 mins if no effect = 2400 mcg
• Then 300 mcg/kg after 2 mins if no effect = 3600 mcg
• Up to a max of 500 mcg/kg = 6000 mcg

Question 6

What are the potential causes of sVt in a 2-year-old?

Answer 6

• Re-entrant congenital conduction pathway abnormality (common)
• Poisoning
• Metabolic disturbance
• After cardiac surgery
• Cardiomyopathy
• Long QT syndrome

Question 7

Describe how you would perform a DC cardioversion in a paediatric case.

pre procedure

+ Induction

Answer 7

• Preprocedure
  ° Consent parents.
  ° Check electrolytes (could do a quick venous blood gas).
  ° Arrange for a second senior anaesthetist and paediatrician to be
  present.
  ° State this is an emergency if signs of decompensation are present.
  ° Performed preferably in an anaesthetic room, if not in an area where
  equivalent monitoring can occur.
• Induction
  ° Full AAGBI monitoring
  ° IV access (if not going to distress the child)
  ° RSI if not starved, otherwise gas induction and maintenance
  ° Endotracheal intubation if aspiration risk; otherwise, may be able to
  use guedel airway and mask

Question 8

Describe how you would perform a DC cardioversion in a paediatric case.

Answer 8

Maintenance
° Volatile versus propofol boluses

• Shock
  ° Paddles front to back
  ° Synchronised shock at 1 J/kg up to 2 J/kg
• Amiodarone
  ° Consider amiodarone 5 mg/kg
• 12-lead ECG
  ° To confirm no longer in SVT
• Emergence/recovery
  ° Allow to wake in left lateral position
  ° Prolonged cardiac monitoring in recovery or on paediatric ward
• Follow-up
  ° Will need review and follow-up by paediatricians
  and/or paediatric cardiologist