Cardiology
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Question 98 of 148
An 8 year old child is brought in by his mother. He is poorly responsive, pale and cool to the touch. His observations are: BP 75/35, HR 260 bpm, SpO2 undetectable. ECG shows a tachyarrhythmia. What is the most likely heart rhythm in this patient?
Answer:
Most serious disease or injury states are associated with a sinus tachycardia. In infants this may be as high as up to 220 bpm and in children up to 180 bpm. Rates over these figures are highly likely to be tachyarrhythmias. In any case of significant tachycardia i.e. 200 bpm in an infant and 150 bpm in a child, an ECG rhythm strip should be examined and, if in doubt, a full 12-lead ECG performed. Supraventricular tachycardia is the most common non-arrest arrhythmia during childhood and is the most common arrhythmia that produces cardiovascular instability during infancy.Paediatric Arrhythmias
Cardiology
Last Updated: 1st November 2022
Recognition
- Bradycardia:
- An abnormally slow pulse rate is defined as one less than 60 bpm or a rapidly falling heart rate associated with poor systemic perfusion. Bradycardia is usually a pre-terminal rhythm, seen as the final response to profound hypoxia and ischaemia.
- Tachycardia
- Most serious disease or injury states are associated with a sinus tachycardia. In infants this may be as high as up to 220 bpm and in children up to 180 bpm. Rates over these figures are highly likely to be tachyarrhythmias. In any case of significant tachycardia i.e. 200 bpm in an infant and 150 bpm in a child, an ECG rhythm strip should be examined and, if in doubt, a full 12-lead ECG performed.
- Tachyarrhythmia with absent P-waves and a narrow QRS complex on the ECG is most likely supraventricular tachycardia (SVT). SVT is the most common non-arrest arrhythmia during childhood and is the most common arrhythmia that produces cardiovascular instability during infancy. Tachyarrhythmia with a wide QRS complex on the ECG is most likely ventricular tachycardia.
Causes
- Bradyarrhythmias:
- Pre-terminal event in hypoxia or shock
- Raised intracranial pressure
- Conduction pathway damage following cardiac surgery
- Congenital heart block (rare)
- Long QT syndrome
- Poisoning e.g. digoxin, beta-blockers
- Tachyarrhythmias:
- Re-entrant congenital conduction pathway abnormality
- Poisoning e.g. tricyclic antidepressants, procainamide or quinidine
- Metabolic disturbance e.g. hyperkalaemia
- Post cardiac surgery
- Cardiomyopathy or myocarditis
- Channelopathies e.g. long QT syndrome
Presentations
- Palpitations (verbal)
- Poor feeding (pre-verbal)
- Heart failure or shock
Management of bradycardias
Airway, breathing and circulation should always be assessed and treated if needed before pharmacological management of bradycardia. Bradycardia may also be precipitated by vagal stimulation as occurs in tracheal intubation and suctioning.
- If there is hypoxia and shock, treat with:
- High concentration oxygen, bag-mask ventilation, intubation and intermittent positive pressure ventilation
- Volume expansion (10 ml/kg of crystalloid, repeated as recommended in the treatment of shock)
- Chest compressions
- If the above is ineffective, titrate slowly adrenaline 10 micrograms/kg IV
- If the above is ineffective, infuse adrenaline 0.05-2 micrograms/kg/min IV
- If there has been vagal stimulation, treat with:
- Adequate ventilation
- Give atropine 20 micrograms/kg IV/IO (min dose 100 micrograms, max dose 600 micrograms), repeated after 5 minutes if necessary (max total dose 1 mg in child and 2 mg in adolescent)
- If there has been poisoning:
- Seek expert toxicology help
Management of supraventricular tachycardia
Patient shocked:
- Only try vagal manoeuvres if they don't delay further treatment
- If establishing vascular access is quicker than obtaining defibrillator, give adenosine as below
- Otherwise, give synchronous DC shock 1 J/kg, followed by synchronous DC shock 2 J/kg if unsuccessful (consider amiodarone)
Patient not shocked:
- Try vagal stimulation while continuing ECG monitoring, techniques include:
- Elicit the 'diving reflex' (can be done by the application of a rubber glove filled with iced water over the face, or wrapping the infant in a towel and immersing the face in iced water for 5 seconds)
- One-sided carotid sinus massage
- Valsalva manoeuvre in an older child e.g. blowing hard through a straw
- If vagal stimulation is unsuccessful, give:
- Intravenous adenosine:
- Start with rapid iv bolus dose of 100 micrograms/kg
- If unsuccessful, after 2 minutes use 200 micrograms/kg, followed by 300 micrograms/kg after further 2 minutes
- Consider further 400-500 microgram/kg dose
- The max single dose that should be given is 500 micrograms/kg (300 micrograms/kg in child under 1 month), and up to a total max of 12 mg
- If the stable SVT of a child has not been converted to a normal rhythm with iv adenosine, it is essential to seek the advice of a paediatric cardiologist before further treatment, further treatment options include:
- Synchronous DC shock
- Amiodarone
- Other antiarrhythmics e.g. propranolol, flecainide, digoxin, verapamil
- Intravenous adenosine:
Management of ventricular tachycardia (with pulse)
Patient shocked:
- DC shock 2 J/kg, this can be repeated and dose increased if needed to 4 J/kg (consider amiodarone)
- Initially the shock should be synchronous, but if this is ineffectual because the defibrillator cannot recognise the abnormal QRS, the shocks may have to be given asynchronously recognising this is a more risky procedure
Patient not shocked:
- Early consultation with a paediatric cardiologist is needed, treatment options include:
- Amiodarone (5 mg/kg over 20 minutes; 30 minutes in neonates)
- Procainamide
- Verapamil
- Synchronous DC shock
- It is important not to delay safe therapeutic intervention for longer than necessary in VT as the rhythm often deteriorates quite quickly into pulseless VT or VF
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
