As for the primary assessment of shock, special attention should be paid to the adequacy of circulation. If significant tachycardia ie 200 in infant, 150 in child, an ECG rhythm strip is more reliable than manual count or pulse oximeter. Look for signs of heart failure.
ABC as usual. If heart rate below 60 in a patient with shock, cardiac compressions should be commenced.
If a narrow complex tachyarrhythmia and shock, up to 3 synchronous electrical shocks at 0.5, 1 and 2 J should be given. If broad complex, give asynchronous shocks to avoid possible delays in detecting favourable shock times.
If shock and SVT, IV/IO adenosine can be used if it would be quicker than a synchronous electrical shock.
From the ECG, the arrhythmia can be identified by the following questions:
Bradycardia is most usually a preterminal rhythm is response to profound hypoxia and ischaemia. Also provoked by vagal stimulation, raised intracranial pressure, poisoning with digoxin or beta-blockers.
A rapid heart rate with a narrow QRS complex is SVT, usually regular.
A rapid heart rate with a wide QRS is VT, can be provoked by hyperkalaemia and tricyclic antidepressants poioning, combination of cisapride and macrolide antibiotic or terfenadine and grapefruit juice.
Treat hypoxia and shock vigorously, including epinephrine IV bolus and infusion if necessary.
Bradycardia after vagal stimulation eg tracheal suctioning or intubation, volume expansion is unlikely to be needed but good ventilation should be ensured prior to giving atropine 0.02 mg/kg IV (mimimum dose 0.1 mg, maximum 2 mg/dose). Small amounts may produce paradoxical bradycardia. The dose can be repeated in 5 mins. If IV/IO access is not readily available, atropine 0.04 mg/kg can be administered tracheally, although absorption may be unreliable.
To distinguish sinus tachycardia and SVT:
Cardiopulmonary stability in SVT depends on age, duration, prior ventricular function and ventricular rate. Older children usually complain of dizziness or chest discomfort, but very rapid rates may be undetected for long periods in young infants until they develop a low cardiac output state and shock.
If shock present, child should receive synchronous DC shock unless vascular access can be established more quickly for administration of adenosine. Vagal manoeuvres can be attempted but there should be no delay in treatment with DC shock or adenosine.
Synchronous DC shock 0.5 J/kg then 1 J/kg if unsuccessful then 2 J/kg. Further shocks should be at 2 J/kg and anti-arrhythmics should be considered.
Vagal stimulation with ECG monitoring:
If these are unsuccessful, give:
Ask about congenital heart disease and surgery, possibility of poisoning (presence of drugs in home), renal disease (hyperkalaemia).
Look for torsades de pointes on ECG, check K, Mg, Ca.
If haemodynamically stable, treatment should always include early consultation with a paediatric cardiologist. If is important not to delay a safe therapeutic intervention as the rhythm often deteriorates into pulseless VT or VF.
If pulseless, follow VF protocol.
If shock present, give asynchronous DC shock 0.5 J/kg, then 1 J/kg if unsuccessful, then 2 J/kg. Further shocks should be at 2 J/kg and anti-arrhythmics should be considered.
If not shocked, Amiodarone 5 mg/kg IV over 30 min should be given. Can cause hypotension which should be treated with volume expansion. If unsuccessful, consider synchronous DC shock or lignocaine.
Torsades de pointes is a polymorphic ventricular tachycardia charaterised bya n ECG appearance of QRS complexes with change in ampltude and polarity so that they appear to rotated around an isoelectric line. It is seen in long QT interval eg quinidine, disopyramide, amiodarone, tricyclic antidepressants, digoxin, interaction of cisapride and erythromycin. Treatment is Magnesium sluphate in rapid IV infusion (several minutes) 25-50 mg/kg (up to 2 g).