Drugs

Although many drugs have been tried in paediatric life support, few have retained their place in the resuscitation treatment protocols.

Adrenaline (Epinephrine)

Adrenaline is the mainstay of paediatric life support. It is used mainly for its alpha-adrenergic activity causing peripheral vasoconstriction, raising the peripheral vascular resistance, increasing the end diastolic filling pressure and thereby improving coronary blood flow^13,90. Adrenaline's beta-adrenergic activity is also useful as it has a direct inotropic and chronotropic effect on the myocardium.

The recommended initial dose of adrenaline is 10mcg.kg^-1 when administered via the intravenous or intraosseous routes. 10mcg.kg^-1 is 0.01mg.kg^-1 or 0.1ml.kg^-1 of a 1 in 10,000 solution. Recent studies in and children have suggested the benefit of a higher dose of adrenaline for the unresponsive asystolic child⁹¹. Therefore, should the child not respond to the initial dose of adrenaline then a second dose of 100mcg.kg^-1 (0.1ml.kg^-1 of a 1 in 1000 solution) is recommended. If the child does not respond to this or additional 100mcg.kg^-1 doses of adrenaline then the eventual outcome is likely to be poor; the results of studies show that no children have survived to discharge who have received more than two doses of adrenaline^5,9,15.

Atropine

Atropine is a parasympathetic blocking drug that will block the cardiac activity of the vagus nerve. It is used to treat bradycardia in a dose of 20mcg.kg^-1. Atropine should be considered in the peri-arrest scenario especially as it will prevent bradycardias of vagal origin (for example a vagal bradycardia during eye surgery) before they progress to cardiopulmonary collapse. Atropine is not recommended during resuscitation from cardiac arrest as the adrenergic effects of adrenaline are considered to over-ride the parasympathetic bradycardic effects on the heart.

Bicarbonate

Sodium bicarbonate is an alkalyzing agent used to correct the acidosis often associated with resuscitation. However, sodium bicarbonate is a solution with a high osmolarity containing a high level of sodium. The recommended dose is 1mmol.kg^-1 (1ml.kg^-1 of an 8.4% solution). Sodium bicarbonate should only be given if the child is being effectively ventilated as any carbon dioxide that is released by the process of acid neutralisation must be removed from the body via the lungs or paradoxical intracellular acidosis will result. 

Treatment Algorithms

The administration of adrenaline plays a pivotal role in the advanced life support algorithms of paediatric life support. Establishing venous access and ventilating with oxygen are the first steps in advanced life support and form the basis for the advanced treatment protocol. The algorithm then divides into two pathways according to the presenting cardiac rhythm - Non Ventricular Fibrillation (or Tachycardia) or Ventricular Fibrillation (or Tachycardia).

Non Ventricular Fibrillation or Tachycardia (Asystole or Pulseless Electrical Activity)

A profound bradycardia or asystole is the most common rhythm associated with cardiac arrest in infants and children. The profound bradycardia (usually described as being a pulse beat at less than one beat per second) may precede asystole but in itself the bradycardia does not produce an adequate cardiac output. A profound bradycardia should therefore be treated in the same way as an asystole. The treatment is an initial dose of adrenaline at 10mcg.kg^-1 given by the intravenous or intraosseous route (or ten times this dose via the tracheal tube if venous access has not been established). Second and subsequent doses of adrenaline should be at 100mcg.kg^-1.

Where there is a cardiac rhythm but no cardiac output (Pulseless Electrical Activity) it is also necessary to treat any of the underlying reversible causes of cardiac arrest. These are the 4'H's and 4'T's of cardiac arrest.

Adrenaline should be administered every three minutes according to the schedule described previously and resuscitation should not be abandoned until a reasonable attempt has been made to correct these potentially reversible causes of cardiac arrest.

Ventricular Fibrillation and Tachycardia

These rhythms, though common in adults, are relatively rare in infants and children. Although one study ¹¹ reported an incidence of 23% ventricular fibrillation in children, other studies report an incidence of between 0 and 10%^86,92,93. Therefore the physician must always be aware of the occasional need to treat ventricular fibrillation in children by defibrillation.

The recommended sequence is to give two rapid defibrillatory shocks of 2 joules.kg^-1, followed by a single shock at 4 joules.kg^-1. All further defibrillation attempts should then be made at 4 joules.kg^-1 in a rapid repeated series of 3 shocks. Following the first cycle of three defibrillation attempts adrenaline 10mcg.kg^-1 should be given and, in accordance with previous explanations, a further dose of 100mcg.kg^-1 should be given following the second cycle of three shocks and between all subsequent cycles. When ventricular fibrillation occurs in children there is often an underlying cause and the correction of hypothermia, drug overdose (tricyclic antidepressant overdose) and electrolyte imbalance (hyperkalaemia) should be considered. 

(Continued ...)

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