Epidemiology

Previous studies of paediatric Out-of-Hospital Cardiac Arrest (OHCA) have reported poor survival rates with severe neurological sequelae,^2,3 however more recent publications have challenged this reporting a similar rates of survival to hospital discharge as that of adults who sustain OHCA.^4,5

The incidence of out-of-hospital arrest is reported as ranging from 2.6 to 19.7 per year per 100 000 paediatric population (age < 18 years), in the region of 30% achieving return of spontaneous circulation (ROSC), 24% surviving to hospital admission, and 12% surviving to discharge.⁶

Less than 10% of paediatric OHCA victims have a shockable rhythm on arrival of the prehospital care providers.^4,5

Aetiology

The most common causes of cardiac arrest in children relate to the development of hypoxia and/or shock, the two pathways which, untreated, result in cardiopulmonary arrest. Shock is the clinical state of poor tissue perfusion. Thus, the primary organ systems involved are the respiratory and cardiovascular systems, and the central nervous system (CNS), which becomes compromised by hypoxia or decreased cerebral perfusion. Injury or diseases progressing to failure of these systems may then lead to cardiac arrest. CNS disorders, either with direct dysfunction or due to raised intracranial pressure, may cause respiratory arrest with the resulting hypoxia leading to cardiac arrest. The primary causes of cardiac arrest are heterogeneous and include trauma, sepsis, drug overdose, poisoning, immersion, critical respiratory illness and sudden infant death syndrome (SIDS). This list is by no means complete, and many other conditions may also progress to cardiac arrest.

Pathophysiology

Significant hypoxic and hypoperfusion insults to the myocardium are the common pathways that may progress to cardiac arrest in children. Hence, fluid or blood loss leading to shock, if left untreated, result in myocardial ischaemia and resultant cardiac arrest. Similarly, severe hypoxia also results in global myocardial dysfunction and subsequently cardiac arrest. Thus, preventive strategies must identify hypoxia and shock early and instigate appropriate management to improve oxygenation and organ perfusion, thereby preventing progress to cardiac arrest. Poisonings or ingestions may have a direct effect on the heart, causing an arrhythmia, coma, with subsequent respiratory arrest and hypoxia.

Outcome

Generally, the survival from respiratory arrest alone is much better than from cardiopulmonary arrest. Survival to discharge for children with respiratory arrest (pulse present) is around 75%, and of these up to 88% have a good neurological outcome. Reported survival rates from cardiac arrest in children have varied from 0% to 17%. Survival to discharge from hospital for paediatric OHCA is 7%^4,5 and 36% for in-hospital cardiac arrests.⁷ ‘Survival to discharge’ is a very crude marker of ‘success’ as it does not include a measure of neurological function. Proactive early resuscitation of the pre-arrest child is important in order to have the most impact on outcome.

Unfortunately, the perception of the public, and even doctors and nurses, is that the expected survival rate is higher than this. Lay rescuers, physicians and nurses estimate the survival rate for cardiopulmonary arrest in children as being 63%, 45% and 41% respectively (compared to 53%, 30% and 24% for adult cardiopulmonary arrest).⁸ Undoubtedly, fictional medical television programmes contribute to this bias, and even non-fictional medical programmes rarely show death as an outcome.

Differences compared to adults

When comparing children to adults in relation to cardiopulmonary arrest, there are several important differences. The aetiology of the event is usually different. Adults who collapse are more likely to have ventricular fibrillation or pulseless ventricular tachycardia, hence the time to defibrillation is the single greatest determinant of survival. Thus the ‘phone first’ principle that applies to adults is not applicable to most infants and children, in whom the response should be ‘phone fast’ (see Chapter 2.2 on Basic life support).

There are several anatomical and physical differences between children and adults. It is important to consider these differences in relation to the primary event leading to arrest and to the resuscitation techniques subsequently required (Table 2.1.1).

Table 2.1.1 Important differences between children and adults

Difference in children Implication AIRWAY Prominent occiput tends to cause neck flexion Neck extension, into a neutral or sniffing position (slight extension), is required to optimise the airway for an infant or child respectively Mandible is relatively smaller More difficult intubation Tongue is relatively larger Tends to obstruct airway
More difficult intubation Larynx is more cephalad (located almost at base of tongue)