Airway management

There is a focus on early ventilation and early effective oxygenation in paediatric resuscitation because cardiac arrest is often secondary to respiratory failure. The most common cause of airway obstruction in the unconscious paediatric patient is the tongue. Head tilt chin lift or jaw thrust particularly in suspected cervical spine instability is important to maintain a patent airway. There is suggestion that blind removal or attempted visualization of unsuspected foreign body is unlikely to be effective because foreign bodies causing airway obstruction is unlikely to be visible and attempted removal may dislodge it further distally.

Current recommendation is for mouth to mouth and nose ventilation for infants up to 1 year old. The number of initial attempted resuscitative breath remains debatable ranging between 2 to 5 in the various algorithms, delivered over 1 to 1.5 seconds. The long inspiratory time is recommended to reduce the airway pressure and hopefully reduce gastric insufflation. Insufflation of the stomach may splint the diaphragm, decrease the lung volume and increase the risk of aspiration. Face mask ventilation with cricoid pressure has reduced gastric gas volume and increased exhaled volume. Ideal ventilation frequency during CPR is unknown. Current recommendation is based on normal ventilatory rates for age, the need for coordination with chest compression and the practical ability to perform them. The rescuer should pause between breaths to maximise oxygen and minimise carbon dioxide in the delivered breaths.

Infrequent intubation experience of the paediatric population may result in less than optimal airway management of these patients. Effective bag-valve-mask ventilation especially with a self inflating bag is more important than fumbled and prolonged attempts at intubation at the scene of cardiac arrest. Gausche et al demonstrated no improvement in survival or neurological outcome between paediatric patients who were randomized to be intubated compared to those who received bag-valve-mask ventilation. Also, two rescuers were able to deliver greater tidal volumes than one with a bag-valve-mask device. Recent literature suggests that the laryngeal mask airway (LMA) can be used in resuscitation and the skills for insertion can be easily acquired. The LMA, though, can only be used in patients with no gag reflex and there is still a small risk of aspiration.

Circulation

The objective of CPR is to provide adequate oxygenation and perfusion to the vital organs until the return of sustained adequate spontaneous circulation. In animal studies, CPR is able maintain cerebral and myocardial perfusion at only 20% the pre arrest values. Hence, optimal cardiac compression technique and timing is important. There is documented difficulty in reliably assessing the pulse in the paediatric resuscitation and therefore, resuscitative intervention should not be delayed more than 10 seconds to detect pulse. Chest compression should be started in all pulseless or profound bradycardia paediatric patients over the lower half of the sternum taking care not to compress the xiphoid and to approximately one third the depth of the chest at a rate of 100 compressions per minute. Three studies have confirmed that the heart lies beneath the lower third of the sternum in all ages and chest compression over the lower third produces better arterial pressures and stroke volume than over the midsternum with no other organ injuries.

Although the most practical assessment of chest compression is pulse detection, there is suggestion it may represent retrograde venous flow. End tidal CO2 detection represents pulmonary blood flow may be a better assessment of chest compression and is predictive of ROSC. The most efficient blood flow is achieved when the cardiac compression lasts 50% of the cycle to allow sufficient time for chest recoil. Cardiac compression can be done with one hand in children up to 8 years old. However, the size of the victim and the strength of the rescuer may necessitate the use of 2 hands in younger children. In infants, encircling the infant's chest and compressing with overlapping thumbs (Thaler-Strobie manoeuvre) may produce higher mean arterial, pulse pressures and cardiac output, possibly by greater increase in intrathoracic pressure. However, in an older child, the encircling hand may not allow full re-expansion of the chest, reducing venous return.

The ideal compression-ventilation ratio is unknown but the current consensus is 3: 1 in newborns and 5: 1 in infants and children. This difference from the adult resuscitation guidelines emphasises that respiratory problems are the most common etiology in paediatric cardiac arrest and that the physiological respiratory rates in this age group is faster. Interposition of compression and ventilation is recommended to avoid simultaneous compression and ventilation.

There are 2 theories of mechanism of blood flow during CPR: direct cardiac compression and "thoracic pump" mechanism. The "thoracic pump" mechanism postulates the global increase in intrathoracic pressure associated with cardiac compression results in forward blood flow. Direct cardiac compression assumes that the blood flow is produced by direct compression of the heart between the sternum and the vertebral bodies. This mechanism may play a greater role in the paediatric population as compared to the adults due to the more compliant chest wall.