Alternative methods of artificial
circulation


Active compression decompression CPR (ACD-CPR) was developed after a report of a man who used a plunger to resuscitate a person. This device, which is attached to the chest wall, increases the intrathoracic pressure during compression to promote forward blood flow. During active decompression, it augments the negative intrathoracic pressure that increases the venous return and myocardial perfusion.

The advantages of ACD-CPR are rescuers can perform alone; it is portable and relatively inexpensive. However, it is associated with increased incidence of local chest trauma and increased fatigue. Clinical studies on ACD-CPR in adults have been inconclusive, mainly due to inadequate power. Currently, no study has been done to assess the use of ACD-CPR in the paediatric population although increased chest wall compliance and flexibility would make ACD-CPR device of significant value. There is also a need to manufacture several sizes and overcome the 15-17% incidence of the device not adhering to the chest wall.

Interposed abdominal compression CPR (IAC-CPR) or counterpulsation is a CPR technique that involves applying pressure to the abdomen during decompression phase of chest compression. This method apparently increases venous return and acts like an intra-aortic balloon pump by pushing retrograde aortic blood flow to the brain and heart. A second rescuer applies abdominal pressure manually with two hands during diastole and avoids injury to the liver. Animal studies have been promising and some studies in adults have demonstrated improved cerebral and myocardial blood flow leading to increased ROSC and survival to hospital discharge. However, the optimal method of abdominal compression is still unclear. Again, there have been no paediatric studies and there are still concerns about potential abdominal organ injuries in children. Another limitation of the technique is the need for 3 rescuers.

Abdominal binding and simultaneous compression-ventilation CPR (SCV-CPR) is thought to increase cardiac output by augmenting the thoracic pump mechanism. It was able to generate higher arterial pressures in adults but there was no difference in ROSC or survival.

Other invasive circulation methods involve the use of an intra-aortic balloon pump, extracorporeal membrane oxygenation (ECMO) or cardiopulmonary bypass. These methods require time, sophisticated resources and technical skills to implement. Open cardiac massage should be reserved for penetrating chest injuries who acutely deteriorate in hospital. Paediatric blunt trauma patients appear not to benefit from open chest massage.

Vascular access

Successfully resuscitated patients had vascular access significantly earlier than those not resuscitated. Rapid delivery of drugs into the central circulation combined with effective chest compression is necessary to deliver adrenaline to its site of action in the vascular tree.

Intravenous and intraosseous route is preferred for delivery of drugs. Central venous drug administration produces a more rapid and higher peak concentration than peripheral venous administration in adults. A fluid bolus improves the delivery of drugs into the central circulation. Injection into veins that drain into the superior vena cava is better than to veins that drain into the inferior vena cava because the inferior vena cava does not effectively collapse resulting in to and fro blood flow.

There is consensus that the tibial intraosseous route is useful for vascular access for patients up to 6 years age. The peak effects and duration of action of drugs given intra-osseously were comparable to central and peripheral venous routes. Small risk associated with intraosseous route such as fractures, growth plate injuries, subcutaneous or subperiosteal infusions, compartment syndrome, fat embolism and osteomyelitis, which occurred only after infusion of hypertonic solution or prolonged infusions. Contraindications to intraosseous route include osteogenesis imperfecta, osteopetrosis, ipsilateral limb fracture or local infection.

The endotracheal route may be used if vascular access is delayed. Certain lipid-soluble drugs such as adrenaline, lignocaine and atropine can be given via the endotracheal tube but the drug absorption kinetics is not favourable. However, drugs such as bicarbonate, glucose and calcium can cause serious lung injuries. Ten times the amount of drugs given intravascularly needs to be given through the endotracheal tube to achieve the same plasma drug concentration and peak drug action. However, the lung acts as a depot for these large amounts of drugs and the child may have profound and prolong hypertension upon ROSC due to slow absorption of the adrenaline depot. Drug absorption is most efficient at the alveoli and small airway. Therefore, drugs should be delivered via a catheter into the lower airways beyond the tip of the tracheal tube or followed by a 5ml saline flush and 5 mechanical insufflations to aid distribution. After 15 minutes of CPR, the tracheal route may be less effective due to pulmonary edema and atelectasis.