NUS : Department of Paediatrics

The system of modern cardiopulmonary resuscitation (CPR) is a relatively new phenomenon, starting only about 60 years ago. The road leading to its development, however, stretches back many centuries and has been a process of gradual evolution¹. Inaccurate and inadequate techniques have been attempted and rejected along the way as we have learnt more about the science of resuscitation. Examining the history of resuscitation is a useful first step to understanding the evolution to modern practice. The evidence for current practice will be presented, detailing the rationale behind the most recently published guidelines. Possibilities for future research and improvement in the field of resuscitation science will also be discussed.

The Past

Airway and Breathing

The earliest recorded attempt at resuscitation is from the Old Testament of the Bible, in the book of 2 Kings, by the prophet Elisha.

"And when Elisha was come into the house, behold, the child was dead, and laid upon his bed. He went in therefore, and shut the door upon them twain, and prayed unto the LORD. And he went up, and lay upon the child, and put his mouth upon his mouth, and his eyes upon his eyes, and his hands upon his hands: and stretched himself upon the child; and the flesh of the child waxed warm. Then he returned, and walked in the house to and fro; and went up, and stretched himself upon him: and the child sneezed seven times, and the child opened his eyes." (2 Kings 4: 32-35)

Little mention of this method, however, is made in the following 2 millennia until the Renaissance when scientists attempted to understand the basic workings of the human body. In 1542, Andreas Vesalius, the famed Flemish anatomist, observed that when he opened the chest of an experimental animal, the heartbeat and pulsation of the great vessels stopped but returned again after he introduced a reed into the airway and inflated the lungs with bellows².

This knowledge unfortunately, lay dormant until the 18^th century because the lack of appreciation of its applicability to humans. In the 1500s, Paracelsus had already documented the use of fireside bellows to nose resuscitation in humans but it was not till the 1700s that reports of early mouth-to-mouth techniques were reported.

In 1767, the Society for the Recovery of Drowned Persons was founded in Amsterdam. Physicians and laypeople collaborated to aid victims of drowning in the numerous canals in the city. Methods of resuscitation were set up and disseminated and monetary rewards distributed for success. The use of mouth-to-mouth respiration, however, fell out of favour compared to the use of bellows, as the expired air was perceived to have been "devitalized" by passing through the rescuer's lungs.

It was only in the mid 1950s, though, that methodical investigation in the techniques of resuscitation was carried out by Peter Safar and James Elam in Baltimore City Hospital. In a series of daring experiments, Safar paralysed volunteers with curare or succinylcholine and demonstrated that optimal patency was attained with the neck extended and the mandible supported. He also elegantly demonstrated that expired air contained enough oxygen to maintain normal saturations ^3-4.

Circulation

Chest compressions in resuscitation were largely thought to aid only in ventilation till the end of the 19^th century. In 1874, Moritz Schiff performed the first cardiac compressions when he noted carotid pulsation after manually squeezing a canine heart through an open chest⁵. Boehm and Mickwitz demonstrated closed chest compression soon after by squeezing the ribs and sternums of cats⁶. The first successful case of closed chest cardiac massage was actually reported by Friedrich Maass in 1892. Unfortunately, the medical community overlooked this important contribution for almost 70 years.

With the advent of anaesthesia in the form of chloroform in the latter half of the 19^th century, anaesthetic related cardiac arrests occurred and these were deemed fatal until the first successful open cardiac massage performed by Kristian Ingelsrud in 1901. For the next 60 years, sudden cardiac death was only survivable in a hospital setting where open cardiac massage could be performed¹.

It was only the late 1950s, when Guy Knickerbocker, James Jude and William Kouwenhoven were researching defibrillation in dogs, that the technique of external cardiac compression was rediscovered. They noticed that when the defibrillator paddles were applied firmly on the sternum, there was a simultaneous rise in femoral arterial pressure. The technique of external chest compression was reintroduced to the patient care setting in 1958 and quickly eclipsed open cardiac massage as a resuscitation technique⁷.

The connection of mouth-to-mouth ventilation and chest compression to create CPR as it is practiced today occurred when Safar, Jude and Kouwenhoven presented their findings at the annual Maryland Medical Society Meeting on September 16^th 1960. The moderator at the meeting stated that the two techniques “cannot be considered any longer as separate units but parts of a whole and complete approach to resuscitation. In 1966, the first CPR guidelines were published by the National Academy of Sciences in the Journal of the American Medical Association⁸.

Defibrillation

The first recorded instance of closed chest defibrillation took place in 1775 when Abilgaard, a Danish veterinarian, "shocked a single chicken into lifelessness and on repeating the shock, the bird took off and eluded further experimentation.^"9

The first successful (open) cardiac defibrillation was performed by Dr. Claude Beck in 1947 in a 14-year-old boy who underwent an operation to correct a sternal deformity. When his chest was closed, he arrested and when the sternotomy was reopened, he was noted to be ventricular fibrillation. After 70min of open cardiac massage and 2 direct shocks, a regular pulse was restored and there was no adverse neurological sequelae¹⁰. In 1955, Paul Zoll recorded the first successful closed chest defibrillation in a man with recurrent syncope and ventricular fibrillation¹¹.

Current Practice Today

The International Liaison Committee on Resuscitation (ILCOR) was formed in 1993 and consists of representatives from resuscitation councils all over the world. Its mission is to identify and review international science and research relevant to CPR and emergency cardiovascular care and to generate consensus on treatment recommendations. Guidelines are revised every five years by ILCOR-the current set was published in 2005¹².

The basic building blocks of paediatric life support remain the same through the many revisions-(1) prevention, (2) basic CPR (3) early access to emergency services and (4) prompt paediatric advanced life support (PALS). These 4 links form the American Heart Association paediatric chain of survival¹³.

The 2005 algorithm is shown below. The step-wise sequence of airway, breathing and circulation remain comfortingly familiar-in reality however, with either multiple bystanders or when the arrest occurs in-hospital, the ABCs occur in parallel rather than sequentially.

For both inside and outside the hospital, the measures taken to open the airway and assess for breathing remain the same. In-hospital, however, bag mask ventilation is likely to be used to deliver breaths instead of mouth to mouth or mouth to nose ventilation.

Bag mask ventilation can be as effective as ventilation through an endotracheal tube and may be safer over short transport distances. However, it requires training and periodic retraining in the necessary skills such as selecting the right size, forming an effective seal, delivering effective ventilation and assessing effectiveness of ventilation.

Airway adjuncts such as oropharyngeal or nasopharyngeal airways may be used in the pre-hospital setting but once in hospital, an advanced airway should be placed. Successful placement of endotracheal tubes with a low incidence of complications are related to the length of training, supervised training in the operating room and in the field, adequate ongoing experience and the use of rapid sequence intubation. ILCOR strongly recommends that the placement of the tube is checked clinically, with the use of end tidal CO2 detection and with a chest radiograph in the hospital setting. There is not enough evidence for or against the use of the laryngeal mask (LMA) in cardiac arrest. When endotracheal intubation is not possible, the LMA can be used by experienced providers but it is associated with a higher rate of complications in young children¹⁴.

Care needs to be taken to prevent hyperventilation. In the adrenaline soaked atmosphere of a resuscitation, healthcare providers often deliver excessive ventilation particularly when an advanced airway is in place. Hyperventilation can lead to impaired venous return, cause air trapping and barotrauma and may increase gastric distension and risk of regurgitation and aspiration. The aim should be 8-10 breaths per minute during CPR and 12-20 breaths per minute in rescue breathing¹³.

Studies have shown that healthcare providers as well as lay people are unable to reliably detect a pulse and may falsely detect a pulse when there is none¹³. Therefore, if a pulse cannot be felt or cannot be reliably detected within 10 seconds, chest compressions are to be commenced.

The ratio for compressions to breaths has been changed to 30:2 for basic life support with single rescuers. The emphasis is on good quality chest compressions at 100/min (“Push hard, push fast”), allowing for chest recoil and minimizing interruptions.

The optimum compression to ventilation ratio is unknown. In the 2000 ILCOR guidelines, a ratio of 5:1 was recommended but subsequent studies but subsequent studies showed that at that rate, fewer than 60 compressions a minute was achieved on a paediatric manikin, even under ideal circumstances¹⁵. It was also shown that it takes a number of compressions to raise coronary perfusion pressure which drops every time CPR is interrupted¹⁶. Long and frequent interruptions in CPR in both in-hospital and out-hospital settings have been documented by lay-rescuers as well as healthcare providers¹⁷. Interruptions in chest compressions have been associated with a decrease in the rate of return of spontaneous circulation¹⁸.

The depth of compression is also important-the aim should be to compress the antero-posterior diameter of the chest by one third to one half. Dana Edelson and her colleagues showed in 2006 that successful defibrillation was associated with shorter pre-shock pauses (adjusted odds ratio (OR) 1.86 for every 5s, 95% CI 1.10-3.85) and with higher mean compression depth in the 30s prior to defibrillation (adjusted OR 1.99 for every 5mm increased, 95% CI 1.08-3.66)¹⁹. One of the major limiting factors in achieving quality CPR is rescuer fatigue. In the 2005 ILCOR guidelines, rescuers doing chest compressions should alternate every 2 minutes so as to minimize fatigue and optimize quality CPR delivery.

There has been some recent controversy in the literature surrounding adult CPR comparing conventional CPR and compression-only CPR. In the adult population where most arrests are primary cardiac arrests, compression-only CPR while awaiting the arrival of the defibrillator may be as effective as conventional CPR. However, in the paediatric population where most arrests are due to hypoxia-asphyxia, the ILCOR recommendation remains to deliver prompt ventilation and chest compressions to achieve the optimal results ¹².

Once pulseless ventricular tachycardia (VT) or ventricular fibrillation (VF) is detected, immediate defibrillation is required. VF occurs in 5-15% of paediatric out-of-hospital cardiac arrests and is reported in 20% of in-hospital arrests at some point during the resuscitation¹⁴.

The 1^st shock is at 2J/kg; subsequent shocks should be at 4J/kg. Effective, good quality CPR should be delivered until the shock is delivered and CPR resumed immediately following the shock. If 1 shock fails to eliminate VF, the incremental benefit of a second shock delivered is likely to be low and resumption of CPR is likely to be of greater value.

Automated external defibrillators (AEDs) are now widely used in the public and many have high specificity in detecting paediatric shockable rhythms. Some are also equipped to lower the energy delivered, making them suitable for use in children 1-8 years of age. The ILCOR 2005 guidelines do recommend the use of AEDs in children from 1-8 years, preferably those with a paediatric attenuator system. If in an emergency, only a standard AED is available, use the AED as data has shown that many AEDs can detect VF in children of all ages. The lowest energy dose for successful defibrillation and the upper safety limit is not known but energy doses > 4 J/kg (energy up to 9J/kg) has successfully defibrillated children and paediatric animal models with negligible adverse effects¹⁴.

The use of high dose adrenaline (1:1000) in resuscitation is no longer recommended as there was no improvement in survival rates and may be associated with poorer neurological outcome. A prospective, randomized controlled trial by Perondi and colleagues in 2004, comparing standard dose (1: 10000) with high dose adrenaline (1: 1000) for the second and subsequent rescue doses in resuscitation showed reduced 24 hours survival rates in the high dose group²⁰.

While we appear to have all the tools in place, outcomes from cardiopulmonary resuscitation remain poor. Survival from out-of-hospital CPR is usually reported as between 2-14% and most have severe neurological disability. Bystander CPR is provided to only approximately 30% of pediatric cardiac arrest victims before reaching hospital so it is not surprising that the outcomes are poor²¹. Outcomes for CPR for out-of-hospital arrest due to trauma is also poor with one study reporting survival to discharge at 8.75%²².

In-hospital CPR outcomes are unsurprisingly much better due to the availability of experienced staff and paediatric advanced life support. Age, the presence of a shockable rhythm as the first documented rhythm and the 24 hour presence of paediatric residents and fellows are all associated with better survival rates and neurological outcomes.

However, can we do better? Can we improve the dismal outcomes from out-of-hospital arrests and ensure even higher survival rates and better neurological outcomes from those that occur in-hospital?

There are 4 phases of cardiac arrest, common to all ages: (1) pre-arrest; (2) no flow (untreated cardiac arrest); (3) low flow (CPR) and (4) post resuscitation. Interventions can be targeted at each phase to improve outcomes and selected to focus on the timing, intensity and duration of resuscitation to the physiology and metabolic state of the cardiac arrest patient.

Interventions at this phase are mainly targeted at community level preventative strategies for arrests outside of the hospital as well as monitoring high-risk patients in hospital. Campaigns such as for child road and water safety and awareness of sudden infant death syndrome (e.g. the “Back to Sleep” Campaign) help to raise public knowledge and prevent harm to children.

As for in-hospital strategies, recent literature has shown that among the adult population, the formation of in-house Medical Emergency Teams (MET) that respond when certain critical clinical parameters are breached result in better outcomes following CPR. In his 2006 paper, Prof Tibballs of the Royal Children's Hospital in Melbourne described a similar set up for a paediatric Medical Emergency Team. The MET team was activated when early signs of respiratory failure and/or shock occurred and aimed to treat these children early. Though there was no statistical significance in the reduction of cardiac arrests, one of the key changes that arose as a result of the study was the empowerment of all nursing and medical staff to call for help once they felt a patient was deteriorating rapidly^23-24. Though the formation of a specialized team would be redundant in our context, the awareness of all staff to escalate rapidly and get help when certain parameters are breached is important.

Interventions during these phase focus on early recognition of cardiac arrest, effective monitoring and prompt initiation of basic and advanced life support. Public awareness and lay rescuer education in CPR is vital in improving outcomes outside of the hospital. The use of educational tools such as the Voice Advisory Manikin (Laerdal) which provides immediate audio feedback during training may improve the incidence and quality of bystander CPR²⁵. An effective nationwide emergency response system is also important.

In hospital, an effective Code Blue/Crash team Response system should be in place and the interval between basic and advanced life support should be minimal.

Once CPR has commenced, the focus should be on delivering high-quality, effective CPR to optimize coronary perfusion pressure and cardiac output to critical organs to support organ viability during the low flow phase.

Feedback systems in conjunction with AEDs (e.g. Phillips HeartStart) are already available and have been shown to optimize the quality of CPR. Perhaps in the future, these feedback systems can become pocket-sized and have prompts for rate and quality of CPR. Popular songs may even be incorporated to ensure the right rate of CPR! In order to alleviate rescuer fatigue, adjuncts such as mechanical compression devices (e.g. the Autopulse), may be used in the community to deliver quality CPR.

In hospital, though feedback systems will also be useful, the key will be to ensure training and education so that quality BLS as well as ALS will be delivered promptly.

Junior medical staff are usually the first to respond to an arrest situation and it is well recognized that there is a lack of confidence and fear in dealing with these situations without adequate training. A recent study by Turner et al in 2007 showed that residents perceived a significantly increased self-efficacy following attendance in the Advanced Paediatric Life Support course and this effect lasted 6 months²⁶.

ILCOR and all professional bodies such as the Royal Colleges of Paediatrics and Child Health recommend that clinicians maintain their advanced resuscitation knowledge and skills and that failure to do so contravenes the principles of clinical governance and has implications for clinical negligence. This is particularly important for middle and senior grade staff, the majority of whom have completed an advanced resuscitation course at some point in their career but have not retrained and let their provider status lapse²⁷.

Recent changes in working practice with reduced hours and shorter training may also result in trainees attending fewer arrests and thus reduce their experience, skills, knowledge and confidence to perform effective resuscitation. Studies from mock codes and simulation training have showed that there are often alarming delays and deviations from paediatric basic life support protocols and delays in administering treatment^28-29.

However simulation training also provides a safe platform for controlled clinical practice without putting patients or others at risk. The training can be targeted to the need of the learner, allowing multiple practice attempts in order to achieve competence. Learners are also allowed to “fail” and learn from these experiences. Simulators also allow objective feedback on performance, allowing learners to evaluate their performance in detail. This powerful tool allows medical and nursing staff to retrain, gain confidence and aid teamwork in dealing with resuscitation situations³⁰.

The immediate post resuscitation phase is a high-risk period for arrhythmias and reperfusion injuries. Interventions at this phase target goal directed therapies to match oxygen and substrate delivery to meet metabolic demands and therefore minimize reperfusion injury and support cellular recovery²¹.

Careful attention therefore to maintaining homeostasis is required. Management of temperature, glucose, blood pressure, coagulation and ventilation may be particularly important in this phase. The 2005 ILCOR guidelines suggested consideration of induced hypothermia in children 12-24 hours post arrest may have potential benefits in improving outcome. At a minimum, avoiding mild hyperthermia in children post CPR is advisable as fever following cardiac arrest is associated with poor outcome.

These measures though, remain crude and future strategies are likely to be targeted at the cellular level as we learn more about the physiology of cardiac arrest and recovery. The roles of anti-oxidants, anti-inflammatory agents, thrombolytics, mediator cascades, modulation of excitatory neurotransmitters are likely to become increasingly important in the future of post-resuscitation care.

Cardiopulmonary resuscitation has evolved remarkably over its history but the goal of saving lives through early and effective techniques has remained the same. Achieving high quality CPR and acquiring and retaining confidence and skill in advanced paediatric life support are key areas for all clinicians. As we learn more about the physiology of cardiac arrest and recovery, survival and neurological outcomes from cardiac arrest are likely to improve.

CARDIOVASCULAR RESUSCITATION-THE PAST, THE PRESENT AND THE FUTURE

Dr Jacequeline Ong

Registrar, The Children's Medical Institute, National University Hospital