Advanced life support relates to the underlying causes of a cardiorespiratory arrest. If there is no circulation because the heart is in ventricular fibrillation, then only prompt defibrillation with an appropriate electric shock can restore the normal rhythm. If the heart is in an abnormal rhythm and going very fast, such as in ventricular tachycardia, then a defibrillating electric shock can also restore a normal rhythm. Various other treatments can help or restore normal circulation. For example, if during basic life support the circulation is inadequate because of a very slow pulse from heart block (when the electrical impulses that control the beating of the heart are disrupted), medications such as atropine or adrenaline can be given by intravenous injection to speed up the heart rate, and many modern defibrillators can perform external electrical stimulation, which can also increase and pace the heart rate. If blood pressure is inadequate because of a weakened heart, then medications such as adrenaline can be injected to stimulate the force of contraction of the heart thereby raising the blood pressure. Abnormally fast heart rhythm disorders can be treated with anti-arrhythmic drugs, such as amiodarone.
The results of resuscitation depend crucially on where the cardiopulmonary arrest has occurred, and the previous medical history. Resuscitation in hospital should be, and usually is, prompt and more likely to be effective, whereas outside hospital there may be a delay and therefore the outcome is less likely to be as good. Secondly, if there is no previous medical history of cardiopulmonary disorder, and there is good cardiac and lung function, then the outcome can be good; in this circumstance, successful resuscitation can usually result in the patient returning to normal activities and having a normal life expectancy. On the other hand, if there is a history of advanced heart failure or end-stage lung disease, then the outcome is often poor; in this scenario, resuscitation can be technically successful in the very short term, but is unlikely to result in the patient surviving to discharge from hospital. The success rates reported as regards resuscitation from cardiorespiratory arrest will also depend crucially on the selection of patients. If every patient who is dying is resuscitated, then the success rate to survival at discharge from hospital will be low. Conversely, if resuscitation is not attempted on all those patients who are near death from an untreatable condition, and in all others who are considered medically inappropriate to be resuscitated, then the success rate will be much higher.
An audit of 1,368 cardiac arrests occurring in forty-nine hospitals in the United Kingdom in 1997 showed that eighteen per cent of patients were discharged alive, and of these eighty-two per cent were still alive six months later. [10]
In thirty-one per cent of these patients there was a treatable cardiac rhythm disorder such as ventricular fibrillation or ventricular tachycardia, and within this group forty-two per cent were discharged alive. If the cause of the cardiac arrest was not an easily treatable cardiac rhythm abnormality, then only six per cent were discharged alive. In this audit, factors associated with an improved chance of survival included an easily treatable cardiac arrhythmia as the cause of the arrest, a prompt return of the circulation in response to cardio-pulmonary resuscitation, and the age of the patient, with those under seventy being more likely to survive. The Resuscitation Council (UK) and The Intensive Care National Audit & Research Centre (ICNARC) are collaborating to develop a national database regarding cardio-pulmonary arrests that take place in hospital† to enable analysis of the frequency of, and outcome from, resuscitation in the United Kingdom. This should result in more consistent reporting and a better understanding of what might result in improved success rates.
The statistical likelihood of success in cardio-pulmonary resuscitation is not reflected in popular television dramas! A study of ninety-seven episodes of television medical dramas in the United States of America in 1994-1995 analysed sixty occurrences of cardio-pulmonary arrest; sixty-five per cent of these arrests occurred in children, teenagers, or young adults and sixty-seven per cent appear to have survived to hospital discharge.[11] Such rates are significantly higher than even the most optimistic survival rates in the medical literature and the portrayal of cardio-pulmonary resuscitation on television may lead the viewing public to have an unrealistic impression of the procedure, and its chances of success.
In 2004 the Ontario Pre-hospital Advanced Life Support Study of 5,638 patients who had had an out-of-hospital cardiac arrest reported that only five per cent survived to discharge from hospital.f There did not seem to be any trend towards improved survival over time with the introduction of community-based initiatives. The registry of cardiac arrests in the community of Goteborg in Sweden reported that of 5,505 patients who had suffered an out-of-hospital cardiac arrest between 1980 and 2000, between eight and nine per cent of these survived to hospital discharge.[12] Again there was no trend towards improvement in survival rates over the time period of the study. A systematic review and meta-analysis published in 2010 detailing seventy-nine studies of out-of-hospital cardiac arrests involving 142,740 patients reported that twenty-four per cent reached hospital alive, but the rate of survival to hospital discharge was 7.6 per cent overall and this survival rate has remained unchanged over the last thirty years.[13] Again survival ratio depended on many of the same factors as in-hospital cases i.e. the speed of response, whether the patient received cardio-pulmonary resuscitation from a bystander, if the cardiac rhythm abnormality was easily treatable, or if there was an early return of spontaneous circulation.
In 2004, a study of nearly 1,000 communities in twenty-four North American Regions reported that survival to hospital discharge was twenty-three per cent in those areas equipped with staff trained in using Automated External Defibrillators (AEDs), whereas survival was fourteen per cent in those areas without.[14] Increasingly, cardiac arrests which occur out-of-hospital are also being automatically treated by a special type of implanted pacemaker known as an Internal Cardiac Defibrillator (ICD). These have been available for more than ten years, and have been implanted in those people at the highest risk of developing lethal cardiac rhythm disorders. When implanted, the devices promptly diagnose and treat almost all lethal cardiac rhythm disorders within a few seconds, using an internal electric defibrillator shock. The widespread use of these devices might paradoxically skew the statistics regarding survival rates, as those not fitted with the device are likely to have less easily treatable conditions and are therefore less likely to be successfully resuscitated following a cardiac arrest.
In 2006 the Termination of Resuscitation Study investigators in Ontario reported on the development of a theoretical rule which would predict a low chance of survival from out-of-hospital cardiac arrest to hospital discharge.[15] Where there was no return of spontaneous circulation, no defibrillation shocks had been administered, and the arrest was not witnessed by the emergency services, the rule recommended termination of resuscitation. Of 776 patients with cardiac arrest for whom the rule recommended termination of resuscitation, only four survived (0.5 per cent) to hospital discharge. If the additional criteria of an emergency services response interval of more than eight minutes, were included, together with the arrest not being witnessed by a bystander, then this rule would have proved 100 per cent accurate. These factors should not be used to avoid resuscitation in all such cases, and they should not be applied automatically or be allowed to over-ride clinical assessments. However, they can be very helpful in judging the value or futility of attempting resuscitation or continuing resuscitation of victims of an out-of-hospital cardiac arrest.
10
Gwinnutt C, Columb M, Harris R. Outcome after cardiac arrest in adults in UK hospitals: effect of the 1997 guidelines. Resuscitation 2000; 47: 125-135. http://www.resuscitationjournal.com/article/S0300-9572(00)00212-4/abstract f National Cardiac Arrest Audit (NCAA). https://www.icnarc.org/
11
Diem SJ, Lantos JD, TulskyJA. Cardiopulmonary Resuscitation on Television - Miracles and Misinformation.
12
Stiell IG, Wells GA, Field B et al, for the Ontario Prehospital Advanced Life Support Study Group. Advanced Cardiac Life Support in Out-of-Hospital Cardiac Arrest.
13
Sasson C, Rogers MAM, Dahl J, Kellermann AL. Predictors of Survival From Out-of-Hospital Cardiac Arrest. A Systematic Review and Meta-Analysis.
14
The Public Access Defibrillation Trial Investigators. Public-Access Defibrillation and Survival after Out-of-Hospital Cardiac Arrest.
15
Morrison LJ, Visentin LM, Kiss A, Theriault R, Eby D, Vermeulen M, Sherbino J, Verbeek PR, for the TOR Investigators. Validation of a Rule for Termination of Resuscitation in Out-of-Hospital Cardiac Arrest.