Most cases of sudden cardiac death (SCD) are due to malignant ventricular tachyarrhythmias, such as ventricular tachycardia (VT) and ventricular fibrillation (VF)(see Fig. 36.1). Both VF and pulseless VT require defibrillation as definitive therapy. If these or other arrhythmias persist despite basic life support and defibrillation, the current international advanced cardiac life support guidelines (ILCOR 2005) recommend administration of pharmacologic agents to help stabilize rhythm and restore cardiac output.

The pathophysiologic substrate of cardiac arrest: therapeutic implications

The pathophysiology of sudden cardiac death is relevant to both acute and long-term management. In most instances, the underlying cardiac pathology is ischemia and coronary artery disease. For instance, Liberthson and coworkers reported that 81% of a series of SCD victims had significant coronary artery disease. In another series, up to 50% of the victims of out-of-hospital cardiac arrest had suffered a recent acute myocardial infarction. Although the majority have a coronary disease etiology, numerous other pathologies can be involved in the genesis of sudden cardiac death, such as ventricular hypertrophy, cardiomyopathies, congenital disorders of ion channels (“channelopathies”), but also massive pulmonary embolism, as well as coronary dissection, and coronary inflammation or embolism to the coronary arteries. Froma clinical perspective, it is appropriate to assume that the cause of sudden death is coronary artery disease unless circumstances suggest otherwise. Although the creatine kinase (CK) and its MB fraction may not be diagnostic of acute myocardial ischemia, cardiac troponins can identify myocardial ischemic damage and thus prompt invasive coronary studies, which may make longterm antiarrhythmic treatment irrelevant.

Introduction

Over 300 000 Americans die each year from catastrophic medical and surgical emergencies. New interventions, based on sound research, could save lives. These research studies must be done in an ethical framework that traditionally includes obtaining prospective informed consent from the research subject. The ethical framework for the conduct of Human Research began with the development of the Nuremberg Code in 1949. This code states that (1) informed consent of volunteers must be obtained without coercion of any form, (2) human experiments should be based on prior animal experiments, (3) the anticipated scientific results should justify the experiment, (4) only qualified scientists should conduct medical research, (5) physical and mental suffering should be avoided, and (6) no death or disabling injury should be expected from the research study.

The Declaration of Helsinki was issued in 1964 and defines rules for clinical research. It repeats the ethical concerns stated in the Nuremberg Code, but also gives a provision for enrolling certain patients in clinical research without their consent, by using either proxy consent, or waiver of consent in minimal risk studies.

The subsequent Belmont Report, which was published in 1979, is the cornerstone of ethical principles upon which current federal regulations for the protection of subjects are based. The Report conveys the three major premises of ethical conduct of studies: respect for persons, beneficence, and justice. The Report also provides elements used by Institutional Review Boards for evaluating the ethical standards for individual research proposals.

For much of recorded history, humans have viewed death as irreversible. For religious and scientific reasons it was considered impossible, or even blasphemous, to attempt to reverse death. It was not until the latter part of the eighteenth century that humans began to believe that resuscitation was possible. Another 200 years passed before the skills for resuscitation were developed to a degree that made the reversibility of cardiac arrest a practical reality in the 1960s. Many important observations and much real progress had nevertheless been made during the intervening years. But the clinical problems were poorly understood, the implications of new discoveries were not always appreciated, single components of life-saving were attempted in isolation, procedures that were potentially effective were often displaced by those of no value, and suitable technology was lacking. Resuscitation had to await its time. Nevertheless, its history is of interest and has important lessons for us today.

The earliest years

The first written account of a resuscitation attempt is that of Elijah the prophet. The story in the Bible tells of a griefstricken mother who brought her lifeless child to Elijah and begged for help. Elijah stretched himself upon the child three times and, with the assistance of God, brought the child back to life. An even more detailed account of a resuscitation attempt is that of the prophet Elisha, a disciple of Elijah. The child of a Shunemite couple whom Elisha had befriended suffered from a severe headache. He cried out, “Oh, my head, my head!” and collapsed. Was this a subarachnoid bleed? The Bible gives no further clues. The boy died several hours later.

Introduction

Clinical guidelines aredefinedby the Institute ofMedicine in the United States as“systematically developed statements to assist practitioner and patient decisions about appropriate health care for specific clinical circumstances.” The main objective of guidelines is to improve the quality of care received by patients by closing the gap between what clinicians do and what scientific evidence supports. Guidelines provide a point of referencefor auditing performanceof clinicians or hospitals and may improve effectiveness and efficiency. The development of guidelines requires appropriate resources: expert clinicians, group process leaders, and financial support. All these statements refer to guideline development in general, but they are particularly relevant to the development of resuscitation guidelines that have existed for at least 40 years. The steps involved in the process for developing evidence-based guidelines have been outlined by the Grades of Recommendation Assessment, Development and Evaluation (GRADE) Working Group (Table 71.1).

This chapter will review the history of consensus development in resuscitation, the role of the International Liaison Committee on Resuscitation (ILCOR), the process involved in undertaking a systematic review of resuscitation science, and the writing of clinical guidelines based on a consensus of the science.

The history of international CPR consensus and guideline development

The modern approach to cardiopulmonary resuscitation (CPR) was described in the late 1950s and early 1960s. Although this was undoubtedly the birth of CPR, it was immediately realized that the challenge was to spread the word and educate healthcare workers and laypeople throughout the world. This same challenge faces us today whenever CPR guidelines are modified and updated.

History of AEDs

Automated external defibrillators (AEDs) as we now know them have had a rapid and interesting evolution. The first report of an “automatic cardiac resuscitator” was made by Diack et al. in 1979, who had developed the defibrillator, the Heart-Aid. A first clinical report on successful ambulance use was published in 1982. The design of this defibrillator was unusual for several reasons. First, it used a tongue electrode together with a chest electrode for defibrillation. Second, the tongue blade also contained a sensor for respiration, which prevented the defibrillator from delivering a shock as long as an air stream was detected over the tongue. Confidence in the algorithm to detect ventricular fibrillation (VF) by the ECG was not sufficient: a second independent sign of circulatory arrest was desired. Further automated analysis of the ECG and defibrillation in cardiac arrest was investigated first in defibrillators that were used by traditional responders such as Emergency Medical Technicians. Then, when safety and efficacy were confirmed, the use was extended to fire fighters who were already part of the Emergency Medical Services (EMS) and to police squads who had never been part of the EMS. It became clear that the future of automated defibrillation was with lay rescuers with limited training, without the ability to interpret ECGs. Ease of use was paramount.

Therefore, new AEDs were designed with the lay rescuer in mind, with increasing simplicity and decreasing weight, volume, and cost.

There is a no more frightening experience for a clinician than a patient's sudden and complete loss of vital signs. The need to initiate multiple complex therapies, all the while knowing that each minute that passes dramatically decreases the chances for a good outcome, makes sudden death the penultimate medical emergency.

Premature death is the adversary of physicians. For millennia, the loss of life signs was considered the victory of death. Students were taught that once patients had succumbed they were beyond the healing arts. Only relatively recently have physicians regularly attempted to wrest such patients back from death.

Accurate numbers are difficult to obtain. It is said that more than 300,000 persons die each year from sudden cardiac death in the United States alone. Worldwide the figure is in the millions. Sudden death is not, however,caused by coronary artery disease alone. Hemorrhage and asphyxiation, among others, can kill physiologically competent patients without warning. Sudden death is not defined by etiology; it is the circumstance of cardiopulmonary arrest in a person with functional vital organ systems. It is death in the midst of life, and it is always tragic.

We are just beginning to appreciate the magnitude of this problem and the potential for therapy. Just a 5% improvement in outcome – something that could be achieved in many communities by better application of standard care – would save more lives than therapies that have received far more attention. The potential for good is astounding; the relationship of cost to benefit compelling.