New horizons (Baltimore, Md.)最新文献

In this presentation from the Wolf Creek IV Conference, the panel reviewed data requirements for documenting the processes and outcomes associated with the treatment of out-of-hospital cardiac arrest. It was recognized that this was a multifaceted task and that at least three areas warrant consideration: a) emergency medical services system management, b) monitoring and improving the quality of care, and c) the establishment of databases for research. There was complete agreement that the desired outcome is the victim's survival with intact neurologic function. However, the means of improving outcome, short of speedy initiation of treatment, were less clear. It was suggested that the Utstein guidelines, modified for practicability, can serve as a framework to characterize the arrest and to describe the temporal aspect of interventions. However, it was recognized that there were major deficits in understanding the importance of specific interventions, including their timing. Additionally, means to evaluate the quality of care delivered on the scene are usually wanting. The availability of recording electrocardiograms with accompanying voice was regarded as a major opportunity to better monitor the care that was delivered at the scene. Some of the problems incurred with cardiopulmonary resuscitation research in animals were discussed.

The instruction of cardiopulmonary resuscitation (CPR) faces new challenges. With the current poor resuscitation outcomes of victims of sudden death syndrome, the impetus to include early defibrillation as a basic skill for laypersons imposes the need to simplify CPR instruction and reduce the time required to teach this technique. The exploration of an alternative paradigm has gained both public and academic interest. Some of the constraints have evolved around the urgent need to bring both CPR and automated external defibrillation instruction to a much larger population segment and at the same time reduce the time needed to accomplish this task. Additional debate exists with respect to maintaining the current traditional training methods or the use of new media such as video-based instruction, interactive computer-based software, and public service announcements. To answer any one of these questions we are tasked with having to objectively document not only retention and performance of learned skills, but the ultimate impact that any of these elements have on survival and outcome. This has to balance against the ongoing scourge of sudden cardiac death, which claims the lives of 350,000 Americans each year.

Efforts to minimize hypoxic injury may gain insight from considering treatments directed at different levels of biological organization, from cellular physiology to societal norms. At the cellular level, it appears that cells do not actually die during ischemia, but rather during reperfusion or resuscitation. Free radicals are implicated because antioxidants reduce cell death from ischemia/reperfusion, but typically fail to protect when only given during reperfusion. In preliminary work, two synergistic antioxidants were seen to offer significant protection even if used only during reperfusion. These findings suggest some cell death may be treatable at reperfusion and antioxidants targeted specifically at radical generation hold promise as a future therapy. On the organism level, blood flow during cardiopulmonary resuscitation (CPR) may be improved with a new manual device that combines the advantages of active-decompression CPR with interposed-abdominal-compression CPR; preliminary hemodynamic data in animals are encouraging. Possible worsening of injury in the postarrest period may occur from overuse of beta-agonists, excessive defibrillation energy, untreated hypotension, and lack of attention to intensive care principals. At the societal level, we have failed to provide simple treatments that are known to save lives, particularly basic CPR and early defibrillation. Bystander CPR suffers from poor quality of performance and from lack of initiation due to concern over disease transmission. The technology for rapid public defibrillation exists, yet is not commonly employed. Collectively, survival likelihood may be predicted with a multifactor equation which may be useful as we develop future therapies.

The "ABCs" of CPR, i.e., airway, breathing, and circulation, represent the sequence of interventions currently advised and taught to providers of both basic life support (BLS) and advanced life support (ALS) by the American Heart Association. Nevertheless, in the settings of suspected or confirmed ventricular fibrillation, the ABCs may be deferred such that external electrical countershock(s) take(s) precedence. However, efforts to restore circulation by chest compression (or alternative mechanical means) remain the lowest of the three priorities for both BLS and ALS as presently prescribed. This ordering of priorities is based largely on the consensus rather than objective experimental or clinical evidence of improved outcomes. During the last 5 yrs, both clinical and experimental studies demonstrated that the A and B of these ABCs, and specifically positive-pressure ventilation, may not be essential during the initial 6 to 12 mins of CPR under conditions of sudden dysrhythmic cardiac arrest and in the absence of asphyxia. Recent studies further suggested that either or both precordial compression and spontaneous gasping may of itself generate sufficient alveolar ventilation during the initial 6 mins of CPR. Defibrillation now emerges as the highest priority. Automated defibrillators have a pivotal role. The need for objective controlled research, including experience with devices in clinical settings and technical improvements of operation, are essential.

Victims of out-of-hospital cardiac arrest in most communities are not the beneficiaries of an optimal healthcare system response capable of providing survivors who live to hospital discharge. The public at large, including family members and bystander witnesses of cardiac arrest, must be expected to participate in this optimal response capability. The American Heart Association Chain of Survival defines the elements of a system capable of saving lives of victims of ventricular fibrillation cardiac arrest. Widespread dissemination of only the essential elements of life-saving steps, probably through media not yet used for this function, will be needed to reach the largest number of people possible. Emergency medical services systems need to devise innovative approaches to rapid provision of automated external defibrillation, in many cases no doubt outside the boundaries of traditional means of delivery of this intervention. Finally, it is likely that targeted responders among the public will be participants in a public access defibrillation approach to dealing with sudden cardiac death.

The purpose of this session at the Wolf Creek IV Conference was to explore future improvements in automatic external defibrillators (AEDs). Rather then conduct a general brain-storming session where any and all ideas are encouraged, participant comments were based on either direct personal experience or based on the experience of others. This article captures the comments in the words of the speakers. Generic improvements in AEDs such as making them smaller, lighter, less expensive, more reliable, and easy to use are always desired. The importance of data collection and analysis was stressed. Of particular concern was the importance of time and time interval measurements. System clock and defibrillator clock synchronization is desired. Concern over liability was voiced by many. The role of the American Heart Association was discussed by both panel members and members of the audience.

Alternative techniques to precordial compression are sought to improve the return of spontaneous circulation after cardiopulmonary arrest. The pathophysiology of cardiac arrest and the methods to determine the efficacy of a new technique need critical re-examination. Vest cardiopulmonary resuscitation (CPR), active compression/decompression with abdominal counterpulsation (LifeStick [Datascope, Fairfield, NJ]) CPR, and ascending aortic balloon inflation with saline infusion are promising methods that have been shown to augment coronary perfusion pressure and improve the return of spontaneous circulation in animals. Preliminary studies in human cardiopulmonary arrest have been performed with vest CPR and ascending aortic balloon inflation with saline infusion, with favorable hemodynamic results. In parallel with the development of new methods, the availability and adequacy of bystander CPR should be re-emphasized.

Biphasic defibrillation waveforms are now the standard of care in clinical use for defibrillation with implantable cardioverter-defibrillators (ICDs), due to the superior performance demonstrated over that of comparable monophasic waveforms. To better understand these significantly different outcomes, ICD research has developed cardiac cell response models to defibrillation. Waveform design criteria have been derived from these first principles and have been applied to monophasic and biphasic waveforms to optimize their parameters. These principles-based design criteria have produced significant improvements over the current art of waveforms. Monophasic defibrillation waveforms remain the standard of care in clinical use for transthoracic defibrillation. Waveform design has not yet been influenced by the important gains made in ICD research. The limitations of present transthoracic waveforms may be due in part to a lack of application of these design principles to determine optimal waveform characteristics. To overcome these limitations, design principles based on cell response have recently been developed for external defibrillation waveforms. The transthoracic model incorporates elements into a cell response model that extends it to external defibrillation. External waveform design principles demonstrate reductions in capacitance, voltage, duration, and delivered energy. Therefore, design principles based on cardiac electrophysiology may provide a means to significantly reduce the energy required for safe and efficacious external defibrillation. Footnotes, formulae, and figures augment this presentation in order to clarify the defibrillation waveform theory.

At present, there are only a limited number of objective measures available to clinicians resuscitating patients from cardiac arrest. The electrocardiogram and end-tidal CO2 are easily applied, but the data they produce are of only limited utility in evaluating the efficacy of chest compression and in choosing the sequence of therapies. In particular, we are in need of an objective test that can tell us when the myocardium will defibrillate into a perfusing rhythm. The ventricular fibrillation waveform holds information that we have not yet begun to utilize. Parameters derived from power spectrum analysis, such as ventricular fibrillation median frequency, appear promising. Combination of both old and new parameters may allow us to more accurately evaluate the efficacy of therapy.