BRIEF REVIEW Approaches to modern management of cardiac arrest

Public access defibrillation The time delay to defibrillation can be reduced by five minutes if performed by a first responder to the cardiac arrest rather than by the usual paramedic service. In a review of five controlled trials in which emergency medical technicians were taught to defibrillate, odds ratios for improved survival ranged from 3.3 to 6.9. Emergency medical technicians were taught to recognise cardiac arrhythmias and to operate a manual defibrillator in four trials; an automatic external defibrillator was used in the remaining trial. The validity of emergency medical technicians using automatic external defibrillators has also been tested in controlled trials. There were no significant diVerences in hospital admission or discharge rates for patients with cardiac arrest treated by emergency medical technicians (trained to recognise VF) using either a manual defibrillator or an automatic external defibrillator. However, the delay to the first shock was significantly shorter in the automatic external defibrillator group. Successful use of automatic external defibrillators by emergency medical technicians has raised the possibility of these devices being used by minimally trained individuals. Automatic external defibrillators have already been used successfully by family members of survivors of out-of-hospital cardiac arrest and by security staV at large public gatherings. The use of these devices by the lay public could reduce further the time to defibrillation. Several issues concerning the widespread dissemination of automatic external defibrillators for public use need to be discussed. It is essential that automatic external defibrillators have a very high specificity for shockable rhythms. Inappropriate delivery of direct current (DC) shocks has been reported. 10 Such instances may have important medical and legal implications. Non-electrocardiographic sensors therefore have a role in independent confirmation of cardiac arrest before a shock is delivered. One of the earliest automatic external defibrillators used a breath detector to confirm indirectly the lack of blood flow to the brain. This sensor was subsequently abandoned because of the delay in delivery of a DC shock, probably as a result of agonal respiration. The impedance cardiogram also confirms pulselessness due to cardiac arrest. The optimum strategy for deployment of an automatic external defibrillator must be identified. As most arrests occur in the home it remains to be proved that a policy of placing automatic external defibrillators in public places will have a major impact on overall survival from cardiac arrest. Furthermore, can the public retain the skills required to use an automatic external defibrillator over a prolonged period of time? This issue was examined in two reports at the recent meeting of the American Heart Association. In one report, police oYcers were trained to use an automatic external defibrillator. Their skills were tested by written and practical examination. Although written performance declined over a three month period, their skill in the use of an automatic external defibrillator remained satisfactory. In the other study, Cummins et al found that three quarters of individuals who received training in the use of automatic external defibrillators omitted one or more critical steps required for their correct use two to four months after training. They suggest that the process needs to be simplified. There are issues of cost and cost eVectiveness. The cost of automatic external defibrillators is likely to decrease. However, the cost of deployment and maintenance must be considered—for example, in a shopping mall where there may be less than one cardiac arrest per annum. This issue was examined in a decision analysis model presented at the recent meeting of the American Heart Association. The potential cost eVectiveness of standard emergency medical services was compared with that of emergency medical services with public access defibrillation. The diVerence between the two services was calculated using input data from published studies and fiscal databases as US$36 302 per quality adjusted life-year. The authors concluded that the incremental cost eVectiveness of public access defibrillation was similar to that of other common medical treatments. Heart 1998;80:397–401 397