Outcomes with Automated External Defibrillators
January 1, 2001 5 minutes read
Outcomes with Automated External Defibrillators
Abstracts & Commentary
Synopsis: Rapid defibrillation by minimally trained nonmedical personnel using an automatic external defibrillator results in a high salvage rate for victims of cardiac arrest.
Sources: Valenzuela TD, et al. N Engl J Med 2000;343:1206-1209; Page RL, et al. N Engl J Med 2000;343:1210-1216.
Valenzuela and colleagues performed a study of the efficacy of automatic external defibrillators (AEDs) used by security officers in the treatment of cardiac arrest victims in gambling casinos. Valenzuela et al collected data from a total of 32 casinos over a period of 32 months. Security officers in these casinos underwent training in basic cardiopulmonary resuscitation that consisted of a 5-6 hour training course that included orientation to the use of an AED. Participating casinos purchased AEDs and management of cardiac arrest with these devices became part of the security officers’ routine training program. In gambling casinos, security cameras mounted in the ceiling randomly scanned public areas allowing for the rapid identification of patients who appear to be in distress. The first officer on the scene initiated manual cardiopulmonary resuscitation and a second officer brought the nearest AED to the patient. The protocol for this specific AED model used was followed and resuscitative efforts by the security officers were continued until either the return of spontaneous pulse and respiration or until the arrival of paramedics.
During the period of the study, there were 148 patients at the 32 casinos with a confirmed cardiac arrest. The mean age was 64 ± 12 years and 80% were male. Of the 148 total cardiac arrests, 90 of the patients were observed by the security cameras at the time of collapse. The start of the episode was not recorded by the security cameras in the remaining 58 cases. The initial rhythm was ventricular fibrillation in all of the witnessed arrests and in 71% of the total population. Delivery of emergency cardiac care was rapid. Among the patients with a witnessed arrest, the intervals from collapse to initiation of resuscitation was 2.9 ± 2.8 minutes, from collapse to attachment of the AED was 3.5 ± 2.9 minutes, and from collapse to first defibrillation was 4.4 ± 2.9 minutes. Paramedics arrived 9.8 ± 4.3 minutes after a witnessed collapse.
The primary outcome variable in this study was survival to discharge from the hospital. The survival rates were excellent. Among the 90 patients with a witnessed arrest, 53 (59%) survived to discharge from the hospital. In the total group of 148 patients, 38% survived to hospital discharge. If the cardiac arrest victim received their first defibrillation no more than three minutes after collapse, the survival rate to hospital discharge was 74%. Valenzuela et al concluded that rapid defibrillation by minimally trained nonmedical personnel using an automatic external defibrillator results in a high salvage rate for victims of cardiac arrest that occurs in a public area with high security.
In the second article, Page and colleagues report on the experience of a single U.S. airlines, American Airlines, with the use of AEDs aboard their aircraft. Currently, all American Airlines’ flight attendants receive four hours of instruction followed annually by a 1.5-hour refresher course. This paper reports data from the use of the AEDs on 200 occasions with 191 uses aboard an aircraft and the remaining nine in the terminal. An AED was used in 99 patients who had transient or persistent loss of consciousness whereas, as in the 101 remaining patients, the device was placed in response to possible cardiac symptoms, usually either chest pain or dyspnea. A physician was present to assist placement and use of the AED in 139 patients. Because of memory failure, electrocardiograms were available in only 185 of the 200 cases. In 145 patients, the initial rhythm was sinus rhythm. Thirteen patients had a supraventricular rhythm; an agonal rhythm was seen in 13 patients and ventricular fibrillation was found in 14 patients. In each of the 14 patients with documented ventricular fibrillation, the arrhythmia was recognized and defibrillation was recommended. Two unconscious patients received shocks but their electrocardiograms were not stored. A shock was not delivered in one patient with a terminal illness at the request of the patient’s family. Of the 15 patients who received the shocks, six (40%) were subsequently discharged home with full neurologic and functional recovery. Four of the 15 had received shocks for cardiac arrest in the terminal. None of these survived. By contrast, six of the 11 patients with documented or presumed ventricular fibrillation who received shocks aboard the aircraft survived to hospital discharge. Page et al noted that in 101 cases, the AED was placed on a patient without documented loss of consciousness, generally on the recommendation of a physician passenger. The absence of ventricular fibrillation was recognized appropriately by these devices and shock was never recommended. Statistics show that a defibrillator was used once for every 3288 flights and a death or resuscitation after cardiac arrest occurred once in every 21,654 flights. Page et al extrapolate these numbers to estimate that approximately 93 lives per year would be saved if all commercial airlines were so equipped and similar results were realized.
Comment by John P. DiMarco, MD, PhD
These two papers demonstrate the value of AEDs in public settings when they are used by minimally trained personnel. The national average for survival to hospital discharge after an out-of-hospital cardiac arrest is approximately 5%. Studies have clearly shown that time to defibrillation is the most critical predictor of survival. Before the introduction of AED technology, many hours of training were required to ensure competent arrhythmia recognition and management of cardiac arrest by emergency service personnel. This effectively limited the ability of communities, organizations, and individuals to deliver early defibrillation. The casino study was performed in perhaps the ideal setting for use of an AED. In a casino, security cameras continuously monitor most public gaming areas and security personnel are immediately available to respond to emergencies. Therefore, the very high survival to hospital discharge rates in the casino study will probably not be reproduced in other settings but should serve as the goal for other trials. Cardiac arrest on an airplane is a much different situation. As shown in this study, some patients with cardiac arrest may be thought to be sleeping. The social norm among passengers and crew is often not to disturb someone in this situation; therefore, it is not surprising that the results of resuscitation on an airplane were not as good as they were in casinos. However, there is no other way to deliver emergency care once the plane has left the gate and, with that in mind, the results are excellent.
The concept of early defibrillation is so well established that the issue now is one of cost-effectiveness rather than demonstration of efficacy. The use of the AED is simple enough that even untrained individuals can often follow instructions if they know the general purpose of the device. Over time, hopefully, we will see more and more public places with AEDs. Whether or not the concept will ever be effective in the home situation remains to be demonstrated.
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