Lawrence Bergner

Treatment of Out-of-Hospital Cardiac Arrests with Rapid Defibrillation by Emergency Medical Technicians

The survival rate for patients with out-of-hospital cardiac arrest is low in communities where emergency service is provided solely by emergency medical technicians. We trained such technicians in a suburban community of 79,000 to recognize and treat out-of-hospital ventricular fibrillation with up to three defibrillatory shocks without the use of medications or special airway protection. Outcomes from cardiac arrest due to underlying heart disease were determined during two periods: two years with standard care by emergency medical technicians and one year with defibrillator-trained technicians. During the period with standard care, four of 100 patients with cardiac arrest were resuscitated and discharged alive from the hospital, as compared with 10 of 54 patients during the period with defibrillator-trained technicians (P less than 0.01). In 12 of 38 patients with ventricular fibrillation, a stable perfusing cardiac rhythm followed defibrillatory shocks given by defibrillator technicians. The enhanced survival after cardiac arrest is encouraging, and further trials of defibrillation by emergency medical technicians are warranted.

Paramedic programs and out-of-hospital cardiac arrest: I. Factors associated with successful resuscitation.

As part of an evaluation of whether the addition of paramedic services can reduce mortality from out-of-hospital cardiac arrest compared to previously existing emergency medical technician (EMT) services, factors associated with successful resuscitation were studied. A surveillance system was established to identify cardiac arrest patients receiving emergency care and to collect pertinent information associated with the resuscitation. Outcomes (death, admission, and discharge) were compared in two areas with different types of prehospital emergency care (basic emergency medical technician services vs. paramedic services). During the period April 1976 through August 1977, 604 patients with out-of-hospital cardiac arrest received emergency resuscitation. Eighty-one per cent of these episodes were attributed to primary heart disease. Considered separately, four factors were found to have a significant association with higher admission and discharge rates :1) paramedic service, 2) rapid time to initiation of cardiopulmonary resuscitation (CPR), 3) rapid time to definitive care, and 4) bystander-initiated CPR. Using multivariate analysis, rapid time to initiation of CPA and rapid time to definitive care were most predictive of admission and discharge. Age was also weakly predictive of discharge. These findings suggest that if reduction in mortality is to be maximized, cardiac arrest patients must have CPR initiated within four minutes and definitive care provided within ten minutes.

Epidemiology of cardiac arrest and resuscitation in children

A surveillance system identified all out-of-hospital cardiac patients under the age of 18 who received emergency care in suburban King County, Washington. The etiology, cardiac rhythm, and outcome were identified for each case. During a 6 1/2-year period, 119 cardiac arrests occurred (annual incidence, 12.7/100,000 among individuals less than 18). Sudden infant death was the most common etiology (32%), and drowning was the second most common (22%). The most common rhythm was asystole, accounting for 66% of all rhythms. Six percent of patients treated with basic EMT care were discharged, compared with 7% of patients treated with EMT and paramedic care. In contrast to resuscitation from cardiac arrest in adults, the likelihood of successful resuscitation in children is very poor. This is due to different etiologies and the higher proportion of asystole seen in pediatric cardiac arrest as compared with adults.

OUT-OF-HOSPITAL CARDIAC ARREST: IMPROVED SURVIVAL WITH PARAMEDIC SERVICES

Survival after out-of-hospital cardiac arrest was studied in a suburban community (population 304000) before and after addition of paramedic services. During period 1 emergency medical technicians provided basic emergency care (cardiopulmonary resuscitation at the scene of collapse and during the journey to hospital). In period 2 additional care was given at the scene of collapse by paramedics capable of advanced emergency care (defibrillation, endotracheal intubation, drugs). During the 3-yr study 585 patients with cardiac arrest caused by heart disease received prehospital emergency resuscitation. Paramedic services improved the rate of live admission to the coronary-care or intensive-care unit from 19% to 34% (p less than 0.001) and the rate of discharge from 7% to 17% (p less than 0.01). The mean time from collapse to delivery of advanced emergency care was 27.5 min during period 1 with technician services, and 7.7 min during period 2 with paramedic services. Ventricular fibrillation caused cardiac arrest in nearly all patients who survived; it occurred in 91 of the 160 (57%) patients during period 1 whose rhythms were determined and in 192 of the 343 (56%) patients during period 2. The decreased time from collapse to delivery of advanced emergency care accounted for the improved survival with paramedic services.

Emergency CPR instruction via telephone.

We initiated a program of telephone CPR (cardiopulmonary resuscitation) instruction provided by emergency dispatchers to increase the percentage of bystander-initiated CPR for out-of-hospital cardiac arrest. Cardiac arrests in King County, Washington were studied for 20 months before and after the telephone CPR program began. Bystander-initiated CPR increased from 86 of 191 (45 per cent) cardiac arrests before the program to 143 of 255 (56 per cent) cardiac arrests after the program. During the after period, 58 patients received CPR as a result of telephone instruction, 12 of whom were discharged. We estimate that four lives may have been saved by the program. A review of hospital records revealed no excess morbidity in the group of patients receiving dispatcher-assisted CPR.

SENSITIVITY, ACCURACY, AND SAFETY OF AN AUTOMATIC EXTERNAL DEFIBRILLATOR: Report of a Field Evaluation

An automatic external defibrillator (AED) was used by paramedics to detect ventricular fibrillation and deliver countershocks in 39 people with out-of-hospital cardiac arrests. The AED identified and delivered at least 1 countershock to 13 of the 16 people in ventricular fibrillation (81% sensitivity). The AED responded correctly to all 21 of the non-ventricular-fibrillation rhythms (8 other electrical rhythms, 13 asystole) with no countershocks (100% specificity). In 2 patients the rhythm could not be assessed. The device caused no injuries to patients or personnel. The performance of the AED was also analysed by considering each 15 s segment of ventricular fibrillation as a separate challenge; the device delivered a countershock in 19 of 29 such segments (66%).

Health status of survivors of cardiac arrest and of myocardial infarction controls.

We interviewed 308 survivors of out-of-hospital cardiac arrest and matched controls who had suffered a myocardial infarction. The Sickness Impact Profile (SIP) scores of controls were somewhat lower (better) than those of cases, but responses of cases and controls to additional questions about stair climbing, irritability and mood were virtually identical. Half as many (18 per cent) controls as cases (38 per cent) reported poorer memory function; nevertheless, 63 per cent of cases and 79 per cent of controls who had been working outside the home at the time of the event were employed at the time of the interview.

Paramedic programs and out-of-hospital cardiac arrest: II. Impact on community mortality.

Out-of-hospital cardiac arrest was studied in suburban King County, Washington in an attempt to determine the impact of paramedic services on community cardiac mortality. A portion of the study area received paramedic services and the remainder received basic emergency medical technician (EMT) services. A surveillance system identified all prehospital cardiac arrest incidents. The etiology and outcome were determined. Deaths due to primary heart disease (ICDA) codes 410-414) were compared to community cardiac mortality figures for the same period of time and in the paramedic and EMT areas. Between April 1, 1976 and August 31, 1977, 1,449 deaths due to primary heart disease occurred (annual rate of 19.2/10,000 in the EMT area and 13.4/10,000 in the paramedic area). For the same period, 487 patients with out-of-hospital cardiac arrest received emergency resuscitation. The annual incidence of out-of-hospital cardiac arrest was similar in the EMT and paramedic areas (5.6 and 6.0/10,000 respectively). Proportionately more lives of persons with cardiac arrest were saved in the paramedic area than in the MET area. During this 17 month period, the reduction in community cardiac mortality was 8.4 per cent in the paramedic area and 1.3 per cent in the EMT area. These findings suggest that paramedic services have a small but measurable effect on community cardiac mortality.

Out-of-hospital cardiac arrest: a review of major studies and a proposed uniform reporting system.

The scientific literature from January 1970 to June 1979 was reviewed for articles reporting outcomes from out-of-hospital cardiac arrest treated by paramedic programs. Only articles appearing in refereed professional journals and reporting 25 or more attempted resuscitations were included. A total of 21 articles from 15 U.S. locations were found. Four separate case definitions were distinguished. Methods and reporting formats varied considerably. Few studies used an experimental or quasi-experimental design, or control or comparison groups. The range of attempted resuscitations varied from 26 to 1.106 patients. Patients admitted to hospital varied between 22 per cent and 65 per cent (mean 38 per cent, S.D. +/- 12.4 per cent). Patients discharged alive varied from 3.5 per cent to 31 per cent (mean 17.2 per cent, S.D. +/- 7.1 per cent). Post discharge survival was either not reported or reported in different formats. A simplified reporting format is proposed using factors known to be associated with successful resuscitation: 1) underlying heart disease etiology; 2) witnessed arrest; 3) cardiac rhythm of ventricular fibrillation/ventricular tachycardia; 4) hospital admission and discharge and, when possible, by time from collapse to initiation of CPR and definitive care. Uniform reporting of outcomes will improve comparability and accurate measurement of the impact of emergency programs on out-of-hospital cardiac arrest.

Automatic external defibrillation: Evaluations of its role in the home and in emergency medical services

Many recent efforts to improve emergency medical services (EMS) and increase survival rates are simply efforts to get defibrillation to patients as rapidly as possible. In the 1960s physicians traveled in mobile coronary care units to bring the defibrillator to cardiac arrest patients. Later, paramedics, rather than physicians, were used. During the late 1970s the concept of early out-of-hospital defibrillation expanded as emergency medical technicians (EMTs) learned to defibrillate. Researchers in several settings confirmed the effectiveness of early defibrillation by EMTs. The automatic detection of ventricular fibrillation (VF) creates new opportunities for the early defibrillation concept. This includes both automatic implantable defibrillators and automatic external defibrillators (AED). The King County, Washington, EMS is conducting two projects to evaluate AEDs. One is a randomized, controlled crossover study in which EMTs use either an AED or a standard manual defibrillator. Outcome measurements include time to countershock, conversion rates, and survival rates. In the second project family members of patients who have survived out-of-hospital VF randomly receive an AED and cardiopulmonary resuscitation (CPR) instruction, or CPR instruction alone. This study was designed to determine whether family members can be trained adequately to use the device effectively. Psychological tests measure the effect of learning about, living with, and using such technology. These studies may help define the role of AEDs in the future management of out-of-hospital VF.