Use of the automatic external defibrillator in the management of out-of-hospital cardiac arrest

Managed care organizations: a link in the chain of survival?

Managed care organizations (MCOs) have proliferated throughout the United States. Interaction by patients, physicians, and emergency medical services systems with MCOs is evolving. Although MCOs have had some notable successes in reducing health care expenditures, the way in which MCO enrollees gain access to emergency medical care remains a contested issue. We present the cases of two patients who died after they delayed calling 911 in keeping with the rules of their MCO.

Multicenter comparison of truncated biphasic shocks and standard damped sine wave monophasic shocks for transthoracic ventricular defibrillation. Transthoracic Investigators

BACKGROUND

The most important factor for improving out-of-hospital ventricular fibrillation survival rates is early defibrillation. This can be achieved if small, lightweight, inexpensive automatic external defibrillators are widely disseminated. Because automatic external defibrillator size and cost are directly affected by defibrillation waveform shape and because of the favorable experience with truncated biphasic waveforms in implantable cardioverter-defibrillators, we compared the efficacy of a truncated biphasic waveform with that of a standard damped sine monophasic waveform for transthoracic defibrillation.

METHODS AND RESULTS

The principal goal of this multicenter, prospective, randomized, blinded study was to compare the first-shock transthoracic defibrillation efficacy of a 130-J truncated biphasic waveform with that of a standard 200-J monophasic damped sine wave pulse using anterior thoracic pads in the course of implantable cardioverter-defibrillator testing. Pad-pad ECGs were also examined after transthoracic defibrillation. After the elimination of data for 24 patients who did not meet all protocol criteria, the results from 294 patients were analyzed. The 130-J truncated biphasic pulse and the 200-J damped sine wave monophasic pulse resulted in first-shock efficacy rates of 86% and 86%, respectively (P = .97). ST-segment levels measured 10 seconds after the shock in 151 patients in sinus rhythm were -0.26 +/- 1.58 and -1.86 +/- 1.93 mm for the 130- and 200-J shocks, respectively (P < .0001).

CONCLUSIONS

We found that 130-J biphasic truncated transthoracic shocks defibrillate as well as the 200-J monophasic damped sine wave shocks that are traditionally used in standard transthoracic defibrillators and result in fewer ECG abnormalities after the shock.

Comparative assessment of shockable ECG rhythm detection algorithms in automated external defibrillators

The sensitivity and specificity to ventricular fibrillation (VF) and ventricular tachycardia (VT), classified as requiring immediate DC shock, of four automated external defibrillators (AEDs) and three advisory defibrillators were assessed using the Department of Health Arrhythmia library. This library collected mostly from patients in hospital, includes a wide variety of ECG rhythms including many with additional noise and interference artefact. The library comprised 278 16-s rhythms, 59 of which were VF, 36 were VT requiring cardioversion and 183 were deemed non-shockable. Non-shockable rhythms included asystole, pacing, slow VT, idioventricular rhythms, sinus and atrial based rhythms, some of which contained ventricular ectopic activity of differing grades. For the AEDs, a positive result (indicating detection of a shockable rhythm) was recorded if charging started or was able to be started at any time during the 16 s of rhythm output and energy subsequently available for discharge. For the advisory defibrillators, a positive result was recorded if a 'shock advised' alert was issued at any time during output of the rhythm. The AEDs exhibited sensitivities to VF in the range 81-94%, and to VF plus shockable VT 64-73%, or 72-83% depending whether VT > 150 beats/min or > 180 beats/min is considered to be shockable. The specificities recorded were in the range 90-94% and 86-92%, respectively. All but one of the advisory defibrillators performed similarly. Excluding the artefact rhythms, specificities in the range 79-91% were obtained. All figures stated are at the lower limit of the 95% confidence interval.

Out-of-hospital cardiac arrests in Helsinki: Utstein style reporting

OBJECTIVE

To determine the epidemiology of out-of-hospital cardiac arrests and survival after resuscitation and to apply the Utstein style of reporting to data collection.

DESIGN

Prospective cohort study.

SETTING

A middle-sized urban city (population 516,000) served by a single emergency medical services system.

PATIENTS

Consecutive prehospital cardiac arrests occurring between 1 January and 31 December 1994.

INTERVENTION

Advanced cardiac life support according to the recommendations of American Heart Association.

MAIN OUTCOME MEASURES

Survival from cardiac arrest to hospital discharge, and factors associated with survival.

RESULTS

Four hundred and twelve patients were considered for resuscitation. The overall incidence of out-of-hospital cardiac arrest was 79.8/100,000 inhabitants/year. Fifty seven patients (16.6%) survived to discharge when resuscitation was attempted. 32.5% survived when cardiac arrest was bystander witnessed and was of cardiac origin with ventricular fibrillation as the initial rhythm. When asystole or pulseless electrical activity was the first rhythm recorded, discharge rates were 6.2 and 2.7% respectively. The cause of cardiac arrest was cardiac in 66.5%, and ventricular fibrillation was the initial rhythm in 65.0% of bystander witnessed cardiac arrests of cardiac origin. 22.1% of patients received bystander initiated cardiopulmonary resuscitation. The mean time intervals from the receipt of the call to the arrival of a first response advanced life support unit and mobile intensive care unit at the patient's side and to the return of spontaneous circulation were 7.0 and 10.3 and 12.6 and 16.7 min respectively. In the logistic regression model bystander witnessed arrest, age, ventricular fibrillation as initial rhythm, and the call-to-arrival interval of the first response unit were independent factors relating to survival. Utstein style reporting with modification of time zero was found to be an appropriate form of data collection in this emergency medical services system.

CONCLUSIONS

After implementation of major changes in the emergency medical services system during the 1980s survival from out-of-hospital cardiac arrest markedly increased. However, early access, which has turned out to be the weakest link in the chain of survival, should receive major attention in the near future. Utstein style reporting with a modified time zero was found to be appropriate, although laborious, protocol for data collection.

Effectiveness of emergency medical services for victims of out-of-hospital cardiac arrest: a metaanalysis

STUDY OBJECTIVE

To determine the relative effectiveness of differences in response time interval, proportion of bystander CPR, and type and tier of emergency medical services (EMS) system on survival after out of hospital cardiac arrest.

METHODS

We performed a comprehensive literature search, excluding EMS systems other than those of interest (systems of interest were those comprising one tier with providers of basic life support [BLS] or advanced life support [ALS] and those comprising two tiers with providers of BLS or BLS-defibrillation followed by ALS), patient population of fewer than 100 cardiac arrests, studies in which we could not determine the total number of arrests of presumed cardiac origin, and studies lacking data on survival to hospital discharge. Metaanalysis using generalized linear model with dispersion estimation for random effects was then performed.

RESULTS

Increased survival to hospital discharge was significantly associated with tier (P < .01), response time interval (P < .01), and bystander CPR (P = .04). A significant interaction was detected between response time interval and bystander CPR (P = .02). For the studies analyzed, survival was 5.2% in a one-tier EMS system or 10.5% in a two-tier EMS system. A 1-minute decrease in mean response time interval was associated with absolute increases in survival rates of .4% and .7% in a one-tier and two-tier EMS systems, respectively.

CONCLUSION

Increased survival to hospital discharge may be associated with decreased response time interval and with the use of a two-tier EMS system as opposed to a one-tier system. The data available for this analysis were suboptimal. Policymakers need more methodologically rigorous research to have more reliable and valid estimates of the effectiveness of different EMS systems.

Advanced life support: role of the rural registered nurse

This paper provides a human face to advanced life support (ALS) and its assention within rural nursing practice. Over the past 5 years the issue of defibrillation and who performs it has been debated. This paper will add to the discussion. It examines the history surrounding the development of ALS, education within the hospital and isolated rural setting competency testing. It questions the limited role of current nursing practice and makes recommendations for stretching the boundaries of the nursing role in ALS. Emphasis is placed on the rural perspective and its consequent implications for individuals living in a rural environment.

The effect of experience of on-site physicians on survival from prehospital cardiac arrest

Outcome from prehospital cardiac arrest was studied 1 year before (Period I) and after (Period II) a reorganisation of the work and the simultaneous change of all physicians participating in the care of prehospital patients in the emergency medical service system in Helsinki. There were 444 patients during Period I and 395 patients during Period II. Resuscitation was initiated in 279 patients during Period I and in 323 patients (P < 0.001) during Period II. The number of patients with ventricular fibrillation who suffered a witnessed cardiac arrest due to presumed heart disease was 120 and 130, respectively. During Period I, 70 of these patients were successfully resuscitated and admitted to hospital, 41 (34%) survived to discharge home from hospital. Corresponding figures during Period II were 79 and 33 (25%, NS). Compared with Period I, a larger proportion of the successfully resuscitated patients either died in hospital or were discharged to an institution during Period II (P < 0.05).

Type of arrhythmia at EMS arrival on scene in out-of-hospital cardiac arrest in relation to interval from collapse and whether a bystander initiated CPR

Outcome after cardiac arrest is strongly related to whether the patient has ventricular fibrillation at the time the emergency medical service (EMS) arrives on the scene. The occurrence of various arrhythmias at the time of EMS arrival among patients with out-of-hospital cardiac arrest was studied in relation to the interval from collapse and whether cardiopulmonary resuscitation (CPR) was initiated by a bystander. The patients studied were all those with out-of-hospital cardiac arrest in Goteborg, Sweden, between 1980 and 1992 in whom CPR was attempted by the arriving EMS and for whom the interval between collapse and the arrival of EMS was known. In all, information on the time of collapse and the arrival of EMS was available for 1,737 patients. Among patients for whom EMS arrived within 4 minutes of collapse, 53% were found in ventricular fibrillation/tachycardia. There was a successive decline in occurrence of such arrhythmias with time. However, when the interval exceeded 20 minutes, ventricular fibrillation/tachycardia was still observed in 27% of cases. Bystander CPR increased the occurrence of such arrhythmias regardless of the interval between collapse and EMS arrival.

Optimal defibrillation strategy and follow-up of out-of-hospital cardiac arrest. The Belgian CPCR Study Group

In the current climate of rising healthcare cost, resuscitation efforts performed outside the hospital are critically evaluated because of their limited success rate in some settings. As part of a quality assurance program between the 1st January 1991 and 31st December 1993, six centres of the Belgian CPCR study group prospectively registered cardiac arrest (CA) patients and their treatment according to the Ustein Style recommendations. In the group (n = 511) of patients initially found in ventricular fibrillation (VF) a significantly better survival rate was observed for those patients who received a 1st defibrillatory shock by the 1st tier (n = 142 (27.8%)) as compared to those defibrillated after arrival of the 2nd tier (n = 369 (72.2%)). Median time to delivery of the first shock was significantly shorter (5 min) in the 1st tier group. In a second part of the study we describe long-term management of the 28 surviving VF patients, treated by the single EMS system of Brugge between 1st January 1991 and 30th April 1995: only 6 patients eventually received an implantable cardioverter defibrillator (ICD), whereas coronary revascularization was performed in 9 patients, and 3 patients were discharged on amiodarone only. Satisfactory long-term survival after out-of-hospital VF can be achieved by an early shock followed by advanced life support and appropriate definitive treatment.

EMS characteristics in an Asian Metropolis

A prospective citywide cohort study was conducted from August 1, 1993, through May 31, 1994 to analyze the epidemiological characteristics of emergency medical services (EMS) in an Asian city. Of 5,459 studied cases, the leading 3 causes were trauma (49.7%), alcohol intoxication (8.6%), and altered mental status (AMS) (6.9%). Half of the studied cases needed no prehospital care and 16.4% needed advanced life support (ALS) care. Traffic accidents accounted for 68% of trauma cases. Of 897 cases requiring ALS care, the two most common causes were AMS and dead on arrival (DOA) (32.1% and 21.2% in medical group, 10.1% and 4.5% in trauma group, respectively). The response time, time on scene, and transportation time were 4.6, 4.3, and 9.4 minutes, respectively. This Oriental EMS system experienced very short prehospital times, many traffic accidents, and extremely few DOA cases. Because few patients required ALS care, an emergency medical technician-based EMS system would probably be able to handle the majority of prehospital patients.

Measuring the call-receipt-to-defibrillation interval: evaluation of prehospital methods

STUDY OBJECTIVE

Successful resuscitation of cardiac arrest depends partly on the time of first defibrillation. An accurate, practical method of measuring this time has not been devised. We attempted to determine the interval from receipt of a call by emergency medical services personnel to first defibrillation (total defibrillation interval) with synchronized clocks between computer-aided dispatch operations and an event-recording defibrillator.

DESIGN

A 7-month prospective study measuring the total defibrillation interval. An automated code summary was to be submitted for each participant.

SETTING

An urban, all-advanced life support, public utility model system.

PARTICIPANTS

All primary ventricular fibrillation patients seen during the study period.

RESULTS

Ninety-two patients met study criteria. Data are presented as median (interquartile range). The total defibrillation interval was 9.8 minutes (7.9 to 11.8 minutes). The call-receipt-to-vehicle-at-scene interval was 5.98 minutes (4.4 to 7.3 minutes). The vehicle-at-scene-to-defibrillation interval was 3.6 minutes (2.5 to 4.6 minutes).

CONCLUSION

The use of synchronized clocks in automated event-recording systems may provide a method of accurately measuring the time elapsed before defibrillation.

Defibrillation by basic emergency medical technicians: effect on survival

Several studies have examined the effect of early defibrillation by basic EMTs on patient survival. Although the studies have a common theme of early basic EMT defibrillation, they are diverse in locations, devices, control groups, caregivers, and protocols. They provide a confusing array of information that is difficult to review, synthesize, and interpret. Metaanalysis allows data pooling of these primary studies to combine results and statistically compare the observed variation in study outcomes. The purpose of this metaanalysis was to examine the published studies of early basic EMT defibrillation to learn whether this treatment has an effect on survival of out-of-hospital cardiac arrest. Analysis of the 10 studies that met inclusion criteria showed that despite variations in design, the overall effect size for all the studies was .092, indicating a 9.2% increase in survival over what would have been expected had the EMT-Ds not intervened.

Ventricular fibrillation, automatic external defibrillators, and the United States Food and Drug Administration: confrontation without comprehension

More people die in the United States each day of potentially reversible VF than of any other cause of death, reversible or not. Early defibrillation is the definitive treatment. Automated external defibrillation is a proven technology now confirmed to have saved thousands of lives. As with all medical devices and technology, perfection is not possible. Some problems, such as those represented by the two cases discussed in this article, are inevitable and acceptable and give little cause for alarm. One would not stop penicillin from being manufactured and distributed because of a sudden, unexpected allergic reaction in one patient (error of commission) or an unexpected resistant organism in another (error of omission). The FDA must understand that AEDs, even if they are imperfect, are not anywhere near as dangerous as no defibrillator at all. AEDs have finally allowed many EMS systems to achieve early defibrillation. Discontinuing use of AEDs or closing AED manufacturers could mean a significant number of lives lost unnecessarily. Therefore EMS agencies planning to implement early-defibrillation programs should continue with such plans. Why the agents of an important federal regulatory agency have singled out this technology for an intense review puzzles many observers in the medical-device field. Two meetings have been hosted by officials of the FDA to discuss the continuing concern the FDA officials have expressed over automated defibrillation technology. These meetings included representatives from the AHA, the American College of Cardiology, ACEP, defibrillator manufacturers, and other interested organizations. The FDA leadership has repeatedly focused on data acquired through the FDA Medical Device Reporting systems. Congress requires the FDA to investigate reports of problems with "critical medical devices." Because the indication for the use of a defibrillator is cardiac arrest, there will inevitably be a high association between defibrillator use and patient deaths. FDA personnel may view such reports of device problems in association with patient deaths as evidence that an intrinsically flawed technology has reached the marketplace without rigorous testing and evaluation. From the clinician's perspective, however, these reports represent a small numerator over a huge denominator of daily, lifesaving clinical use. The non-FDA participants at the two meetings have stated that the FDA complaints appear to be random and reveal a lack of understanding of AED technology.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of out-of-hospital defibrillation by basic life support providers on cardiac arrest mortality: a metaanalysis

STUDY OBJECTIVE

Although some studies demonstrate otherwise, we hypothesized that metaanalysis would demonstrate a reduction in the relative risk of mortality when basic life support (BLS) providers can defibrillate out-of-hospital cardiac arrest patients.

DESIGN

Metaanalysis of studies meeting the following criteria: single-tier or two-tier emergency medical service (EMS) system, survival to hospital discharge for patients in ventricular fibrillation, and manual and/or automatic external defibrillators. The alpha error rate was .05.

RESULTS

Seven trials qualified for metaanalysis. Across all trials, the risk of mortality for BLS care with defibrillation versus that without was .915 (P = .0003). Separate subset analyses of single-tier and two-tier EMS systems demonstrated similar results.

CONCLUSION

BLS defibrillation can reduce the relative risk of death for out-of-hospital cardiac arrest victims in ventricular fibrillation. Weaknesses in individual study designs and regional clustering limit the strength of this metaanalysis and conclusion.

Truncated biphasic pulses for transthoracic defibrillation

BACKGROUND

Early defibrillation is the single most important factor for improving out-of-hospital ventricular fibrillation resuscitation rates. To achieve the earlier response times required for survival, typically < 6 minutes from time of collapse, it will be necessary to equip a far wider network of first responders (firefighters, police, and other individuals with responsibility for public safety) with small, lightweight, and inexpensive automatic external defibrillators (AEDs). An important step in reducing the size and cost of AEDs will be to improve defibrillation efficacy. Because biphasic waveform defibrillation has had a favorable impact on implantable cardioverter-defibrillators (ICDs), there are reasons to believe that biphasic waveforms would also improve transthoracic defibrillators. Our purpose, therefore, was to examine the efficacy of two different low-energy biphasic truncated waveforms referenced to a standard damped sine waveform for transthoracic defibrillation in humans.

METHODS AND RESULTS

We prospectively and randomly compared the transthoracic defibrillation efficacy of two different truncated biphasic waveforms, 115 J (70 microF) and 130 J (105 microF), with that of a standard 200-J (36-microF, 28-mH) damped sine wave pulse using right anterior and left lateral thoracic pads (R2 Medical Systems) in 30 cardiac arrest survivors during transvenous ICD surgery. The right anterior patch electrode was used as the cathode and the left lateral thoracic pad as the anode. Transthoracic ventricular defibrillation rescue shocks were tested after a failed transvenous defibrillation shock delivered in the course of ICD testing. Each of the three different rescue shocks was tested in random order in each patient. All shocks were delivered at end expiration. The investigators responsible for determining transthoracic shock efficacy were blinded throughout the study to the transthoracic rescue waveform used. A total of 33 patients were considered for study, but three patients failed to satisfy all entry criteria or did not have a sufficient number of ventricular fibrillation inductions to allow for testing of all three waveforms. Percent efficacy for the three waveforms was then compared in the 30 patients who satisfied entry criteria and completed the protocol. The study population had a mean age of 61 +/- 11 years, with 22 (73%) being men. The mean left ventricular ejection fraction was 0.39 +/- 0.14. Coronary artery disease was present in 22 (73%). The 115-J (70-microF) biphasic pulse, the 130-J (105-microF) biphasic pulse, and the 200-J (36-microF, 28-mH) damped sine wave pulse were equally effective, resulting in a 97% first-shock ventricular defibrillation efficacy rate. Each waveform failed to defibrillate once, with each waveform failing in a different patient.

CONCLUSIONS

The results of this study suggest that biphasic truncated transthoracic shocks of low energy (115 and 130 J) are as effective as 200-J damped sine wave shocks used in standard transthoracic defibrillators. This finding may contribute significantly to the miniaturization and cost reduction of transthoracic defibrillators, which could enable the development of a new generation of AEDs appropriate for an expanded group of out-of-hospital first responders and, eventually, layperson use.

Out-of-hospital cardiac arrest: two and a half years experience of an accident and emergency department in Hong Kong

The results are presented of 2 1/2 years of experience of patients with out-of-hospital cardiac arrests who were resuscitated in an accident and emergency department (A&E) attached to an acute district hospital in Hong Kong. Out of 263 cases of out-of-hospital cardiac arrest as a result of a variety of causes only seven patients survived (3%) and among the 135 patients with cardiac aetiology only four survived (3%). Ways to improve the outcome for out-of-hospital cardiac arrest are discussed.

Hospital mortality after out-of-hospital cardiac arrest among patients found in ventricular fibrillation

The aim of this study was to describe factors associated with in-hospital mortality among patients being hospitalised after out-of-hospital cardiac arrest and who were found in ventricular fibrillation. The study was set in the community of Göteborg, Sweden. The subjects consisted of all patients who were hospitalised alive after out-of-hospital cardiac arrest, being reached by our mobile coronary care unit and who were found in ventricular fibrillation, between 1981 and 1992. In all, 488 patients fulfilled the inclusion criteria of which 262 (54%) died during initial hospitalization. In a multivariate analysis including age, sex, history of cardiovascular disease, chronic medication prior to arrest and circumstances at the time of arrest, the following appeared as independent predictors of hospital mortality: (1) interval between collapse and first defibrillation (P < 0.001); (2) on chronic medication with diuretics (P < 0.01); (3) age (P < 0.01); (4) bystander initiated CPR (P < 0.05); and (5) a history of diabetes (P < 0.05). In a multivariate analysis considering various aspects of status on admission to hospital, the following were independently associated with death: (1) degree of consciousness (P < 0.001) and (2) systolic blood pressure (P < 0.05). In conclusion, among patients with out of hospital cardiac arrest found in ventricular fibrillation and being hospitalised alive, 54% died in hospital. The in-hospital mortality was related to patient characteristics before the cardiac arrest as well as to factors at the resuscitation itself.

Strengthening the in-hospital chain of survival with rapid defibrillation by first responders using automated external defibrillators: training and retention issues

STUDY OBJECTIVE

To determine whether staff outside critical care areas who were proficient in basic life support (BLS) could be easily trained to use automated external defibrillators (AEDs) and whether they would retain these skills.

DESIGN

Prospective, longitudinal cohort series.

SETTING

Two university teaching hospitals.

PARTICIPANTS

One hundred forty nurses who had previously learned BLS and constituted the staff from three medical/surgical nursing units from each study hospital.

INTERVENTIONS

The nurses were taught how to use the Heartstart 1000s, a lightweight portable shock-advisory AED, in a 2-hour class with an instructor and manikin-to-student ratio of 1:5. The course emphasized hands-on practice of the BLS-AED algorithm on a computerized manikin.

RESULTS

Using a similar scenario, each nurse was evaluated on the computerized manikin immediately after training (posttest). At 1 to 3, 4 to 6, and 7 to 9 months after the initial training, convenience samples of the cohort in three different groups were evaluated for retention. Satisfactory performance was defined as delivery of the first AED shock within 2 minutes of recognition of the arrest. At the posttest after training, 139 of 140 nurses (99%) demonstrated satisfactory performance. Of 77 nurses evaluated, 31 of 32 at 1 to 3 months, 18 of 18 at 4 to 6 months, and 24 of 27 at 7 to 9 months after initial training (95% overall) performed satisfactorily.

CONCLUSION

As has been demonstrated with prehospital emergency personnel, nurses outside critical care areas who are proficient in BLS can easily learn and retain the knowledge and skills to use AEDs. Automated external defibrillation, a BLS skill, should be incorporated into BLS programs (BLS-AED) for all hospital personnel expected to respond to a patient in cardiac arrest, with rapid defibrillation taking priority over CPR.

Observations of ventilation during resuscitation in a canine model

BACKGROUND

Fear of infection limits the willingness of laymen to do cardiopulmonary resuscitation (CPR). This study assessed the time course of change in arterial blood gases during resuscitation with only chest compression (no ventilation) in an effort to identify the time for which ventilation could be deferred.

METHODS AND RESULTS

Aortic pressures and arterial blood gases were monitored in seven 20- to 30-kg dogs in ventricular fibrillation (VF) at 2-minute intervals during chest compression alone (no ventilation) at 80 to 100 compressions per minute. Before the induction of ventricular fibrillation, all animals were intubated and ventilated with room air, 10 mL/kg. The endotracheal tube was removed when VF was induced. Pre-VF arterial pH, PCO2, and O2 saturation were (mean +/- SEM) 7.39 +/- 0.02, 27.0 +/- 1.5 mm Hg, and 97.5 +/- 0.5%, respectively, with aortic pressures being 143.2 +/- 5.7/116.2 +/- 4.6 mm Hg. At 4 minutes of chest compression alone, the corresponding values were 7.39 +/- 0.03, 24.3 +/- 3.1 mm Hg, and 93.9 +/- 3.0%, with an arterial pressure of 48.1 +/- 7.7/22.6 +/- 3.9 mm Hg. Mean minute ventilation during the fourth minute of CPR, measured with a face mask-pneumotachometer, was 5.2 +/- 1.1 L/min.

CONCLUSIONS

These data suggest that in the dog model of witnessed arrest, chest compression alone during CPR can maintain adequate gas exchange to sustain O2 saturation > 90% for > 4 minutes. The need for immediate ventilation during witnessed arrest should be reexamined.

Public perceptions of a rural emergency medical services system

INTRODUCTION

To determine the awareness of citizens and physicians concerning the capabilities of a rural emergency medical services (EMS) system.

HYPOTHESIS

Citizens and physicians are unaware of the capabilities of the EMS system.

METHODS

Residents were selected randomly from the local telephone directory and asked a series of structured questions about their EMS agency. A written survey was distributed to area physicians. Chi-square analysis was used to compare the proportion of respondents who knew the available interventions in their community with the proportion of those who did not. Statistical significance was inferred at p < 0.01.

RESULTS

A total of 49% of the citizens were able to identify available skills, and 41.4% of the physicians were able to identify available skills. Physicians were less likely than were the citizens to be able to identify the skills performed by each provider (p < 0.001).

CONCLUSION

This study indicates that both physicians and the lay public have little understanding of the capabilities of their EMS system.

Methodology-dependent variation in documentation of outcome predictors in out-of-hospital cardiac arrest

OBJECTIVE

To identify variation in outcome predictor documentation in out-of-hospital cardiac arrest associated with two different methods of data collection: concurrent questioning of personnel following a resuscitation attempt and archival report review.

METHODS

All patients > or = 18 years old who had out-of-hospital cardiac arrests, verified using the New York City 911 telephone system, between October 1, 1990, and April 1, 1991, were eligible for inclusion. The authors reviewed the first 200 cases of presumed primary cardiac arrest involving a resuscitation attempt among 3,243 consecutive ambulance call reports for cardiac arrest occurring during the study period. This archival data set was compared with data for the same 200 cases gathered through direct interview of field personnel by trained paramedics. The two data sets had been compiled independently by different individuals, using the same data collection instrument, which conformed to the Utstein template.

RESULTS

Comparison of the data obtained from ambulance records with the data obtained from interviews of prehospital personnel revealed several areas of variance. Of note was a significantly lower proportion of bystander-witnessed ventricular fibrillation (VF) in the data set gathered from written reports (7% vs 18%; 95% CI for the difference 4-18%; p = 0.001).

CONCLUSION

differences in methods of collection of out-of-hospital cardiac arrest data are associated with a more than twofold variation in the reported incidences of witnessed cardiac arrests manifesting as VF. Methodology-dependent variation in this important "denominator" may produce substantially different estimates of survival within the same cohort of patients.

Methodology for data collection to study prehospital cardiac arrest in New York City: the PHASE methodology. PreHospital Arrest Survival Evaluation Group

STUDY OBJECTIVE

To describe an effective methodology for the investigation of prehospital cardiac arrest in large cities.

DESIGN

Observational cohort study.

SETTING

New York City emergency medical services system.

PARTICIPANTS

All cardiac arrests dispatched by the 911 system between October 1, 1990, and March 31, 1991.

INTERVENTIONS

Trained paramedics performed immediate postarrest interviews with prehospital and hospital care providers using a standardized data collection instrument.

RESULTS

Of 3,239 consecutive, confirmed cardiac arrests in which resuscitation was attempted, 2,329 (72%) were of cardiac etiology. Information was sought for 15 of the 17 core events and times recommended by the Utstein Consensus Conference Data were obtained in more than 98% of cases for all except one of these core events and times. One core time yielded data in 96% of cases. All patients were followed until death or discharge home. None were lost to follow-up.

CONCLUSION

Concurrent, interactive acquisition of prehospital cardiac arrest data in a large urban setting captured over 98% of the core data recommended for completion of the Utstein template. This methodology may be a suitable means of investigating prehospital cardiac arrest in large cities.

Case definition in survival studies of out-of-hospital cardiac arrest

The purpose of this investigation was to determine problems with case definition and selection biases in studies of survival from out-of-hospital cardiac arrest, by comparing characteristics of subjects with cardiac arrest who entered the emergency medical services (EMS) system and those who did not enter the system. Data for 143 prehospital cardiac arrest patients in Johnson County, Iowa, were obtained from death certificates and EMS reports. Approximately one half of cardiac arrest patients entered the EMS system. Mean total number of causes of death listed on death certificates was significantly higher in subjects who did not enter the EMS system. Several factors, including age, sex, and number of causes of death listed on death certificates were significant univariate factors in whether a cardiac arrest victim entered the EMS system, but multivariate logistic regression indicated age by itself was the most significant factor. These results indicate there are possible initial biases determining who will enter the EMS system, which affects the generalizability of previous studies.

Differential prehospital benefit from paramedic care

STUDY OBJECTIVES

To determine whether prehospital outcome of patients who receive care from emergency medical technicians-paramedic (EMT-Ps) differs from that of patients who receive care from emergency medical technicians-defibrillation (EMT-Ds), as rated by the treating EMTs using standardized scales, and to determine whether the patient's seriousness of illness is relevant to any differential benefit of one level of care over the other.

DESIGN

Historical (retrospective) cohort.

SETTING

An urban and semiurban region of southwest Ontario comprising an area of 1,136 square kilometers (438 square miles) with a population of more than 445,000.

TYPE OF PARTICIPANTS

Patients (10,291) who were transported by the Hamilton-Wentworth EMS system between January 1, 1991, and December 31, 1991.

METHODS AND MEASUREMENTS

EMTs rated the prehospital outcome of their own patients, using scales that had been tested in a previous study. Comparisons between EMT-P- and EMT-D-treated patients were made by chi 2, chi 2 by trend, and Fisher's exact test as appropriate.

RESULTS

More seriously ill or injured EMT-P-treated patients were rated as improved and fewer EMT-P-treated patients were rated as worsened compared with similar patients who were cared for and rated by EMT-Ds. The differential benefit from EMT-P to EMT-D care ranged from 8% to 25% for patients rated as "severe" and from 27% to 49% for patients rated as "life-threatened."

CONCLUSION

According to the ratings of prehospital care providers, patients classified as "severe" or "life-threatened" had their conditions "improve" by the time they arrived at the hospital more often when care was provided by an EMT-P team than when it was provided by an EMT-D team.

Early defibrillation by police: initial experience with measurement of critical time intervals and patient outcome

STUDY OBJECTIVE

To assess the feasibility of consistent acquisition of precise and clinically important time intervals in a city police department defibrillation study.

DESIGN

On a daily basis, clocks at 911 dispatch were synchronized with those at ambulance dispatch, and all clocks on all defibrillators were synchronized to this time. Times were obtained from recordings at dispatch centers and from defibrillator memory modules.

SETTING

City with a population of 70,745 and an area of 30 square miles.

PARTICIPANTS

All patients in ventricular fibrillation (VF) treated by police officers using semiautomated defibrillators.

INTERVENTIONS

On receipt of a call at 911 dispatch, the nearest squad car was dispatched. If police arrived before the ambulance and a cardiac arrest was confirmed, the closest squad car with a defibrillator was dispatched. Police delivered up to three shocks before ambulance arrival.

RESULTS

Of 44 patients in VF, 14 were initially treated by police. Seven of 14 regained a spontaneous circulation with police shocks and seven required additional advanced life support care for restoration of pulses. Ten of the 14 were discharged home. The 911 call-to-shock time interval was 4.9 +/- 1.3 minutes for the seven who regained a spontaneous circulation with police shocks and 6.1 +/- 0.7 minutes for the seven without restoration of pulses by police (P = .035, one-sided, two-sample t-test).

CONCLUSION

Acquisition of precise times for determination of time intervals is feasible with a concerted effort to synchronize all clocks from which times are derived. Even small differences in call-to-shock time intervals appear to be critical determinants of restoration of a spontaneous circulation.

Survival after cardiac arrest outside hospital over a 12-year period in Gothenburg

BACKGROUND

A two-tiered ambulance system with a mobile coronary care unit and standard ambulance has operated in Gothenburg (population 434,000) since 1980. Mass education in cardiopulmonary resuscitation (CPR) commenced in 1985 and in 1988 semiautomatic defibrillators were introduced.

AIM

To describe early and late survival after cardiac arrest outside hospital over a 12-year period.

TARGET POPULATION

All patients with prehospital cardiac arrest in Gothenburg reached by mobile coronary care unit or standard ambulance between 1980 and 1992.

RESULTS

The number of patients with cardiac arrest remained fairly steady over time. Among patients with witnessed ventricular fibrillation, the time to defibrillation decreased over time. The proportion of patients in whom bystander initiated CPR was increased only moderately over time. The proportion of patients given medication such as lignocaine and adrenaline successively increased. The number of patients with cardiac arrest who were discharged from hospital per year remained steady between 1981 and 1990 (20 per year), but increased during 1991 and 1992 to 41 and 31 respectively.

CONCLUSIONS

Improvements in the emergency medical service in Gothenburg over a 12-year period have lead to: (1) a shortened delay time between cardiac arrest and first defibrillation and (2) an improved survival of patients with cardiac arrest outside hospital probably explained by this shortened delay time.

Early defibrillation by emergency physicians or emergency medical technicians? A controlled, prospective multi-centre study

In a controlled, prospective multi-centre study, defibrillation by emergency medical technicians (EMTs) was compared with the current standard of care in Germany--defibrillation by emergency physicians (EPs)-in order to answer the following questions: can EMTs in a two-tiered emergency medical services (EMS) system with physicians in the field defibrillate earlier than, and as safely as EPs? Does defibrillation by EMTs (study group) affect survival rate and long-term prognosis of patients in ventricular fibrillation (VF), as compared with the current national standards in resuscitation (basic cardiopulmonary resuscitation (CPR) by EMTs, and defibrillation by physicians: control group?

METHODS

Prior to the onset of the study, all EMTs completed retraining in basic life support (BLS). Randomly assessed EMTs were then trained to use semi-automatic defibrillators. With the help of on-line tape recordings, the complete resuscitation sequence was evaluated. Follow-up of the patients was carried out with the help of the Glasgow Coma Scale as well as Pittsburgh Cerebral and Overall Performance Categories.

RESULTS

A total of 159 patients with VF were included in the study. In 121 cases, collapse was witnessed. Of the patients receiving defibrillation by EMTs 25% were discharged from hospital alive, compared to 24% of the patients defibrillated by EPs. Of the study patients 67% were defibrillated within 12 min, while the percentage of control patients was 46%. Study patients were defibrillated earlier (P < 0.01), the return of spontaneous circulation (ROSC) was achieved earlier (P < 0.05), and the rate of patients requiring no adrenalin during resuscitation was higher in the study group (P < 0.05). The total amount of adrenalin administered in the study group was lower (P < 0.05). No statistically significant differences were found concerning the neurologic long-term prognosis.

CONCLUSIONS

In our study, EMT defibrillation was equally effective as defibrillation by EPs, but failed to improve survival rates or long-term outcome of patients in VF significantly, compared to EP defibrillation. Due to a reduction in the time intervals from collapse to defibrillation and to ROSC, as well as in adrenalin doses, by EMT-defibrillation, EMTs in Germany should defibrillate if they reach a patient prior to an EP, provided they have received continuous medical training and supervision.

Characteristics of fatal ambulance crashes during emergency and non-emergency operation

OBJECTIVE

To analyze the characteristics of fatal ambulance crashes to assist emergency medical services (EMS) directors in objectively developing their EMS system's policy governing ambulance operations.

HYPOTHESIS

No difference exists between the characteristics of fatal ambulance crashes during emergency and nonemergency use.

DESIGN

Retrospective, cross-sectional, comparative analysis of ambulance crashes resulting in fatalities reported to the Fatal Accident Reporting System (FARS) from 1987 to 1990.

METHODS

Twenty variables, representing characteristics of fatal ambulance crashes, were selected from the National Highway Traffic Administration FARS Codebook and were evaluated using tests of significance for categorical data grouped by emergency use and nonemergency use. Crash variable categories examined included demographics, accident configuration, accident severity, vehicle description, and ambulance operator action.

RESULTS

During the four-year study period, 109 fatal ambulance crashes occurred producing 126 deaths. Four states, New York, Michigan, California, and North Carolina, accounted for 37.5% of all fatal crashes. Seventy-five fatal crashes (69%) occurred during emergency use (EU) and 34 fatal crashes (31%) occurred during nonemergency use (NEU). The total number of fatal crashes varied in a downward trend (1987:32; 1988:24; 1989:28; 1990:25). The number of fatal EU crashes also varied in a downward trend (1987:28; 1988:16; 1989:19; 1990:12), while the number of fatal NEU crashes increased each year [1987:4; 1988:8; 1989:9; 1990:13](p = .016). Most EU fatal crashes occurred between 1200 h and 1800 h (p = .009). Most NEU fatal crashes occurred during times when light conditions were poor (p = .003). When a violation was charged to the ambulance driver (17 cited), the vehicle was more likely to be in EU (p = .056). No statistically significant differences between EU and NEU were identified by: 1) day of week; 2) season; 3) atmospheric conditions; 4) roadway surface type; 5) roadway surface condition; 6) speed limit; 7) roadway alignment; 8) relationship to junction; 9) manner of collision; 10) year manufactured; 11) vehicle role; 12) vehicle maneuver; 13) manner leaving scene; 14) extent of deformation; 15) violations charged; or 16) number of persons killed in accident.

CONCLUSION

Few characteristics differentiate between fatal ambulance crashes during EU and NEU. The difference between EU and NEU were statistically significant in only three out of the 20 variables examined: 1) year occurred; 2) time of day; and 3) light condition. These data provide few objective measures that may be used to develop ambulance operation policies to decrease fatal ambulance crashes.

Early defibrillation by EMTs: the Brussels experience

Considering that in Brussels the first-aid ambulance team reaches the patient in cardiac arrest 10 min before the physician-manned ambulance, we instituted a feasibility study of early defibrillation by emergency medical technicians (EMTs). Three hundred EMTs received a 20-h automatic external defibrillation (AED) training course followed by a refresher course every 6 months. Of 316 cardiac arrests included in this study, asystole was encountered in 53% and ventricular fibrillation/ventricular tachycardia (VF/VT) in 33% of the cases on arrival of the EMTs. In the VF/VT group, defibrillation was performed by EMTs with a Laerdal Heartstart 7-9 min before the medical team arrived. The overall cardiac arrest survival rate improved from 7% in 1989 to 19% in 1992. However, the long-term survival rate (14/105) of ventricular fibrillation remained low because of excessive delays in emergency medical service (EMS) access and in early ACLS. In conclusion, this work shows that in Brussels: (1) early defibrillation of cardiac arrest victims in VF is feasible by EMTs when a training and a follow-up program are implemented; (2) the weakest link of the chain of survival is the early EMS access, and the early ACLS; and (3) AED program increases the interest and the efficacy of EMTs and medical teams in the management of cardiac arrests.

The causative rhythm in out-of-hospital cardiac arrests witnessed by the emergency medical services in the Heartstart Scotland Project

Out-of-hospital defibrillation has been shown to improve survival in out-of-hospital cardiac arrests. The maximum performance of defibrillation-based systems is dependent on the proportion of cardiac arrests due to tachyarrhythmias. We reviewed 4248 reported arrests in the Heartstart Scotland database. We identified 3489 arrests due to cardiac or unknown cause. From this group we selected 258 cases known to be conscious on arrival of the crew. We were able to retrieve electrocardiographic data on the period within 2 min of the arrest in 106 cases. The first recorded rhythm at the arrest was ventricular fibrillation in 64%, ventricular tachycardia 4%, bradycardia in 28% and electromechanical dissociation in 4%. Defibrillatory shocks were delivered to 96% of patients in ventricular fibrillation and 60% of these patients survived. None of the patients with bradycardic arrests survived. Preceding chest pain was noted in 79% of patients subsequently developing ventricular fibrillation as the cause of arrest compared to only 37% of those suffering bradycardic arrests. It would appear that public awareness of the importance of early contact with the emergency services after the onset of chest pain could substantially improve the survival from out-of-hospital arrests.

Willingness of male homosexuals to perform mouth-to-mouth resuscitation

BACKGROUND

Providing mouth-to-mouth resuscitation (MMR) during cardiopulmonary resuscitation (CPR) is a proven effective lifesaving procedure. However, the perceived risk to the rescuer of contracting infectious diseases, especially acquired immunodeficiency syndrome (AIDS), by performing MMR on a possibly human immunodeficiency virus (HIV) positive individual is probably affecting the number of people willing to perform MMR. Physicians and nurses constitute a major part of citizen cardiopulmonary resuscitation (CPR) responders and serve as CPR educators and resource personnel. Currently, the fear of physicians and nurses of contracting infectious disease has dampened their willingness to perform MMR, and thus has reduced the number of strangers who will receive MMR. Homosexual males, like the medical community, have an increased perceived risk of acquiring infectious diseases, especially AIDS, and have been the target of intense educational efforts concerning the transmission of HIV. By (a) determining the willingness of various groups to perform MMR, (b) elucidating the factors which affect their willingness to perform MMR, and (c) comparing this willingness to the actual, not perceived, risk of acquiring HIV by performing MMR, either appropriate changes can be made to educate people in the performance of MMR, by informing them of the actual risks of contracting infectious diseases, or alternative methods of resuscitation, involving 'lay-on' masks, can be recommended. Thus the willingness of homosexual males to perform MMR was determined and compared to the previously determined actual reluctance of the medical community to perform MMR in similar hypothetical scenarios.

METHODS

During interviews, 200 male homosexuals in Los Angeles were asked to assume that they knew how to perform CPR and MMR and to indicate how they would respond to four hypothetical cardiac arrest scenarios. These scenarios included cardiac arrests of a child, a trauma victim, a young man in a gay neighbourhood, and a victim of unknown history. Demographical data concerning the respondents was also obtained.

RESULTS

Of the homosexual men surveyed, 93 and 85% stated they would perform MMR on a stranger of unknown history, if they, the rescuer, were HIV negative or positive, respectively, (P < 0.001). Similarly, a high percentage of the presumed HIV negative and HIV positive respondents stated a high willingness to perform MMR in response to hypothetical cardiac arrest scenarios involving a trauma victim, a child, and a young man in a gay neighbourhood.

CONCLUSIONS

The willingness of male homosexuals to perform MMR is high, in contrast to the general reluctance of internists and medical nurses to perform MMR in the same outpatient scenarios. The different perceived risks of male homosexuals and physicians acquiring infectious diseases by performing MMR is probably responsible for the difference in willingness of these two groups to perform MMR. The high perceived risk of acquiring infectious diseases due to performance of MMR currently held by physicians in general may be lowered by increasing educational efforts. CPR courses should (a) discuss actual and perceived risks of acquiring infectious diseases by MMR, (b) discuss and weigh a small, and possibly not valid, risk of contracting an infectious disease while performing MMR on a victim, and (c) emphasize techniques involving 'lay-on' barrier masks. The availability of effective 'lay-on' barrier masks' should also be increased.

Circadian variation of sudden cardiac death reflects age-related variability in ventricular fibrillation

BACKGROUND

Previous studies report a morning peak in the occurrence of out-of-hospital sudden cardiac death but lack detailed information on underlying arrhythmias. We used the documentation system of the semiautomated defibrillators used by emergency medical technicians to investigate the circadian pattern of defined arrhythmias and the influence of demographic patient characteristics on this pattern.

METHODS AND RESULTS

From December 1988 to December 1990, 703 consecutive patients (63% men; age, 67 +/- 17 years) with sudden cardiac death were registered in the Klinikum Steglitz area of the Berlin emergency care system. Determination of time of day of the event was based on the arrival time of the rescue squad. A marked circadian variation (P < .0001) in the occurrence of sudden cardiac death was observed with a primary morning peak (6 AM to noon) and a secondary afternoon peak (3 to 7 PM). The subgroup of 294 patients with ventricular fibrillation as initially documented arrhythmia showed a similar circadian variation (P < .0001). In significant contrast (P < .01), patients with asystole (n = 260) or pulseless bradyarrhythmias (n = 149) were more evenly distributed during the daytime with a primary night trough. Multivariate logistic regression analysis revealed that the circadian pattern of ventricular fibrillation was similar in both gender groups but tended to differ with regard to age: patients older than 65 years demonstrated a monophasic distribution, whereas patients aged 65 years or less had a biphasic distribution with peaks in the morning and in the afternoon.

CONCLUSIONS

The circadian pattern of sudden cardiac death reflects primarily a circadian variation in onset of ventricular fibrillation. The different circadian patterns of ventricular fibrillation, pulseless bradyarrhythmias, and asystole suggest different pathophysiological mechanisms of causation of death. The age dependence of the pattern of ventricular fibrillation may indicate different underlying external or endogenous triggers.

Prehospital cardiac arrest treated by urban first-responders: profile of patient response and prediction of outcome by ventricular fibrillation waveform

STUDY OBJECTIVES

To determine the speed and characteristics of patient response to urban first-responder defibrillation and to determine whether amplitude of ventricular fibrillation (VF) can predict outcome in these patients.

TYPE OF PARTICIPANTS

All adult patients in prehospital VF treated by fire department first-responders (265).

DESIGN AND INTERVENTIONS

A prospective observational study occurring between February 1, 1989, and January 1, 1991. Patients were defibrillated according to advanced cardiac life support and first-responder protocols. ECG and time data were recorded digitally.

MAIN RESULTS

Sixty-five percent of patients converted from VF to a more stable rhythm at least once during first-responder monitoring. Fifty-four percent of converted patients refibrillated at least once, and 42% of all stable conversions occurred after at least one episode of refibrillation. Seventy percent of all refibrillations occurred less than six minutes after the defibrillator was turned on, and 23% occurred after more than ten minutes. The proportion of stable conversions decreased from 30% on first conversion to 2% on fourth conversion. With each successive conversion the interval to refibrillation grew shorter, and development of a pulse or blood pressure became less likely. Presence of blood pressure or pulse after conversion had a sensitivity for hospital discharge of 54% and a specificity of 98%. Maximum VF amplitude before countershock was highly predictive of postshock rhythm, stable conversion in the field, time interval before refibrillation, inpatient admission, and hospital discharge. VF amplitude was unrelated to response interval or interval to defibrillation but was positively related to bystander CPR. Logistic regression identified VF amplitude as the most important predictor of hospital discharge; traditional variables such as response interval and bystander CPR were not predictive once amplitude had been accounted for. Changes in VF amplitude during the course of resuscitation efforts were frequent and also predictive of outcome.

CONCLUSION

Patients in VF who were treated by early countershock refibrillated much more frequently than previously reported. Refibrillations occur both early and late. Initial VF maximum amplitude is strongly predictive of outcome. Future reports of VF cardiac arrest should control for this previously neglected variable. Increased amplitude of VF during repeated refibrillation episodes is associated with increased hospital discharge, so future studies of advanced cardiac life support interventions should explore changes in VF amplitude as an outcome variable.

Comparative assessment of the ventricular fibrillation detection algorithms in five semi-automatic or advisory defibrillators

The sensitivity and specificity of ventricular fibrillation (VF) detection in three semi-automatic defibrillators (Laerdal Heartstart 3000, Spacelabs First Medic 610, Physio-Control Lifepak 300) and two advisory defibrillators (S&W DMS940, Marquette Responder 1500) were assessed with 25 ECG recordings, each of length 40 s. Of the 25 ECG recordings, 12 contained VF requiring defibrillation, three contained a tachyarrhythmia with a waveform similar to VF but which self-terminated, and 10 were selected from abnormal rhythms and artefacts which contained some features similar to VF. Sensitivity was assessed from the VF data. Specificity was assessed from both the rhythm preceding VF or the tachyarrhythmias, and from the VF-like data. The response to a changing rhythm was assessed from the self-terminating tachyarrhythmias. Each recording was replayed to the defibrillators at three signal amplitudes (normal, half and double). For each defibrillator, requests to check the patient and advice to shock were noted separately. The sensitivity for recommending a shock when a shock was required varied from 81 to 97%. The sensitivity for drawing attention to VF, either through requesting the patient to be checked or advising a shock, varied from 92% to 100%. There were no false detections in the rhythms preceding VF or the tachyarrhythmias (specificity with good quality signals 100%). The specificity with the VF-like data ranged from 63 to 90% for recommending a shock, and from 63% to 70% for requesting the patient be checked or shocked. There was no difference between the defibrillators for VF detection, but there was a significant difference between the semi-automatic and advisory defibrillators (P < 0.05) for the specificity of the final recommendation.

Preventing Sudden Death

In brief To address the leading cause of brief sudden death in high school and college athletes, the sports medicine team can consider using automated external defibrillators. When incorporated into an emergency response plan, these devices have dramatically improved cardiac arrest survival rates. Issues to review carefully include safety, efficacy, personnel training, medical control, pertinent regulations, and cost.

Engineering excellence: options to enhance firefighter compliance with standing orders for first-responder defibrillation

STUDY OBJECTIVE

To assess the quality of care delivered during first-responder defibrillation and to determine the potential efficacy of modifying existing automated external defibrillator designs to improve first-responder performance.

DESIGN

Prospective case series.

SETTING

An urban emergency medical services system providing first-responder defibrillation and paramedic care.

TYPE OF PARTICIPANTS

Firefighters who completed a four-hour (two-session) course in automated external defibrillator operation.

METHODS

Heartstart 2000 defibrillators (Laerdal Medical Corp, Armonk, New York) were used in 241 consecutive resuscitation attempts. Written reports and memory module printouts were abstracted to assess firefighter performance of 11 critical actions. The firefighter's response to each opportunity to perform a critical action was scored using explicit pass/fail criteria.

RESULTS

Records of 235 automated external defibrillator uses (97.5%) were submitted for analysis. Firefighters shocked within 15 seconds of a "shock indicated" message in 95% of opportunities and reanalyzed the rhythm within 90 seconds of the third consecutive shock (ie, after one minute of CPR) in 80% of cases. However, firefighters reanalyzed the patient's rhythm too soon in 75% of cases, thereby interfering with recommended intervals of CPR. Firefighters failed to reanalyze the patient's rhythm after device-initiated "check patient" prompts 62% of the time. Memory modules were left in the automated external defibrillator during practice sessions in 64 cases, decreasing available memory to monitor automated external defibrillator use in the field. Three instances of failure to withhold CPR during rhythm analysis resulted in a single inappropriate patient shock. No firefighter was shocked inadvertently.

CONCLUSION

Current device algorithms result in effective delivery of the initial three shocks. However, firefighters often fail to interpose recommended intervals of CPR between further attempts at defibrillation. Modification of existing device algorithms to provide additional visual and auditory cues may be preferable to relying on the user to recall accurately all the steps in this infrequently performed procedure.

Establishment and results of an EMT-D program in a two-tiered physician-escorted rescue system. The experience in Berlin, Germany

Early defibrillation by emergency medical technicians or even less qualified personnel has been shown to improve survival rates for out-of-hospital cardiac arrest caused by ventricular fibrillation. It has been questioned whether these favourable results can be applied within the context of physician-attended emergency medical systems. Taking into consideration the results of a pilot study and after a careful analysis of the logistic and epidemiological background, the first German EMT-D program was introduced in the former West Berlin in December 1988. The first 2 years of experience with 499 technician-initiated resuscitation attempts in which the mobile intensive care unit of Klinikum Steglitz was involved, confirmed the results of the pilot study with an improved long-term survival rate (18%) for patients with ventricular fibrillation. We conclude that EMT defibrillation should be introduced in emergency physician-attended two-tiered emergency medical systems, whenever a thorough analysis of the existing rescue systems exhibits a 'relevant frequency' of resuscitation and response interval of 15 min or less.

Performance of an established system of first responder out-of-hospital defibrillation. The results of the second year of the Heartstart Scotland Project in the 'Utstein Style'

The Heartstart Scotland project for out-of-hospital defibrillation covers the whole of Scotland, a population of approximately 5,102,400 (14.9% > 65 years, 48.3% male). All 395 ambulances in Scotland have been equipped with an automated external defibrillator and crews are trained in basic cardiopulmonary resuscitation and defibrillator use (EMT-D). Between 1 May 1990 and 30 April 1991 a total of 1700 cardiac arrests was reported by the ambulance service. Of the 1676 arrests which we could trace, 63% were witnessed. A total of 1383 (83%) of all patients were declared dead on arrival at hospital or in the emergency department, 119 (7%) died in hospital and 174 (10%) were discharged alive. Of the 174 survivors, 87% were conscious and normal at discharge, 9% had moderate residual disability and 2% severe disability. Survival of patients discharged alive from hospital was 85% at 1 year. Defibrillation was undertaken in 71% of the reported cardiac arrests. Survival of bystander witnessed arrests was increased from 7 to 15% with bystander CPR (P < 0.005). If the cardiac arrest was witnessed by the ambulance crew and required defibrillation, survival to discharge was 39%. Of bystander witnessed arrests reached while still in VF (n = 643), 11% were discharged alive. Patients who were defibrillated within 4 min of arrest had a 43% survival rate to hospital discharge.

Effect of first-responder automated defibrillation on time to therapeutic interventions during out-of-hospital cardiac arrest. The Multicenter High Dose Epinephrine Study Group

STUDY OBJECTIVES

The effect of automated defibrillation provided by basic emergency medical technician (EMT) first-responder units on the time intervals to other critical interventions in the management of out-of-hospital cardiac arrests is unknown. The purpose of this study was to define and compare elapsed time intervals to basic CPR, paramedic arrival, initial countershock, endotracheal intubation, IV access, and initial adrenergic drug therapy in first-responder automated defibrillation/paramedic versus basic EMT/paramedic emergency medical services systems.

DESIGN

Prospectively collected data from a 15-month multicenter study of out-of-hospital, nontraumatic cardiac arrests were analyzed. The mean time intervals to critical therapeutic interventions between first-responder automated defibrillation/paramedic and basic EMT/paramedic groups were compared using the Student's t-test with Bonferroni correction.

SETTING

Three first-responder automated defibrillation/paramedic and three basic EMT/paramedic urban emergency medical services systems.

PARTICIPANTS

1,578 patients with out-of-hospital cardiac arrest.

INTERVENTIONS

The first-responder automated defibrillation/paramedic group received initial ECG analysis and/or automated countershock by first-responder/EMTs; the basic EMT/paramedic group received initial ECG analysis and/or manual countershock by paramedics.

RESULTS

Elapsed time intervals in minutes +/- SD for first-responder automated defibrillation/paramedic versus basic EMT/paramedic groups, respectively, were as follows: Collapse to CPR, 4.3 +/- 3.9 versus 5.4 +/- 5.2 (P = .017); collapse to countershock, 10.7 +/- 5.9 versus 13.0 +/- 6.0 (P = .017); collapse to paramedic arrival, 13.0 +/- 5.4 versus 10.3 +/- 6.1 (P = .0001); paramedic arrival to IV access, 5.1 +/- 3.9 versus 7.0 +/- 5.0 (P = .0001); paramedic arrival to endotracheal intubation, 4.8 +/- 4.0 versus 6.8 +/- 5.8 (P = .0001); paramedic arrival to initial adrenergic drug therapy, 7.4 +/- 4.5 versus 8.2 +/- 4.7 (P = .015); collapse to IV access, 17.7 +/- 6.1 versus 16.6 +/- 7.4 (P = .10); collapse to endotracheal intubation, 17.3 +/- 6.4 versus 16.6 +/- 7.8 (P = .32); collapse to initial adrenergic drug therapy, 20.4 +/- 6.7 versus 18.1 +/- 7.2 (P = .010). The time intervals from paramedic arrival to IV access, endotracheal intubation, and initial adrenergic drug therapy remained shorter in the first-responder automated defibrillation/paramedic systems despite stratification by presenting cardiac rhythm.

CONCLUSION

First-responder automated defibrillation/paramedic systems provide not only shorter times to initial countershock, as compared with basic EMT/paramedic systems, but by having delegated initial countershock to first-responders, they also allow for significantly shorter times from paramedic arrival to IV access, endotracheal intubation, and initial adrenergic drug therapy interventions.

Out-of-hospital cardiac arrest: racial differences in outcome in Seattle

OBJECTIVES

Out-of-hospital sudden cardiac arrest is a key area in which to study the dual problem of the poorer health status of minority populations and their poorer access to the health care system. We proposed to examine the relationship between race (Black/White) and survival.

METHODS

We determined the incidence and outcome of cardiac arrests in Seattle for which medical assistance was requested.

RESULTS

Over a 26-month period, the age-adjusted incidence of out-of-hospital cardiac arrest was twice as great in Blacks than in Whites (3.4 vs 1.6 per 1000 aged 20 and over). The initial resuscitation rate was markedly poorer in the Black victims (17.1% vs 40.7%), and rates of survival to hospital discharge were also lower in Blacks (9.4% vs 17.1%). Both effective initial resuscitation and survival were significantly related to White race following adjustment for other covariates.

CONCLUSION

The differences in outcomes were not fully explained by features of the collapse or relevant service factors. Possible explanations include delays in instituting therapy, less bystander-initiated cardiopulmonary resuscitation, poorer levels of health, and differences in the underlying cardiac disorders.

Survival from out-of-hospital cardiac arrest: effects of patient age and presence of 911 Emergency Medical Services phone access

The purpose of this investigation was to determine factors associated with survival from out-of-hospital cardiac arrest, including effects of 911 Emergency Medical Services telephone access and the age of patient. Subjects included 1,753 prehospital cardiac arrest patients in Iowa. Patient survival status and other variables were compared for patients with access to a 911 service with those who did not, and for different age categories, using univariate associations and multivariate logistic regression analysis. The presence of 911 telephone access was significantly associated with survival from out-of-hospital cardiac arrest (9.18% versus 5.35% survival for 911 versus no 911 groups, respectively). This association was partially the result of the significant association of 911 with decreased time from collapse to call for help, decreased time to cardiopulmonary resuscitation (CPR), and decreased time to first shock (if in ventricular fibrillation [VF]). Younger age was significantly associated with survival in univariate analyses (8.94% versus 6.26% survival for younger versus older age groups, respectively), but this was not an independent association, which is indicated by the lack of significance of age in the multivariate model.