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

Outcomes of out-of-hospital ventricular fibrillation: their association with time to defibrillation and related issues in the defibrillation program in Japan

The aim of this study was to provide data on the outcomes of out-of-hospital cardiac arrest caused by ventricular fibrillation (VFOHCA) and analyze factors influencing patient outcomes in order to further improve EMS system performance in the resuscitation of VFOHCA patients in Japan. A datasheet was mailed to the fire defense headquarters throughout Japan, and returned data were analyzed for 614 cases of VFOHCA that occurred from January 1 through December 31, 1996. In relation to the time interval from receipt of emergency call to defibrillation, the subjects were stratified into five groups: 0-8 (n = 39), 9-12 (n = 87), 13-16 (n = 154), 17-20 (n = 118) and more than 21 min (n = 216). The discharge survival rates were 18*, 13.8*, 5.2, 4.2 and 4.2%, respectively (*P < 0.05). When defibrillation was delivered within 12 min after a call, 30.2% (38/126) converted to pulse-generating rhythm (PGR) after defibrillation and 43.6% (17/39) of patients with PGR on arrival at the hospital survived to discharge. In spite of these findings, a marked delay to defibrillation (more than 13 min) was observed in the majority (79.5%). The data shown in this study demonstrated that important issues that limit the benefits of an early defibrillation program reside in the EMS system.

Cardiopulmonary resuscitation of older, inhospital patients: immediate efficacy and long-term outcome

OBJECTIVE

To determine the independent effect of advancing age on prognosis after cardiopulmonary resuscitation (CPR).

DESIGN AND SETTING

Retrospective analysis of clinical records of patients who received CPR in a geriatric department equipped with an intensive care unit.

PATIENTS

A total of 245 patients (146 men, 99 women; mean age, 70+/-11 yrs) received CPR. Of these, 221 had a cardiocirculatory arrest (CA) in the intensive care unit and 24 had a CA in the general ward of the department. Acute myocardial infarction was the most frequent admission diagnosis.

INTERVENTIONS

CPR according to standard guidelines in all cases.

MEASUREMENTS AND MAIN RESULTS

Immediate, short-term (hospital discharge), and long-term (median follow-up, 31.5 months; range, <1-124 months) survival. Older patients had a lower immediate survival (<70 yrs [72/137] 52.6% vs. > or =70 yrs [43/108] 39.4%; p < .05) and, less frequently, ventricular tachycardia/ fibrillation (VT/VF) as a cause of CA. VT/VF bore the lowest immediate mortality rate (19/104; 18.3%) as compared with asystole/complete heart block (66/102; 64.7%) or pulseless electrical activity (40/49; 81.6%; p < .001). Acute myocardial infarction, acute heart failure, hypotension, and occurrence of CA in the intensive care unit were also univariate predictors of unfavorable, immediate prognosis. However, in a multiple logistic analysis model, the mechanism of CA (asystole/complete heart block or pulseless electrical activity vs. VT/VF), acute myocardial infarction, heart failure, and hypotension were independent predictors of unfavorable immediate prognosis, whereas advancing age was not. Similarly, after initially successful CPR, short-term survival was independently associated with acute myocardial infarction, hypotension before CA, initial rhythm at CA, and need for mechanical ventilatory support after CPR, but not with age. Longterm survival (42 patients; 17.2% of the original cohort; median survival, 32 months) was also independent of age, whereas it was negatively associated with heart failure.

CONCLUSION

Immediate, short- and long-term prognosis after in hospital CPR is independent of age, at least when possible confounders are simultaneously taken into account.

Automatic external defibrillators: changing the way we manage ventricular fibrillation

OBJECTIVE

To discuss recent developments in automatic defibrillation and to review the evidence that first-responders equipped with automatic external defibrillators (AEDs) improve survival from out-of-hospital cardiac arrest.

DATA SOURCES

MEDLINE search from 1966 to 1999 (articles in English only) and examination of bibliographies.

STUDY SELECTION

Published studies of out-of-hospital cardiac arrest and first-responders equipped with AEDs. Studies had to have a control group and to report survival to hospital discharge from ventricular fibrillation (VF).

DATA EXTRACTION

Six studies met the selection criteria (two prospective randomised trials, two prospective controlled trials, and one cohort study and one retrospective study, both with historical controls).

DATA SYNTHESIS

A random effects meta-analysis of odds ratios for survival from VF.

CONCLUSIONS

Meta-analysis suggests that equipping first-responders with AEDs increases the probability of survival to hospital discharge after out-of-hospital cardiac arrest (odds ratio, 1.74; 95% CI, 1.27-2.38; P < 0.001). However, most of the studies lacked sufficient power to draw definitive conclusions. Until the impact of wide deployment of AEDs is fully understood, first-responder defibrillation in Australia should only occur as part of coordinated multicentre research studies.

Incidence, duration and survival of ventricular fibrillation in out-of-hospital cardiac arrest patients in sweden

The chance of survival from ventricular fibrillation (VF) is up to ten times higher than those with other cardiac arrest rhythms. To calculate the effect of out-of-hospital resuscitation organisations on survival, it is necessary to know the percentage of cardiac arrest patients initially in VF and the relationship between delay time to defibrillation and survival.

AIM

To study the incidence of VF at the time of cardiac arrest and on first ECG, the duration of VF and the relation between time to defibrillation and survival.

METHOD

The Swedish Cardiac Arrest Registry has collected standardised reports on out-of-hospital cardiac arrests from ambulance organisations in Sweden, serving 60% of the Swedish population.

RESULTS

In 14065 cases of out-of-hospital cardiac arrest collected between 1990 and 1995, resuscitation was attempted in 10966 cases.

INCIDENCE

The first ECG showed VF in 43% of all patients. The incidence of VF at the time of cardiac arrest was estimated to be 60-70% in all patients and 80-85% in the cases with probable heart disease.

DURATION

The estimated disappearance rate of VF was slow. Thirty minutes after collapse approximately 40% of the patients were in VF.

SURVIVAL

Overall survival to 1 month was only 1.6% for patients with non-shockable rhythms and 9.5% for patients found in VF. With increasing time to defibrillation, the survival rate fell rapidly from approximately 50% with a minimal delay to 5% at 15 min.

CONCLUSIONS

This study suggests a high initial incidence of VF among out-of-hospital cardiac arrest patients and a slow rate of transformation into a non-shockable rhythm. The survival rate with very short delay times to defibrillation was approximately 50%, but decreased rapidly as the delay increased.

A randomized study of the prevention of sudden death in patients with coronary artery disease. Multicenter Unsustained Tachycardia Trial Investigators

BACKGROUND

Empirical antiarrhythmic therapy has not reduced mortality among patients with coronary artery disease and asymptomatic ventricular arrhythmias. Previous studies have suggested that antiarrhythmic therapy guided by electrophysiologic testing might reduce the risk of sudden death.

METHODS

We conducted a randomized, controlled trial to test the hypothesis that electrophysiologically guided antiarrhythmic therapy would reduce the risk of sudden death among patients with coronary artery disease, a left ventricular ejection fraction of 40 percent or less, and asymptomatic, unsustained ventricular tachycardia. Patients in whom sustained ventricular tachyarrhythmias were induced by programmed stimulation were randomly assigned to receive either antiarrhythmic therapy, including drugs and implantable defibrillators, as indicated by the results of electrophysiologic testing, or no antiarrhythmic therapy. Angiotensin-converting-enzyme inhibitors and beta-adrenergic-blocking agents were administered if the patients could tolerate them.

RESULTS

A total of 704 patients with inducible, sustained ventricular tachyarrhythmias were randomly assigned to treatment groups. Five-year Kaplan-Meier estimates of the incidence of the primary end point of cardiac arrest or death from arrhythmia were 25 percent among those receiving electrophysiologically guided therapy and 32 percent among the patients assigned to no antiarrhythmic therapy (relative risk, 0.73; 95 percent confidence interval, 0.53 to 0.99), representing a reduction in risk of 27 percent). The five-year estimates of overall mortality were 42 percent and 48 percent, respectively (relative risk, 0.80; 95 percent confidence interval, 0.64 to 1.01). The risk of cardiac arrest or death from arrhythmia among the patients who received treatment with defibrillators was significantly lower than that among the patients discharged without receiving defibrillator treatment (relative risk, 0.24; 95 percent confidence interval, 0.13 to 0.45; P<0.001). Neither the rate of cardiac arrest or death from arrhythmia nor the overall mortality rate was lower among the patients assigned to electrophysiologically guided therapy and treated with antiarrhythmic drugs than among the patients assigned to no antiarrhythmic therapy.

CONCLUSIONS

Electrophysiologically guided antiarrhythmic therapy with implantable defibrillators, but not with antiarrhythmic drugs, reduces the risk of sudden death in high-risk patients with coronary disease.

Biphasic truncated exponential waveform defibrillation

This paper presents data from studies that have compared the efficacies of biphasic truncated exponential (BTE) and monophasic damped sine (MDS) waveform defibrillation in patients with out-of-hospital cardiac arrest and in in-hospital defibrillation. When a shock is delivered, rhythms evolve rapidly in a variety of directions and take different courses, even over a short time. When defibrillation is defined as termination of ventricular fibrillation at 5 seconds postshock, whether to an organized rhythm or asystole, low-energy BTE shocks appear to be more effective than high-energy MDS shocks in out-of-hospital arrest. For future research, the terms associated with defibrillation should be standardized and used uniformly by all investi-gators. In particular, there should be an agreed-upon definition of shock efficacy.

Sudden cardiac death

SCD continues to be an important cause of death and morbidity. Despite expanding insight into the mechanisms causing SCD, the population at high risk is not being effectively identified. Although there is still much to do in the management phase of SCD (predicting the efficacy of various therapies), recent clinical trials have helped define the relative risks and benefits of therapies in preventing SCD. Trials are underway to determine whether treating other patient populations, including asymptomatic patients after MI, will improve survival rate. The approach to reducing mortality rate will always be multifaceted; primary prevention of coronary artery disease and prompt salvage of jeopardized myocardium are 2 important aspects of this approach. In addition to interventions for MI, such as myocardial revascularization when indicated, simple and easily administered therapies that are likely to remain the most effective prophylactic interventions are aspirin, ACE inhibitors, beta-blockers, and cholesterol-lowering agents. However, the MADIT and AVID data clearly demonstrate a role for ICD therapy in a subgroup of patients who have VT/VF and are at risk of cardiac arrest. Even though the absolute magnitude of benefit associated with ICDs is still to be determined, the AVID study and other recent reports provide convincing evidence that patients who have VT/VF fare better with ICDs than with antiarrhythmic drug therapy. For the high-risk population described in this article, in addition to aggressive anti-ischemic and heart failure therapy, ICDs are now a mainstay of life-saving treatment. Still to be surmounted is the challenge of identifying patients who have nonischemic substrates and of providing them with the appropriate therapy. Guided by genetic studies and new insight into the mechanisms of such problems as congenital long QT syndrome, life-saving and life-enhancing therapies may soon be available for the management of SCD.

Automatic external defibrillators: lessons from the past, present and future

Coronary artery disease remains the leading cause of death in the United States and most developed countries. Many of the victims die from sudden cardiac arrests, resulting from dysrhythmias-most commonly ventricular fibrillation. Since most cardiac arrests occur outside the hospital, implementing emergency services in the field will have a great impact on survival. With the development of the modern automatic external defibrillator (AED), early recognition and correction of these dysrhythmias by lay rescuers can significantly improve outcome from sudden death. This paper reviews the past, present and future development and applications of AEDs.

Intraoperative use of automated external defibrillator

We report on the anesthetic management of a patient with peripartum cardiomyopathy and frequent episodes of ventricular tachycardia, who underwent surgery for tracheal stenosis. Prior to this surgery, the patient had been implanted with an automatic implantable cardioverter-defibrillator (AICD), placed abdominally. In the operating room, the AICD was deactivated, and an automated external defibrillator (AED) was placed. Intraoperatively, the AED identified and treated the patient's ventricular tachycardia. Advantages of the AED in this hospital setting included rapid response to the cardiomyopathy, safe, hands-free operation, and minimal disruption of the surgical procedure. Safety concerns when using the AED are also detailed.

A comparison of two automated external defibrillator algorithms

OBJECTIVE

To compare the interval to delivery of the first shock by first responders in mannequin-based cardiac arrest scenarios using two automated external defibrillator (AED) algorithms.

METHODS

Thirty-six (18 pairs) of Toronto firefighters (FFs) trained in two AED algorithms, algorithm I (A-I) and algorithm II (A-II), were studied. A-II mandates the immediate application of the AED once pulselessness is established. In contrast to A-I, A-II dictates that no CPR be initiated until it is required by the AED voice prompts. Each FF pair alternated roles while performing "shock-indicated," mannequin-based scenarios according to A-I and A-II. The interval from mannequin contact to delivery of the first shock was recorded. Five pairs were videotaped. The intervals to complete predetermined steps were compared between algorithms to determine in which step(s) time saving occurred.

RESULTS

The mean (+/-SD) interval to the first shock in A-I was 80.7 seconds (+/-10.5 sec) (95% CI = 77.2 to 84.2 sec) vs 61.1 seconds (+/-8.75 sec) (95% CI = 58.2 to 64.0 sec) in A-II (p < 0.001). A-II shortened the interval to the first shock by 19.6 sec (+/-11.5) (95% CI = 15.8 to 23.4 sec). The time saving was a direct result of delaying CPR in A-II.

CONCLUSION

A-II reduced the interval from mannequin contact to the first shock in standard training scenarios.

Long-term survival after out-of-hospital cardiac arrest: an 8-year follow-up

Between 1988 and 1994, 441 patients were successfully resuscitated outside hospital in the city of Rotterdam, of whom 276 (63%) were discharged from hospital alive. Long-term survival was studied amongst those who were discharged alive. The duration of follow-up averaged 6.71 years. A survival rate of 88% after 1 year, 81% after 3 years, 77% after 5 years and 73% after 7 years was found. After multivariate analysis, age, diagnosis and gender were found to be independent and significant predictors of survival. No significant difference in survival was found in patients who had been resuscitated by emergency personnel, physicians and bystanders. Patients who were still alive were sent a EuroQol-questionnaire. No differences in outcomes between the four groups were found. Since long-term prognosis after out-of-hospital resuscitation is satisfactory, learning programmes for resuscitation should be continued.

The automated external cardiac defibrillator: lifesaving device for medical emergencies

BACKGROUND

More than 350,000 adult Americans die each year of sudden cardiac arrest, or SCA. The event is unpredictable and can occur in patients with no history of cardiac disease or cardiac symptoms. Drugs and cardiopulmonary resuscitation, or CPR, save only a small percentage of victims. The necessary response is rapid application of electrical shock, and the chances of success are reduced 10 percent for every minute of delay.

TYPES OF STUDIES REVIEWED

The author reviewed the literature on resuscitation of people who have undergone SCA, and examined the emerging technology of automated external defibrillators, or AEDs, for correcting cardiac ventricular fibrillation. Included is a review of the controversies surrounding AED waveforms and energy levels.

RESULTS

Automated cardiac defibrillators are becoming readily available because of improved technology and decreasing prices. AEDs are now commonly found in commercial aircraft, gambling casinos, sports arenas and public buildings, and will soon become as readily available as fire extinguishers. The use of AEDs is being taught in standard CPR courses.

CLINICAL IMPLICATIONS

AEDs are being installed in more public locations, including some dental offices. As costs decrease and availability increases, there is significant potential use for AEDs in managing SCAs in dental offices.

Modifiable factors associated with improved cardiac arrest survival in a multicenter basic life support/defibrillation system: OPALS Study Phase I results. Ontario Prehospital Advanced Life Support

STUDY OBJECTIVES

This study was conducted to identify modifiable factors associated with survival for prehospital cardiac arrest in a large, multicenter EMS system with basic life support/defibrillation (BLS-D) level of care.

METHODS

This observational cohort study constitutes Phase I of the 3-phase Ontario Prehospital Advanced Life Support (OPALS) Study. Included were all adults who had cardiac arrest before EMS arrival in 21 urban/suburban communities that operate under the jurisdiction of 1 ambulance services branch, have 911 telephone service, and provide ambulance defibrillation but no prehospital advanced life support (ALS). Central dispatch and ambulance records were reviewed according to the Utstein guidelines. Associations between multiple patient and EMS factors and survival to discharge were assessed by univariate then stepwise logistic regression analyses.

RESULTS

From January 1, 1991, to January 31, 1995, 5,335 eligible patients were treated. Of these, 46.8% of cardiac arrests were witnessed by citizens, 14.5% received bystander CPR, 25.6% received CPR by fire or police, and 38.2% had an initial rhythm of ventricular fibrillation/ventricular tachycardia (VF/VT). The mean interval from call received to vehicle stopped was 6.7 minutes. Survival was 3.5% overall and 8.8% for VF/VT. Multivariate analysis found the following factors to be independently associated with survival (odds ratio with 95% confidence intervals): age.81 (. 73,.89), bystander-witnessed arrest 4.05 (2.78, 5.90), bystander CPR 2.98 (2.07, 4.29), CPR by fire or police 2.20 (1.46, 3.31), and response interval call received to vehicle stopped.76 (.71,.82).

CONCLUSION

This represents the largest multicenter BLS-D study of prehospital cardiac arrest yet conducted and clearly indicates that patient survival may be improved by optimization of EMS response intervals, bystander CPR, as well as first-responder CPR by fire or police.

Resuscitation from out-of-hospital cardiac arrest: is survival dependent on who is available at the scene?

OBJECTIVE

To determine whether survival from out-of-hospital cardiac arrest is influenced by the on-scene availability of different grades of ambulance personnel and other health professionals.

DESIGN

Population based, retrospective, observational study.

SETTING

County of Nottinghamshire with a population of one million.

SUBJECTS

All 2094 patients who had resuscitation attempted by Nottinghamshire Ambulance Service crew from 1991 to 1994; study of 1547 patients whose arrest were of cardiac aetiology.

MAIN OUTCOME MEASURES

Survival to hospital admission and survival to hospital discharge.

RESULTS

Overall survival from out-of-hospital cardiac arrest remains poor: 221 patients (14.3%) survived to reach hospital alive and only 94 (6.1%) survived to be discharged from hospital. Multivariate logistic regression analysis showed that the chances of those resuscitated by technician crew reaching hospital alive were poor but were greater when paramedic crew were either called to assist technicians or dealt with the arrest themselves (odds ratio 6.9 (95% confidence interval 3.92 to 26.61)). Compared to technician crew, survival to hospital discharge was only significantly improved with paramedic crew (3.55 (1.62 to 7.79)) and further improved when paramedics were assisted by either a health professional (9.91 (3.12 to 26.61)) or a medical practitioner (20.88 (6.72 to 64.94)).

CONCLUSIONS

Survival from out-of-hospital cardiac arrest remains poor despite attendance at the scene of the arrest by ambulance crew and other health professionals. Patients resuscitated by a paramedic from out-of-hospital cardiac arrest caused by cardiac disease were more likely to survive to hospital discharge than when resuscitation was provided by an ambulance technician. Resuscitation by a paramedic assisted by a medical practitioner offers a patient the best chances of surviving the event.

Relative efficacy of monophasic and biphasic waveforms for transthoracic defibrillation after short and long durations of ventricular fibrillation

BACKGROUND

Recently, interest has arisen in using biphasic waveforms for external defibrillation. Little work has been done, however, in measuring transthoracic defibrillation efficacy after long periods of ventricular fibrillation. In protocol 1, we compared the efficacy of a quasi-sinusoidal biphasic waveform (QSBW), a truncated exponential biphasic waveform (TEBW), and a critically damped sinusoidal monophasic waveform (CDSMW) after 15 seconds of fibrillation. In protocol 2, we compared the efficacy of the more efficacious biphasic waveform from protocol 1, QSBW, with CDSMW after 15 seconds and 5 minutes of fibrillation.

METHODS AND RESULTS

In protocol 1, 50% success levels, ED50, were measured after 15 seconds of fibrillation for the 3 waveforms in 6 dogs. In protocol 2, defibrillation thresholds were measured for QSBW and CDSMW after 15 seconds of fibrillation and after 3 minutes of unsupported fibrillation followed by 2 minutes of fibrillation with femoral-femoral cross-circulation. In protocol 1, QSBW had a lower ED50, 16.0+/-4.9 J, than TEBW, 20.3+/-4.4 J, or CDSMW, 27.4+/-6.0 J. In protocol 2, QSBW had a lower defibrillation threshold after 15 seconds, 38+/-10 J, and after 5 minutes, 41.5+/-5 J, than CDSMW after 15 seconds, 54+/-19 J, and 5 minutes, 80+/-30 J, of fibrillation. The defibrillation threshold remained statistically the same for QSBW for the 2 fibrillation durations but rose significantly for CDSMW.

CONCLUSIONS

In this animal model of sudden death and resuscitation, these 2 biphasic waveforms are more efficacious than the CDSMW at short durations of fibrillation. Furthermore, the QSBW is even more efficacious than the CDSMW at longer durations of fibrillation.

Ventricular tachycardia during follow-up in patients resuscitated from ventricular fibrillation: experience from stored electrograms of implantable cardioverter-defibrillators

OBJECTIVE

The purpose of this study was to use the electrogram storage capabilities of the implantable cardioverter-defibrillator (ICD) to categorize any arrhythmic event during follow-up in a group of patients who had survived an episode of ventricular fibrillation (VF) and to possibly identify clinical predictors of future arrhythmic events.

BACKGROUND

Little is known about the electrophysiologic characteristics of ventricular arrhythmias recurring during follow-up in survivors of VF as the sole documented arrhythmia at the time of resuscitation.

METHODS

Forty patients (58+/-10 years; 73% men; left ventricular ejection fraction 42+/-18%; 70% with coronary artery disease) who had survived an episode of VF and subsequently received an ICD capable of intracardiac electrogram recording and storage were followed for 23+/-11 months. In all patients, the arrhythmogenic substrate was investigated by means of programmed electrical stimulation (PES).

RESULTS

Among the 40 patients, 41 episodes of ventricular arrhythmias were documented in 13 patients (33%): 36 episodes of ventricular tachycardias (VT) were recorded in 11 patients (28%) and 5 episodes of VF were recorded in the remaining 2 patients (5%). Age, gender, cardiac disease and left ventricular ejection fraction failed to distinguish between patients with clinical recurrences and patients without. The sensitivity, specificity and positive accuracy of PES were 29%, 63% and 46%, respectively, for prediction of ventricular arrhythmia recurrence; 45%, 70% and 36%, respectively, for prediction of VT; and 50%, 98% and 50%, respectively, for prediction of VF during follow-up.

CONCLUSIONS

In survivors of VF receiving ICD therapy, VT is the most common ventricular arrhythmia recorded on device-incorporated electrograms during follow-up. This finding, associated with the relatively well-preserved ventricular function, may account for the ability of these patients to survive at time of the index arrhythmia; the use of antitachycardia pacing as a modality to treat arrhythmia recurrences may contribute to reduce the incidence of shock during follow-up in these patients.

Successful automatic external defibrillator operation by people trained only in basic life support in a simulated cardiac arrest situation

OBJECTIVE

To show whether in an in-hospital cardiac arrest, early defibrillation can also be performed by hospital staff trained only in basic life support.

BACKGROUND

The International Liaison Committee on Resuscitation (ILCOR) endorses the concept that in many settings non-medical individuals should be allowed and encouraged to use defibrillators.

METHODS

Five different groups of hospital staff were evaluated whether they were able to correctly operate an automatic external defibrillator in a simulated sudden cardiac arrest situation without any prior instruction. The participants were assigned either to the 'basic life support-trained' group (BLS, n = 40, or to the 'advanced life support-trained' group (ALS, n = 40).

RESULTS

All persons of the 'only BLS-trained' group delivered the three sequential ('stacked') shocks with the automatic external defibrillator when persistent ventricular fibrillation was simulated. The 'ALS-trained' persons successfully delivered the three shocks with the automatic external defibrillator in 98% of the cases. When this group used a conventional defibrillator, only 88% were able to deliver the three shocks, however they were able to do it significantly more quickly.

CONCLUSION

Using an automatic defibrillator without any prior instruction, even persons trained only in BLS were able to deliver three sequential shocks in a simulated persistent ventricular fibrillation cardiac arrest.

[Implanted automatic defibrillator after ventricular fibrillation treated with semi-automatic defibrillation]

We report two cases of out-of-hospital ventricular fibrillation treated without delay, with basic life support practiced by the witness, followed by a successful defibrillation by paramedics with a semi-automatic defibrillator. In the subsequent month, a cardioverter-defibrillator was implanted. In one patient, a ventricular tachycardia occurring 10 months later and a ventricular fibrillation 9 months later in the other respectively, were successfully reversed by the implanted defibrillator. These two cases illustrate the value of the "survival chain" concept (undelayed alert, basic life support by witness, early defibrillation by paramedics with a semi-automatic defibrillator, advanced life support by a physician) as well as the benefit of the implanted cardioverter-defibrillator.

Long-term cardiac arrest survivors of the Vienna emergency medical service

The purpose of this study was to describe the life of survivors after successful resuscitation and to see if there was an association with the type of emergency cardiac care. The 'Utstein-style' data of patients surviving non-traumatic cardiac arrest 24 (14-32) months were prospectively collected. The everyday activities and psychological concerns of patients with a cerebral performance category (CPC) of 1 and 2 using a questionnaire were analyzed. The chi2-square test was used for statistical analysis. The questionnaires of 92 patients (median age 59, IQR 51-68; females 36) were evaluated. Patients enjoy life (84%; n=73), have depression (36%; n=31), consider their survival a 'second chance' (84%; n=73) and fear that they may suffer cardiac arrest again (56%; n = 45). The average quality of life is 7 on a scale from 0 (worst) to 10 (perfect). The majority of cardiac arrest survivors have a satisfactory life. No significant correlation between the type of emergency cardiac care and post cardiac arrest life was found. The fact that there was no association with the type of emergency cardiac care may be due to the narrow selection of patients (CPC 1 and 2), the small number of patients or factors contributing to post cardiac arrest life other than emergency treatment.

The Ontario Prehospital Advanced Life Support (OPALS) Study: rationale and methodology for cardiac arrest patients

The Ontario Prehospital Advanced Life Support Study represents the largest prehospital study yet conducted, worldwide. This study will involve more than 25,000 cardiac arrest, trauma, and critically ill patients over an 8-year period. The study will evaluate the incremental benefit of rapid defibrillation and prehospital Advanced Cardiac Life Support measures for cardiac arrest survival and the benefit of Advanced Life Support for patients with traumatic injuries and other critically ill prehospital patients. This article describes the OPALS study with regard to the rationale and methodology for cardiac arrest patients.

Use of automated external defibrillators by police officers for treatment of out-of-hospital cardiac arrest

OBJECTIVE

To determine the feasibility of police officers providing defibrillation with automated external defibrillators (AEDs) and to assess the effectiveness of this strategy in reducing time to defibrillation of victims of out-of-hospital sudden cardiac arrest.

METHODS

This was a prospective, interventional cohort study with historical controls conducted in 7 suburban communities in which police usually arrived at the scene of medical emergencies before EMS personnel. All adult patients who suffered cardiac arrest before EMS arrival and on whom EMS personnel attempted resuscitation were enrolled. Police officers who were trained to use and equipped with AEDs during the intervention phase were dispatched simultaneously with EMS to medical emergencies. Police were instructed to use the AED immediately on determination of pulselessness. Outcome measures were the difference between control and intervention phases in interval from the time the call was received at dispatch to the time of first defibrillation and in rate of survival to hospital discharge for patients initially in ventricular fibrillation.

RESULTS

EMS personnel attempted 183 resuscitations in the control phase and 283 during the intervention; of these, 80 (44%) and 127 (45%), respectively, involved patients with initial ventricular fibrillation rhythms. Mean time to defibrillation decreased from 11.8+/-4.7 minutes in the control phase to 8.7+/-3.7 minutes in the intervention phase (P<.0001). Survival to hospital discharge of patients in ventricular fibrillation did not differ between phases (6% control versus 14% intervention, P=.1). When police arrived before EMS personnel, shock administered by police compared with shock administered by EMS was associated with improved survival (26% [12/46] versus 3% [1/29], P=.01). Logistic regression analysis revealed AED use was an independent predictor of survival to hospital discharge.

CONCLUSION

In 7 suburban communities, police use of AEDs decreased time to defibrillation and was an independent predictor of survival to hospital discharge.

Anomalous ECG downloads from semi-automatic external defibrillators

The coincidental print-out by two different Laerdal systems (subsequently called 'system A' and 'system B') of the same medical control module (MCM) for a Laerdal Heartstart 2000 semi-automatic external defibrillator (SAED) led to the discovery of three deficiencies in the information storage and printing processes. First, we noted that the impedance reported via system A was consistently higher. Second, we found the attachment of 'mysterious' ECG samples in the reports from system B, but not from system A. A third problem was the unpredictable (in)ability of system B to print out the information from the MCMs. Further investigations with help from the company suggested that the above-mentioned problems were caused by incompatibilities between the software in the different parts of equipment used (i.e. SAED devices, MCMs, printing systems and a computer program to store the information in a database). These observations demonstrate the need for strict medical supervision on all aspects of a SAED project, and for feed-back from clinicians to manufacturers.

Factors influencing hospital transport of patients in continuing cardiac arrest

STUDY OBJECTIVE

Prior research has established the futility of continued resuscitation efforts for patients in cardiac arrest who fail to respond to out-of-hospital advanced cardiac life support. Determination of both medical and nonmedical factors resulting in the transport of patients in continuing cardiac arrest to the hospital may encourage the development of new systems or strategies to increase the appropriateness of these transports.

METHODS

The attending paramedic completed a prospective survey after unsuccessful resuscitation efforts in our urban, hospital-based, two-tier emergency medical services (EMS) system. All nontraumatic adult arrests were included unless they were clearly noncardiac in nature.

RESULTS

Paramedics responded to 259 cardiac arrests between September 12, 1996, and April 31, 1997. Seventy-nine patients were pronounced dead without resuscitation efforts. Of the remaining 180 patients, 44 had return of spontaneous circulation and were transported to the hospital, 68 were pronounced dead in the field, and 68 were transported to the hospital in continuing cardiac arrest. The 68 patients transported while in cardiac arrest are the focus of this study. Rare problems with field termination were identified. Reasons for transport of the 68 patients in continuing cardiac arrest included arrest in ambulance or going to ambulance (n = 6), arrest in a public place (n = 17), environmental factors (n = 6), road hazard to paramedics (n = 1), possible reversible cause (n = 4), persistent ventricular dysrhythmia (n = 5), no intravenous access (n = 5), airway difficulties (n = 5), family unable to accept field termination (n = 3), cultural or language barrier (n = 1), EMS physician ordered transport (n = 1), and obesity (n = 1). A protocol allowing pronouncement of death in the ambulance and transport of the body to a designated area could have prevented lights-and-siren transport to the emergency department in 24 of the 68 cases.

CONCLUSION

Factors other than medical ones often influence the decision to transport patients in continuing cardiac arrest. In our urban system, physician, medical examiner, and paramedic education and protocols were needed to aid decision-making in this situation.

Advanced life support vs basic life support field care: an outcome study

OBJECTIVE

To determine whether the provision of advanced life support (ALS) field care has any impact on patient outcome in the urban Canadian environment.

METHODS

A convenience cohort study was conducted of all emergent ambulance transfers of adults to an urban Canadian hospital from May 22 to July 31, 1996. Data were collected from ambulance call reports regarding presenting complaint and field interventions applied, and from hospital records regarding time in the ED, hospital length of stay (LOS), and discharge disposition. Patient outcomes were compared within 7 presenting complaint groups (chest pain, altered level of consciousness, shortness of breath, abdominal pain, motor vehicle crash, falls, and other) by field care level: level 1--BLS (basic life support) vs levels 2 and 3--ALS.

RESULTS

The study population consisted of 1,397 patients. No significant differences were seen between BLS and ALS patients on baseline demographics. ED triage score did not depend on field care level for any group, implying that those in the ALS group were not inherently sicker. Outcome measures (ED LOS, admission rates, and hospital LOS) showed no significant differences between BLS and ALS for each presenting complaint group. Discharge dispositions were analyzed by chi2 but were not varied enough to allow reliable analysis. Observation of trends suggested no difference between BLS and ALS.

CONCLUSIONS

There was no beneficial impact on the measured patient outcomes found in association with the provision of ALS vs BLS field care in Metropolitan Toronto for patients who were brought to a nontrauma center.

Experience with the use of automated external defibrillators in out of hospital cardiac arrest

AIM

To describe the sequences of arrhythmias, number of shocks delivered and the number of failures in a consecutive series of patients with out-of-hospital cardiac arrest attended by our emergency medical service (EMS) and in whom cardio-pulmonary resuscitation (CPR) was initiated and in whom automated external defibrillators (AEDs) were used.

PATIENTS

All patients with out-of-hospital cardiac arrest attended by the EMS and in whom AEDs were used. Time for inclusion in the study: January 1st, 1987 to December 31st, 1992.

RESULTS

In all there were 1781 out of hospital cardiac arrests during the study period. Among them AEDs were used in 383 cases (22%). The total number of interpreted rhythms delivered in these patients was 2719. Among all rhythm sequences coarse ventricular fibrillation (VF) was found on 375 occasions (14%); fine VF on 107 occasions (4%) and ventricular tachycardia (VT) on 12 occasions (0.4%). In ten cases with coarse VF (nine patients) the AED did not advise a shock (2.7%). In five of those nine patients a human error was interpreted as the explanation and in four there was a possible technical error. In these four patients defibrillation was delayed by 33-43 s, respectively. Among the 2225 rhythm sequences not judged as VF/VT the AED advised a shock on one occasion (0.04%).

CONCLUSION

Among patients with coarse VF AED gave inaccurate instructions in 2.7%. However, the majority of the failures were judged to be caused by human errors.

Performance of police first responders in utilizing automated external defibrillation on victims of sudden cardiac arrest

OBJECTIVE

Rates of resuscitation from cardiac arrest are directly tied to time to defibrillation. To maximize results, the first arriving care provider should be equipped and trained to defibrillate. This would include police in those systems where they serve this function; to date, no training program has been examined for effectiveness in this group. The purpose of this study was to evaluate a training program designed to train police first responders in the use of an automated external defibrillator (AED).

METHODS

One hundred seventy police officers previously trained to the level of first responders underwent a four-hour course to teach incorporation of the AED in their practice. The evaluation of police performance was assessed by written tests prior to, immediately after, and six months post initial training. Actual field use was evaluated by using separate data collection forms filled out at the time of the resuscitation by both police and EMS providers. Each trip sheet was also reviewed. Cassette tapes from the AED were reviewed for continuous ECG tracings and audio recordings to validate and confirm the previous data.

RESULTS

One hundred twenty-eight police cases were reviewed. The officers performed with few errors in AED operation, with the only problem areas being incorrect airway management and delay in performance of CPR to use the AED to reanalyze a nonshockable rhythm. These results were compared with those of the only two other studies examining the performance of first responders, which were EMTs and firefighters. The police results compared favorably with, and in some instances exceeded, those results.

CONCLUSION

Police first responders trained in the use of AEDs performed at a level equivalent or superior to that in other reported studies. Future training strategies should stress proper integration of airway and CPR skills.

Accurate recognition and effective treatment of ventricular fibrillation by automated external defibrillators in adolescents

OBJECTIVES

To evaluate the accuracy and efficacy of automated external defibrillators (AEDs) in patients <16 years old.

BACKGROUND

AEDs are standard therapy in out-of-hospital resuscitation of adults and have led to higher success rates. Their use in children and adolescents has never been evaluated, despite recommendations from the American Heart Association that they be used in children >8 years of age.

METHODS

This was a retrospective cohort study of children <16 years old who underwent out-of-hospital cardiac resuscitation and on whom an AED was used during the resuscitation. The setting was rural and urban prehospital emergency medical systems. Patients were identified by review of a database of cardiac arrests maintained by a large surveillance program of these services.

RESULTS

AEDs were used to assess cardiac rhythm in 18 patients with a mean age of 12.1 +/- 3.7 years. The cardiac rhythms were analyzed 67 times and included ventricular fibrillation (25), asystole/pulseless electrical activity (32), sinus bradycardia (6), and sinus tachycardia (4). The AEDs recognized all nonshockable rhythms accurately and advised no shock. Ventricular fibrillation was recognized accurately in 22 (88%) of 25 episodes and advised or administered a shock 22 times. Sensitivity and specificity for accurate rhythm analysis were 88% and 100%, respectively. One patient with a nonshockable rhythm survived, whereas 3 of 9 patients with ventricular fibrillation survived.

CONCLUSIONS

These data furnish evidence that AEDs provide accurate rhythm detection and shock delivery to children and young adolescents. AED use is potentially as effective for children as it is for adults.

Cardiopulmonary resuscitation: a review for clinicians

Attempts at cardiopulmonary resuscitation (CPR) date from antiquity, but it is only in the last 50 years that a scientifically-based methodology has been developed. External chest compressions is the standard method for managing circulatory arrest, however, numerous alterations of this technique have been proposed in attempts to improve outcome from CPR. Defibrillation is the single most important therapy for the management of ventricular fibrillation or pulseless ventricular tachycardia. Adrenergic agents used to improve myocardial and cerebral perfusion are also the subject of considerable investigation with new agents entering clinical study. This paper reviews the history, current techniques and pharmacotherapy as well as controversial issues in the management of patients with cardiac arrest.

EMT defibrillation does not increase survival from sudden cardiac death in a two-tiered urban-suburban EMS system

OBJECTIVE

The use of automatic external defibrillators (AEDs) by EMS initial responders is widely advocated. Evidence supporting the use of AEDs is based largely on the experience of one metropolitan area, with effect on survival in many systems not yet proved. We conducted this study to determine whether the addition of AEDs to an EMS system with a response time of 4 minutes for first-responder emergency medical technicians (FREMTs) and 10 minutes for paramedics would affect survival from cardiac arrest.

METHODS

This prospective, controlled, crossover study (AED versus no AED) of consecutive cardiac arrests managed by 24 FREMT fire companies took place from 1992 to 1995 in Charlotte, North Carolina, a city of 455,000. Patients were stratified using the Utstein criteria. The primary endpoint was survival to hospital discharge among patients with bystander-witnessed arrests of cardiac origin.

RESULTS

Of the 627 patients, 243 were bystander-witnessed arrests of cardiac origin. Survival to hospital discharge was accomplished in 5 of 110 patients (4.6%; 95% confidence interval [CI] 0.6% to 8.4%) with AED compared with 7 of 133 (5.3%, 95% CI 1.5% to 9.1%) without AED (P = .8). Both groups were comparable with regard to age, gender, history of myocardial infarction, congestive heart failure or diabetes, arrest at home, bystander CPR, and whether or not ventricular fibrillation (VF) was the initial rhythm. For arrests of any cause, witnessed by bystanders or EMS personnel, with an initial rhythm of VF or ventricular tachycardia (VT), 5 of 77 (6.5%, 95% CI 1.0% to 12.0%) with AED survived compared with 8 of 105 patients (7.6%, 95% CI 2.5% to 12.7%) without AED (P = .8). Statistically significant differences were noted in race and EMS response times between the two groups, which did not affect survival.

CONCLUSION

Addition of AEDs to this EMS system did not improve survival from sudden cardiac death. The data do not support routinely equipping initial responders with AEDs as an isolated enhancement, and raise further doubt about such expenditures in similar EMS systems without first optimizing bystander CPR and EMS dispatching.

A rule for early outcome classification of out-of-hospital cardiac arrest patients presenting with ventricular fibrillation

The aim of the study was to develop a scoring system for outcome classification at the start of prehospital first tier resuscitation for patients with cardiac arrest from ventricular fibrillation (VF). We studied a consecutive sample of 100 out-of-hospital cardiac arrest patients, presenting with VF of presumed cardiac etiology on arrival of the first tier (in a two-tiered urban Emergency Medical Services system). The number of patients discharged was 29 ('survivors') and 71 died ('non-survivors'). The electrocardiography (ECG) tracings recorded during resuscitation using a semi-automatic defibrillator were retrospectively analysed. For each patient, VF amplitude in mV (VF_a) and the number of base-line crossings per second (VF_blc) were calculated. Fisher's linear discriminant analysis was applied to discriminate between survivors and non-survivors using the variables VF_a, VF_blc and age. Patients were classed as potential survivors or non-survivors using a survival index = 0.6*(VF_a) + 0.4*(VF_blc)-4.0. If for a given patient the survival index is < 0, he is classified in the non-survivor group, if the survival index is > 0, he is classified in the survivor group. Using this index 79% of the survivors and 70% of the non-survivors could be classified correctly. Adding age to the formula increased the correct classification of survivors to 86 and 73% for the non-survivors. The survival index provides a research tool for the discrimination between potential survivors and non-survivors, which opens the possibility for the development of alternative treatment protocols in cardiac arrest.

Survival after cardiac arrest outside hospital in Sweden. Swedish Cardiac Arrest Registry

The voluntary Swedish Cardiac Arrest Registry has collected and analyzed 14,065 standardised reports on cardiac arrests up until May 1995. The reports have been collected from approximately half of Sweden's ambulance districts, which cover 60% of the population. Resuscitation was attempted in 10,966 cases. The median age was 70 years. In 70.0% the arrest was witnessed, and in 43.3% the first recorded rhythm was VT/VF. Bystander-CPR was initiated in 32.3% of the cases. Most cardiac arrests took place at home (65.8%) and 67.1% were judged to be of cardiac origin. In 1692 cases (15.4%), the patient was admitted alive in hospital and 544 patients (5.0%) were alive after 1 month. Survival to 1 month in the subgroup which presented with VT/VF was 9.5%. We found no significant difference between survival in large cities and smaller communities. The survivors were analysed in relation to time to defibrillation and we found a strong correlation between a short time and increased survival.

Effects of early defibrillation by ambulance personnel on short- and long-term outcome of cardiac arrest survival: the Munich experiment

OBJECTIVES

This study evaluates the feasibility of implementing early defibrillation of out-of-hospital cardiac arrest patients for basic life-support providers (EMT-D) in a two-tier emergency system in the city of Munich, Germany.

DESIGN

Retrospective consecutive analysis of all EMT-D attempts during a 5-year initiation phase (1990 to 1994) and prospective follow-up of all cardiac arrest survivors discharged from hospital.

SETTING

A strictly defined inner-city and suburban area of 978 km2 and a residential population of 1,530,000 inhabitants with 22 ICUs in urban hospitals. One dispatching center to alert a two-tier emergency system with 56 EMT-D-staffed ambulances and physician-staffed mobile ICUs stationed at the nearest of nine hospitals.

METHODS

AH EMT-D cases were identified and data on patients were documented in a standardized manner from patients' records, including the resuscitation protocol in the hospitals to which the patients were referred. For those patients discharged from the hospital, a standardized telephone interview was undertaken with the physician in charge of the patient and with the patient/relative leading to an assessment of the patient's status according to the Glasgow-Pittsburgh cerebral performance categories.

INTERVENTION

None.

RESULTS

During the 5-year initiation phase of the EMT-D program in the two-tier emergency system in Munich, there were 243 resuscitation attempts by EMTs, using the semiautomated defibrillator; 125 patients died immediately on the scene. In 118 patients, spontaneous circulation was reestablished and these patients were admitted to an ICU in 1 of the 22 urban hospitals. Median call-response interval for the EMT-D was 5 min (interquartile range, 3 to 6) and was 10 min (interquartile range, 7 to 13) for the second tier (p < or = 0.0001). In 34 cases (28.8%), EMT-D staff had reestablished spontaneous circulation (ROSC) before the second tier arrived on the scene. Patients with ROSC on the arrival of the second tier were more frequently discharged alive from hospital than were patients without ROSC at that time (p < or = 0.0001). The hospital discharge rate of initially successful resuscitated patients presenting with out-of-hospital ventricular fibrillation was 38.1% (45/118). Overall success rate of all EMT-D attempts was 18.5% (45/243). After a mean follow-up time of 39 (range, 22 to 64) months, 29 (66%) patients were still living. Twenty-five (56.8%) were neurologically not disabled or mildly disabled (CPC 1/2); disability was moderate in 3 (6.8%) patients and was severe in 1 (2.3%) patient. One case was lost to follow-up.

CONCLUSION

The present study demonstrates that the upgrading of basic life support providers with semiautomated defibrillators has a significant benefit for cardiac arrest victims outside the hospital in an urban environment.

An airline cardiac arrest program

BACKGROUND

As many as 1000 lives are lost annually from cardiac arrest in commercial aircraft. Ventricular fibrillation (VF), the most common mechanism, can be treated effectively only with prompt defibrillation, whereas the current policy of most airlines is to continue cardiopulmonary resuscitation pending aircraft diversion. The objective of this study was to assess the impact of making semiautomatic external defibrillators (AEDs) available for use on airline passengers with cardiac arrest.

METHODS AND RESULTS

AEDs were installed on international Qantas aircraft and at major terminals, selected crew were trained in their use, and all crew members were trained in cardiopulmonary resuscitation. Supervision was provided by medical volunteers or (remotely) by airline physicians. During a 64-month period, AEDs were used on 109 occasions: 63 times for monitoring an acutely ill passenger and 46 times for cardiac arrest. Twenty-seven episodes of cardiac arrest occurred in aircraft, often (11 of 27 [41%]) unwitnessed, and they were usually (21 of 27 [78%]) associated with asystole or pulseless idioventricular rhythm. All 19 arrests in terminals were witnessed; VF was present in 17 (89%). Overall, defibrillation was initially successful in 21 of 23 cases (91%). Long-term survival from VF was achieved in 26% (2 of 6 in aircraft and 4 of 17 in terminals). The ability to monitor cardiac rhythm aided decisions on diversion, which was avoided in most passengers with asystole or idioventricular rhythm.

CONCLUSIONS

AEDs in aircraft and terminals, with appropriate crew training, are helpful in the management of cardiac emergencies. Survival from VF is practicable and is comparable with the most effective prehospital ambulance emergency services. Costly aircraft diversions can be avoided in clearly futile situations, enhancing the cost-effectiveness of the program.

What can we expect from prophylactic implantable defibrillators?

Death due to ventricular tachyarrhythmia (VT) remains an important public health problem; patients with prior myocardial infarction (MI) constitute the largest identifiable population for prophylactic interventions. Targeting of progressively higher-risk subgroups of post-MI survivors carries inevitable tradeoffs with respect to the global impact of interventions on overall mortality. Therapy with aspirin, beta blockers, and angiotensin-converting enzyme (ACE) inhibitors comprise the benchmark against which all additional interventions, including implantable defibrillators, must be measured. Initial enthusiasm for empiric amiodarone therapy has been tempered by the limited benefit demonstrated in recent randomized trials. Trials of other class III antiarrhythmic drugs, including both d,l-sotalol and d-sotalol, have also failed to demonstrate survival benefit. The Multicenter Automatic Defibrillator Implantation Trial (MADIT) demonstrated significantly improved survival associated with defibrillators in a small subgroup of post-MI survivors with a high short-term risk of death. The ultimate number and optimal criteria for selection of patients who may benefit from prophylactic defibrillator therapy after MI will undergo continued evolution as new data from current and ongoing trials become available.

Cardiopulmonary resuscitation: a promise as yet largely unfulfilled

After failure of initial external defibrillation, restoration of spontaneous circulation is largely contingent on rapid and effective reversal of myocardial ischemia by both mechanical and pharmacologic means. Despite the introduction of modern cardiopulmonary resuscitation (CPR) more than 35 years ago, its universal acceptance, and its wide implementation, no improvements in outcome excepting early defibrillation have been documented over these many years. The science of CPR therefore is still in its infancy. It was incorrectly assumed that all that needs to be known is known and that the need for scientific research was therefore not apparent. Accordingly, serious resuscitation research was neither encouraged nor equitably supported. The ABCs of CPR currently provide for the establishment of a patent airway (A) and intermittent positive pressure ventilation, preferably with oxygen-enriched air (B). These are to be immediately followed with precordial compression (C). This ordering of priorities, however, is based on consensus rather than objective outcome measurements. The ABCs recently have been seriously challenged on the basis of results of both experimental and clinical studies. Conventional external precordial compression restores systemic blood flow. It may be used by both professional and nonprofessional CPR providers, especially bystanders, because of its apparent simplicity and noninvasiveness. However, manual or mechanical external precordial compression typically generates cardiac outputs that represent less than 30% of normal values. Coronary blood flow, which is critical for restoration of spontaneous circulation, is correspondingly reduced. Accordingly, several alternatives to conventional precordial compression have been proposed with the intent of increasing cardiac output and both coronary and cerebral blood flows. Among the large number of pharmaceutical agents initially recommended for cardiac resuscitation, only agents that produce peripheral vasoconstriction are of proved benefit. Epinephrine has been the preferred vasopressor agent for the management of cardiac arrest for more than 35 years because of its alpha-adrenergic effects. However, the potentially adverse effects of epinephrine are related to its beta-adrenergic inotropic actions. The beta-adrenergic actions account for disproportionate increases in myocardial oxygen consumption with increased severity of myocardial ischemic injury and provocation of ectopic ventricular tachycardia and ventricular fibrillation. Nevertheless, epinephrine remains the drug of choice, although adrenergic drugs with selective alpha-adrenergic actions or nonadrenergic vasoconstrictor drugs are likely to emerge as useful alternatives. Experimental and clinical observations have led to identification of continuous monitoring of both end-tidal carbon dioxide and ventricular fibrillation waveforms as practical noninvasive guides because they are highly correlated with both cardiac output and coronary blood flow. Both end-tidal carbon dioxide and ventricular fibrillation waveforms now serve as predictors of the likelihood of successful resuscitation. These two measurements may now be used to guide interventions and especially to assure optimal precordial compression. It is well established that sudden death among adults is predominantly due to malignant ventricular arrhythmias and ventricular fibrillation. Early defibrillation serves as an unequivocally effective immediate intervention. Minimally trained first responders and members of the general public are being enfranchised to use automated external defibrillators for very early defibrillation. Use of these devices by bystanders is the most promising new intervention since CPR was first proposed in the early 1960s. Postresuscitation ventricular dysrhythmias and heart failure are now called postresuscitation myocardial dysfunction. This complication has been recognized as a leading cause of the high postresuscitation mor

Population density, automated external defibrillator use, and survival in rural cardiac arrest

OBJECTIVE

To determine whether population density is an independent predictor of survival from out-of-hospital cardiac arrest managed by basic life support (BLS) services using automated external defibrillators (AEDs).

METHODS

A retrospective, observational study in Kentucky of 34 BLS services covering 22 counties during the years 1992 to 1994 who used AEDs to treat patients who had out-of-hospital cardiac arrests.

RESULTS

Of 311 patients who had out-of-hospital cardiac arrests, 110 (35%) were defibrillated, 46 (15%) were resuscitated to hospital admission, and 19 (6%) survived to hospital discharge. Univariate predictors for survival to hospital discharge were emergency medical services response interval (from call receipt to ambulance arrival) < 8 minutes, defibrillation by the AED, initial rhythm of ventricular fibrillation or ventricular tachycardia (VF/VT), and population density > 100/square mile (sq mi) for the BLS service area (p < 0.001). A forced logistic regression model of survival to hospital discharge, using these 4 factors plus the presence of a witnessed arrest or bystander CPR, demonstrated that population density > 100/sq mi was highly significant (OR 9.4, 95% CI: 1.7 to 51.4, p < 0.01). Stepwise logistic regression models with combinations of these 6 factors found that survival to hospital discharge was best predicted by an initial rhythm of VF/VT (p = 0.004) and population density > 100/sq mi (p = 0.011).

CONCLUSIONS

Population density is strongly associated with survival from out-of-hospital cardiac arrest. BLS services within areas with population densities < or = 100/sq mi sustained little benefit from the addition of AEDs to their treatment of patients who had out-of-hospital cardiac arrests.

Effectiveness of ambulance paramedics versus ambulance technicians in managing out of hospital cardiac arrest

OBJECTIVE

To determine the effectiveness of extended trained ambulance personnel (paramedics) for the management of out of hospital cardiac arrest.

METHODS

A retrospective cohort study of patients who suffered a cardiac arrest between 1 January 1992 and 31 July 1994, and who were transported to their local accident and emergency (A&E) department. Data were collected on basic demography, operational time intervals, and ambulance crew status. Further clinical data were collected, and outcome measures included status on arrival at A&E, status on leaving A&E (hospital admission), and status on leaving hospital. The data were analysed using univariate and multivariate techniques.

RESULTS

Univariate analysis showed the likelihood of arriving in A&E with a return of spontaneous circulation was more than doubled among patients attended by a paramedic crew compared with those attended by technicians (relative risk = 2.48, 95% confidence interval 1.34 to 4.60). The likelihood of successful hospital admission was also significantly increased (RR = 1.92, 95% CI 1.13 to 3.27); however, beyond this point, further survival benefits appeared to be much smaller. Similar findings were revealed using multivariate analysis. Second level modelling revealed further possible differences between paramedic and technician crews according to type of incident. Patients successfully admitted to hospital who died before discharge remained severely disabled between admission and death.

CONCLUSIONS

There are marked short term survival advantages after cardiac arrest associated with paramedic care, but these probably diminish rapidly over time.

Adverse effects of interrupting precordial compression during cardiopulmonary resuscitation

OBJECTIVES

In the current operation of automated external defibrillators, substantial time may be consumed for a "hands off" interval during which precordial compression is discontinued to allow for automated rhythm analyses before delivery of the electric countershock. The effects of such a pause on the outcomes of cardiopulmonary resuscitation were investigated.

DESIGN

Prospective, randomized, controlled animal study.

SETTING

Research laboratory.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Ventricular fibrillation was electrically induced in 25 Sprague-Dawley rats. After 4 mins of untreated ventricular fibrillation, precordial compression was begun and continued for 6 mins. Animals were then randomized to receive an immediate defibrillation shock or the defibrillation attempt was delayed for intervals of 10, 20, 30, or 40 secs.

MEASUREMENTS AND MAIN RESULTS

Immediate defibrillation restored spontaneous circulation in each instance. When defibrillation was delayed for 10 or 20 secs, spontaneous circulation was restored in three of five animals in each group. After a 30-sec delay, spontaneous circulation was restored in only one of five animals (p < .05). No animal was successfully resuscitated after a 40-sec delay (p < .01). With increasing delays, 24- and 48-hr survival rates were correspondingly reduced.

CONCLUSIONS

During resuscitation from ventricular fibrillation, prolongation of the interval between discontinuation of precordial compression and delivery of the first electric countershock substantially compromises the success of cardiac resuscitation. Accordingly, automated defibrillators are likely to be maximally effective if they are programmed to secure minimal "hands off" delay before delivery of the electric countershock.

Medical issues and emergencies in the dermatology office

We review the medical issues and emergencies potentially encountered in the practice of general or surgical dermatology. Traditional guidelines have largely consisted of dated extrapolations from the nondermatologic literature concerning procedures that are primarily irrelevant to dermatology. This article outlines a rational approach to organizing an office emergency plan for anaphylaxis, stroke, status epilepticus, myocardial infarction, and hypertensive crisis. We discuss the literature that has influenced current office behavior regarding endocarditis prophylaxis, the use of electrosurgery with pacemakers, arrhythmogenic drug interactions, vasovagal syncope, lidocaine "allergy," and bleeding complications from oral anticoagulants. Recommendations for managing these issues in a dermatologic context are provided.

Continuation of CPR on admission to emergency department after out-of-hospital cardiac arrest. Occurrence, characteristics and outcome

AIM

To describe the occurrence, characteristics and outcome among patients with out-of-hospital cardiac arrest who required continuation of cardiopulmonary resuscitation (CPR) on admission to the emergency department.

PATIENTS

all patients in the municipality of Göteborg who suffered out-of-hospital cardiac arrest, were reached by the emergency medical service (EMS) system and in whom CPR was initiated. Period for inclusion in study: 1 Oct. 1980-31 Dec. 1992.

RESULTS

of 334 out-of-hospital cardiac arrests, 2,319 (68%) were receiving on-going CPR at the time of admission to hospital. Of these, 137 patients (6%) were hospitalized alive and 28 (1.2%) could be discharged from hospital. Of these patients, 39% had a cerebral performance categories (CPC) score of 1 (no cerebral deficiency), 18% had a CPC score of 2 (moderate cerebral deficiency), 36% had a CPC score of 3 (severe cerebral deficiency) and 7% had a CPC score of 4 (coma) at discharge. Among patients discharged. 76% were alive after 1 year.

CONCLUSION

among consecutive patients with out-of-hospital cardiac arrest, CPR was ongoing in 68% of them on admission to hospital. Among these patients, 6% were hospitalized alive and 1.2% were discharged from hospital. Thus, among patients with ongoing CPR on admission to hospital, survivors can be found but they are few in numbers and extensive cerebral damage is frequently present.

Checking the carotid pulse check: diagnostic accuracy of first responders in patients with and without a pulse

International guidelines for cardiopulmonary resuscitation (CPR) in adults advocate that cardiac arrest be recognized within 5-10 s, by the absence of a pulse in the carotid arteries. However, validation of first responders' assessment of the carotid pulse has begun only recently. We aimed (1) to develop a methodology to study diagnostic accuracy in detecting the presence or absence of the carotid pulse in unresponsive patients, and (2) to evaluate diagnostic accuracy and time required by first responders to assess the carotid pulse. In 16 patients undergoing coronary artery bypass grafting, four groups of first responders (EMT-1: 107 laypersons with basic life support (BLS) training; EMT-2: 16 emergency medical technicians (EMTs) in training; PM-1: 74 paramedics in training; PM-2: 9 certified paramedics) performed, single-blinded and randomly allocated, carotid pulse assessment either during spontaneous circulation, or during non-pulsatile cardiopulmonary bypass. Time to diagnosis of carotid pulse status, concurrent haemodynamics and diagnostic accuracy were recorded. In 10% (6/59), an absent carotid pulse was not recognized as pulselessness. In 45% (66/147), a pulse was not identified despite a carotid pulse with a systolic pressure > or = 80 mmHg. Thus, although sensitivity of all participants for central pulselessness approached 90%, specificity was only 55%. Both sensitivity and, to a lesser degree, specificity improved with increasing training; blood pressure or heart rate had no significant effect. The median diagnostic delay was 24 s (minimum 3 s). When no carotid pulse was found, delays were significantly longer (30 s: minimum 13 s), than when a carotid pulse was identified (15 s; minimum 3 s) (P < 0.0001). Of all participants, only 15% (31/206) produced correct diagnoses within 10 s. Only 1/59 (2%) identified pulselessness correctly within 10 s. Our cardiopulmonary bypass model of carotid pulse assessment proved to be feasible and realistic. We conclude that recognition of pulselessness by rescuers with basic CPR training is time-consuming and inaccurate. Both intensive retraining of professional rescuers and reconsideration of guidelines about carotid pulse assessment are warranted.