Factors influencing survival after out-of-hospital cardiac arrest

Three-rescuer CPR: the method of choice for firefighter CPR?

STUDY OBJECTIVE

To compare the quality of CPR provided by firefighters performing three-rescuer CPR with that achieved by firefighters trained to provide standard two-rescuer CPR.

DESIGN

Eight months after training a large number of firefighters to perform three-rescuer CPR, we used a quasi-experimental design to compare the performance of a randomly selected subset of these companies to that achieved by a control group of engine companies that received refresher training in standard two-rescuer CPR. Both groups used bag-valve masks to provide rescue ventilations. Testing was conducted on a no-notice basis with a recording mannequin. Key actions were scored by an experienced observer using explicit pass-fail criteria. Mannequin-generated strip charts were used to calculate the rate and depth of chest compressions and the ventilatory rate, volume, and minute ventilation in a blinded manner.

SETTING

Fire stations of the Memphis Fire Department. The department is the sole provider of first-responder emergency care to the citizens of Memphis, Tennessee (population, 610,000).

RESULTS

Three-rescuer teams delivered a mean minute ventilation substantially greater than that produced by two-rescuer teams (7.7 +/- 5.3 L versus 4.9 +/- 4.2 L, P < .001). Intergroup differences in the mean depth of chest compressions were less marked, but they were still significant (17.2 +/- 8.3 mm of recorder-needle deflection versus 13.7 +/- 7.0 mm, P < .001).

CONCLUSION

Three rescuers can produce better CPR than two when a bag-valve-mask device is used. The technique is easily learned and readily retained.

Effect of age on prehospital cardiac resuscitation outcome

To compare resuscitation outcomes in elderly and younger prehospital cardiac arrest victims, we used a retrospective case series over 5 years in rural advanced life support (ALS) units and a University hospital base station. Participants included 563 adult field resuscitations. Excluded were patients with noncardiac etiologies, those less than 30 years old, and those with unknown initial rhythms. Patients were grouped by age. Return of spontaneous circulation (ROSC) and survival to hospital discharge were compared by Yates' chi-square test. ALS treatment of cardiac arrest was by regional protocols and on-line physician direction. Sixty percent (320/532) of patients were over 65 years old. The proportion with initial rhythm ventricular fibrillation (VF) was 50% in the elderly and 48% in younger patients. ROSC was achieved in 18% of elderly and 16% of younger patients; survival was 4% among the elderly and 5% for younger patients. The oldest survivor was 87 years old. Most survivors were discharged, in good Cerebral Performance Categories. There was no difference in outcome by age group when initial cardiac rhythm was considered. Early cardiopulmonary resuscitation (CPR) and ALS and initial rhythm VF were associated with the best resuscitation success. Age has less effect on resuscitation success than other well-known factors such as early CPR and ALS. Advanced age alone should probably not deter resuscitation attempts.

CPR knowledge, self-efficacy, and anticipated anxiety as functions of infant/child CPR training

STUDY OBJECTIVE

To determine the effect of infant/child CPR training on CPR knowledge, self-efficacy, and anticipated anxiety among parents of healthy infants/children.

PARTICIPANTS

Parents (n = 36) undergoing a 4-hour training program in infant/child CPR at a tertiary-care hospital located in a suburb of a large metropolitan region and a control group of parents (n = 47) without CPR training were enrolled in the study.

DESIGN

Two parallel forms developed specifically to assess the impact of infant/child CPR training on CPR knowledge, self-efficacy, and anticipated anxiety were independently evaluated for their psychometric characteristics before being administered to the parents with and without CPR training. The CPR-trained parents were requested to complete one form immediately before and the other 1 month after CPR training, and the control group completed the two forms over a 1-month interval. Estimates of the likelihood of infant/child CPR situations were also rated by the parents at the same times. Demographic data were obtained during administration of the second form.

RESULTS

Self-efficacy had increased significantly and anticipated anxiety about CPR had decreased significantly 1 month after CPR training among CPR-trained parents, compared with controls. We found no significant changes in the CPR-trained parents' CPR knowledge or estimates of the likelihood of experiencing CPR situations over the 1-month interval on comparison with data from the controls.

CONCLUSION

Community-based infant/child CPR training programs affect parents on a variety of levels but may not effect changes in CPR knowledge.

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.

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.

Failure of ambulance crew to initiate cardiopulmonary resuscitation

The Utstein style of reporting out-of-hospital cardiac arrests requires that all confirmed cardiac arrests considered for resuscitation are analysed and that a record is made of the number of cases where no resuscitation is attempted. We report a series of 942 confirmed cardiac arrests considered for resuscitation by South Glamorgan Emergency Medical Service (EMS). There were 370 (39.3%) cases where no resuscitation was attempted by the EMS. The ages, male/female ratio and EMS response times were similar in both the group that received ambulance resuscitation and those that did not. Those not receiving resuscitation were less likely to have had an arrest of cardiac aetiology (51.3% vs. 75%, P < 0.00001). Rigor mortis or decomposition of the body was present in 50.8% of cases and in 20% a doctor had already confirmed the patient dead. In the remainder the ambulance crew failed to start resuscitation for a variety of reasons.

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.

Metabolic determinants of defibrillation. Role of adenosine

BACKGROUND

The single most important determinant of cardiac arrest outcome is the duration of ventricular fibrillation (VF) preceding delivery of a high-energy shock, because of the adverse effect of VF duration on defibrillation threshold (DFT). Although a metabolic mechanism has been proposed, hypoxia, metabolic acidosis, or alkalosis do not adversely affect DFT. However, since (1) catecholamines and adenosine levels are markedly increased during hypoxia, (2) exogenous catecholamines decrease DFT, and (3) adenosine is a potent antagonist of the electrophysiological effects of catecholamines on ventricular myocardium, we hypothesized that release of adenosine during prolonged VF adversely affects DFT and that this effect occurs through an antiadrenergic mechanism.

METHODS AND RESULTS

DFT was determined in dogs during infusion of adenosine (300 micrograms.kg-1.min-1) and dipyridamole (0.25 mg/kg), an adenosine uptake blocker, a regimen that resulted in adenosine levels in the myocardial effluent equivalent to those achieved after 5 minutes of VF. Adenosine increased transthoracic DFT in each dog by 49 +/- 14% (n = 21) (mean +/- SEM) and transmyocardial DFT in a separate group of 10 dogs by 103 +/- 16%, P = .0003. Pretreatment with the specific A1 adenosine receptor antagonist 8-cyclopentyltheophylline (CPT) 5 mg/kg completely abolished the effects of adenosine on DFT. The effects of adenosine on DFT were also examined in the denervated state (propranolol 0.2 mg/kg plus bilateral vagotomy). In contrast to its effect in the innervated condition, adenosine had no effect on DFT in the same dogs when denervated, 49 +/- 11 versus 53 +/- 10 J (P = NS).

CONCLUSIONS

Adenosine significantly increases transthoracic and transmyocardial DFT, effects that are mediated by the A1 adenosine myocardial receptor through an antiadrenergic mechanism. These results suggest that enhanced release of adenosine during VF may have a deleterious effect on defibrillation and that intramyocardial delivery of a specific A1 adenosine antagonist during VF may facilitate defibrillation and significantly reduce defibrillation threshold.

Clinical experience with the implantable cardioverter defibrillator

The implantable cardioverter defibrillator has played an increasingly greater role in the management of episodes of sudden cardiac-related death related to ventricular tachycardia or ventricular fibrillation. This study reviews the cases of 142 patients who underwent insertion of an implantable cardioverter defibrillator, 104 who received a device alone (group I) and 38 who underwent insertion of the device in combination with other cardiac surgical procedures (group II). The overall operative mortality was 3.5% and this did not differ between the two groups. The complication rate was higher for group II than for group I patients, and consisted primarily of an increased incidence of atrial arrhythmias (53% versus 13%; p < 0.001). Late complications included three device infections requiring removal of the defibrillator. The late mortality did not differ between the two groups and was primarily related to congestive heart failure. Sudden cardiac-related death was an uncommon late event, with an actuarial freedom from sudden cardiac-related death of 98%, 97%, and 87% at 1, 2, and 5 years, respectively. The morbidity and mortality rate are low in association with the insertion of an implantable cardioverter defibrillator, even when this is combined with other cardiac surgical procedures. Its insertion is also associated with a low subsequent rate of sudden cardiac-related death.

Out-of-hospital cardiac arrest in an Oriental metropolitan city

To investigate the epidemiology of out-of-hospital cardiac arrest in Taipei City, Taiwan, a prospective chart review and follow-up study was conducted by collecting the prehospital cardiac arrest record from 10 designated responsible emergency departments (EDs) from August 1, 1992 through May 31, 1993. Cases with the restoration of spontaneous circulation (ROSC) were followed up until discharged from hospital. The information gathered included age, sex, bystander cardiopulmonary resuscitation, response time (time elapsed from receiving the call to arrival on the scene), advanced cardiac life support (ACLS) time (time elapsed from receiving the call to arrival at the ED), initial cardiac rhythm in the ED, ROSC, survival to discharge from the hospital, underlying disease, past history, personal history, and neurological outcome at discharge. Of 638 out-of-hospital cardiac arrests, 554 (86.7%) were nontraumatic. Response time, ACLS time, ROSC rates, and survival rates were 7.4 minutes, 21.6 minutes, 15.8%, and 1.4%, respectively. In comparing the trauma and nontrauma group, there were significant differences in age, sex, response time, and ACLS time. Between cases of patients who had ROSC and those who died, the data were statistically significant, P = .0143, showing that ACLS time was shorter in the ROSC group (19.5 v 21.9 minutes). In analysis of underlying disease, definite and probable cardiac-origin sudden deaths were found in only 120 patients, which may extend the annual sudden cardiac death rates to be 0.0053%. In conclusion, the low resuscitation and survival rates in this country were because of delayed initiation of both basic life support and ACLS.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

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.

Cardiopulmonary resuscitation in elderly patients hospitalized in the 1990s: a favorable outcome

OBJECTIVE

To compare the clinical characteristics and survival of elderly and younger hospitalized patients who sustain cardiac arrest and receive cardiopulmonary resuscitation (CPR) in the 1990's and to assess predictors of survival.

DESIGN

Retrospective survey of cardiac arrest database and hospital charts, plus telephone follow-up.

SETTING

450-bed acute care teaching hospital.

STUDY POPULATION

Seventy-eight hospitalized patients 70 years or older and 73 hospitalized patients under 70 years of age.

MEASUREMENTS

Survey of cardiac arrest data base, hospital charts, and telephonic follow-up to allow (1) comparison of clinical characteristics, survival, and long-term follow-up between two age groups and (2) univariate and multivariate analysis of predictors of mortality.

MAIN RESULTS

Pre-arrest clinical characteristics were not significantly different between the age groups. Prior to arrest the majority of patients were functionally active, and over one-third were hospitalized for acute coronary artery syndromes. In approximately 85% of the patients, the arrest was witnessed, and 70% of the patients had their cardiac rhythm monitored at onset of the arrest. Survival was not significantly different between the age groups; 26% of the total 151 patients were discharged. No significant difference was noted in pre-post arrest functional status of survivors. Survival at 1, 2, and 3 years in elderly and younger survivors was 86% versus 80%, 76% versus 67%, and 71% versus 61%, respectively. Multivariate analysis identified the presence of coronary artery disease, admission systolic blood pressure, and functional level to be independent pre-arrest predictors of mortality. At the time of the arrest, the initial cardiac rhythm and duration of CPR were found to be independent predictors of mortality.

CONCLUSIONS

Elderly patients hospitalized in the 1990's who receive CPR have outcomes similar to younger patients who receive CPR. The favorable outcome in the elderly patients may reflect patient selection: the majority of our patients were functionally active prior to hospitalization, without multiple serious illnesses; many were hospitalized for acute coronary artery syndromes; and, in most cases, the arrest was witnessed with the patient's cardiac rhythm monitored at onset of the arrest.

Training St John Ambulance volunteers to use an automated external defibrillator

The key to improving survival from pre-hospital cardiac arrest lies in reducing the time interval between onset of cardiac arrest and defibrillation. Placing automated external defibrillators at strategic points in the community could potentially reduce this time interval, but would necessitate widespread training in defibrillation for lay people in addition to health care workers. There are unanswered questions regarding the ability of lay people to acquire and retain this skill when the training programme is, by necessity, very brief, (otherwise it would not be possible to train large enough numbers of people) and the skill is used infrequently. In this study, nurse and lay volunteer first-aiders were taught to use an automated external defibrillator, either by a 2-h, or a 4-h course, and their skills were assessed at training, and at 3 and 6 months afterwards. Using stringent assessment criteria, 54% of volunteers passed the assessment at every session. Little difference in acquisition or retention of skills between the nurse and lay volunteers, and the 2- and 4-h course groups was found. It is concluded that brief training in defibrillation for volunteer first-aiders is feasible.

The efficacy of an ACLS training program for resuscitation from cardiac arrest in a rural community

STUDY OBJECTIVE

To determine whether an advanced cardiac life support (ACLS) course in a rural hospital will improve resuscitation success from cardiac arrest.

DESIGN

A retrospective case review of all patients in cardiac arrest during a 13-month period before and after the institution of an ACLS training program.

SETTING

Emergency department of a 42-bed rural, community hospital in a community with no prehospital advanced life support or early defibrillation.

PARTICIPANTS

All patients in cardiac arrest were entered into the data base. Twenty-nine patients were included in the pre-ACLS period and 35 in the post-ACLS period. There were no significant differences in age, gender, initial rhythm, comorbid diseases, witnessed versus unwitnessed arrest, or total arrest time in the patients in the pre-ACLS period compared with those in the post-ACLS period.

INTERVENTION

ACLS provider training.

MAIN RESULTS

Patients in cardiac arrest who had ventricular fibrillation/tachycardia as their initial rhythm had significant improvement in resuscitation success compared with patients in ventricular fibrillation/tachycardia in the pre-ACLS period (six of 15 versus none of nine, P < .05). Out-of-hospital cardiac arrest resuscitation was more successful in the post-ACLS period than in the pre-ACLS period (five of 30 versus none of 25, P < .05). Overall, seven of 35 patients (20%) were resuscitated successfully in the post-ACLS period, with two patients surviving to hospital discharge. This was not significantly different than the two of 29 patients (7%) resuscitated in the pre-ACLS period, with one patient surviving to discharge.

CONCLUSION

The institution of an ACLS-provider course in a rural community hospital was associated with improvement in initial resuscitation for patients with ventricular fibrillation/tachycardia and out-of-hospital arrest.

Out-of-hospital resuscitation in East Sussex: 1981 to 1989

OBJECTIVE

To assess the impact of extended training in advanced life support on the outcome of resuscitation.

DESIGN

Analysis of the successful resuscitations from 1981 to 1989.

SETTING

Brighton and East Sussex.

RESULTS

248 patients were resuscitated from cardiac or respiratory arrest in the community and subsequently survived to leave hospital. Their mean age was 64 years and one year survival was 77%. In most cases the cause of collapse was cardiac but 38 (15%) suffered a respiratory arrest. In 140 of the successful resuscitations (56%) collapse occurred before the arrival of the ambulance. Basic life support, with ventilation and chest compression where necessary, was sufficient to revive 35 (14%) of the patients. Defibrillation was also required in 107 patients (43%), and in a further 106 patients (43%) who had prolonged cardiorespiratory arrest requiring endotracheal intubation and the use of several drugs. Review of ambulance forms and case notes showed that in 87 cases (35%) the abilities of the paramedical ambulance staff in advanced resuscitation techniques contributed decisively to the success of resuscitation. These skills are illustrated by eight case reports.

CONCLUSIONS

Extended training for ambulance staff increases the likelihood of successful resuscitation from out-of-hospital cardiopulmonary arrest. Though instruction in defibrillation must have the highest priority, full paramedical training can bring appreciable additional benefits.

Emergency vehicle intervals versus collapse-to-CPR and collapse-to-defibrillation intervals: monitoring emergency medical services system performance in sudden cardiac arrest

STUDY OBJECTIVE

To compare emergency vehicle response intervals with collapse-to-intervention intervals to determine which of these system data better correlated with survival after prehospital sudden cardiac arrest.

STUDY DESIGN

A 22-month case series, collected prospectively, of out-of-hospital cardiac arrests. Times of collapse, dispatch, scene arrival, CPR, and initial defibrillation were determined from dispatch records, recordings of arrest events, interviews with bystanders, and hospital records.

SETTING

Southwestern city (population, 400,000; area, 390 km2) with a two-tiered basic life support-advanced life support emergency medical services system. Emergency medical technician-firefighters without electrical defibrillation capability comprised the first response tier; firefighter-paramedics were the second tier.

PATIENTS

One hundred eighteen cases of witnessed, out-of-hospital cardiac arrest in adults with initial ventricular fibrillation.

MAIN OUTCOME MEASURES

Survival was defined as a patient who was discharged alive from the hospital.

RESULTS

Eighteen of 118 patients (15%) survived. Survivors did not differ significantly from nonsurvivors in age, sex, or basic life support or advanced life support response intervals. Survivors had significantly (P < .05) shorter intervals from collapse to CPR (1.7 versus 5.2 minutes) and to defibrillation (7.4 versus 9.5 minutes).

CONCLUSION

Collapse-to-intervention intervals, not emergency vehicle response intervals, should be used to characterize emergency medical services system performance in the treatment of sudden cardiac death.

Bystander cardiopulmonary resuscitation. Is ventilation necessary?

BACKGROUND

Prompt initiation of bystander cardiopulmonary resuscitation (CPR) improves survival. Basic life support with mouth-to-mouth ventilation and chest compressions is intimidating, difficult to remember, and difficult to perform. Chest compressions alone can be easily taught, easily remembered, easily performed, adequately taught by dispatcher-delivered telephone instruction, and more readily accepted by the public. The principal objective of this study was to evaluate the need for ventilation during CPR in a clinically relevant swine model of prehospital witnessed cardiac arrest.

METHODS AND RESULTS

Thirty seconds after ventricular fibrillation, swine were randomly assigned to 12 minutes of chest compressions plus mechanical ventilation (group A), chest compressions only (group B), or no CPR (group C). Standard advanced cardiac life support was then provided. Animals successfully resuscitated were supported for 2 hours in an intensive care setting, and then observed for 24 hours. All 16 swine in groups A and B were successfully resuscitated and neurologically normal at 24 hours, whereas only 2 of 8 group C animals survived for 24 hours (P < .001, Fisher's exact test). One of the 2 group C survivors was comatose and unresponsive.

CONCLUSIONS

In this swine model of witnessed prehospital cardiac arrest, the survival and neurological outcome data establish that prompt initiation of chest compressions alone appears to be as effective as chest compressions plus ventilation and that both techniques of bystander CPR markedly improve outcome compared with no bystander CPR.

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.

Rhythm changes during resuscitation from ventricular fibrillation

Defibrillation of patients with primary ventricular fibrillation (VF) results in a variety of rhythm changes. We analysed these changes in rhythm in 200 patients, using the American Heart Association's recommendation of two defibrillations prior to drug therapy. Sixty-three (31.5%) patients were immediate survivors with 38 (19%) being discharged from hospital alive. There was no difference between the age of immediate survivors (66.5 years, S.D. = 11.2) and non-survivors (68.3 years, S.D. = 13.7, P = 0.37). Immediate survivors were significantly more likely to be discharged alive from hospital if they were younger (70.0 years, S.D. 8.5 vs. 62.1 years, S.D. 15.8, P = 0.014). Increasing delays to the initiation of basic life support (CPR) and to defibrillation were associated with significantly less likelihood of cardioversion to sinus rhythm (P < 0.005 and P < 0.002, respectively). Those patients who stayed in VF were not more likely to be defibrillated into asystole or electro-mechanical dissociation. Seventeen percent (34) of patients were defibrillated to sinus rhythm after the first defibrillation and 14% (19) after the second, with similar hospital discharge rates (62% and 58%, respectively). Sixty percent (32) of patients in sinus rhythm, after two defibrillations, were discharged alive, compared to only 4% (6) of those patients not in sinus rhythm after two defibrillations. Our data provide new information on rhythm changes during resuscitation and supports the need for the earliest possible initiation of basic life support and defibrillation to improve survival from cardiac arrest due to ventricular fibrillation.

Aeromedical evacuation of rural victims of nontraumatic cardiac arrest

STUDY OBJECTIVES

To determine if the deployment of a helicopter-borne nurse/paramedic team contributed to survival of victims of nontraumatic cardiac arrest in a rural setting.

DESIGN

Retrospective chart review.

SETTING

A university hospital-based helicopter aeromedical program serving a primarily rural region with a volunteer basic life support/advanced life support ground emergency medical services system.

PARTICIPANTS

Victims of nontraumatic cardiac arrest, older than 15 years, in cardiac arrest at the time of request for air evacuation.

MEASUREMENTS AND MAIN RESULTS

Eighty-four patients were identified who met the study inclusion criteria between January 1, 1986, and December 31, 1989. Basic life support care was always available before aeromedical crew arrival; advanced life support care was available in 58% of cases before helicopter arrival. Resuscitative efforts were terminated in the field in 55 cases; of 29 patients transported to the emergency department, only ten (12%) survived to hospital admission. Only one patient (1%) survived to hospital discharge; this patient was resuscitated by ground advanced life support providers before helicopter arrival.

CONCLUSION

Despite providing improved availability of advanced life support care in some cases, deployment of aeromedical teams had a negligible effect on patient survival from nontraumatic cardiac arrest in a rural setting.

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.

Magnetic resonance imaging findings associated with cardiac arrest

BACKGROUND AND PURPOSE

The frequency and prognostic significance of neuroradiological findings after cardiac arrest are unknown. Using healthy volunteers as control subjects, we studied the magnetic resonance imaging (MRI) findings associated with cardiac arrest, adjusted for confounding factors.

METHODS

The presence of cerebral infarcts, leukoaraiosis, atrophy, and edema on ultra-low-field MRI was assessed in 88 community volunteers and 52 cardiac arrest survivors enrolled in a placebo-controlled, randomized, double-blind trial of nimodipine in out-of-hospital ventricular fibrillation.

RESULTS

Cardiac arrest was an independent risk factor for the presence of infarcts in a logistic regression model adjusted for age, sex, and history of myocardial infarction, stroke, coronary heart disease, cardiac failure, and hypertension (odds ratio, 3.6; 95% confidence interval, 1.3 to 9.9; P = .01). Leukoaraiosis was associated with increasing age but not with cardiac arrest. Adjusted for age, the delay of advanced life support had an inverse correlation with the degree of atrophy in placebo-treated patients (r = -.62, P < .0001) but not in patients treated with nimodipine (r = -.10, P = .43). Lack of age-related atrophy, possibly implicating the presence of brain edema, predicted poor outcome after cardiac arrest (odds ratio, 4.6; 95% confidence interval, 1.4 to 15.8; P = .01).

CONCLUSIONS

Cardiac arrest was associated with deep cerebral infarcts but not with leukoaraiosis. MRI findings did not predict the functional outcome at 1 year. Nimodipine treatment had no significant effect on the MRI findings, but delayed resuscitation was associated with probable brain edema only in placebo-treated patients.

Effect of fire department first-responder automated defibrillation

STUDY OBJECTIVE

To examine the effect of fire department first-responder defibrillation on time to defibrillation in a mid-sized community with two tiers of emergency medical services (EMS) ambulance response.

DESIGN

Retrospective cohort.

SETTING

The study area was the region of Hamilton-Wentworth, which has more than 445,000 inhabitants and covers 1,136 km2 (438 square miles).

TYPE OF PARTICIPANTS

We studied 297 victims of out-of-hospital cardiac arrest presenting to the EMS system between May 1, 1990, and April 30, 1991.

MEASUREMENTS AND MAIN RESULTS

The mean defibrillation interval was decreased from 11.96 minutes to 8.50 minutes (P < .001) by the introduction of fire first-responder defibrillation. Survival was significantly greater with bystander-witnessed arrest, initial rhythm of ventricular fibrillation, and presence of a pulse on arrival in the emergency department.

CONCLUSION

In our EMS system, fire first-responders were able to provide defibrillation in significantly shorter times than ambulance attendants. Other EMS systems should review their response times and consider instituting first-responder defibrillation as one means of reducing defibrillation intervals.

Influence of external defibrillator electrode polarity on cardiac resuscitation

Eight hundred forty-seven consecutive patients discovered in cardiac arrest by first responding firefighters received initial defibrillation attempts using automatic external defibrillators. The effect of electrode polarity on defibrillation and resuscitation was determined in the subset of 289 (34%) with ventricular fibrillation in a prospective, randomized trial. The ECG was recorded in 205 consecutive patients whose initial rhythm was ventricular fibrillation. Eighty-seven of 114 patients (76%) in whom the apex chest electrode was positive were defibrillated with the first 200-joule shock, compared to 70 of 91 patients (77%) in whom the apex electrode was negative. There was no difference in the type of rhythm established, e.g., organized versus brady-asystole following defibrillation with either electrode polarity. Resuscitation was possible in 56% of patients in whom the apex electrode was positive and 60% of those in whom the apex electrode was of negative polarity. Hospital survival rates (26% vs 27%) were also similar for both treatment groups. Unlike results during experimental external defibrillation of animals or those obtained using implantable defibrillators, this randomized trial of external defibrillation conducted during attempted out-of-hospital resuscitation showed no difference in outcomes related to electrode polarity.

Implications for present and future applications of the implantable cardioverter-defibrillator resulting from the use of a simple model of cost efficacy

OBJECTIVE

To develop a model to assess the cost-efficacy of the implantable cardioverter defibrillator to prevent sudden death. The model must be sufficiently flexible to allow the use of cost and survival figures derived from different sources.

SETTING

The study was conducted in a teaching hospital department of cardiology with experience of 40 implantable cardioverter defibrillator implants and a large database of over 500 survivors of myocardial infarction.

PROCEDURE

The basic costs of screening tests, stay in hospital, and purchase of implantable cardioverter defibrillators were derived from St George's Hospital during 1991. To assess the cost-efficacy of various strategies for the use of implantable cardioverter defibrillators, survival data taken from published studies or from our own database. Implications of the national cost of the various strategies were calculated by estimating the number of patients a year requiring implantation of a defibrillator if the strategy was adopted.

RESULTS

Use of implantable cardioverter defibrillators in survivors of cardiac arrest costs between 22,400 pounds and 57,000 pounds for each year of life saved. Most of the strategies proposed by the current generation of implantable cardioverter defibrillator trials have cost efficacies in the same range, and adoption of any one of these strategies in the United Kingdom could cost between 2 million pounds and 100 million pounds a year. Future technical and medical developments mean that cost-efficacy may be improved by up to 80%. Due to the limitations of screening tests currently available restriction on the use of implantable cardioverter defibrillators to those groups where it seems highly cost-effective will result in a small impact on overall mortality from sudden cardiac death.

CONCLUSION

Present and possible future applications of the implantable cardioverter defibrillator seem expensive when compared with currently accepted treatments. Technical and medical developments are, however, likely to result in a dramatic improvement in cost efficacy over the next few years.

Survival after out-of-hospital cardiac arrest in elderly patients. Belgian Cerebral Resuscitation Study Group

STUDY OBJECTIVES

To study whether age of the cardiac arrest patient is related to prognostic factors and survival.

STUDY DESIGN

Retrospective analysis of a prospective registration of cardiac arrest events in the mobile ICUs of seven participating hospitals.

STUDY POPULATION

Two thousand seven hundred seventy-six out-of-hospital cardiac arrests in which advanced life support was initiated. Cardiac arrests with a precipitating event requiring specific therapeutic consequences and with specific prognosis were not included in the analysis (eg, trauma, exsanguination, drowning, sudden infant death syndrome).

RESULTS

Neither resuscitation rate (23%) nor mortality caused by a neurologic reason (9%) was significantly different between age groups. Mortality after CPR of non-neurologic etiology was significantly higher in the elderly patient (younger than 40 years, 16%; 40 to 69 years, 19%; 70 to 79 years, 30%; 80 years or older, 34%; P less than .005) and had a negative effect on survival in resuscitated elderly patients (P less than .05). Elderly patients more frequently had a dependent lifestyle before the arrest (P less than .025), an arrest of cardiac origin (P less than .001), electromechanical dissociation as the type of cardiac arrest (P less than .025), and a shorter duration of advanced life support in unsuccessful resuscitation attempts (r = -.178, P less than .0001).

CONCLUSION

Because survival two weeks after CPR was not significantly different between age groups, we suggest that decision making in CPR should not be based on age but on factors with better predictive power for outcome and quality of survival.

Comparison of two methods of transporting paramedics to cardiac arrests outside hospital

OBJECTIVE

To compare the deployment of paramedics in a separate rapid response unit with their deployment in a standard emergency ambulance.

DESIGN

A one year period of each deployment.

SETTING

Throughout the community in some parts of West Yorkshire.

PARTICIPANTS

All patients receiving resuscitation for cardiac arrest by paramedics.

INTERVENTIONS

Using the same group of paramedics and central control, 12 months with the paramedics deployed in separate cars in addition to the standard ambulances (period 1) were followed by another 12 months when they were deployed as one crew member of a standard emergency ambulance (period 2).

MAIN OUTCOME MEASURES

Number of arrests attended, number of patients in ventricular fibrillation at paramedic arrival, response times, survival to leave hospital.

RESULTS

In period 1, 580 arrests were attended with 31 survivors. In period 2, 462 arrests resulted in 25 survivors. The mean response time was shorter in period 1 (6.24 versus 6.60 min, Cl--0.01-0.73 min). In period 1, 217 patients were found in ventricular fibrillation (23 survivors): In period 2, 141 patients were found in ventricular fibrillation (11 survivors).

CONCLUSION

Separating paramedics from the standard emergency ambulances increases the number of survivors of cardiac arrest but the difference may not be sufficiently large to justify the additional expenditure.

Mortality within hospital after resuscitation from ventricular fibrillation outside hospital

OBJECTIVE

To determine factors related to mortality within hospital after successful resuscitation from ventricular fibrillation outside hospital by a mobile coronary care unit manned by a physician.

DESIGN

Retrospective review of records of patients resuscitated and admitted to hospital between 1 January 1966 and 31 December 1987.

SETTING

Mobile coronary care unit, coronary care unit, and cardiology department.

PATIENTS

281 patients (227 male), aged 14-82 (mean 58) successfully resuscitated from ventricular fibrillation outside hospital of whom 182 (65%) developed ventricular fibrillation before the arrival of the mobile coronary care unit. The aetiology of ventricular fibrillation was acute myocardial infarction in 194 patients (69%), ischaemic heart disease without infarction in 71 (25%), and other or unknown in 16 (6%).

MAIN OUTCOME MEASURES

Death within hospital.

RESULTS

There were 91 deaths in hospital (32%). Factors on univariate analysis significantly associated with increased mortality were patient age > or = 60 years, previous myocardial infarction or cerebrovascular disease, prior digoxin or diuretic treatment, collapse without prior chest pain or with pain lasting 30 minutes or less, defibrillation delayed by > or = 5 min, > or = four shocks required to correct ventricular fibrillation, left ventricular failure or pulmonary oedema and cardiogenic shock after successful defibrillation, and coma on admission to hospital. On multivariate analysis the most important factors (in rank order) were cardiogenic shock after defibrillation, coma on admission to hospital, age > or = 60 years and the requirement for four or more shocks to correct ventricular fibrillation.

CONCLUSIONS

The in-hospital mortality of patients resuscitated from ventricular fibrillation outside hospital was related to patient characteristics before the cardiac arrest and to the immediate haemodynamic and neurological status after correction of ventricular fibrillation as well as to factors at the resuscitation itself. The in-hospital mortality of this study compares favourably with the results obtained by units staffed by paramedical workers and emergency medical technicians, although 35% (99/281) of the patients had ventricular fibrillation after the arrival of the mobile unit and defibrillation was thus rapid.

Treatment of prolonged ventricular fibrillation. Immediate countershock versus high-dose epinephrine and CPR preceding countershock

BACKGROUND

Early countershock of ventricular fibrillation has been shown to improve immediate and long-term outcome of cardiac arrest. However, a number of investigations in the laboratory and in the clinical population indicate that immediate countershock of prolonged ventricular fibrillation most commonly is followed by asystole or a nonperfusing spontaneous cardiac rhythm, neither of which rarely respond to current therapy. The use of epinephrine in doses greater than those currently recommended has recently been shown to improve both cerebral and myocardial perfusion during cardiopulmonary resuscitation (CPR). The purpose of this study was to compare cardiac resuscitation outcome between immediate countershock of prolonged ventricular fibrillation with high-dose epinephrine therapy and conventional CPR before countershock of prolonged ventricular fibrillation in a canine model.

METHODS AND RESULTS

After sedation, intubation, induction of anesthesia, and instrumentation, ventricular fibrillation was electrically induced in 28 dogs. After 7.5 minutes of ventricular fibrillation, animals were randomly allocated to two treatment groups: group 1, immediate countershock followed by recommended advanced cardiac life support (ACLS) interventions, or group 2, 0.08 mg/kg epinephrine and manual closed-chest CPR before countershock and ACLS. In both groups, ACLS was continued until a spontaneous perfusing rhythm was restored or for 20 minutes (total arrest time, 27.5 minutes). A spontaneous perfusing rhythm was restored in three of 14 group 1 animals and in nine of 14 group 2 animals (p = 0.014 by sequential analysis method of Whitehead). Coronary perfusion pressure (aortic minus right atrial pressure during CPR diastole) before countershock was significantly greater in group 2 (21 +/- 7 mm Hg) when compared with mean circulatory pressure in group 1 (9 +/- 8, p less than 0.01).

CONCLUSIONS

The findings of this study suggest that a brief period of myocardial perfusion before countershock improves cardiac resuscitation outcome from prolonged ventricular fibrillation.

Epinephrine in cardiopulmonary resuscitation

This review assesses the role of epinephrine in cardiopulmonary resuscitation from the perspective of mechanisms of action, cardiac and cerebral effects, and use in human beings. We reviewed the literature from 1966 onward, using a Medline Search of the National Library of Medicine with the key words: "heart arrest," "resuscitation," and "epinephrine." Pertinent articles that represented original research were critically appraised by at least two authors. We concluded that the Advanced Cardiac Life Support recommended dose of epinephrine (1 mg or 0.007 to 0.014 mg/kg) has little scientific basis. Evidence from animal studies demonstrates that doses of 0.1 to 0.2 mg/kg are required to significantly improve myocardial and cerebral blood flow and resuscitation rates. Limited human data confirm the dose-dependent vasopressor response to epinephrine and the potential for improved immediate survival with higher doses. We suggest that randomized controlled human trials are needed to document the usefulness of higher doses of epinephrine in cardiopulmonary resuscitation.

Single operator cardiopulmonary resuscitation in ambulances. Which ventilation device?

Cardiopulmonary resuscitation en route to hospital is performed by a single-handed operator in many British ambulances. In this study, three emergency ventilation devices, and mouth-to-mouth breathing, were compared for effectiveness in unintubated patients. Seventeen paramedics used each method on a Laerdal manikin in a randomised order, under identical conditions. Three experienced cardiopulmonary resuscitation instructors repeated the tests in a moving ambulance. There were significant differences in minute volume (p less than 0.01) and number of effective chest compressions (p less than 0.05); mouth-to-mouth breathing produced the best overall results and the simplest device was a close second. The value of automatic ventilators for single-operator cardiopulmonary resuscitation in unintubated patients is questioned.

A review of pre-hospital defibrillation by ambulance officers in Perth, Western Australia

Ventricular fibrillation (VF) is the most common presenting rhythm in cardiac arrest occurring outside hospitals. All cases of VF treated with a defibrillation-only protocol by ambulance officers were reviewed. Of the 231 cases entered into the study, 40 (22.7%) patients survived to 28 days after discharge from hospital. The proportion of survivors in this study is similar to that receiving full paramedic services. Further, where time to defribillation is short, the chance of survival improves. The key determinant in survival from VF occurring outside hospital appears to be how rapidly defibrillation can be initiated.

Survival rates from out-of-hospital cardiac arrest: recommendations for uniform definitions and data to report

Survival rates for out-of-hospital cardiac arrest vary widely among locations. We surveyed the definitions used in published studies of out-of-hospital cardiac arrest. Data from 74 studies involving 36 communities showed survival rates ranging from 2% to 44%. There were five different case definitions and 11 different definitions of survivors. The absence of uniform definitions prevents meaningful intersystem comparisons, prohibits explorations of hypotheses about effective interventions, and interferes with the efforts of quality assurance. The most satisfactory numerator for a survival rate appears to be survival to hospital discharge; the most appropriate denominator appears to be witnessed adult cardiac arrest of presumed heart disease etiology, with ventricular fibrillation as the initial identified rhythm. Proposed definitions for the data emergency medical services systems should report as they examine their cardiac arrest survival rates are presented.

Resuscitation of patients with cardiac arrest by ambulance staff with extended training in West Yorkshire

OBJECTIVE

To investigate the results of resuscitation of patients with cardiac arrest by ambulance staff with extended training in West Yorkshire.

DESIGN

Study of all such attempts at resuscitation over 32 months, based on the standard report form for each call made by the ambulance staff and the electrocardiogram that showed the initial rhythm in each patient.

SETTING

Area covered by West Yorkshire ambulance service.

SUBJECTS

1196 Patients with cardiac arrests attended by 29 ambulance staff with extended training.

MAIN OUTCOME MEASURE

Result of resuscitation.

RESULTS

The initial rhythm was asystole or electromechanical dissociation in 740 patients and ventricular fibrillation in 456 patients; overall 65 patients survived to be discharged from hospital. Sixty four of the 456 patients in whom ventricular fibrillation was the initial rhythm recorded, and 46 in whom ventricular fibrillation persisted after the ambulance staff arrived, survived. Only one of the 740 patients who initially had asystole or electromechanical dissociation survived. Factors associated with a greater chance of ventricular fibrillation occurring were: age less than 71, the arrest being witnessed by a bystander, resuscitation by a bystander, the arrest occurring in a public place, and a response time by the ambulance staff of less than six minutes. For patients found in ventricular fibrillation a shorter response time was associated with improved survival but resuscitation by a bystander was not. Additional skills learnt during extended training were used for 51 of the 65 patients who survived.

CONCLUSIONS

Ambulance staff with extended training can save the lives of patients with cardiac arrest due to fibrillation, though asystole and electromechanical dissociation have a poor prognosis and should perhaps receive little attention during extended training.

Early prediction of prognosis in out-of-hospital cardiac arrest

Of 347 victims of out-of-hospital cardiac arrest 196 (56.5%) died before and 109 (31.4%) after admission to hospital, while 42 patients (12.1%) were discharged alive. The 37 patients (10.7%) discharged without severe hypoxic brain damage were assigned to the group with "good", the remaining 310 patients to the group with "poor outcome". From results of stepwise logistic regression, a score was derived to specifically identify victims with poor prognosis (values in brackets = score points; cutpoint: score greater than 3 points): age less than or equal to 70 (0), 71-80 (1), greater than 80 (2); ECG ventricular fibrillation (0), other (1); no aspiration (0), aspiration (1); pupils round (0), not round (1); gasping (0), apnea (1); bystander resuscitation--yes (0), no (1). Evaluation of the score revealed a specificity of 100% (0.95 confidence interval: 80%-100%) and predictive value of 100% (0.95 confidence interval: 95%-100%). A predictive score for specific identification of victims with poor prognosis can contribute to decision making in out-of-hospital cardiac arrest.

The clinical rationale of cardiac resuscitation

After failure of external defibrillation, return of cardiac activity with spontaneous circulation is contingent on rapid and effective reversal of myocardial ischemia. Closed-chest cardiopulmonary resuscitation (CPR) evolved about 30 years ago and was almost universally implemented by both professional providers and lay bystanders because of its technical simplicity and noninvasiveness. However, there is growing concern since the limited hemodynamic efficacy of precordial compression accounts for a disappointingly low success rate; especially so if there is a delay of more than 3 minutes before resuscitation is started. There is also increasing concern with the lack of objective hemodynamic measurements currently available for the assessment and quantitation of the effectiveness of resuscitation efforts. Accordingly, the resuscitation procedure proceeds without confirmation that it increases systemic and myocardial blood flows to levels that would be likely to restore spontaneous circulation. Continuous monitoring of end-tidal carbon dioxide (PETCO2) now appears to be a practical measurement which provides a noninvasive quantitative indication of both systemic blood flow and coronary perfusion pressure. Consequently, PETCO2 predicts the likelihood of successful resuscitation and guides the operator who may modify the technique of precordial compression to improve systemic and myocardial perfusion. Among the large polypharmacy for cardiac resuscitation, only alpha-adrenergic agents (which increase coronary perfusion pressure) and especially epinephrine are of proven benefit. Neither buffer agents nor calcium salts appear to improve outcome except under unique conditions. To the contrary, there is increasing awareness of adverse effects of pharmacologic interventions such that they may hinder the return of viable myocardial and cerebral function. This has constrained the routine use of all drugs except for the use of alpha-adrenergic agonists. More invasive interventions by which blood flow is restored such as open-chest cardiac massage or extra-corporeal pump oxygenation (ECPO) are consistently more effective than conventional CPR. Experimentally, both methods promptly restore systemic and myocardial perfusion to viable levels and thereby increase the likelihood that spontaneous circulation is restored even after prolonged cardiac arrest or failure of conventional CPR.

Prehospital experience with defibrillation of coarse ventricular fibrillation: a ten-year review

Early defibrillation of patients with coarse ventricular fibrillation has been implicated as a predictor of survival in prehospital cardiac arrest. A retrospective study of our experience with prehospital defibrillation was conducted to define the relationship between rapid delivery of first countershock and survival, determine whether a relationship exists between the number of countershocks delivered and the save rate, and assist clinicians with general guidelines for termination of advanced life support efforts in the presence of ventricular fibrillation refractory to multiple defibrillation attempts. During the ten-year study period, adult, nontraumatic, nonpoisoned, witnessed arrests with an initial rhythm of coarse ventricular fibrillation were reviewed. Of 1,497 patients, 25% survived, 13% were paramedic-witnessed (PW) arrests, and 87% were non-paramedic-witnessed (NPW) arrests. The mean PW shock time, defined as time from arrest to first shock, was 1.6 +/- 3.7 minutes with a save rate of 37%. The mean NPW shock time was 10.2 +/- 5.1 minutes with a save rate of 23% (P less than or equal to .001). Thirty-two percent of PW arrests were converted to a spontaneous rhythm with pulses after the first countershock compared with 9% of NPW arrests (P less than or equal to .001). There was a dramatic decrease in PW arrests obtaining a perfusing rhythm after the first countershock attempt with each minute delay in electrical countershock up to three minutes; a plateau effect was evident after three minutes.(ABSTRACT TRUNCATED AT 250 WORDS)