Factors influencing survival after out-of-hospital cardiac arrest

Integration of ambulance staff trained in cardiopulmonary resuscitation with a medical team providing prehospital coronary care

Ambulance staff with advanced training in cardiopulmonary resuscitation and equipped with monitor/defibrillators were used as the initial responders to collapse calls within a medically based prehospital coronary care system. During 21 months, in a population of approximately 120,000, ambulance staff successfully resuscitated six patients from ventricular fibrillation; there were four long term survivors. The median response time of emergency ambulances to collapse calls was eight minutes compared with 20 minutes for the medically manned mobile coronary care unit. None of the patients resuscitated by ambulance staff would have survived if they had been dependent on the mobile coronary care unit acting alone. Nineteen other patients with important arrhythmias were referred for earlier medical management which in some cases may have saved lives. An additional eight long term survivors of out of hospital ventricular fibrillation were resuscitated by medical staff. The integration of paramedical with medical prehospital coronary care improved survival after out of hospital cardiac arrest.

From concept to standard-of-care? Review of the clinical experience with automated external defibrillators

There is now both national and international acceptance of the "principle of early defibrillation," which contends that whoever arrives first at the scene of a cardiac arrest should have a defibrillator. The almost revolutionary technological event that permits widespread implementation of this principle has been the development of automated external defibrillators (AEDs). The simplicity, accuracy, and safety of these devices markedly expands the range of people who can deliver early defibrillation, which includes minimally trained emergency personnel, lay and community responders, and family members of high-risk patients. Even though AEDs now approach the status of "standard of care," the AED, as an example of a new technology, has not followed the classic technology paradigm: conceptualization, experimentation, dissemination, and standard of care. Instead, like many other technical innovations in emergency medicine, the development of AEDs proceeded simultaneously on many fronts, and implementation often occurred before confirmation of important subissues. AEDs may experience the life cycle of many new ideas: initial enthusiasm and widespread adoption, followed by disillusionment and rejection, and finally a mature, proper perspective. Careful implementation and continued evaluation may help emergency personnel avoid periods of disillusionment with AEDs and move steadily and uneventfully to a proper perspective.

Neurological damage in a cardiopulmonary arrest model in the rat

In view of the interest in cerebral protection in the framework of cardiopulmonary arrest (CPA), we assessed the neurological damage in a CPA model in the rat. CPA was induced in anesthetized Wistar rats by discontinuation of the jet ventilation and intracardiac injection of KCl. The animals were resuscitated after a CPA of either 7 min, 10.5 min, or 14 min. Six rats were used as nonischemic controls. All nonischemic rats survived, whereas in the resuscitated rats the 7-day survival rate decreased with increasing CPA duration. In the resuscitated rats, the neurological score was worse than in the control rats, and the score after 10.5-min CPA was worse than after 7-min CPA. Seizures were observed in 68% of resuscitated rats. Histopathological evaluation revealed moderate but selective neuronal necrosis in the hippocampus of all ischemic rats, and no cortical necrosis. However, neither the occurrence of seizures nor the extent of neuronal necrosis was related to the CPA duration. We conclude that in this model survival rate, neurological score, occurrence of seizures, and histopathological assessment can be used to evaluate neurological damage, although the contribution of other organ failure to these effects cannot be excluded.

Dispatcher-assisted cardiopulmonary resuscitation. Validation of efficacy

Dispatcher-delivered telephone instruction in cardiopulmonary resuscitation (CPR) has been proposed to increase rates of bystander CPR in cases of out-of-hospital cardiac arrest. We tested the efficacy of a previously developed CPR message using a recording mannikin in a high stress, simulated cardiac arrest scenario. Community volunteers were unaware they would perform CPR until immediately before each trial. Performance of volunteers without prior CPR training (group A, n = 65) who received telephone instruction was compared with that of previously trained volunteers (group B, n = 43) who received the same message. Performances of both groups were also compared with a third group (group C, n = 43) composed of previously trained volunteers who did not receive the message. Quality of CPR was graded by three CPR instructors using explicit criteria. Printout strips from the recording mannikins were also analyzed. Evaluators were unaware of the training status of volunteers. The three groups were of comparable sex, race, and educational level, but group C was significantly younger than groups A and B (31.7 vs. 37.7 years, p less than 0.001). Because of the time required for telephone instruction, groups A and B started chest compressions a mean of 4.0 minutes after collapse compared with 1.2 minutes for group C (p less than 0.0001). We found that the previously untrained volunteers of group A performed CPR of an overall quality comparable to that performed by previously trained members of group C. Group A performed chest compressions significantly better than group C (p less than 0.02) but had greater problems performing effective ventilations.(ABSTRACT TRUNCATED AT 250 WORDS)

Experience with a mobile coronary care unit in Brisbane

We examined the performance of a hospital-based mobile coronary care unit staffed by emergency physicians, coronary care nurses, and ambulance personnel in a metropolitan setting (Brisbane, Australia). Our unit attended 2,260 calls during 18 months of operation. Standard dispatched ambulances arrived first to 78% of the 2,260 calls. Ten percent of these calls were to patients who had died or had arrested; 45% of these patients were found in ventricular fibrillation and 10% were discharged alive from the hospital. Survival was related to the performance of CPR before the arrival of the unit and to the finding of ventricular fibrillation. As the success of our unit was clearly inferior to that reported from centers where the first-responders are licensed to defibrillate, its operations have ceased and regular ambulance crews are being taught to recognize and treat patients with ventricular fibrillation.

One year's experience of early defibrillation in Stockholm

The effects of resuscitation on patients who died suddenly out of hospital were evaluated after the introduction of early defibrillation performed by ambulance personnel using semi-automatic defibrillators. Resuscitation attempts were initiated in 548 patients during the 1-year study period. Mean ambulance delay was 7.5 min, 22% of the cardiac arrest patients had received bystander cardiopulmonary resuscitation (CPR). Sensitivity and specificity for the semi-automatic defibrillator in the interpretation of ventricular fibrillation was found to be 97 and 100% respectively. Only 28 (14%) of the 206 defibrillated patients regained circulation and were admitted for further hospital care. Only three survived to be discharged. Among the 342 patients in whom defibrillation was not indicated, 16 (5%) regained circulation and were admitted for further hospital care and one (0.3%) survived to be discharged. Semi-automatic defibrillators seem reliable, safe and inexpensive; however, the isolated addition of defibrillation to basal ambulance service seems to be inadequate in Stockholm. We need to evaluate what further resources are of importance to guarantee a successful outcome.

Time to defibrillation: a controlled laboratory study comparing three automated and semi-automated defibrillators

Currently there are three vendors marketing first-responder defibrillation units. Each vendor's unit has its own distinct features, advantages, and disadvantages, making the selection of one vendor's unit a complex decision. However, two critical performance criteria upon which a decision to choose one vendor's unit over another could be 1) differences in dysrhythmia recognition sensitivity and specificity and 2) time to delivery of a defibrillation shock. While there appears to be evidence suggesting no significant differences between the three units in terms of dysrhythmia recognition, there do not appear to be any controlled 'time-to-defibrillation' studies. The purpose of this study was to determine if, under controlled conditions, any performance differences existed between these three units in time to delivery of a defibrillation shock. The results of this study suggest that there are no pragmatic differences between the three defibrillation units. In the absence of time-to-defibrillation differences, EMS systems managers can place more emphasis on other features so as to better address the needs, concerns, and resources of their system.

Emergency medical care requirements for large public assemblies and a new strategy for managing cardiac arrest in this setting

During the 1986 World's Exposition held in Vancouver, British Columbia, the types and frequencies of emergency medical problems were assessed. The average number of patients seeking care was 3.93 +/- 0.95 per 1,000 visitors (daily range, 1.94 to 6.8). Patient loads were linearly related to gate attendance, but the correlation was imperfect (P less than .001, r = .63). Only 4.4% of patients evaluated on site by nurses and paramedics were referred for additional testing and treatment: of these patients, 30% had suspected serious musculoskeletal injury, 16% had abdominal pain, and 25% had complaints of chest pain, dizziness, or loss of consciousness. Lay employees (security personnel) were trained to use automatic external defibrillators. There were six cardiac arrests (0.3 per million visitors). Two patients collapsed with ventricular fibrillation, were defibrillated by lay personnel, quickly regained consciousness, and survived. The other arrests were associated with asystole or electromechanical dissociation; no shocks were inappropriately given, and all four died. We conclude that four of every 1,000 persons at this assembly sought emergency medical care, that 95% of the problems seen were minor with few requiring physician skills, and that the automatic external defibrillator was suited for this setting and could be used by lay responders to provide early definitive treatment.

Bystander cardiopulmonary resuscitation (CPR) in out-of-hospital cardiac arrest. The Cerebral Resuscitation Study Group

Prevalence of bystander CPR and effect on outcome has been evaluated on 3053 out-of-hospital cardiac arrest (CA) events. Bystander CPR was performed in 33% of recorded cases (n = 998) by lay people in 406 cases (family members 178, other lay people 228) and by bystanding health care workers in 592 cases (nurses 86, doctors 506). Family members and lay people mainly applied CPR in younger CA victims at public places, roadside or at the working place. Sudden infant death syndrome (SIDS) and drowning are highly represented. Health care workers performed CPR mainly in older patients, at public places or at the roadside and especially in case of cardiac or respiratory origin. CA caused by trauma/exsanguination and intoxication/metabolic origin received less bystander CPR (23% resp. 22%). Cardiac arrests receiving bystander CPR are more frequently witnessed and have a shorter access time to the emergency medical service (EMS) system and shorter response time of basic life support (BLS). Advanced life support (ALS) response time is significantly longer. In witnessed arrests of cardiac origin receiving bystander CPR a significantly better late survival was observed. In non-witnessed arrests of cardiac origin early and late survival are significantly higher in patients receiving bystander CPR. In CA events where response time of ALS exceeds 8 min, the beneficial effect of bystander CPR is most significant. Furthermore no deleterious effect of bad technique or inefficient bystander CPR can be demonstrated.

Pre-CPR conditions and the final outcome of CPR. The Cerebral Resuscitation Study Group

Outcome of cardiac arrest (CA) is very much influenced by pre-CPR conditions. To assess the importance of these pre-CPR factors, an analysis of the Belgian CPCR registry was made according to some pre-CPR conditions. In this registry, several variables related to pre-arrest, arrest, CPR and post CPR period have been recorded in 4548 patients. The pre-CPR conditions studied were: age, witnessed event or not, pre-arrest health state, underlying disease, site of cardiac arrest, type of respiratory arrest and type of cardiac arrest. Age did not influence outcome significantly. The importance of witnessing is very significant. Severe pre-arrest disability reduces chances on long-term survival (LTS) to half and overall health status longterm survivors is clearly less. Intoxication and metabolic origin of CA have good prognosis (LTS, 21%). Trauma/exsanguination, drowning, SIDS and sepsis have bad prognosis (LTS, 1-3%). Cardiac (LTS, 12%) and respiratory (LTS, 14%) origin have similar outcome, although significant difference exists in occurrence of cerebral failure, suggesting that post-ischemic encephalopathy is more severe in respiratory than in cardiac origin. The most frequent site of CA, the home of the patient, has poor outcome results (LTS, 5%). Gasping is significantly related to successful outcome. In the out-of-hospital setting the type of CA was 25% VF (LTS, 77%), 65% asystole (LTS, 4%) and 10% EMD (LTS, 3%). Outcome of the subgroup out-of-hospital, witnessed, VF is comparable to other reports. This sub-group seems to us the most appropriate for clinical trials.

The effects of a transtelephonic surveillance and prehospital emergency intervention system on the 1-year course following acute myocardial infarction

We evaluated the effect on morbidity and mortality of a post-myocardial infarction management and intervention system. One thousand four patients were prospectively randomized to an intervention group that included routine and emergency transtelephonic follow-up and ECG monitoring or to control; all subjects were followed for 1 year. For symptoms suggestive of myocardial ischemia, intervention patients telephoned the project emergency office, were instructed by a project nurse to self-administer intramuscular lidocaine with an auto-injector, and were then transported to the nearest emergency facility. Cardiac death or arrest was decreased 29% in intervention patients (p = 0.066), while all-cause mortality was decreased by 24% (p less than 0.11). Routine transtelephonic ECG monitoring detected ventricular ectopy in 48% of intervention patients, with almost 50% of these findings classified as complex forms. Ventricular ectopy detected during routine calls within 60 days of the acute myocardial infarction conferred a threefold increase in mortality (p = 0.001). In addition, control patients were 2.4 times more likely to be clinically depressed (p less than 0.03) and returned to work less quickly (p less than 0.03) when compared to intervention patients. Lidocaine injections were associated with an absence of ventricular ectopy on arrival at the Emergency Room in 64% and with a low incidence of lidocaine-associated side effects. There was only one case of unauthorized use of the self-injector. These findings demonstrate that an outpatient post-myocardial infarction transtelephonic surveillance program can be safely and effectively conducted, can detect complex ventricular arrhythmias of prognostic significance, can improve the quality of life, and may reduce 1-year cardiac mortality.

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

The automatic external defibrillator is a simple device that can be used by nonprofessional rescuers to treat cardiac arrest. In 1287 consecutive patients with out-of-hospital cardiac arrest, we assessed the results of initial treatment with this device by firefighters who arrived first at the scene, as compared with the results of standard defibrillation administered by paramedics who arrived slightly after the firefighters. Of 276 patients who were initially treated by firefighters using the automatic defibrillator, 84 (30 percent) survived to hospital discharge (expected rate according to a logistic model, 17 percent; P less than 0.001), as compared with 44 (19 percent) of 228 patients when fire-fighters delivered only basic cardiopulmonary resuscitation and the first defibrillation was performed after the arrival of the paramedic team. Few patients with conditions other than ventricular fibrillation survived. In a multivariate analysis of characteristics that influenced survival after ventricular fibrillation, a better survival rate was related to a witnessed collapse (odds ratio, 3.9; 95 percent confidence interval, 2.0 to 7.6), younger age (odds ratio, 1.2; 95 percent confidence interval, 1.0 to 1.4), the presence of "coarse" (higher-amplitude) fibrillation (odds ratio, 4.2; 95 percent confidence interval, 1.6 to 11.0), a shorter response time for paramedics (odds ratio, 1.4; 95 percent confidence interval, 1.0 to 2.1), and initial treatment by firefighters using an automatic external defibrillator (odds ratio, 1.8; 95 percent confidence interval, 1.1 to 2.9). These findings support the widespread use of the automatic external defibrillator as an important part of the treatment of out-of-hospital cardiac arrest, although the overall impact of the use of this device on community survival rates is still uncertain.

New perspectives on rural EMT defibrillation

In recent years, several studies have produced contradictory data regarding the impact of emergency medical technicians trained in defibrillation on hospital admission and dismissal survival rates in rural areas. Fourteen communities (service area populations, 4,000 to 36,000) in rural south-eastern Minnesota participated in a two-year crossover study to further define the factors necessary for success. Automatic external defibrillators were used to defibrillate and record patient rhythms in the treatment group and to only record in the control group. Although six of 36 patients (17%) in ventricular fibrillation who experienced a witnessed arrest survived in communities using automatic external defibrillators, compared with one of 27 (4%) in the control group, five of the six survivors were from a single large community with a 911 system, full-time emergency medical technicians, police first-responders, and a well-equipped emergency facility. Our data suggest that certain prerequisites, especially CPR prior to ambulance arrival and collapse to defibrillation times of less than ten minutes, are clearly essential to produce significant benefits from emergency medical technicians trained in defibrillation in rural communities.

Successful resuscitation of an elderly patient following cardiac arrest: possible role of reduction of reactive oxygen

The presence of hyperoxia during reperfusion following brain ischemia has been shown in experimental animals to result in increased mortality and increased lipid peroxidation. Although no human studies have been reported, prolonged hyperoxia after resuscitation from cardiac arrest probably would result in increased cerebral injury. We report the case of an 88-year-old man who had a 5- to 6-minute cardiac arrest and then had decerebrate posturing during the post-resuscitation period, indicating that he had suffered a significant ischemic/anoxic insult. Early attention was paid to normalizing the arterial Po2 following resuscitation, which, according to experimental evidence, contributed to his eventual complete recovery of neurologic function, including mental state.

Automatic external defibrillators: importance of field testing to evaluate performance

A new automatic external defibrillator was tested first against a tape-recorded data base of rhythms and then during use by first-responding fire fighters in a tiered emergency system. The sensitivity for correctly classifying ventricular fibrillation and ventricular tachycardia was substantially less during clinical testing in 298 patients than would have been predicted from preclinical results: 52% of ventricular fibrillation analyses in patients were correctly classified versus 88% of episodes in the data base, and 22 versus 86%, respectively, for ventricular tachycardia (p less than 0.001). The detection algorithm was modified and evaluated further in another 322 patients. The modified detector performed substantially better than did the one that had been designed from prerecorded rhythms: with its use, 118 (94%) of 125 patients in ventricular fibrillation were counter-shocked compared with 91 (77%) of 118 similar patients with use of the initial algorithm (p less than 0.001). No inappropriate shocks were delivered. This improvement resulted in a shorter time to first shock (p less than 0.01) and more shocks being delivered for persistent or recurrent episodes of ventricular fibrillation (p less than 0.05). Of 620 patients treated with the automatic defibrillator, 243 (39%) had ventricular fibrillation; 57 (23%) of the 243 regained pulse and blood pressure before paramedics arrived, 141 (58%) were admitted to hospital and 71 (29%) were discharged.(ABSTRACT TRUNCATED AT 250 WORDS)

Experience with an automatic external defibrillator

One emergency ambulance serving an urban part of the greater Stockholm area was equipped with a semi-automatic defibrillator Life Pack 200 Physio Control during an 8-month study period. The equipment advises the user whether defibrillation is required or not, and in cases of detected ventricular fibrillation, defibrillation is advised. The user then has to press a button to defibrillate through the same electrodes that record the electrocardiogram. A built-in tape recorder was used for documentation of the underlying rhythm disturbance. In all, advice was requested 332 times. Accuracy in interpretation of ventricular fibrillation was found to be high. The sensitivity and specificity in interpretation of ventricular fibrillation were 93% and 100%, respectively. No defibrillations were performed in patients without ventricular fibrillation. All instances of ventricular fibrillation were converted to another rhythm or asystole. Seven percent of the patients with cardiac arrest caused by ventricular fibrillation survived.

Self-adhesive monitor/defibrillation pads improve prehospital defibrillation success

We compared self-adhesive, dual-function monitor/defibrillation electrode pads to standard chest monitoring leads and hand-held electrode paddles in the management of prehospital ventricular fibrillation in a single urban paramedic service. Shocks were delivered more quickly following paramedic arrival with self-adhesive pads than with hand-held paddles (1.6 vs 2.5 min; P less than .001). Ventricular fibrillation was terminated more frequently when shocks were delivered using the self-adhesive pads (55 of 58 patients, 95%) than when shocks were delivered using hand-held paddles (49 of 69 patients, 71%; P less than .005). Initial shocks delivered with self-adhesive pads were especially effective, converting 40 of 58 (69%) patients to an organized rhythm on the first or second shock; this was true of only 24 of 69 (35%) patients shocked with hand-held paddles (P less than .001). Patient survival to hospital admission improved when self-adhesive pads were used: 30 of the 58 (52%) patients shocked with self-adhesive pads achieved hospital admission, while only 21 of 69 patients (30%; P less than .025) survived to admission when hand-held paddles were used. In addition, electrical artifact that interfered with accurate rhythm interpretation was far more prevalent when standard monitoring electrodes were used, including artifact that resulted in inappropriate shock delivery (23% of patients monitored with standard electrodes vs 3% of patients monitored with self-adhesive pads; P less than .005). Self-adhesive monitor/defibrillation pads are superior to standard monitoring leads and hand-held electrode paddles in the management of prehospital ventricular fibrillation.

Cost of a saved life following out-of-hospital cardiac arrest resuscitated by specially trained ambulance personnel

During a 1-year-study period three emergency ambulances manned by specially trained emergency medical technicians (EMTs) were successful in the resuscitation of 28 out-of-hospital cardiac arrest patients, who were admitted to hospital for further treatment. Nineteen patients died in hospital while nine were discharged to their homes, a survival rate corresponding to 3.5 saved lives per 100,000 inhabitants per year. The extra pre-hospital costs and the estimated costs for hospital treatment of the admitted patients amounted to 929,600 Swedish kronor (SEK). The program cost of the early defibrillation by trained EMTs accounted for only 12% of this amount, or 113,600 SEK. The cost of hospital treatment accounted for the remaining 88%, or 816,000 SEK. Intensive care accounted for 53% of the hospital costs, coronary care 4%, treatment in a general ward 33% and in a ward for rehabilitation or long-term care 10%. Non-survivors accounted for 58% of the hospital expenditure. The marginal prehospital cost (program cost) for each survivor was 12,622 SEK or approximately 1800 US dollars. The total cost per life saved was 103,000 SEK or approximately 14,700 US dollars. The estimated cost to each taxpayer of providing this extra emergency resource would be approximately 0.5 SEK a year.