Alfred P. Hallstrom

Predicting survival from out-of-hospital cardiac arrest: A graphic model

STUDY OBJECTIVE To develop a graphic model that describes survival from sudden out-of-hospital cardiac arrest as a function of time intervals to critical prehospital interventions. PARTICIPANTS From a cardiac arrest surveillance system in place since 1976 in King County, Washington, we selected 1,667 cardiac arrest patients with a high likelihood of survival: they had underlying heart disease, were in ventricular fibrillation, and had arrested before arrival of emergency medical services (EMS) personnel. METHODS For each patient, we obtained the time intervals from collapse to CPR, to first defibrillatory shock, and to initiation of advanced cardiac life support (ACLS). RESULTS A multiple linear regression model fitting the data gave the following equation: survival rate = 67%-2.3% per minute to CPR-1.1% per minute to defibrillation-2.1% per minute to ACLS, which was significant at P < .001. The first term, 67%, represents the survival rate if all three interventions were to occur immediately on collapse. Without treatment (CPR, defibrillatory shock, or definitive care), the decline in survival rate is the sum of the three coefficients, or 5.5% per minute. Survival rates predicted by the model for given EMS response times approximated published observed rates for EMS systems in which paramedics respond with or without emergency medical technicians. CONCLUSION The model is useful in planning community EMS programs, comparing EMS systems, and showing how different arrival times within a system affect survival rate.

Amiodarone for resuscitation after out-of-hospital cardiac arrest due to ventricular fibrillation.

Background Whether antiarrhythmic drugs improve the rate of successful resuscitation after out-of-hospital cardiac arrest has not been determined in randomized clinical trials. Methods We conducted a randomized, double-blind, placebo-controlled study of intravenous amiodarone in patients with out-of-hospital cardiac arrest. Patients who had cardiac arrest with ventricular fibrillation (or pulseless ventricular tachycardia) and who had not been resuscitated after receiving three or more precordial shocks were randomly assigned to receive 300 mg of intravenous amiodarone (246 patients) or placebo (258 patients). Results The treatment groups had similar clinical profiles. There was no significant difference between the amiodarone and placebo groups in the mean (±SD) duration of the resuscitation attempt (42±16 and 43±16 minutes, respectively), the number of shocks delivered (4±3 and 6±5), or the proportion of patients who required additional antiarrhythmic drugs after the administration of the study drug (66...

Cardiopulmonary resuscitation by chest compression alone or with mouth-to-mouth ventilation.

BACKGROUND Despite extensive training of citizens of Seattle in cardiopulmonary resuscitation (CPR), bystanders do not perform CPR in almost half of witnessed cardiac arrests. Instructions in chest compression plus mouth-to-mouth ventilation given by dispatchers over the telephone can require 2.4 minutes. In experimental studies, chest compression alone is associated with survival rates similar to those with chest compression plus mouth-to-mouth ventilation. We conducted a randomized study to compare CPR by chest compression alone with CPR by chest compression plus mouth-to-mouth ventilation. METHODS The setting of the trial was an urban, fire-department-based, emergency-medical-care system with central dispatching. In a randomized manner, telephone dispatchers gave bystanders at the scene of apparent cardiac arrest instructions in either chest compression alone or chest compression plus mouth-to-mouth ventilation. The primary end point was survival to hospital discharge. RESULTS Data were analyzed for 241 patients randomly assigned to receive chest compression alone and 279 assigned to chest compression plus mouth-to-mouth ventilation. Complete instructions were delivered in 62 percent of episodes for the group receiving chest compression plus mouth-to-mouth ventilation and 81 percent of episodes for the group receiving chest compression alone (P=0.005). Instructions for compression required 1.4 minutes less to complete than instructions for compression plus mouth-to-mouth ventilation. Survival to hospital discharge was better among patients assigned to chest compression alone than among those assigned to chest compression plus mouth-to-mouth ventilation (14.6 percent vs. 10.4 percent), but the difference was not statistically significant (P=0.18). CONCLUSIONS The outcome after CPR with chest compression alone is similar to that after chest compression with mouth-to-mouth ventilation, and chest compression alone may be the preferred approach for bystanders inexperienced in CPR.

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

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

Biobehavioral variables and mortality or cardiac arrest in the Cardiac Arrhythmia Pilot Study (CAPS)

The frequency of ventricular premature complexes and the degree of impairment of left ventricular ejection fraction are major predictors of cardiac mortality and sudden death in the year after acute myocardial infarction. Recent studies have implicated psychosocial factors, including depression, the interaction of social isolation and life stress, and type A-B behavior pattern, as predictors of cardiac events, controlling for known parameters of disease severity. However, results tend not to be consistent and are sometimes contradictory. The present investigation was designed to test the predictive association between biobehavioral factors and clinical cardiac events. This evaluation occurred in the context of a prospective clinical trial, the Cardiac Arrhythmia Pilot Study (CAPS). Five-hundred two patients were recruited with greater than or equal to 10 ventricular premature complexes/hour or greater than or equal to 5 episodes of nonsustained ventricular tachycardia, recorded 6 to 60 days after a myocardial infarction. Baseline behavioral studies, conducted in approximately 66% of patients, included psychosocial questionnaires of anxiety, depression, social desirability and support, and type A-B behavior pattern. In addition, blood pressure and pulse rate reactivity to a portable videogame was assessed. The primary outcome was scored on the basis of mortality or cardiac arrest. Results indicated that the type B behavior pattern, higher levels of depression and lower pulse rate reactivity to challenge were significant risk factors for death or cardiac arrest, after adjusting statistically for a set of known clinical predictors of disease severity. The implication of these results for future research relating behavioral factors to cardiac endpoints is discussed.

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

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

Factors influencing survival after out-of-hospital cardiac arrest.

Survival to hospital discharge was related to the clinical history and emergency care system factors in 285 patients with witnessed cardiac arrest due to ventricular fibrillation. Only the emergency care factors were associated with differences in outcome. Both the period from collapse until initiation of basic life support and the duration of basic life support before delivery of the first defibrillatory shock were shorter in patients who survived compared with those who died (3.6 +/- 2.5 versus 6.1 +/- 3.3 minutes and 4.3 +/- 3.3 versus 7.3 +/- 4.2 minutes; p less than 0.05). A linear regression model based on emergency response times for 942 patients discovered in ventricular fibrillation was used to estimate expected survival rates if the first-responding rescuers, in addition to paramedics, had been equipped and trained to defibrillate. Expected survival rates were higher with early defibrillation (38 +/- 3%; 95% confidence limits) than the observed rate (28 +/- 3%). Because outcome from cardiac arrest is primarily influenced by delays in providing cardiopulmonary resuscitation and defibrillation, factors affecting response time should be carefully examined by all emergency care systems.

Bystander-Initiated Cardiopulmonary Resuscitation in the Management of Ventricular Fibrillation

We assessed the influence of bystander-initiated cardiopulmonary resuscitation upon outcome in 316 consecutive patients treated for out-of-hospital ventricular fibrillation. Of 109 patients who received bystander-initiated cardiopulmonary resuscitation, 47 (43%) were ultimately discharged home. Of 207 patients for whom resuscitation was delayed until arrival of fire department personnel, 43 (21%) survived (P less than 0.001). Improved survival was largely due to a reduction in subsequent hospital mortality rather than to a higher rate of initially effective resuscitation. In a separate analysis of 118 patients treated at a single institution after resuscitation, the reduced hospital mortality reflected a decrease in deaths due to shock and to anoxic encephalopathy. In addition, neurologic dysfunction was significantly less common if bystanders had initiated cardiopulmonary resuscitation. Bystander participation in cardiopulmonary resuscitation represents an important adjunct to a rapid-response emergency care system.

Automatic External Defibrillators for Public Access Defibrillation: Recommendations for Specifying and Reporting Arrhythmia Analysis Algorithm Performance, Incorporating New Waveforms, and Enhancing Safety A Statement for Health Professionals From the American Heart Association Task Force on Automatic External Defibrillation, Subcommittee on AED Safety and Efficacy

These recommendations are presented to enhance the safety and efficacy of AEDs intended for public access. The task force recommends that manufacturers present developmental and validation data on their own devices, emphasizing high sensitivity for shockable rhythms and high specificity for nonshockable rhythms. Alternative defibrillation waveforms may reduce energy requirements, reducing the size and weight of the device. The highest levels of safety for public access defibrillation are needed. Safe and effective use of AEDs that are widely available and easily handled by nonmedical personnel has the potential to dramatically increase survival from cardiac arrest.

Myocardial infarction triage and intervention project—Phase I: Patient characteristics and feasibility of prehospital initiation of thrombolytic therapy☆

Prehospital initiation of thrombolytic therapy by paramedics, if both feasible and safe, could considerably reduce the time to treatment and possibly decrease the extent of myocardial necrosis in patients with acute coronary thrombosis. Preliminary to a trial of such a treatment strategy, paramedics evaluated the characteristics of 2,472 patients with chest pain of presumed cardiac origin; 677 (27%) had suitable clinical findings consistent with possible acute myocardial infarction and no apparent risk of complication for potential thrombolytic drug treatment. Electrocardiograms (ECGs) of 522 of the 677 patients were transmitted by cellular telephone to a base station physician; 107 (21%) of the tracings showed evidence of ST segment elevation. Of the total 2,472 patients, 453 developed evidence of acute myocardial infarction in the hospital; 163 (36%) of the 453 had met the strict prehospital screening history and examination criteria and 105 (23.9%) showed ST elevation on the ECG and, thus, would have been suitable candidates for prehospital thrombolytic treatment if it had been available. The average time from the onset of chest pain to prehospital diagnosis was 72 +/- 52 min (median 52); this was 73 +/- 44 min (median 62) earlier than the time when thrombolytic treatment was later started in the hospital. Paramedic selection of appropriate patients for potential prehospital initiation of thrombolytic treatment is feasible with use of a directed checklist and cellular-transmitted ECG and saves time. This strategy may reduce the extent and complications of infarction compared with results that can be achieved in a hospital setting.