Bystander/first responder CPR: ten years experience in a paramedic system

Analyzing the Effectiveness of Different Forms of Cardiopulmonary Resuscitation

BACKGROUND

In order to simulate a heartbeat in a cardiac arrest patient, cardiopulmonary resuscitation (CPR) requires that chest compressions be delivered with a force of at least 560 N at a rate >100 compressions/min. Many new learners initially use CPR forms that may not meet these parameters sufficiently. We examined three forms of CPR: the form recommended by the American Heart Association (AHA) and two forms that are common among new learners but that are considered incorrect, using a CPR manikin placed on a force plate. Four trained CPR users tested the different methods.

DISCUSSION

AHA-recommended CPR is the most effective, delivering a force of 737.2 ± 5.3 N at a rate of 103.2 ± 1.2 compressions/min. Compressions using a bent arms method delivered compressions with a force of 511.8 ± 4.1 N at a rate of 112.8 ± 3.0 compressions/min. Compressions using a different hand position from that recommended by the AHA delivered compressions with a force of 433.3 ± 3.2 N at a rate of 115.2 ± 1.2 compressions/min.

CONCLUSIONS

AHA-recommended CPR more effectively compresses a patient's heart than the bent-arms method or the alternate hand-position method, and, of the three methods, only the AHA-recommended form can reliably simulate a patient's heartbeat.

Outcomes following cardiopulmonary resuscitation in an emergency department of a low- and middle-income country

BACKGROUND

Cardiopulmonary resuscitation (CPR) is a key component of emergency care following cardiac arrest. A better understanding of factors that influence CPR outcomes and their prognostic implications would help guide care. A retrospective analysis of 800 adult patients that sustained an in- or out-of-hospital cardiac arrest and underwent CPR in the emergency department of a tertiary care facility in Karachi, Pakistan, between 2008 and 15 was conducted.

METHODS

Patient demographics, clinical history, and CPR characteristics data were collected. Logistic regression model was applied to assess predictors of return of spontaneous circulation and survival to discharge. Analysis was conducted using SPSS v.21.0.

RESULTS

Four hundred sixty-eight patients met the study's inclusion criteria, and overall return of spontaneous circulation and survival to discharge were achieved in 128 (27.4%) and 35 (7.5%) patients respectively. Mean age of patients sustaining return of spontaneous circulation was 52 years and that of survival to discharge was 49 years. The independent predictors of return of spontaneous circulation included age ≤ 49 years, witnessed arrest, ≤ 30 min interval between collapse-to-start, and 1-4 shocks given during CPR (aOR (95% CI) 2.2 (1.3-3.6), 1.9 (1.0-3.7), 14.6 (4.9-43.4), and 3.0 (1.4-6.4) respectively), whereas, age ≤ 52 years, bystander resuscitation, and initial rhythm documented (pulseless electrical activity and ventricular fibrillation) were independent predictors of survival to discharge (aOR (95% CI) 2.5 (0.9-6.5), 1.4 (0.5-3.8), 5.3 (1.5-18.4), and 3.1 (1.0-10.2) respectively).

CONCLUSION

Our study notes that while the majority of arrests occur out of the hospital, only a small proportion of those arrests receive on-site CPR, which is a key contributor to unfavorable outcomes in this group. It is recommended that effective pre-hospital emergency care systems be established in developing countries which could potentially improve post-arrest outcomes. Younger patients, CPR initiation soon after arrest, presenting rhythm of pulseless ventricular tachycardia and ventricular fibrillation, and those requiring up to four shocks to revive are more likely to achieve favorable outcomes.

Pneumothorax During CPR Training: Case Report and Review of the CPR Literature

Cardiopulmonary resuscitation is taught widely to both lay persons and health care oworkers. It is a challenging psychomotor skill. Concerns about its safety to the rescuer have centered around the risk of infectious disease exposure. A young nursing assistant developed a minimally symptomatic pneumothorax during CPR training. This case is the first reported example of this complication for a CPR trainee or provider. The literature is reviewed for complications for CPR provider and recipient and the relevant issues regarding the current status and future direction of this intervention.

Paramedic and emergency medical technicians views on opportunities and challenges when forgoing and halting resuscitation in the field

OBJECTIVES

The objective was to assess paramedic and emergency medical technicians (EMT) perspectives and decision-making after a policy change that allows forgoing or halting resuscitation in prehospital atraumatic cardiac arrest.

METHODS

Five semistructured focus groups were conducted with 34 paramedics and 2 EMTs from emergency medical services (EMS) agencies within Los Angeles County (LAC), 6 months after a policy change that allowed paramedics to forgo or halt resuscitation in the field under certain circumstances.

RESULTS

Participants had an overwhelmingly positive view of the policy; felt it empowered their decision-making abilities; and thought the benefits to patients, family, EMS, and the public outweighed the risks. Except under certain circumstances, such as when the body was in public view or when family members did not appear emotionally prepared to have the body left on scene, they felt the policy improved care. Assuming that certain patient characteristics were present, decisions by paramedics about implementing the policy in the field involve many factors, including knowledge and comfort with the new policy, family characteristics (e.g., agreement), and logistics regarding the place of arrest (e.g., size of space). Paramedic and EMT experiences with and attitudes toward forgoing resuscitation, as well as group dynamics among EMS leadership, providers, police, and ED staff, also play a role.

CONCLUSIONS

Participants view the ability to forgo or halt resuscitation in the field as empowering and do not believe it presents harm to patients or families under most circumstances. Factors other than patient clinical characteristics, such as knowledge and attitudes toward the policy, family emotional preparedness, and location of arrest, affect whether paramedics will implement it.

Clinical evaluation of an inspiratory impedance threshold device during standard cardiopulmonary resuscitation in patients with out-of-hospital cardiac arrest*

OBJECTIVE

To determine whether an impedance threshold device, designed to enhance circulation, would increase acute resuscitation rates for patients in cardiac arrest receiving conventional manual cardiopulmonary resuscitation.

DESIGN

Prospective, randomized, double-blind, intention-to-treat.

SETTING

Out-of-hospital trial conducted in the Milwaukee, WI, emergency medical services system.

PATIENTS

Adults in cardiac arrest of presumed cardiac etiology.

INTERVENTIONS

On arrival of advanced life support, patients were treated with standard cardiopulmonary resuscitation combined with either an active or a sham impedance threshold device.

MEASUREMENTS AND MAIN RESULTS

We measured safety and efficacy of the impedance threshold device; the primary end point was intensive care unit admission. Statistical analyses performed included the chi-square test and multivariate regression analysis. One hundred sixteen patients were treated with a sham impedance threshold device, and 114 patients were treated with an active impedance threshold device. Overall intensive care unit admission rates were 17% with the sham device vs. 25% in the active impedance threshold device (p = .13; odds ratio, 1.64; 95% confidence interval, 0.87, 3.10). Patients in the subgroup presenting with pulseless electrical activity had intensive care unit admission and 24-hr survival rates of 20% and 12% in sham (n = 25) vs. 52% and 30% in active impedance threshold device groups (n = 27) (p = .018, odds ratio, 4.31; 95% confidence interval, 1.28, 14.5, and p = .12, odds ratio, 3.09; 95% confidence interval, 0.74, 13.0, respectively). A post hoc analysis of patients with pulseless electrical activity at any time during the cardiac arrest revealed that intensive care unit and 24-hr survival rates were 20% and 11% in the sham (n = 56) vs. 41% and 27% in the active impedance threshold device groups (n = 49) (p = .018, odds ratio, 2.82; 95% confidence interval, 1.19, 6.67, and p = .037, odds ratio, 3.01; 95% confidence interval, 1.07, 8.96, respectively). There were no statistically significant differences in outcomes for patients presenting in ventricular fibrillation and asystole. Adverse event and complication rates were also similar.

CONCLUSIONS

During this first clinical trial of the impedance threshold device during standard cardiopulmonary resuscitation, use of the new device more than doubled short-term survival rates in patients presenting with pulseless electrical activity. A larger clinical trial is underway to determine the potential longer term benefits of the impedance threshold device in cardiac arrest.

Cost-effectiveness of training unselected laypersons in cardiopulmonary resuscitation and defibrillation

PURPOSE

The cost-effectiveness of cardiopulmonary resuscitation (CPR) and defibrillation training for laypersons unselected for risk of encountering cases of cardiac arrest is not known. We compared the costs and health benefits of alternative resuscitation training strategies for adults without professional first-responder duties who are at average risk of encountering cases of out-of-hospital cardiac arrest.

METHODS

We constructed a cost-effectiveness analytic model. Data on cardiac arrest epidemiology and the effectiveness of CPR/defibrillation training were obtained from the medical literature. Instructional costs were determined from a survey of training programs. Downstream cardiac arrest survivor quality-adjusted life expectancy and long-term health care costs were derived from prior studies. We compared three strategies for training unselected laypersons: CPR/defibrillation training alone, training combined with home defibrillator purchase, and no training. The main outcome measures were total instructional costs for trainees combined with health care costs for additional cardiac arrest survivors, and quality-adjusted survival for additional patients resuscitated by trainees.

RESULTS

CPR/defibrillation training yielded 2.7 quality-adjusted hours of life at a cost of 62 US dollars per trainee (202,400 US dollars per quality-adjusted life-year [QALY] gained). Training laypersons in CPR/defibrillation with subsequent defibrillator purchase cost 2,489,700 US dollars per QALY. In contrast, CPR/defibrillation training cost less than 75,000 US dollars per QALY if trainees lived with persons older than 75 years or with persons who had cardiac disease, or if total training costs were less than 10 US dollars.

CONCLUSION

Training unselected laypersons in CPR/defibrillation is costly compared with other public health initiatives. Conversely, training laypersons selected by occupation, low training costs, or having high-risk household companions is substantially more efficient.

Death by hyperventilation: A common and life-threatening problem during cardiopulmonary resuscitation

CONTEXT

This translational research initiative focused on the physiology of cardiopulmonary resuscitation (CPR) initiated by a clinical observation of consistent hyperventilation by professional rescuers in out-of-hospital cardiac arrest. This observation generated scientific hypotheses that could only ethically be tested in the animal laboratory.

OBJECTIVE

To examine the hypothesis that excessive ventilation rates during performance of CPR by overzealous but well-trained rescue personnel causes a significant decrease in coronary perfusion pressure and an increased likelihood of death.

DESIGN AND SETTING

In the in vivo human aspect of the study, we set out to objectively and electronically record rate and duration of ventilation during performance of CPR by trained professional rescue personnel in a prospective clinical trial in intubated, adult patients with out-of-hospital cardiac arrest. In the in vivo animal aspect of the study, to simulate the clinically observed hyperventilation, nine pigs in cardiac arrest were ventilated in a random order with 12, 20, or 30 breaths/min, and physiologic variables were assessed. Next, three groups of seven pigs in cardiac arrest were ventilated at 12 breaths/min with 100% oxygen, 30 breaths/min with 100% oxygen, or 30 breaths/min with 5% CO2/95% oxygen, and survival was assessed.

MAIN OUTCOME MEASURES

Ventilation rate and duration in humans; mean intratracheal pressure, coronary perfusion pressure, and survival rates in animals.

RESULTS

In 13 consecutive adults (average age, 63 +/- 5.8 yrs) receiving CPR (seven men) the average ventilation rate was 30 +/- 3.2 breaths/min (range, 15 to 49 breaths/min) and the average duration of each breath was 1.0 +/- 0.07 sec. The average percentage of time in which a positive pressure was recorded in the lungs was 47.3 +/- 4.3%. No patient survived. In animals treated with 12, 20, and 30 breaths/min, the mean intratracheal pressures and coronary perfusion pressures were 7.1 +/- 0.7, 11.6 +/- 0.7, 17.5 +/- 1.0 mm Hg/min (p < .0001) and 23.4 +/- 1.0, 19.5 +/- 1.8, 16.9 +/- 1.8 mm Hg (p = .03) with each of the different ventilation rates, respectively (p = comparison of 12 breaths/min vs. 30 breaths/min for mean intratracheal pressure and coronary perfusion pressure). Survival rates were six of seven, one of seven, and one of seven with 12, 30, and 30 + CO2 breaths/min, respectively (p = .006).

CONCLUSIONS

Despite seemingly adequate training, professional rescuers consistently hyperventilated patients during out-of-hospital CPR. Subsequent hemodynamic and survival studies in pigs demonstrated that excessive ventilation rates significantly decreased coronary perfusion pressures and survival rates, despite supplemental CO2 to prevent hypocapnia. This translational research initiative demonstrates an inversely proportional relationship between mean intratracheal pressure and coronary perfusion pressure during CPR. Additional education of CPR providers is urgently needed to reduce these newly identified and deadly consequences of hyperventilation during CPR. These findings also have significant implications for interpretation and design of resuscitation research, CPR guidelines, education, the development of biomedical devices, emergency medical services quality assurance, and clinical practice.

Evolution of the stone heart after prolonged cardiac arrest

OBJECTIVES

We hypothesized that progressive impairment in diastolic function during cardiopulmonary resuscitation (CPR) precedes evolution of the "stone heart" after failure of CPR. We therefore measured sequential changes in left ventricular (LV) volumes and free-wall thickness of the heart during CPR in an experimental model.

DESIGN

Prospective, observational animal study.

SETTING

Medical research laboratory in an university-affiliated research and educational institute.

SUBJECTS

Domestic pigs.

METHODS

Ventricular fibrillation (VF) was induced in 40 anesthetized male domestic pigs weighing between 38 kg and 43 kg. After 4 min, 7 min, or 10 min of untreated VF, electrical defibrillation was attempted. Failing to reverse VF in each instance, precordial compression at a rate of 80/min was begun coincident with mechanical ventilation. Coronary perfusion pressures (CPPs) were computed from the differences in time-coincident diastolic aortic and right atrial pressures. Left ventricular (LV) systolic and diastolic ventricular volumes and thickness of the LV free wall were estimated with transesophageal echocardiography. The stroke volumes (SVs) were computed from the differences in decompression diastolic and compression systolic volumes. Free-wall thickness was measured on the hearts at autopsy.

RESULTS

Significantly greater CPPs were generated with the 4 min of untreated cardiac arrest. Progressive reductions in LV diastolic and SV and increases in LV free-wall thickness were documented with increasing duration of untreated VF. A stone heart was confirmed at autopsy in each animal that failed resuscitative efforts. Correlations with indicator dilution method and physical measurements at autopsy corresponded closely with the echocardiographic measurements.

CONCLUSION

Progressive impairment in diastolic function terminates in a stone heart after prolonged intervals of cardiac arrest.

Factors affecting short- and long-term prognosis among 1069 patients with out-of-hospital cardiac arrest and pulseless electrical activity

AIMS

To describe the epidemiology, resuscitation factors and prognosis among a consecutive population of patients suffering from out-of-hospital cardiac arrest (OHCA) where pulseless electrical activity (PEA) was the first arrhythmia recorded on emergency medical services (EMS) arrival.

METHODS

Analysis of data collected prospectively on all patients regardless of age succumbing to OHCA during 1980-1997 in the community of Gothenburg where EMS initiated resuscitative measures.

RESULTS

4662 patients with OHCA were attended by the EMS during the study period. Of these, 1069 (23%) were judged as having PEA as the first recorded arrhythmia; 158 (15%) of these were admitted alive to hospital and 26 (2.4%) were discharged alive. Survivors to discharge had a significantly larger share of bystander cardiopulmonary resuscitation (CPR) (28 vs. 8%, P=0.008), significantly higher levels of consciousness (8% awake vs. 0%, P<0.001) and higher median systolic blood pressure (145 vs. 106 mmHg, P<0.001) on arrival at hospital. No patient with unwitnessed cardiac arrest and PEA over 80 years old survived.

CONCLUSION

Survival among patients suffering from OHCA and PEA is poor, especially among the elderly unwitnessed cases and those who do not receive bystander CPR. The latter seems to be of utmost importance among these patients.

Outcomes of cardiopulmonary arrest in an acute rehabilitation setting

OBJECTIVE

Fifty consecutive cases of cardiopulmonary arrest with administration of cardiopulmonary resuscitation (CPR) during a 6-yr period at a freestanding academic acute rehabilitation hospital were identified.

DESIGN

Medical records of 49 patients were available for review. Outcomes of survival of arrest, survival to 24 hr postarrest, survival to discharge from the hospital were determined, and chi2 or Fisher's exact tests were performed to investigate relationships between survival and admission functional status, age, gender, and medical comorbidities.

RESULTS

Forty-three percent of patients survived the initial arrest, 37% survived to 24 hr post-CPR, and 18% survived to hospital discharge. We were unable to identify any statistically significant predictors of survival post-CPR. Six of the nine survivors returned to the acute rehabilitation setting after cardiopulmonary arrest, and five of these patients made significant functional gains.

CONCLUSIONS

Outcomes after CPR in patients undergoing acute rehabilitation in one setting were not significantly different from those reported for patients in other healthcare settings. These data may be used by healthcare professionals to enhance discussions concerning advance healthcare planning (including resuscitation plans) with patients and families. Larger studies are needed to clarify the prognostic role of prior functional status in predicting CPR outcomes, particularly in the context of various diagnostic categories and age groups.

The added diagnostic value of automated QT-dispersion measurements and automated ST-segment deviations in the electrocardiographic diagnosis of acute cardiac ischemia

The purpose of this study was to determine the added value of automated QT dispersion and ST-segment measurements to physician interpretation of 12-lead electrocardiograms (ECGs) in patients with chest pain. To date, poor reproducibility of manual measurements and lack of shown added value have limited the clinical use of QT dispersion. Twelve-lead ECGs (n = 1,161) from the Milwaukee Prehospital Chest Pain Database were independently classified by 2 physicians into 3 groups (acute myocardial infarction (AMI), acute cardiac ischemia (ACI), or nonischemic), and their consensus was obtained. QT-end and QT-peak dispersions were measured by a computerized system. The computer also identified ST-segment deviations. Sensitivity, specificity, and positive predictive values (PPVs) and negative predictive values (NPV) for AMI and ACI were evaluated independently and in combinations. For AMI, physicians' consensus classification was remarkably good (sensitivity, 48%, specificity, 99%). Independent classification by QT-end and QT-peak dispersions or ST deviations was not superior to the physicians' consensus. Optimal classification occurred by combining automated QT-end dispersion and ST deviations with physicians' consensus. This combination increased sensitivity for the diagnoses of AMI by 35% (65% vs 48%, P < .001) and ACI by 55% (62% vs 40%, P < .001) compared with physicians' consensus, while maintaining comparable specificity. This study supports a potential clinical role for automated QT dispersion when combined with other diagnostic methods for detecting AMI and ACI.

Long term outcome after out-of-hospital cardiac arrest with physician staffed emergency medical services: the Utstein style applied to a midsized urban/suburban area

OBJECTIVE

To test the effect of a physician staffed advanced cardiac life support (ALS) system on patient outcome following out-of-hospital cardiac arrest.

DESIGN

Observational study.

SETTING

Two tier basic life support (BLS) and physician staffed ALS services in the midsized urban/suburban area of Heidelberg, Germany.

PATIENTS

All patients suffering out-of-hospital cardiac arrest of cardiac aetiology between January 1992 and December 1994 and who were covered by ALS services.

INTERVENTIONS

Physician staffed ALS services.

MAIN OUTCOME MEASURES

Return of spontaneous circulation, hospital discharge, and one year survival, according to the Utstein style.

RESULTS

Of 330 000 inhabitants, 755 suffered from cardiac arrest covered by the Heidelberg ALS services. In 512 patients, cardiopulmonary resuscitation had been initiated. Of 338 patients with cardiac aetiology, return of spontaneous circulation was achieved in 164 patients (49%), 48 (14%) were discharged alive, and 40 (12%) were alive one year later; most of these patients showed good neurological outcome. Thus, 4.85 patients with cardiac aetiology were saved by the ALS services and discharged alive per 100 000 inhabitants a year. Ventricular fibrillation or tachycardia was detected in 106 patients (31%), other cardiac rhythms in 40 (12%), and asystole in 192 (57%). Hospital discharge rates (and one year survival) in these subgroups were 34.0% (29.2%), 12.5% (7.5%), and 3.6% (3.1%), respectively. Discharge rates increased if cardiac arrest was witnessed (bystander, 20.0%; BLS/ALS personnel, 21.4%; non-witnessed arrest, 3.3%; p < 0.01), and if the time period between the alarm and the arrival of the ALS unit was four minutes or less (</= 4 minutes, 30.6%; 4-8 minutes, 10.4%; > 8 minutes, 8. 1%; p < 0.001). In 69 patients with bystander witnessed cardiac arrest with ventricular fibrillation, the discharge rate was 37.7%; 21 patients were alive after one year.

CONCLUSIONS

A two tier BLS and physician staffed ALS system is associated with good long term outcome of patients suffering from out-of-hospital cardiac arrest of cardiac aetiology in a midsized urban/suburban area. Further studies, however, are required to assess whether having a physician in the ALS unit is an independent determinant for improved long term outcome.

Cardiac arrest in Saudi Arabia: a 7-year experience in Riyadh

All out-of-hospital and Emergency Department (ED) cardiac arrests treated at a tertiary care hospital in Riyadh, Saudi Arabia, from 1989 through 1995 were studied. Of patients arresting out-of-hospital, 3.0% received bystander cardiopulmonary resuscitation (CPR), 9.1% had some prehospital CPR, 12.1% were transported via ambulance, and 13.6% had ventricular fibrillation (VF) on ED arrival. In the witnessed arrests (80%), the estimated interval from arrest to initiation of CPR was 21.1 +/- 14.7 min. None of these variables was shown to influence outcome. Survival to hospital discharge from out-of-hospital arrest was 5.1% for adults and 7.4% for children; all had poor neurologic outcome. For patients arresting in the ED, an initial rhythm of ventricular tachycardia (VT) or VF was strongly correlated with survival. Survival from ED arrest was 30.4% in adults, 42.9% in children; all but one had normal neurologic outcome. These results are similar to those reported from large cities and EDs elsewhere. The unique set of variables influencing out-of-hospital care and transportation in Riyadh are discussed, and potential areas for improvement are noted.

A preliminary study of the reliability of immediate vs. delayed interviews of cardiac arrest witnesses

INTRODUCTION

Methods to characterize the interval between a collapse from cardiac arrest until a 911 call is made have not yet been developed.

OBJECTIVE

To determine the concordance of cardiac arrest data obtained by two methods: an immediate nurse interview of out-of-hospital cardiac arrest (OHCA) witnesses, and a follow-up phone interview performed two weeks later.

METHODS

This was a prospective study of OHCA witnesses dating from January 1997 to May 1998. Witnesses were briefly interviewed at the time of emergency department presentation, and two weeks later a more lengthy structured phone interview was performed. The authors identified key data elements: 1) was the arrest witnessed? (Wit); 2) was CPR administered prior to EMS arrival? (BCPR); 3) was the first call placed to 911? (c911); and 4) was the estimated collapse to call interval <4 minutes? (ECCI). The analysis utilized Cohen's kappa statistic and Spearman's correlation coefficient.

RESULTS

A convenience sample of 42 matched pairs of OHCA cases was analyzed. Kappa statistics for agreement between methods were: 1) Wit(kappa = 0.750), 2) BCPR(kappa = 0.892), 3) c911 (kappa = 0.892), and 4) ECCI(kappa = 0.571, Spearman's 0.528).

CONCLUSION

There is good to excellent agreement between immediate and phone interview data retrieval methods. Phone interviews appear to yield data comparable to that with the more difficult and expensive, direct interview method.

Developing a foundation for the evaluation of expanded-scope EMS: a window of opportunity that cannot be ignored

EMS systems are about to undergo a major transformation. Not only will the scope of EMS change, but many experts believe that it will dramatically expand. Some see the "expanded scope" as entailing relatively limited changes, whereas others consider them to be more broad. Although no agreement is evident about the definition for expanded-scope EMS, it is hoped that all EMS professionals can agree that it must be implemented in a manner that can be carefully evaluated to determine its effects on patients and EMS systems. We present a framework for evaluating the effect of expanded-scope EMS in the various types of systems that currently exist. Special consideration must be given to the indirect effects that system changes may have on survival from out-of-hospital cardiac arrest. Numerous issues will affect our ability to properly assess expanded-scope EMS. The basic research models necessary to assess the impact of system change are lacking. Few EMS systems consistently produce significant volumes of good systems research ... that is, there are few "EMS laboratories." Cost-effectiveness and issues surrounding the "societal value" of EMS remain essentially unstudied. Reliable scoring methods, severity scales, and outcome measures are lacking: and, it is ethically and logistically difficult to justify withholding the "standard of care" in an effort to understand the impact of EMS interventions. Despite all of these barriers, it is time to pay the price of doing methodologically sound evaluations that ensure the most optimal societal impact by the EMS systems of the future.

Predicting survival from out-of-hospital cardiac arrest: a multivariate analysis

From 954 attempts to resuscitate patients from out-of-hospital cardiac arrest two datasets were derived, namely 861 cases of cardiac arrest and 906 cases of either cardiac or primary respiratory arrest. For each dataset, multivariate analysis was performed by fitting a number of explanatory variables with respect to the outcomes of admission to hospital and discharge home in logistic regression models. There were numerous interactions between these variables. Being conscious at the time of the arrival of the ambulance crew and subsequently having cardiac arrest strongly predicted survival, as did both the presence of a witness to the arrest and the initiation of cardiopulmonary resuscitation (CPR) by a bystander; this latter effect was a marker for early CPR. The strongest predictor of a poor outcome was delay to CPR or delay to advanced cardiac life support.

One-year survival after out-of-hospital cardiac arrest in Bonn city: outcome report according to the 'Utstein style'

Outcome after prehospital cardiac arrest was examined in the EMS system of Bonn, a midsized urban community, and presented according to the Utstein style. The data were collected from January 1st, 1989 to December 31st, 1992 by the Bonn-north ALS unit, which serves 240,000 residents. Fifty-six patients suffered from cardiac arrest of non-cardiac aetiology and were excluded; 464 patients were resuscitated after cardiac arrest of presumed cardiac aetiology (incidence of CPR attempts: 48.33 per year/100,000 population). The collapse was unwitnessed, bystander witnessed or EMS personnel witnessed in 178, 214 or 72 patients, respectively. In these subgroups discharge rates and 1-year survival accounted for 7.3% (4.5%), 22.9% (15.9%) and 16.7% (11.1%), respectively. Thirty-four patients were discharged without neurological deficits (cerebral performance category 1: CPC 1), 22 and nine patients scored CPC 2 or CPC 3, respectively. Nine patients were comatose (CPC 4) when they were discharged and remained in this state until they died. Of the 50 1-year survivors 35 lived without neurological deficit, eight demonstrated mild (CPC 2) and five severe (CPC 3) cerebral disability at 1-year after resuscitation, and, finally, two patients remained comatose for more than 1 year. The Utstein template recommends the selection of patients who were found in VF after bystander witnessed collapse. In our cohort 118 patients met these criteria. Of them 41 (35%) could be discharged from hospital and 28 (24%) lived more than 1 year. The comparison of our data with those from double-response EMS systems of other communities revealed that, in midsized urban and suburban communities the highest discharging rates could be achieved. Our study demonstrated that survival depends crucially on short response intervals and life support which will be performed by well-trained emergency technicians, paramedics and physicians.

Test of the acute cardiac ischemia time-insensitive predictive instrument (ACI-TIPI) for prehospital use

STUDY OBJECTIVES

To test diagnostic performance for acute cardiac ischemia (ACI) in a manually calculated and in a computerized, ECG-calculated ACI time-insensitive predictive instrument (ACI-TIPI) in prehospital chest pain patients.

METHODS

We carried out prospective inclusion and data acquisition with retrospective analysis. Over a 6-month period, 439 adult emergency medical services patients with chest pain underwent prehospital electrocardiography. Because of incomplete data, 77 cases were excluded, leaving a study sample of 362 patients. Excluded patients did not differ significantly with respect to age, sex, final diagnosis, or history of myocardial infarction, heart surgery, diabetes, or stroke. ACI-TIPI probabilities of ACI were computed on the basis of the prehospital ECGs as interpreted retrospectively and independently by two study investigators blinded to patient outcome, with a specially programmed electrocardiograph, and with a computer algorithm further modified by logistic-regression analysis.

RESULTS

Diagnostic performance on the basis of receiver operating characteristic (ROC) curve areas of the ACI-TIPI was scored, by the two physician readers, .73 and .74; and by ECG, .75. Patients with low ACI-TIPI probability (0% to 9%) had no acute myocardial infarctions, a 2.3% incidence of angina, and no prehospital life-threatening events.

CONCLUSION

ACI-TIPI probabilities of ACI as generated by a specially programmed electrocardiograph are comparable to those based on physician ECG interpretations and may be useful in the prehospital evaluation of chest pain.

Cardiac arrest

This article reviews the critical resuscitations necessary during prehospital and emergency department treatment of cardiac arrest. Standard therapy for cardiac arrest rhythms is presented. Novel pharmacologic agents, types of cardiopulmonary resuscitation, and circulatory-assist devices are discussed.

Standard and higher doses of atropine in a canine model of pulseless electrical activity

OBJECTIVE

To determine whether standard or increased doses of atropine improve the return of spontaneous circulation (ROSC) rate in a canine model of pulseless electrical activity (PEA).

METHODS

A prospective, controlled, blinded laboratory investigation was performed using an asphyxial canine cardiac arrest model. After the production of asphyxial PEA, 75 dogs remained in untreated PEA for 10 minutes and then were randomized to receive placebo (group 1) or one of four doses of atropine (group 2, 0.04 mg/kg; group 3, 0.1 mg/kg; group 4, 0.2 mg/kg; group 5, 0.4 mg/kg). All the animals received mechanical external CPR and epinephrine (0.02 mg/kg every 3 minutes) throughout resuscitation.

RESULTS

The ROSC rates were not significantly different between the groups (group 1, 73%; group 2, 67%; group 3, 40%; group 4, 47%; group 5, 27%; p = 0.06). The heart rates and hemodynamics during resuscitation were not significantly different between the groups.

CONCLUSION

In this canine model of asphyxial PEA cardiac arrest, standard-dose atropine did not improve ROSC rates, compared with placebo. Increasing doses of atropine tended to decrease ROSC rates, compared with placebo and standard-dose atropine.

Bystander vs EMS first-responder CPR: initial rhythm and outcome in witnessed nonmonitored out-of-hospital cardiac arrest

OBJECTIVES

To assess whether outcome and first-monitored rhythm for patients who sustain a witnessed, nonmonitored, out-of-hospital cardiac arrest are associated with on-scene CPR provider group.

METHODS

A retrospective, cohort analysis was conducted in a suburban, heterogeneous EMS system. Patients studied were > or = 19 years of age, had had an arrest of presumed cardiac origin between July 1989 and January 1993, had gone into cardiac arrest prior to ALS arrival, and had received CPR on collapse. First-monitored rhythms and survival rates were compared for two patient groups who on collapse either: 1) had received CPR by nonprofessional bystanders (BCPR) or 2) had received CPR by on-scene EMS system first responders (FRCPR).

RESULTS

Of 217 cardiac arrest victims, 153 (71%) had received BCPR and 64 (29%) had received FRCPR. The BCPR patients were slightly younger (62.4 vs 68.4 years, p = 0.01) and had slightly shorter ALS response intervals (6.4 vs 7.7 minutes, p = 0.02). There was no difference in BLS response time intervals or automatic external defibrillator (AED) use rates. The percentage of patients with a first-monitored rhythm of pulseless ventricular tachycardia/ventricular fibrillation (VT/VF) and the percentage of patients grouped by CPR provider who survived to hospital admission or to hospital discharge were: [see text]

Bystander CPR, ventricular fibrillation, and survival in witnessed, unmonitored out-of-hospital cardiac arrest

STUDY OBJECTIVE

To assess whether bystander CPR (BCPR) on collapse affects initial rhythm and outcome in patients with witnessed, unmonitored out-of-hospital cardiac arrest (OHCA).

DESIGN

Prospective cohort study. Student's t test, the chi 2 test, and logistic regression were used for analysis.

SETTING

Suburban emergency medical service (EMS) system.

PARTICIPANTS

Patients 19 years or older with witnessed OHCA of presumed cardiac origin who experienced cardiac arrest before EMS arrival between July 1989 and July 1993.

RESULTS

Of 722 patients who met the entry criteria, 153 received BCPR. Patients who received BCPR were younger than those who did not: 62.5 +/- 15.4 years versus 66.8 +/- 15.1 years (P < .01). We found no differences in basic or advanced life support response intervals or in frequency of AED use. More patients initially had ventricular fibrillation (VF) in the BCPR group: 80.9% versus 61.4% (P < .01). The interval to definitive care for ventricular tachycardia (VT)/VF was longer for the BCPR group (8.59 +/- 5.3 versus 7.45 +/- 4.7 minutes; P < .05). The percentage of patients discharged alive who were initially in VT/VF was higher in the BCPR group: 18.3% versus 8.4% (P < .001). In a multivariate model, BCPR is a significant predictor for VT/VF and live discharge with adjusted ORs of 2.7 (95% CI, 1.7 to 4.4) and 2.4 (95% CI, 1.5 to 4.0), respectively. For those patients in VT/VF, BCPR predicted live discharge from hospital with an adjusted OR of 2.1 (95% CI, 1.2 to 3.6).

CONCLUSION

Patients who receive BCPR are more often found in VT/VF and have an increased rate of live discharge, with controls for age and response and definitive care intervals. For VT/VF patients, BCPR is associated with an increased rate of live discharge.

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.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

STUDY OBJECTIVE

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

DESIGN

Observational cohort study.

SETTING

New York City emergency medical services system.

PARTICIPANTS

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

INTERVENTIONS

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

RESULTS

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

CONCLUSION

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

Resuscitation skills of lay public after recent training

STUDY OBJECTIVE

To investigate the ability of laypeople to apply basic CPR techniques after recent training.

DESIGN

Cross-sectional assessment of practical CPR skills.

TYPE OF PARTICIPANTS

151 laypeople who were trained twice in the preceding 20 to 24 months.

MEASUREMENTS AND MAIN RESULTS

Practical skills were tested using six primary recorded variables that describe the quality of CPR techniques in a training situation. A total score on the skills of each participant was computed on the basis of a predefined scoring system. Thirty-three percent of the participants were able to perform adequate CPR. The compression:relaxation ratio, the breathing volume, and the breathing interval were points of concern.

CONCLUSION

Practical skills in basic CPR after a 12-month training interval, though better in this study than in many previous studies, are insufficient in the majority of laypeople. The results of this study could be used to design a better tailored (re)instruction program, with an emphasis on regular, frequent refresher courses.

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.

Evaluation of ST segment elevation criteria for the prehospital electrocardiographic diagnosis fo acute myocardial infarction

STUDY OBJECTIVE

To determine retrospectively the diagnostic accuracy of various ECG ST segment elevation criteria for the prehospital ECG diagnosis of acute myocardial infarction.

DESIGN AND SETTING

During a six-month period, paramedics acquired prehospital 12-lead ECGs on adult chest pain patients. Investigators interpreted ECGs independently, retrospectively, and blinded to patient outcome. ECGs were classified as meeting or not meeting the six ST segment elevation criteria regardless of ECG morphology if the criteria were present in two or more anatomically contiguous leads: 1 mm or more ST segment elevation; 2 mm or more ST segment elevation; 1 mm or more ST segment elevation in the limb leads or 2 mm or more ST segment elevation in the precordial leads; and the first three criteria with the simultaneous presence of reciprocal changes. ECGs that did not meet any ST segment elevation criteria were classified as normal, nonspecific ST/T wave changes, abnormal but not ischemic, and ischemic. Hospital charts were reviewed for final cardiac diagnosis.

TYPE OF PARTICIPANT

Four hundred twenty-eight stable adult prehospital chest pain patients in whom paramedics acquired prehospital 12-lead ECGs.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of the 428 cases, 123 (29%) met 1 mm or more ST segment elevation criteria. Sixty-three (51%) of these 123 patients did not have myocardial infarctions. ECG characteristics most frequently associated with these non-myocardial infarction ECGs were left bundle branch block (21%) and left ventricular hypertrophy (33%). The three criteria that required the presence of reciprocal changes had the highest positive predictive values (93% to 95%), with sensitivities ranging from 20% to 33%. The criteria of 1 mm or more ST segment elevation with the simultaneous presence of reciprocal changes had a positive predictive value of 94% and included 18 of the 21 (86%) myocardial infarction patients who had ST segment elevation and received thrombolytic therapy within five hours after hospital arrival. Of the 428 cases, 305 (71%) did not meet any ST segment elevation criteria and had a sensitivity of 81% and a negative predictive value of 49% for the absence of acute myocardial infarction.

CONCLUSION

Fifty-one percent of patients whose prehospital 12-lead ECG met 1 mm or more ST segment elevation criteria had non-myocardial infarction diagnoses. ST segment elevation alone lacks the positive predictive value necessary for reliable prehospital myocardial infarction diagnosis. Inclusion of reciprocal changes in prehospital ECG myocardial infarction criteria improved the positive predictive value to more than 90% and included a significant majority (62% to 86%) of acute myocardial infarction patients with ST segment elevation who received thrombolytic therapy within five hours after hospital arrival. ST segment elevation criteria that include reciprocal changes identify patients who stand to benefit most from early interventional strategies.

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.

Quality and efficiency of bystander CPR. Belgian Cerebral Resuscitation Study Group

Incorrectly performed bystander CPR might compromise survival of the cardiac arrest patient. We therefore evaluated the outcome in 3306 out-of-hospital primary cardiac arrests of which 885 received bystander CPR. bystanders performed CPR correctly in 52%, incorrectly in 11%, 31% performed only external chest compressions (ECC) and 6% only mouth-to-mouth ventilation (MMV). The initial ECG in cases without bystander CPR was ventricular fibrillation in 28% (95% confidence interval: 27-30%); 45% (41-50%) and 39% (29-48%), respectively when bystander CPR was performed correctly or incorrectly; 43% (37-49%) when only ECC was applied and 22% (11-33%) when only MMV was practiced. Long term survival, defined as being awake 14 days after CPR, was 16% (13-19%) in patients with correct bystander CPR; 10% (7-14%) and 2% (0-9%), respectively when only ECC or only MMV was performed; 7% (6-8%) when no bystander was involved; 4% (0-8%) when bystander CPR was performed incorrectly. Bystander CPR might have a beneficial effect on survival by maintaining the heart in ventricular fibrillation by ECC. A negative effect of badly performed bystander CPR was not observed compared to cases which had not received bystander CPR.

Out-of-hospital transcutaneous pacing by emergency medical technicians in patients with asystolic cardiac arrest

BACKGROUND

Transcutaneous cardiac pacemakers generate electrical stimuli that pace the heart through external electrodes that adhere to the chest wall. Transcutaneous pacing has been useful in some patients with bradycardia, but its efficacy in patients with asystole and full cardiac arrest has been limited, possibly because of delays in the initiation of pacing. We studied the efficacy of early transcutaneous pacing in patients with out-of-hospital asystolic cardiac arrest.

METHODS

For three years we provided transcutaneous pacemakers to about half the fire districts in a large emergency-medical-services system (the intervention group). In these districts, we authorized emergency medical technicians (EMTs) to begin transcutaneous pacing in patients with cardiac arrest and primary asystole or post-defibrillation asystole. Pacing was done as early as possible, before endotracheal intubation or intravenous medication. EMTs in the other fire districts (the control group) treated similar patients with basic cardiopulmonary resuscitation but without transcutaneous pacing.

RESULTS

The EMTs in the intervention group initiated transcutaneous pacing in 112 of the 278 patients with primary asystole. Of these patients, 22 (8 percent) were admitted to the hospital, and 11 (4 percent) were discharged. Among the 259 patients treated by the EMTs in the control group, 21 (8 percent) were admitted to the hospital, and 5 (2 percent) were discharged. The two groups did not differ significantly with respect to the rate of hospital admission or survival. Survival after early pacing for post-defibrillation asystole was no better than survival after pacing for primary asystole.

CONCLUSIONS

Transcutaneous pacing appears to offer no benefit in patients with asystolic cardiac arrest, even when it is performed as early as possible by EMTs in the field. Our data suggest that the widespread implementation of early transcutaneous pacing for out-of-hospital asystolic cardiac arrest would be ineffective.

Prospective validation of a new model for evaluating emergency medical services systems by in-field observation of specific time intervals in prehospital care

STUDY OBJECTIVE

To develop and validate a new time interval model for evaluating operational and patient care issues in emergency medical service (EMS) systems. DESIGN/SETTING/TYPE OF PARTICIPANT: Prospective analysis of 300 EMS responses among 20 advanced life support agencies throughout an entire state by direct, in-field observation.

RESULTS

Mean times (minutes) were response, 6.8; patient access, 1.0; initial assessment, 3.3; scene treatment, 4.4; patient removal, 5.5; transport, 11.7; delivery, 3.5; and recovery, 22.9. The largest component of the on-scene interval was patient removal. Scene treatment accounted for only 31.0% of the on-scene interval, whereas accessing and removing patients took nearly half of the on-scene interval (45.8%). Operational problems (eg, communications, equipment, uncooperative patient) increased patient removal (6.4 versus 4.5; P = .004), recovery (25.4 versus 20.2; P = .03), and out-of-service (43.0 versus 30.1; P = .007) intervals. Rural agencies had longer response (9.9 versus 6.4; P = .014), transport (21.9 versus 10.3; P < .0005), and recovery (29.8 versus 22.1; P = .049) interval than nonrural. The total on-scene interval was longer if an IV line was attempted at the scene (17.2 versus 12.2; P < .0001). This reflected an increase in scene treatment (9.2 versus 2.8; P < .0001), while patient access and patient removal remained unchanged. However, the time spent attempting IV lines at the scene accounted for only a small part of scene treatment (1.3 minutes; 14.1%) and an even smaller portion of the overall on-scene interval (7.6%). Most of the increase in scene treatment was accounted for by other activities than the IV line attempts.

CONCLUSION

A new model reported and studied prospectively is useful as an evaluative research tool for EMS systems and is broadly applicable to many settings in a demographically diverse state. This model can provide accurate information to system researchers, medical directors, and administrators for altering and improving EMS systems.

Extracorporeal circulation as an alternative to open-chest cardiac compression for cardiac resuscitation

Open-chest direct cardiac compression represents a more potent but highly invasive option for cardiac resuscitation when conventional techniques of closed-chest cardiac resuscitation fail after prolonged cardiac arrest. We postulated that venoarterial extracorporeal circulation might be a more effective intervention with less trauma. In the setting of human cardiac resuscitation, however, controlled studies would be limited by strategic constraints. Accordingly, the effectiveness of open-chest cardiac compression was compared with that of extracorporeal circulation after a 15-min interval of untreated ventricular fibrillation in a porcine model of cardiac arrest. Sixteen domestic pigs were randomized to resuscitation by either peripheral venoarterial extracorporeal circulation or open-chest direct cardiac compression. During resuscitation, epinephrine was continuously infused into the right atrium, and defibrillation was attempted by transthoracic countershock at 2-min intervals. Systemic blood flows averaged 198 ml.kg-1.min-1 with extracorporeal circulation. This contrasted with direct cardiac compression, in which flows averaged only 40 ml.kg-1.min-1. Coronary perfusion pressure, the major determinant of resuscitability on the basis of earlier studies, was correspondingly lower (94 vs 29 mm Hg). Extracorporeal circulation, in conjunction with transthoracic DC countershock and epinephrine, successfully reestablished spontaneous circulation in each of eight animals after 15 min of untreated ventricular fibrillation. This contrasted with the outcome after open-chest cardiac compression, in which spontaneous circulation was reestablished in only four of eight animals (p = .038). We conclude that extracorporeal circulation is a more effective alternative to direct cardiac compression for cardiac resuscitation after protracted cardiac arrest.

Use of cardiopulmonary bypass, high-dose epinephrine, and standard-dose epinephrine in resuscitation from post-countershock electromechanical dissociation

STUDY OBJECTIVE

To determine the effects of cardiopulmonary bypass with standard-dose epinephrine, high-dose epinephrine, and standard-dose epinephrine on perfusion pressures, myocardial blood flow, and resuscitation from post-countershock electromechanical dissociation.

DESIGN

Prospective, controlled laboratory investigation using a canine cardiac arrest model randomized to receive one of three resuscitation therapies.

INTERVENTIONS

After the production of post-countershock electromechanical dissociation, 25 animals received ten minutes of basic CPR and were randomized to receive cardiopulmonary bypass with standard-dose epinephrine, high-dose epinephrine, or standard-dose epinephrine.

MEASUREMENTS AND MAIN RESULTS

Myocardial blood flow was measured using a colored microsphere technique at baseline, during basic CPR, and after intervention. Immediate and two-hour resuscitation rates were determined for each group. Return of spontaneous circulation was achieved in eight of eight cardiopulmonary bypass with standard-dose epinephrine compared with four of eight high-dose epinephrine and three of eight standard-dose epinephrine animals (P less than .04). One animal was resuscitated with CPR alone and was excluded. Survival to two hours was achieved in five of eight cardiopulmonary bypass with standard-dose epinephrine, four of eight high-dose epinephrine, and three of eight standard-dose epinephrine animals (NS). Coronary perfusion pressure increased significantly in the cardiopulmonary bypass with standard-dose epinephrine group when compared with the other groups (cardiopulmonary bypass with standard-dose epinephrine, 76 +/- 45 mm Hg; high-dose epinephrine, 24 +/- 12 mm Hg; standard-dose epinephrine, 3 +/- 14 mm Hg; P less than .005). Myocardial blood flow was higher in cardiopulmonary bypass with standard-dose epinephrine and high-dose epinephrine animals compared with standard-dose epinephrine animals but did not reach statistical significance. Cardiac output increased during cardiopulmonary bypass with standard-dose epinephrine (P = .001) and standard-dose epinephrine (NS) compared with basic CPR but decreased after epinephrine administration in the high-dose epinephrine group (NS).

CONCLUSION

Resuscitation from electromechanical dissociation was improved with cardiopulmonary bypass and epinephrine compared with high-dose epinephrine or standard-dose epinephrine alone. However, there was no difference in survival between groups. Cardiopulmonary bypass with standard-dose epinephrine resulted in higher cardiac output, coronary perfusion pressure, and a trend toward higher myocardial blood flow. A short period of cardiopulmonary bypass with epinephrine after prolonged post-countershock electromechanical dissociation cardiac arrest can re-establish sufficient circulation to effect successful early resuscitation.

Community trends in CPR training and use: the Minnesota Heart Survey

STUDY OBJECTIVE

To examine community changes in self-reported CPR training and use from 1980-82 to 1985-87 using data obtained from the Minnesota Heart Survey. A comparative investigation of CPR training among blacks and whites in 1985-86 also was completed.

DESIGN

Data were obtained in 1980-81, 1981-82, 1985-86, and 1986-87 from four population-based samples drawn from the seven-county Minneapolis-St Paul metropolitan area. To increase sample sizes and to compare prevalences of CPR training and use in the early 1980s with prevalences in the mid-1980s, the four Minnesota Heart Survey surveys were combined into two time periods, 1980-82 and 1985-87. A separate survey of black individuals was conducted in 1985, and these data were used in the comparisons between blacks and whites in 1985-86.

RESULTS

The prevalence of whites trained in CPR increased significantly between 1980-82 and 1985-87 in both nonhealth professionals (18.5% vs 30.9%) and health professionals (71.9% vs 86.8%). No significant change was observed between the two periods in the percentage of nonhealth professionals who had ever used their CPR skills (9.7% vs 10.7%), whereas use among health professionals increased significantly (40.2% vs 53.4%). Training within the prior two or three years decreased from 1980-82 to 1985-87 among nonhealth professionals, but increases in recent training were observed among health professionals. There were no significant differences between black and white nonhealth professionals in the prevalence of CPR training. Black trainees, however, reported a higher percentage of ever using CPR skills than white trainees (15.4% vs 9.8%, respectively). Black trainees also had higher rates of recent CPR training than white trainees. No differences were observed between black and white health professionals regarding CPR training and use, or recency of certification.

CONCLUSION

These results suggest that the percentage of individuals trained in CPR is increasing. Improvement is needed, however, in the rates of recent certification among nonhealth professionals.

Prehospital bicarbonate use in cardiac arrest: a 3-year experience

The American Heart Association no longer recommends the routine use of sodium bicarbonate in cardiac arrests. Reasons cited include the lack of documented effect on clinical outcome and potential adverse effects of metabolic alkalosis and hypernatremia. We reviewed 36 months of experience with 619 nontrauma adult, prehospital cardiac arrest patients to identify 273 successful resuscitations who had emergency department blood gases and electrolytes performed. Determination of complications associated with prehospital intravenous sodium bicarbonate and its impact on survival in resuscitated patients was undertaken. Fifty-eight patients did not receive sodium bicarbonate (NO HCO3 group) and had short cardiopulmonary resuscitation (CPR) times (7.4 +/- 5.5 minutes). Two hundred fifteen patients did receive sodium bicarbonate (HCO3 group) and had significantly longer CPR times (23.3 +/- 13.5 minutes, P less than or equal to .001). Both groups demonstrated routine early chest compression and hyperventilation as evidenced by no significant difference in paramedic response time or rate of intubations. Initial emergency department blood gas results of both groups were not significantly different. No patients in the NO HCO3 group had hypernatremia (sodium [Na]+ greater than 150), whereas four patients (2%) in the HCO3 group were hypernatremic. Eight patients (14%) in the NO HCO3 group and 37 patients (17%) in the HCO3 group were alkalotic with pH values greater than 7.49 (P = NS). Six patients (10%) of the NO HCO3 group and 24 patients (11%) of the HCO3 group had a metabolic component to the alkalosis as defined by a positive base excess value (P = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

The diagnostic impact of prehospital 12-lead electrocardiography

STUDY HYPOTHESIS

It is feasible to apply prehospital 12-lead electrocardiography to most stable prehospital chest pain patients. Prehospital diagnostic accuracy is improved compared with single-lead telemetry.

POPULATION

One-hundred sixty-six stable adult patients who sought paramedic evaluation for a chief complaint of nontraumatic chest pain.

METHODS

One-hundred fifty-one prehospital 12-lead ECGs of diagnostic quality were obtained by paramedics on 166 adult patients presenting with nontraumatic chest pain. Paramedics and base station physicians were blinded to the information on acquired prehospital 12-lead ECGs and treated patients according to current standard of care-clinical diagnosis and single-lead telemetry. Final hospital diagnoses were classified into three groups: acute myocardial infarction (24); suspected angina or ischemia (61); and nonischemic chest pain (66). Paramedics and base station physicians' clinical diagnoses and prehospital and emergency department ECGs were similarly classified and compared. Prehospital and ED 12-lead ECGs were read retrospectively by two cardiologists.

RESULTS

Paramedics achieved a high success rate (98.7%) in obtaining diagnostic quality prehospital 12-lead ECGs in 94.6% of eligible prehospital patients. For patients with acute myocardial infarction, prehospital ECG alone had significantly higher specificity than did the paramedic clinical diagnosis (99.2% vs 70.9%; P less than .001), and significantly higher positive predictive value (92.9% vs 32.7%; P less than .001). For patients with angina, combining the paramedic clinical diagnosis and the prehospital ECG significantly improved sensitivity (90.2% vs 62.3%; P less than .001) and increased negative predictive value (88.9% vs 71.3%; P less than .02) compared with paramedic clinical diagnosis alone. There was a high concordance between prehospital and ED ECG diagnosis (99.3% for acute myocardial infarction and 92.8% for angina). Furthermore, ten patients whose prehospital ECGs demonstrated ischemia and who had final hospital diagnoses of angina or acute myocardial infarction were mistriaged by paramedics and/or received no base station physician-directed therapy.

CONCLUSION

It is feasible to apply prehospital 12-lead electrocardiography to most stable prehospital chest pain patients. Prehospital 12-lead ECGs have the potential to significantly increase the diagnostic accuracy in chest pain patients, approach congruity with ED 12-lead ECG diagnoses, and may allow for consideration of altering and improving prehospital and hospital-based management in this patient population.

Prehospital prophylactic lidocaine does not favorably affect outcome in patients with chest pain

STUDY OBJECTIVES

The purpose of our study was to determine the morbidity and mortality in initially stable patients presenting to paramedics with chest pain; to examine possible beneficial effects of its use, including reduction of sudden death syndrome in the prehospital and emergency department setting; and to determine if prophylactic lidocaine is associated with adverse effects in this patient population.

DESIGN AND SETTING

This was a randomized, prospective study using prophylactic lidocaine in patients complaining of chest pain who presented to our paramedic system between January 1984 and January 1988.

TYPE OF PARTICIPANTS

All patients aged 18 years or older with chest pain of suspected cardiac origin who presented to paramedics during the study period were included. Excluded were patients presenting with warning arrhythmias, second- or third-degree heart block, bradycardias of less than 50, hypotension of less than 90 mm Hg systolic, or known allergy to lidocaine.

INTERVENTIONS

Patients were randomized into two groups, the lidocaine-treated group and the control group. An initial bolus of 1 mg/kg IV lidocaine was administered to the lidocaine-treated group. A simultaneous 2 mg/min IV drip was established. Ten minutes after the first dose of lidocaine, a second bolus of 0.5 mg/kg was administered.

MEASUREMENTS AND MAIN RESULTS

During the study period, 1,427 patients were entered; 704 received lidocaine, and 723 did not. Discharge diagnoses included acute myocardial infarction (31%), unstable angina (33%), other cardiac problems (7%), and noncardiac problems (29%); overall mortality rate was 7.4%. There was an equal distribution of deaths between the lidocaine-treated group (57) and the control group (48). Six patients had a cardiac arrest in the prehospital setting, and 15 had a cardiac arrest in the ED. Malignant ventricular arrhythmias as the precipitating arrest rhythm in patients with acute myocardial infarctions were similar for the lidocaine-treated and control groups. The incidence of adverse effects, including hypotension, bradycardias, second- or third-degree heart blocks, tinnitus, and altered mental status, was similar in both groups.

CONCLUSION

There are no benefits from the administration of prehospital prophylactic lidocaine in stable patients with chest pain; therefore, routine use in this setting appears unwarranted.

Prehospital cardiac arrest: the impact of witnessed collapse and bystander CPR in a metropolitan EMS system with short response times

OBJECTIVE

Numerous studies have shown initiation of bystander CPR to significantly improve survival from prehospital cardiac arrest. However, in emergency medical services (EMS) systems with very short response times, bystander CPR has not been shown to impact outcome. The purpose of this study was to determine the effect of bystander CPR on survival from out-of-hospital cardiac arrest in such a system.

DESIGN

Prehospital, hospital, and death certificate data from a medium-sized metropolitan area were retrospectively analyzed for adult, nontraumatic cardiac arrest during a 16-month period.

RESULTS

A total of 298 patients met study criteria. One hundred ninety-five arrests (65.4%) were witnessed, and 103 (34.6%) were unwitnessed. Twenty-five witnessed victims (12.8%) were discharged alive, whereas no unwitnessed victims survived (P less than .001). Patients suffering a witnessed episode of ventricular fibrillation/tachycardia (VF/VT) were more likely to survive (21.9%) than were other patients (2.0%, P less than .0001). Among witnessed patients, initiation of bystander CPR was associated with a significant improvement in survival (20.0%) compared with the no-bystander CPR group (9.2%, P less than .05). Bystander CPR was also associated with improved outcome when witnessed patients with successful prehospital resuscitation were evaluated as a group; 18 had bystander CPR, of whom 13 (72.2%) survived compared with only 12 of 38 patients with no bystander CPR (31.6%, P less than .01).

CONCLUSION

Our data revealed improved survival rates when bystander CPR was initiated on victims of witnessed cardiac arrest in an EMS system with short response times.

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.

The effectiveness of bystander CPR in an animal model

Several clinical studies have yielded conflicting results in examining the effectiveness of bystander CPR (BCPR). The purpose of this pilot study was to determine the effectiveness of BCPR in an animal model of cardiac arrest and resuscitation. Ten swine were instrumented for hemodynamic and regional blood flow measurements with tracer microspheres. After two minutes of ventricular fibrillation (VF), the animals received eight minutes of either BCPR (five) or no-bystander CPR (NBCPR; five). Defibrillation was then attempted in both groups. If unsuccessful, CPR was begun and epinephrine 0.02 mg/kg was administered. Defibrillation was attempted again three and one-half minutes after epinephrine administration. Regional myocardial and cerebral blood flows were measured 30 seconds and five and one-half minutes after initiation of BCPR and one minute after epinephrine administration. In the BCPR group, myocardial blood flow was initially 29.0 +/- 33.2 and decreased to 15.0 +/- 21.5 mL/min/100 g during the last two and one-half minutes of BCPR. Cortical cerebral blood flow was initially 2.0 +/- 2.8 and fell to 0.6 +/- 0.8 mL/min/100 g during the last two and one-half minutes of BCPR. There were no statistical differences in myocardial blood flow and cerebral blood flow between the initial or late stages of BCPR (P greater than .14). There were no statistical differences in myocardial blood flow and cerebral blood flow between BCPR and NBCPR groups after epinephrine administration (P greater than .09).(ABSTRACT TRUNCATED AT 250 WORDS)

Prehospital resuscitation in Helsinki, Finland

Helsinki, a city of 500,000 inhabitants, is served by a two-tiered emergency medical system with basic emergency medical technicians in ordinary ambulances and one physician-staffed prehospital emergency care unit. All 266 patients with prehospital cardiopulmonary resuscitation during 1987 were studied. Two hundred twelve patients with presumed heart disease and a witnessed arrest were analyzed further. Their response times for basic life support and advanced life support were 5.5 and 10.7 minutes, respectively. The initial cardiac rhythm in 144 patients (68%) was ventricular fibrillation. In 79 of these patients, cardiopulmonary resuscitation was successful, and 39 patients (27%) were discharged from hospital. The patients who survived had shorter response times for basic life support and their arrest locations was more often outside home, compared with the nonsurvivors. The results seem comparable with emergency medical systems in the United States, but a need to reduce response times is identified.

Cardiac arrest and resuscitation: a tale of 29 cities

Published reports of out-of-hospital cardiac arrest give widely varying results. The variation in survival rates within each type of system is due, in part, to variation in definitions. To determine other reasons for differences in survival rates, we reviewed published studies conducted from 1967 to 1988 on 39 emergency medical services programs from 29 different locations. These programs could be grouped into five types of prehospital systems based on the personnel who deliver CPR, defibrillation, medications, and endotracheal intubation; the five systems were three types of single-response systems (basic emergency medical technician [EMT], EMT-defibrillation [EMT-D], and paramedic) and two double-response systems (EMT/paramedic and EMT-D/paramedic). Reported discharge rates ranged from 2% to 25% for all cardiac rhythms and from 3% to 33% for ventricular fibrillation. The lowest survival rates occurred in single-response systems and the highest rates in double-response systems, although there was considerable variation within each type of system. Hypothetical survival curves suggest that the ability to resuscitate is a function of time, type, and sequence of therapy. Survival appears to be highest in double-response systems because CPR is started early. We speculate that early CPR permits definitive procedures, including defibrillation, medications, and intubation, to be more effective.