Influence of emergency medical services systems and prehospital defibrillation on survival of sudden cardiac death victims

Emergency system prospective performance evaluation for cardiac arrest in Lombardia, an Italian region

BACKGROUND

The aim of this research is to evaluate quality of out-of-hospital medical services in our country, using performance indicators and a new computerised database.

METHODS

(a)

EXPERIMENTAL DESIGN

Data were collected prospectively in three emergency dispatch centres for 90 days. Follow-up was evaluated at 1 day and 1 month after the event. This paper presents data on the cardiac arrest cohort only. (b)

SETTING

Three emergency dispatch centres in Lombardia. (c)

PATIENTS

One hundred and seventy-eight patients in non-traumatic cardiac arrest were enrolled. (d)

INTERVENTIONS

None. The study was observational only.

RESULTS

Mean interval between phone call and arrival on scene was 8.5+/-3.5 min. BLS manoeuvres were carried out from bystanders only in 15% of the cohort; this was associated with significant mortality reduction (85.7 versus 95.8%, chi(2) P<0.05). One hundred and thirty-three patients (75%) received assistance from BLS crews while only 45 patients (25%) were assisted by ALS medical personel, with a significant mortality reduction (ALS deaths 86.7%, BLS deaths 97%). Total 24 h survival was 9% and survival at 1 month declined to 6.17%.

CONCLUSIONS

Quality monitoring produces objective information on interventions and outcomes. Only with this information, is it possible to implement improvement programmes that are planned according to the data presented.

Out-of-hospital defibrillation with automated external defibrillators: postshock analysis should be delayed

STUDY OBJECTIVE

The American Heart Association protocols for use of automated external defibrillators (AEDs) recommend that a rhythm analysis be done immediately after each defibrillation attempt. However, shock is often followed by electrical silence or marginally organized electrical activity before ventricular fibrillation (VF) or ventricular tachycardia (VT) recurs. The optimal timing of postshock analysis for identification of recurrent VF/VT is unknown. This study examines the time to recurrence of VF/VT after a defibrillation attempt with AED.

METHODS

Over an 18-month period, all tapes from patients with out-of-hospital cardiac arrest who received shocks at least once with an AED were screened for recurrent VF/VT. All cases come from a single emergency medical services system providing basic life support, defibrillation with AED, and intubation with an esophageal-tracheal twin-lumen airway device (Combitube) for a population of 633,511 individuals. Pediatric and traumatic cases were excluded. When VF/VT recurred within 3 minutes of the defibrillation attempt, rhythm strips were printed and included in the study. Two cardiology fellows, blinded to the study objectives, measured the time from defibrillation to recurrent VF/VT for each strip.

RESULTS

Over the study period, 222 tapes from 96 patients met the inclusion criteria. Only 44 (20%) occurrences of VF/VT had recurred within 6 seconds of defibrillation, 162 (73%) at 60 seconds, and 200 (90%) at 90 seconds.

CONCLUSION

Eighty percent of VF/VT recurred more than 6 seconds after defibrillation and were missed when using current American Heart Association AED protocols. Subsequent analysis should be postponed until at least 30 seconds after defibrillation. Performing 30 seconds of chest compressions after defibrillation before subsequent AED rhythm analysis would increase AED identification of VF/VT to 52%.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Out-of-hospital cardiac arrest in a rural area: a 16-year experience with lessons learned and national comparisons

STUDY OBJECTIVE

To evaluate the effectiveness of the emergency medical services (EMS) system in a rural island community in resuscitating victims of out-of-hospital cardiac arrest over the past 16 years.

METHODS

We conducted a retrospective analysis of all EMS responses to cardiac arrests on San Juan Island, a rural island community of 5,000 people in the Pacific Northwest. Data were collected between January 1977 and July 1994 on the basis of the Utstein criteria. From these data, we calculated survival rates and compared them with published data from other rural and nonrural areas in the United States.

RESULTS

During this study, 22% of all the patients who sustained a cardiac arrest of cardiac origin on the island survived to hospital discharge. The survival rate for witnessed cases of ventricular fibrillation and ventricular tachycardia was 43%.

CONCLUSION

The combined paramedic/emergency medical technician system used on San Juan Island has yielded survival rates comparable to those of urban areas. This system may serve as a model for other rural communities, especially those with well-defined geographic areas and established 911 central dispatching.

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.

Prehospital cardiac arrest treated by urban first-responders: profile of patient response and prediction of outcome by ventricular fibrillation waveform

STUDY OBJECTIVES

To determine the speed and characteristics of patient response to urban first-responder defibrillation and to determine whether amplitude of ventricular fibrillation (VF) can predict outcome in these patients.

TYPE OF PARTICIPANTS

All adult patients in prehospital VF treated by fire department first-responders (265).

DESIGN AND INTERVENTIONS

A prospective observational study occurring between February 1, 1989, and January 1, 1991. Patients were defibrillated according to advanced cardiac life support and first-responder protocols. ECG and time data were recorded digitally.

MAIN RESULTS

Sixty-five percent of patients converted from VF to a more stable rhythm at least once during first-responder monitoring. Fifty-four percent of converted patients refibrillated at least once, and 42% of all stable conversions occurred after at least one episode of refibrillation. Seventy percent of all refibrillations occurred less than six minutes after the defibrillator was turned on, and 23% occurred after more than ten minutes. The proportion of stable conversions decreased from 30% on first conversion to 2% on fourth conversion. With each successive conversion the interval to refibrillation grew shorter, and development of a pulse or blood pressure became less likely. Presence of blood pressure or pulse after conversion had a sensitivity for hospital discharge of 54% and a specificity of 98%. Maximum VF amplitude before countershock was highly predictive of postshock rhythm, stable conversion in the field, time interval before refibrillation, inpatient admission, and hospital discharge. VF amplitude was unrelated to response interval or interval to defibrillation but was positively related to bystander CPR. Logistic regression identified VF amplitude as the most important predictor of hospital discharge; traditional variables such as response interval and bystander CPR were not predictive once amplitude had been accounted for. Changes in VF amplitude during the course of resuscitation efforts were frequent and also predictive of outcome.

CONCLUSION

Patients in VF who were treated by early countershock refibrillated much more frequently than previously reported. Refibrillations occur both early and late. Initial VF maximum amplitude is strongly predictive of outcome. Future reports of VF cardiac arrest should control for this previously neglected variable. Increased amplitude of VF during repeated refibrillation episodes is associated with increased hospital discharge, so future studies of advanced cardiac life support interventions should explore changes in VF amplitude as an outcome variable.

Aeromedical evacuation of rural victims of nontraumatic cardiac arrest

STUDY OBJECTIVES

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

DESIGN

Retrospective chart review.

SETTING

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

PARTICIPANTS

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

MEASUREMENTS AND MAIN RESULTS

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

CONCLUSION

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

Survival from out-of-hospital cardiac arrest: effects of patient age and presence of 911 Emergency Medical Services phone access

The purpose of this investigation was to determine factors associated with survival from out-of-hospital cardiac arrest, including effects of 911 Emergency Medical Services telephone access and the age of patient. Subjects included 1,753 prehospital cardiac arrest patients in Iowa. Patient survival status and other variables were compared for patients with access to a 911 service with those who did not, and for different age categories, using univariate associations and multivariate logistic regression analysis. The presence of 911 telephone access was significantly associated with survival from out-of-hospital cardiac arrest (9.18% versus 5.35% survival for 911 versus no 911 groups, respectively). This association was partially the result of the significant association of 911 with decreased time from collapse to call for help, decreased time to cardiopulmonary resuscitation (CPR), and decreased time to first shock (if in ventricular fibrillation [VF]). Younger age was significantly associated with survival in univariate analyses (8.94% versus 6.26% survival for younger versus older age groups, respectively), but this was not an independent association, which is indicated by the lack of significance of age in the multivariate model.

Management of cardiopulmonary arrest in the rehabilitation setting

Life-threatening cardiac and respiratory arrests are stressful emergency situations. Nurses may be anxious and unsure of what needs to be done if their roles are not clearly defined. This article describes a system one rehabilitation hospital uses when responding to arrests, reviews the steps in basic cardiopulmonary resuscitation, and presents an algorithm of a cardiopulmonary arrest.

Prehospital care: the future of emergency medical services

Most prehospital interventions, both pharmacologic and procedural, have been accepted without clear demonstrations of their abilities to impact patient outcomes or without clear indications that withholding or delaying the intervention pending arrival at a definitive emergency department will adversely affect the patient. Interventions that have the benefit of supportive research have been applied equally to urban and nonurban emergency medical services environments. In selecting interventions, inadequate consideration has been given to the differences in emergency medical services personnel training, frequencies of their exposure to patients, frequencies of skill use, and availabilities of effective continuing education programs in the urban and nonurban environments. These issues are discussed, and the necessary focus of the future of emergency medical services in urban, suburban, and rural environments is predicted.

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.

Geographic variation in sudden coronary death

To describe geographic variations in an indicator of sudden coronary death, data from the National Center for Health Statistics were examined for deaths occurring out of hospital or in emergency rooms in 1984 to 1986 in 42 states. In white males aged 55 to 64 years, the percent of ischemic heart disease deaths coded as occurring out of hospital or in the ER ranged from 49.6% to 70.4%. The percents tended to be higher in mountain states and around Lake Michigan. However, neighboring states sometimes had very different percents. Within regions, percents were higher in nonmetropolitan than in metropolitan areas. Standard mortality ratios for white males of all ages revealed that several states had relatively high rates of death out of hospital or in the ER. These included New York, Michigan, and Wisconsin. High rates of coronary death out of hospital or in the ER may be due to high overall coronary death rates, high percent of coronary deaths occurring out of hospital or in the ER, or both. Further studies are needed of geographic variation in sudden coronary death and cardiac arrest and factors that might explain the variation such as emergency medical services. Place of death data from death certificates may be useful in monitoring efforts to prevent sudden coronary death.