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PubMed1990

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

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

Aged↗
PubMed1992

Automated external defibrillators: implications for training qualified ambulance staff.

STUDY OBJECTIVE: To investigate the performance of basic trained ambulance personnel using an automated external defibrillator (AED) after a short training program. METHODS: One hundred ninety ambulance attendants working in London received six and one-half hours training in the use of an AED, with written feedback and continuing education regarding performance after training. Performance was assessed over a period of 15 months by analysis of report forms and ECG/audible cassette tapes from the patients who were treated. RESULTS: Staff were able to operate the defibrillator correctly in 96% of cases and followed the protocol sequence taught in 34% of cases. The median time taken to activate the defibrillator following arrival of the ambulance at the scene of cardiac arrest was four minutes (range, one to 13 minutes). In 32% of cases, patients were intubated erroneously or moved to the ambulance before the AED was attached. CONCLUSION: The short course with continuing education was sufficient to train staff in AED operation, but errors in protocol compliance occurred throughout the trial.

Clinical Protocols↗
PubMed1985

Automatic external defibrillators: clinical, training, psychological, and public health issues.

Automatic external defibrillators (AEDs) will be used by spouses, family members, emergency first-responders, and the citizenry at large. Such use, however, raises a number of clinical, training, psychological, and public health issues. Clinical issues: Is cardiac arrest to be verified by the operator or the AED? Second verification systems, such as breath detectors, produce errors of omission, but greatly expand the pool of potential users. The relative merits of high sensitivity and low specificity in arrest verification must be defined by clinicians relative to the setting and the potential users. AEDs require cessation of basic CPR during their assessment periods; clinicians must determine the tradeoff between long interruption of basic life support and much earlier delivery of countershocks. Training issues: Criteria for those to be trained include consideration of who the patient will be and who the AED operator might be. AEDs pose a familiar adult education problem, that is, acquisition of a new psychomotor skill and retention of that skill for long periods before performance. What are the best teaching techniques? Currently available AEDs have different designs for device-operator interaction. Which design is most likely to assure proper performance during an actual arrest? Psychological issues: What are the psychological effects of learning about, living with, and eventually using an AED? The development of the automatic external defibrillator constitutes the most recent attempt to achieve early defibrillation of patients in cardiac arrest. The potential public health effect of such devices is enormous.

Electric Countershock↗
PubMed1987

Lay person use of automatic external defibrillation.

The ability of lay persons to learn and retain defibrillation skills using an automatic external defibrillator (AED) was assessed. Thirty-four family members of cardiac arrest survivors were trained in CPR techniques and defibrillation, and evaluated for performance of skills immediately following training and at six-week and three-month follow-ups. All but two were successfully trained to complete three cycles of CPR interspersed with three defibrillatory shocks in an average of four minutes with the first shock delivered in an average of two minutes. Although there were decrements in the speed and quality of performance at each follow-up period (P less than .01), we conclude that most lay persons can learn to operate an AED safely and under simulated conditions provide defibrillatory shocks an average of eight minutes faster than typical response times of emergency medical technicians. These results suggest that AEDs can be placed in many homes of patients at high risk for cardiac arrest.

Adult↗
PubMed1989

Automatic external defibrillators.

Early electrical therapy for patients with ventricular fibrillation and ventricular tachycardia can result in a significant increase of lives saved from sudden cardiac death. Rapid defibrillation has become a goal of prehospital and emergency department cardiac care, and the use of automatic external defibrillators can aid in reaching this objective. The history, mechanics, and implications of automatic external defibrillators are presented.

Animals↗
PubMed1995

Defibrillation by basic emergency medical technicians: effect on survival.

Several studies have examined the effect of early defibrillation by basic EMTs on patient survival. Although the studies have a common theme of early basic EMT defibrillation, they are diverse in locations, devices, control groups, caregivers, and protocols. They provide a confusing array of information that is difficult to review, synthesize, and interpret. Metaanalysis allows data pooling of these primary studies to combine results and statistically compare the observed variation in study outcomes. The purpose of this metaanalysis was to examine the published studies of early basic EMT defibrillation to learn whether this treatment has an effect on survival of out-of-hospital cardiac arrest. Analysis of the 10 studies that met inclusion criteria showed that despite variations in design, the overall effect size for all the studies was .092, indicating a 9.2% increase in survival over what would have been expected had the EMT-Ds not intervened.

Effect Modifier, Epidemiologic↗
PubMed1996

High discharge survival rate after out-of-hospital ventricular fibrillation with rapid defibrillation by police and paramedics.

STUDY OBJECTIVE: To assess outcome in patients with ventricular fibrillation (VF) treated by defibrillator-equipped police and emergency medical technician-paramedics in an advanced life support (ALS) emergency medical services (EMS) system. METHODS: We carried out a retrospective observational outcome study of all consecutive adult patients with atraumatic cardiac arrest treated from November 1990 through July 1995. The study was carried out in a city with a population of 76,865 in an area of 32.6 square miles. Central 911 dispatched police and an ALS ambulance simultaneously. Accurate intervals were obtained with the synchronization of all defibrillator clocks with the 911 dispatch clock. The personnel who arrived first delivered the initial shock. After shocks delivered by police, paramedics provided additional treatment if needed. Main outcome measures were time elapsed before delivery of the first shock, restoration of spontaneous circulation (ROSC), and survival to discharge home. RESULTS: Of 84 patients, 31 (37%) were first shocked by police. Thirteen of the 31 demonstrated ROSC, without need for ALS treatment. All 13 survived to discharge. The other 18 patients required ALS; 5 (27.7%) survived. Among the 53 patients first shocked by paramedics, 15 had ROSC after shocks only, and 14 survived. The other 38 needed ALS treatment; 9 survived. Call-to-shock time for all patients was less in the police group than in the paramedic group (5.6 versus 6.3 minutes, P = .038). For all patients, call-to-shock time was less in those with ROSC after shocks only than in those who needed ALS (5.4 versus 6.3 minutes, P = .011). Survival to discharge was 49% (41 of 84), with 18 of 31 (58%) in the police group and 23 of 53 (43%) in the paramedic group. Call-to-shock time for survivors was 5.8 minutes; it was 6.4 minutes for the nonsurvivors (P = .020). Neither ROSC nor discharge survival was significantly different between police and paramedic-shocked patients. ROSC after initial shock and call-to-shock time were major determinants of survival, whether the first shocks were administered by police or by paramedics. With ROSC after shocks only, 27 of 28 (96%) survived, whereas 14 of 56 (25%) needing ALS survived (P < .001). CONCLUSION: A high discharge-to-home survival rate was obtained with early defibrillation by both police and paramedics. When shocks resulted in ROSC, the overwhelming majority of patients survived (96%). Even brief time decreases (eg. 1 minute) in call-to-shock time increase the likelihood of ROSC from shocks only, with a consequent decrease in the need for ALS intervention. Short call-to-shock time and ROSC response to shocks only are major determinants of a high rate of survival after VF.

Adult↗
PubMed1997

Effect of electrode position and gel-application technique on predicted transcardiac current during transthoracic defibrillation.

STUDY OBJECTIVE: In transthoracic defibrillation, the American Heart Association (AHA) recommends wide separation of electrodes and avoidance of gel smearing between electrodes. Few data support this recommendation. Our objective was to determine the importance of electrode placement and gel-application technique on transcardiac defibrillation current and the effect of changes caused by postexercise vasodilation and sweating. METHODS: Our subjects were 10 normal adults, 5 men and 5 women, who ranged in age from 22 to 48 years. We determined interelectrode impedance (Z) using a validated test-pulse method that does not require shock delivery. Electrode placement/gel-application techniques were varied among four types: (1) AHA-recommended technique (apex-to-anterior electrode placement, no smearing of gel between electrodes); (2) parasternal-to-anterior placement, electrodes within 2 cm of each other, no smearing of gel between electrodes; (3) parasternal-to-anterior placement, electrodes within 2 cm of each other with smearing of gel between electrodes (worst-case scenario); and (4) apex-to-anterior placement, smearing of gel between electrodes. To assess the effect of cutaneous vasodilation and sweating on interelectrode impedance, we repeated these measurements after the subjects performed 12 to 18 minutes of treadmill exercise. The ratio of predicted transcardiac current of the AHA technique to that of the nonstandard technique was estimated with this formula: square root of Z, non-standard technique divided by square root of Z, AHA technique. RESULTS: Resting interelectrode impedance declined 38% from 58 +/- 10.3 omega (AHA-recommended technique) to 36 +/- 7.6 omega (electrode paddles adjacent, gel smeared between) (P < .01). Predicted transcardiac current ratio was reduced to .78 +/- .09 (P < .01), a 22% reduction. We noted no change in the results after exercise. CONCLUSION: Adjacent placement of electrodes and smearing of gel between electrodes creates a low-impedance pathway along the chest wall, which shunts current away from the heart. Thus improper application of electrodes and gel substantially degrades transcardiac current and may result in failed defibrillation. Sweating and vasodilation did not cause a similar problem.

Adult↗
PubMed2000

Transthoracic monophasic and biphasic defibrillation in a swine model: a comparison of efficacy, ST segment changes, and postshock hemodynamics.

OBJECTIVE: Biphasic waveforms for transthoracic defibrillation (DF) have been tested extensively after brief (15 s) episodes of VF in animal models and in patients undergoing electrophysiologic testing. The purpose of this study was to compare the effects mono- and biphasic waveforms for DF on postdefibrillation ST segments and left ventricular pressure, markers of myocardial injury, after more extended periods of VF (30 and 90 s). METHODS: 21 anesthetized and instrumented swine were randomized to truncated exponential monophasic or biphasic waveform DF. VF was induced electrically and 30 s later, DF with the designated waveform was attempted with a shock dose of 200 J. If unsuccessful, 300 J and then 360 J were administered if necessary. Following return to control hemodynamic values and normalization of the surface ECG, VF was again induced and, after 90 s, DF was attempted as in the 30 s VF period. CPR was not performed during VF and each animal was countershocked with only one waveform for both VF episodes. Waveforms were compared for frequency of first shock defibrillation success, surface ECG indicators of myocardial injury (ST segment changes at 10, 20, and 30 s after countershock) and time to return to pre-VF hemodynamics after successful DF, an indicator of postshock ventricular function. RESULTS: Successful first shock conversion rates at 30 and 90 s were 60 and 63% for monophasic and 64 and 82% for biphasic (NS). Biphasic DF after 30 s produced ST segment changes (measured 10 s after DF) in 1/10 animals while six of eight animals in the monophasic group showed ST segment changes (P=0.013). After 90 s of VF, ST segment changes were observed in 6/8 in the monophasic group and 2/10 in the biphasic group (P=0.054). Differences in the time to hemodynamic recovery (return to control peak left ventricular pressure) were not observed between biphasic and monophasic waveforms after 30 or 90 s of VF. CONCLUSIONS: Monophasic and biphasic transthoracic defibrillation are equally effective in terminating VF of 30 and 90 s duration and restoring a perfusing rhythm. The biphasic waveform produced less ECG evidence of transient myocardial injury. However, there was no difference in the rate of return to control hemodynamics. ST segment changes following countershock of VF of brief duration are transient and of questionable significance.

Animals↗
PubMed2001

"Probability of successful defibrillation" as a monitor during CPR in out-of-hospital cardiac arrested patients.

The frequency spectrum of the ECG in ventricular fibrillation (VF) correlates with myocardial perfusion and might predict defibrillation success defined as return of spontaneous circulation (ROSC). The predictive power increases when more spectral variables are combined, but the complex information can be difficult to handle during the intensity of CPR. We therefore developed a method for expressing this multidimensional information in a single reproducible variable reflecting the probability of defibrillation success. This is based on the highest performing predictor for ROSC after 883 shocks given to 156 patients with VF. This was a combination of two decorrelated spectral features based on a principal component analysis of an original feature set with information on centroid frequency, peak power frequency, spectral flatness and energy. The function "Probability of defibrillation success" (P(ROSC)(v)) was developed by a 2-dimensional histogram technique. P(ROSC)(v) discriminated between shocks followed by ROSC and No-ROSC (P<0.0001). The present methodology indicates a possible way to develop a CPR monitor.

Cardiopulmonary Resuscitation↗
PubMed2000

Minimally invasive direct cardiac massage and defibrillation.

Direct massage of the heart may be performed using a specifically designed device inserted via a limited thoracic incision. The technique is simple to perform and has been shown in experimental studies to be physiologically similar to formal open-chest cardiac massage. Preliminary human studies have been encouraging and pre-hospital and in-hospital studies are in progress. Modification of the device allows combined epicardial-transthoracic defibrillation. Energy requirements for successful defibrillation using this method are considerably lower than standard external defibrillation.

Animals↗
PubMed2002

Automated external defibrillators and first responders: a satisfaction survey.

PRIMARY OBJECTIVE: Automated external defibrillators (AEDs) are used with increasing frequency in the United States by first responders (FR) such as police officers (PO) or firefighters (FF). However, FR satisfaction with use of AEDs has not been investigated. We hypothesized that FR satisfaction is comparable with that of paramedics (PA) and that, among those who have defibrillated with AEDs, those who have restored a pulse before PA arrival have a higher level of satisfaction than those who have not restored a pulse. MATERIALS AND METHODS: A 21-item questionnaire with closed answers was sent to FR and PA in four communities. Each answer was scored 0, 1 or 2. A score between 10 and 16 correlated with the highest satisfaction level. RESULTS: 276 out of 311 questionnaires were returned (89%). Two hundred and eleven respondents (35 PA, 70 FF and 106 PO) had used an AED and 99 FF and PO had restored a pulse before PA arrival. The satisfaction level of PO, FF and PA was high as demonstrated by the scores: 13.26, 13.07 and 13.39, respectively. Use of AED and pulse restoration resulted in higher scores than those of groups who had been trained only and who had not restored a pulse. CONCLUSION: FR demonstrated a high level of satisfaction with using AEDs, and also had a favorable attitude toward implementation of AED use. Restoration of a pulse was clearly a factor responsible for a higher satisfaction. This positive attitude should encourage further implementation of early defibrillation programs in non-medical first responder settings.

Allied Health Personnel↗
PubMed2002

Automated external defibrillation as part BLS: implications for education and practice.

The latest Adult Basic Life Support (BLS) guidelines support the inclusion of the use of the automated external defibrillator (AED), as part of basic life support (BLS). Emphasis on the provision of early defibrillation as part of BLS acknowledges the importance of this manoeuvre in the successful termination of ventricular fibrillation. The ramifications of such changes for both first responders and organisations implementing the guidelines should not be underestimated. Issues relating to resourcing, content and duration of training and retraining, auditing and evaluation require further exploration. To consider these issues now seems particularly pertinent, given the recent launch of the UK Government's paper on public health, 'Saving Lives-Our Healthier Nation' which seeks to deploy AEDs in busy public places for use by trained members of the lay public. Additionally, defibrillation has been identified as one of the key competencies that all trained nurses and other health care providers should be able to undertake. This paper will consider the background to the current guideline changes, analyse the wider implications of translating the recommendations into practice, and offer possible solutions to address the issues raised. Whilst the analysis is particularly pertinent to the United Kingdom, many of the issues raised have international importance.

Automation↗
PubMed2002

Refibrillation, resuscitation and survival in out-of-hospital sudden cardiac arrest victims treated with biphasic automated external defibrillators.

PRIMARY OBJECTIVE: Defibrillation is essential for victims of sudden cardiac arrest (SCA) with ventricular fibrillation (VF), yet it does not terminate the underlying causes of VF. Prior to more definitive interventions, these same causes may result in recurrence of VF following defibrillation (refibrillation). The incidence and course of refibrillation, and its relation to patient outcomes, has not been previously described in the context of treatment of out-of-hospital SCA with biphasic waveform automated external defibrillators (AEDs). MATERIALS AND METHODS: ECGs were recovered from all shocks delivered with biphasic AEDs by Basic Life Support (BLS) first responders, primarily police, in witnessed cardiac arrests occurring from December 1996 to December 2001 in the Rochester, MN public service area. Only events prior to administration of cardio-active medications were considered. Frequency and time to occurrence of refibrillation were compared in patients in relation to the progress of their resuscitation and survival. RESULTS AND CONCLUSIONS: One hundred and sixteen of 128 shocks delivered under BLS care to 49 patients with witnessed cardiac arrests presenting with VF terminated VF. Most patients (61%) refibrillated while under BLS care, many (35%) more than once. Occurrence of and time to refibrillation were unrelated to achievement of return of spontaneous circulation (ROSC) under BLS care (BLS ROSC), to survival to hospital discharge and to neurologically intact survival.

Adult↗
PubMed1997

Variation in defibrillation modes after synchronized cardioversion: a potential hazard.

We conducted a survey of all defibrillators currently on the European market that offer synchronized cardioversion. The mode after cardioversion can be classed into one of four categories: (1) remain in synchronized mode; (2) defer to asynchronized mode; (3) 'intelligent'; and (4) configurable. The different modes and the lack of standardization present a potential hazard because they cause confusion among the user of the defibrillator. Uniformity should be obtained after broad agreement between clinicians and manufacturers of defibrillators.

Atrial Fibrillation↗
PubMed1998

The influence of chest compressions and external defibrillation on the release of creatine kinase-MB and cardiac troponin T in patients resuscitated from out-of-hospital cardiac arrest.

OBJECTIVES: This study sought to determine the influence of resuscitative procedures, such as chest compressions and external defibrillation, on the release of creatine kinase (CK)-MB and cardiac troponin T (cTnT). METHODS: In 87 patients with out-of-hospital cardiac arrest and successful cardiopulmonary resuscitation (CPR), the initial ECG rhythm, the duration of cardiac arrest and CPR, and the number of defibrillations were assessed on arrival in the hospital. The serum CK-MB and cTnT were measured 12 h after the event. We also assessed whether the patient developed cardiogenic shock within 12 h, and if the patient had acute myocardial infarction (AMI), which was confirmed or eliminated by of typical ECG findings, thallium-201 myocardial scintigraphy, or autopsy within the hospital stay. A backward stepwise linear regression model was applied to assess the association between the markers of myocardial injury (CK-MB and cTnT) and the above clinical variables. RESULTS: CK-MB concentrations were independently associated with the presence of AMI [B 68.5 (SE 28.5, P = 0.018)], the duration of CPR (as a measure of trauma to the chest by means of chest compressions) [B 2.07 (SE 1.01, P = 0.045)] and cardiogenic shock [B 52.3 (SE 23.4, P = 0.03)]. The remaining clinical variables listed were excluded by the model. Cardiac troponin T concentrations were only associated with the presence of AMI [B 4.86 (SE 1.34, P = 0.0005)]. There was a non-significant association between increasing serum cTnT concentrations and the presence of cardiogenic shock [B 2.51 (SE 1.46, P = 0.09)]. The remaining clinical variables were excluded by the model. CONCLUSION: The release of CK-MB appears to be influenced by the duration of resuscitation and the presence of cardiogenic shock. This has to be considered when interpreting serum CK-MB concentrations after CPR. The release of cTnT seems to be only associated with acute myocardial infarction, but not with the duration of chest compressions, or with the number of defibrillations administered.

Aged↗
PubMed1998

Seven years' experience with early defibrillation by police and paramedics in an emergency medical services system.

PRIMARY OBJECTIVE: To assess the outcome of patients with out-of-hospital cardiac arrest with ventricular fibrillation as the presenting rhythm in an emergency medical services system utilizing a combined police/paramedic response to provide early defibrillation. MATERIALS AND METHODS: Police and paramedics were dispatched from law enforcement and ambulance communications centers, respectively. First-arriving personnel delivered initial shocks, all using automated external defibrillators. Patients were classified according to response to initial shocks: restoration of pulses with shocks only or in need of advanced life support, including epinephrine. Discharge survival was defined as return to home without disabling neurologic injury. RESULTS: Over the 7-year period of study 131 patients presented with ventricular fibrillation: 58 were first treated by police and 73 by paramedics. Restoration of pulses with shocks only and discharge survival were not different in police and paramedic groups, with overall survival of 40% (53 of 131 patients). Among the survivors, 19% (18/95 patients) obtained a spontaneous circulation only after administration of epinephrine and other ALS interventions. CONCLUSION: Both restoration of a functional circulation, without need for advanced life support interventions, and discharge survival without neurologic disability are very dependent upon the rapidity with which defibrillation is accomplished, regardless of who delivers the shocks. In addition, a smaller but significant number of patients who require ALS interventions, including epinephrine, for restoration of a spontaneous circulation survive to discharge. Short time differences, on the order of 1 min, are significant determinants of both immediate response to shocks and discharge survival.

Adolescent↗
PubMed1985

The automatic implantable cardioverter-defibrillator: an overview.

The automatic implantable cardioverter-defibrillator continuously monitors the heart, identifies malignant ventricular tachyarrhythmias and then delivers electrical countershock to restore normal rhythm. There are two defibrillating electrodes which are also used for waveform analysis; one is located in the superior vena cava and the other is placed over the cardiac apex. A third bipolar right ventricular electrode is used for rate counting and R wave synchronization. When ventricular fibrillation occurs, a 25 J pulse is delivered; when ventricular tachycardia faster than the preset rate is detected, the discharge is R wave-synchronized. The clinical evaluation study of this therapeutic method began in February 1980 in patients with recurrent refractory life-threatening ventricular tachyarrhythmias. So far, the device has been implanted in nearly 500 patients with a follow-up period of up to 59 months. The risks and complications associated with this treatment were found to be moderate. Actuarial analysis has demonstrated significant impact on the survival rate of the patients receiving implants with 1 year arrhythmic mortality rate reduced to 2% or less in all groups analyzed. The available data indicate that the automatic cardioverter-defibrillator can reliably identify and correct potentially lethal ventricular tachyarrhythmias, leading to a substantial improvement in survival in properly selected high risk patients.

Adolescent↗