A trial of an impedance threshold device in out-of-hospital cardiac arrest.

BACKGROUND: The impedance threshold device (ITD) is designed to enhance venous return and cardiac output during cardiopulmonary resuscitation (CPR) by increasing the degree of negative intrathoracic pressure. Previous studies have suggested that the use of an ITD during CPR may improve survival rates after cardiac arrest. METHODS: We compared the use of an active ITD with that of a sham ITD in patients with out-of-hospital cardiac arrest who underwent standard CPR at 10 sites in the United States and Canada. Patients, investigators, study coordinators, and all care providers were unaware of the treatment assignments. The primary outcome was survival to hospital discharge with satisfactory function (i.e., a score of ≤3 on the modified Rankin scale, which ranges from 0 to 6, with higher scores indicating greater disability). RESULTS: Of 8718 patients included in the analysis, 4345 were randomly assigned to treatment with a sham ITD and 4373 to treatment with an active device. A total of 260 patients (6.0%) in the sham-ITD group and 254 patients (5.8%) in the active-ITD group met the primary outcome (risk difference adjusted for sequential monitoring, -0.1 percentage points; 95% confidence interval, -1.1 to 0.8; P=0.71). There were also no significant differences in the secondary outcomes, including rates of return of spontaneous circulation on arrival at the emergency department, survival to hospital admission, and survival to hospital discharge. CONCLUSIONS: Use of the ITD did not significantly improve survival with satisfactory function among patients with out-of-hospital cardiac arrest receiving standard CPR. (Funded by the National Heart, Lung, and Blood Institute and others; ROC PRIMED ClinicalTrials.gov number, NCT00394706.).

Association between survival and early versus later rhythm analysis in out-of-hospital cardiac arrest: do agency-level factors influence outcomes?

STUDY OBJECTIVE: Effectiveness of a resuscitation strategy may vary across communities. We hypothesize that a strategy that prioritizes initial emergency medical services (EMS) rhythm analysis (analyze early) will be associated with survival advantage among EMS systems with lower baseline (pretrial) ventricular fibrillation survival, whereas a strategy that prioritizes initial EMS cardiopulmonary resuscitation (analyze late) will be associated with survival advantage among systems with higher ventricular fibrillation baseline survival. METHODS: We conducted a secondary, post hoc study of a randomized trial of out-of-hospital cardiac arrest. Subjects were stratified according to randomization status (analyze early versus analyze late) and EMS agency baseline ventricular fibrillation survival. We used a mixed-effects model to determine whether the association between favorable functional survival to hospital discharge and trial intervention (analyze late versus analyze early) differed according to EMS agency baseline ventricular fibrillation survival (<20% or >20%). RESULTS: Characteristics were similar among patients randomized to analyze early (n=4,964) versus analyze late (n=4,426). For EMS agencies with baseline ventricular fibrillation survival less than 20%, analyze late compared with analyze early was associated with a lower likelihood of favorable functional survival (3.8% versus 5.5%; odds ratio [OR]=0.67 [95% CI 0.50, 0.90]). Conversely, among agencies with a ventricular fibrillation survival greater than 20%, analyze late compared with analyze early was associated with higher likelihood of favorable functional survival (7.5% versus 6.1%; OR=1.22 [95% CI 0.98, 1.52]). In the multivariable-adjusted model, for every 10% increase in baseline ventricular fibrillation survival, analyze late versus analyze early was associated with a 34% increase in odds of favorable functional survival (OR=1.34 [95% CI 1.07 to 1.66]). CONCLUSION: The findings suggest that system-level characteristics may influence resuscitation outcomes.

Perishock pause: an independent predictor of survival from out-of-hospital shockable cardiac arrest.

BACKGROUND: Perishock pauses are pauses in chest compressions before and after defibrillatory shock. We examined the relationship between perishock pauses and survival to hospital discharge. METHODS AND RESULTS: We included out-of-hospital cardiac arrest patients in the Resuscitation Outcomes Consortium Epistry-Cardiac Arrest who suffered arrest between December 2005 and June 2007, presented with a shockable rhythm (ventricular fibrillation or pulseless ventricular tachycardia), and had cardiopulmonary resuscitation process data for at least 1 shock (n=815). We used multivariable logistic regression to determine the association between survival and perishock pauses. In an analysis adjusted for Utstein predictors of survival, the odds of survival were significantly lower for patients with preshock pause ≥20 seconds (odds ratio, 0.47; 95% confidence interval, 0.27 to 0.82) and perishock pause ≥40 seconds (odds ratio, 0.54; 95% confidence interval, 0.31 to 0.97) compared with patients with preshock pause <10 seconds and perishock pause <20 seconds. Postshock pause was not independently associated with a significant change in the odds of survival. Log-linear modeling depicted a decrease in survival to hospital discharge of 18% and 14% for every 5-second increase in both preshock and perishock pause interval (up to 40 and 50 seconds, respectively), with no significant association noted with changes in the postshock pause interval. CONCLUSIONS: In patients with cardiac arrest presenting in a shockable rhythm, longer perishock and preshock pauses were independently associated with a decrease in survival to hospital discharge. The impact of preshock pause on survival suggests that refinement of automatic defibrillator software and paramedic education to minimize preshock pause delays may have a significant impact on survival.

The relationship between shocks and survival in out-of-hospital cardiac arrest patients initially found in PEA or asystole.

OBJECTIVE: To describe survival rates from out-of-hospital cardiac arrest for patients who present with pulseless electrical activity or asystole according to whether they remained in a non-shockable rhythm or converted to ventricular fibrillation and were shocked appropriately. RESULTS: Observational analysis of a cardiac arrest registry collected as part of a randomized trial. SETTING: Five urban/suburban cities in the United States and Canada. PARTICIPANTS: Trial subjects (adult, treated, non-traumatic) whose first documented heart rhythm/state following cardiac arrest was asystole or pulseless electrical activity. INTERVENTION: Periodic pauses to assess for shockable rhythm. MAIN OUTCOME MEASURE: Survival to hospital discharge. RESULTS: Of 1377 cardiac arrest patients, 738 presented with an initial arrest rhythm/state of either pulseless electrical activity or asystole. Of the 738, 78% (n=574) subsequently remained in a non-shockable rhythm/state at each evaluation throughout the resuscitation (No-Shock group) while 22% (n=164) converted to ventricular fibrillation and were shocked by emergency medical service (Shock group). Survival to hospital discharge was significantly greater in the No-Shock group (4.9% versus 0.6%, p=0.01). Shock group remained a predictor (odds ratios=0.18, p=0.036) of death after adjustment for potential confounders. CONCLUSIONS: These results suggest that patients with cardiac arrest who develop VF during the course of treatment for initially observed pulseless electrical activity or asystole do not benefit from conventional approaches to treatment such as defibrillation. Further study is warranted to define the optimal treatment of this patient cohort.

Consent in resuscitation trials: benefit or harm for patients and society?

CONTEXT: Research in an emergency setting is challenging because there may not be sufficient opportunity or time to obtain informed consent from the patient or their legally authorized representative. Such research can be conducted without prior consent if specific criteria are met. However consent is sometimes required for continued participation and may bias the results of the study. OBJECTIVE: To review regulations related to waiver of consent in emergency research, and evidence of whether such regulations introduce bias. RESULTS: Emergency research can be conducted without consent, either through community disclosure and consultation followed by patient or family notification and consent for continued participation after the intervention was applied, or under a minimal risk waiver. Review of the clinical record is necessary to determine important outcomes such as survival to discharge. If consent is required for this review but not granted, then these data are missing during analysis. If seriously ill or disadvantaged patients are less likely to assent, then investigators cannot determine reliably whether these vulnerable patients were harmed by the intervention. If missing data are different from complete data, then the analysis is susceptible to bias, and the conclusions could be misleading. Extrapolation from non-consent rates in resuscitation studies to results from the DAVID trial demonstrates that the rate of absence of data and information due to lack of assent can influence whether there is a significant difference between treatment groups (survival of control versus intervention: p=0.04 for complete data; p=0.08 for 10.8% lack of assent; p=0.40 for 19.7% lack of assent). CONCLUSIONS: Exception from consent for emergency research should extend to review of the hospital record as the standard in emergency research. The only potential risk to patients associated with review of the clinical record after the intervention is loss of privacy and confidentiality. Appropriate safeguards can be taken to minimize this risk.

Manual chest compression vs use of an automated chest compression device during resuscitation following out-of-hospital cardiac arrest: a randomized trial.

CONTEXT: High-quality cardiopulmonary resuscitation (CPR) may improve both cardiac and brain resuscitation following cardiac arrest. Compared with manual chest compression, an automated load-distributing band (LDB) chest compression device produces greater blood flow to vital organs and may improve resuscitation outcomes. OBJECTIVE: To compare resuscitation outcomes following out-of-hospital cardiac arrest when an automated LDB-CPR device was added to standard emergency medical services (EMS) care with manual CPR. DESIGN, SETTING, AND PATIENTS: Multicenter, randomized trial of patients experiencing out-of-hospital cardiac arrest in the United States and Canada. The a priori primary population was patients with cardiac arrest that was presumed to be of cardiac origin and that had occurred prior to the arrival of EMS personnel. Initial study enrollment varied by site, ranging from late July to mid November 2004; all sites halted study enrollment on March 31, 2005. INTERVENTION: Standard EMS care for cardiac arrest with an LDB-CPR device (n = 554) or manual CPR (n = 517). MAIN OUTCOME MEASURES: The primary end point was survival to 4 hours after the 911 call. Secondary end points were survival to hospital discharge and neurological status among survivors. RESULTS: Following the first planned interim monitoring conducted by an independent data and safety monitoring board, study enrollment was terminated. No difference existed in the primary end point of survival to 4 hours between the manual CPR group and the LDB-CPR group overall (N = 1071; 29.5% vs 28.5%; P = .74) or among the primary study population (n = 767; 24.7% vs 26.4%, respectively; P = .62). However, among the primary population, survival to hospital discharge was 9.9% in the manual CPR group and 5.8% in the LDB-CPR group (P = .06, adjusted for covariates and clustering). A cerebral performance category of 1 or 2 at hospital discharge was recorded in 7.5% of patients in the manual CPR group and in 3.1% of the LDB-CPR group (P = .006). CONCLUSIONS: Use of an automated LDB-CPR device as implemented in this study was associated with worse neurological outcomes and a trend toward worse survival than manual CPR. Device design or implementation strategies require further evaluation. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00120965.

Predictors of cardiopulmonary resuscitation and automated external defibrillator skill retention.

BACKGROUND: Few data exist regarding the retention of cardiopulmonary resuscitation (CPR) and automated external defibrillator (AED) skills over time in relationship to characteristics of lay volunteer responders, training, or risk of exposure to victims. The purpose of this study was to describe the characteristics associated with adequate CPR and AED skill retention. METHODS AND RESULTS: Skill retention was tested 3 to 18 months (mean 6.9 +/- 3.5 months) after initial training. Instructors judged adequacy of performance of essential CPR or AED skills and provided an overall assessment (adequate/inadequate), which was used as the outcome. Data on 7261 laypersons trained in CPR (4358 also received AED training) in 24 sites across the United States and Canada were available from the Public Access Defibrillation (PAD) Trial. Characteristics of the volunteers, classes, and facilities were evaluated as predictors of performance adequacy. Adjusting for site, intervention assignment (CPR-only or CPR + AED), and time since initial training, volunteer characteristics associated with adequate CPR performance were age (OR 0.78 per 10-year increment), male sex (OR 1.44), minority (OR 0.62), married (OR 1.35), prior emergency experience (OR 1.66), prior CPR class (OR 1.68), prior advanced training (OR 1.59), and extracurricular CPR training (OR 1.91) (all P < .05). Characteristics associated with AED performance included age (OR 0.69), college education (OR 1.34), and native language other than English (OR 0.51) (all P < .05). CONCLUSIONS: Certain subgroups of lay volunteers may need targeted outreach programs in CPR and AED use, classes with longer training time, more practice, or more intense retraining to maintain their CPR and/or AED skills.

Wide variability in drug use in out-of-hospital cardiac arrest: a report from the resuscitation outcomes consortium.

BACKGROUND: Despite the publication and dissemination of the Advanced Cardiac Life Support guidelines, variability in the use of drugs during resuscitation from out-of-hospital cardiac arrest may exist between different Emergency Medical Services throughout North America. The purpose of this study was to characterize the use of such drugs and evaluate their relationship to cardiac arrest outcomes. METHODS AND RESULTS: The Resuscitation Outcomes Consortium Registry-Cardiac Arrest collects out-of-hospital cardiac arrest data from 264 Emergency Medical Services agencies in 11 geographical locations in the U.S. and Canada. Multivariable logistic regression was used to assess the association between drug use, characteristics of the cardiac arrest and a pulse at emergency department arrival and survival to discharge. A total of 16,221 out-of-hospital cardiac arrests were attended by 74 Emergency Medical Services agencies. There was a considerable variability in the administration of amiodarone and lidocaine for the treatment of shock resistant ventricular tachycardia/ventricular fibrillation. For non-shockable rhythms, atropine use ranged from 29 to 95% and sodium bicarbonate use ranged from 0.2 to 73% across agencies in the 89% of agencies that used the drug. Epinephrine use ranged from 57 to 98% within agencies. Neither lidocaine nor amiodarone was associated with a survival benefit while there was an inverse relationship between the administration of epinephrine, atropine and sodium bicarbonate and survival to hospital discharge. CONCLUSIONS: There is considerable variability among Emergency Medical Services agencies in their use of pharmacological therapy for out-of-hospital cardiac arrests which may be resolved by performing large randomized trials examining effects on survival.

Variation in out-of-hospital cardiac arrest resuscitation and transport practices in the Resuscitation Outcomes Consortium: ROC Epistry-Cardiac Arrest.

OBJECTIVES: To identify variation in patient, event, and scene characteristics of out-of-hospital cardiac arrest (OOHCA) patients assessed by emergency medical services (EMS), and to investigate variation in transport practices in relation to documented prehospital return of spontaneous circulation (ROSC) within eight regional clinical centers participating in the Resuscitation Outcomes Consortium (ROC) Epistry-Cardiac Arrest. METHODS: OOHCA patient, event, and scene characteristics were compared to identify variation in treatment and transport practices across sites. Findings were adjusted for site and standard Utstein covariates. Using logistic regression, these covariates were modeled to identify factors related to the initiation of transport without documented prehospital ROSC as well as survival in these patients. SETTING: Eight US and Canadian sites participating in the ROC Epistry-Cardiac Arrest. POPULATION: Persons ≥ 20 years with OOHCA who (a) received compressions or shock by EMS providers and/or received bystander AED shock or (b) were pulseless but received no EMS compressions or shock between December 2005 and May 2007. RESULTS: 23,233 OOHCA cases were assessed by EMS in the defined period. Resuscitation (treatment) was initiated by EMS in 13,518 cases (58%, site range: 36-69%, p < 0.0001). Of treated cases, 59% were transported (site range: 49-88%, p < 0.0001). Transport was initiated in the absence of documented ROSC for 58% of transported cases (site range: 14-95%, p < 0.0001). Of these transported cases, 8% achieved ROSC before hospital arrival (site range: 5-21%, p < 0.0001) and 4% survived to hospital discharge (site range: 1-21%, p < 0.0001). In cases with transport from the scene initiated after documented ROSC, 28% survived to hospital discharge (site range: 18-44%, p < 0.0001). CONCLUSION: Initiation of resuscitation and transport of OOHCA and the reporting of ROSC prior to transport markedly varies among ROC sites. This variation may help clarify reported differences in survival rates among sites and provide a target for identifying EMS practices most likely to enhance survival from OOHCA.

Two simple questions to assess neurologic outcomes at 3 months after out-of-hospital cardiac arrest: experience from the public access defibrillation trial.

BACKGROUND: Two simple questions have been used to classify neurologic outcome in patients with stroke. Could they be similarly applied to patients with cardiac arrest? METHODS: As part of a randomized trial, study personnel interviewed by telephone survivors of out-of-hospital cardiac arrest to assess their outcomes 3 months after discharge. They asked two simple questions: (1) In the last 2 weeks, did you require help from another person for your everyday activities? and (2) Do you feel that you have made a complete mental recovery form your heart arrest? Next they administered the Mini-Mental State Examination (MMSE) from the Adult Lifestyles and Function Interview (ALFI) to assess cognition on a scale from 0 to 22 and the Health Utilities Index Mark 3 (HUI3) to assess quality of life on a scale from 0 (death) to 1 (perfect health). RESULTS: Based on responses to the two simple questions, 32 survivors were classified as dependent (n=5, 16%), independent (n=3, 9%) and full recovery (n=24, 75%). The mean ALFI-MMSE score was 19.1 (standard deviation 5.1), and the mean HUI3 score was 0.76 (standard deviation 0.28). The classification based on the two simple questions was significantly correlated with ALFI-MMSE (p=0.002) and HUI3 (p=0.001). Scores for the HUI3 were missing in eight survivors. CONCLUSIONS: Neurologic outcomes based on the two simple questions after cardiac arrest can be easily determined, sensibly applied, and readily interpreted. These preliminary findings justify further evaluation of this simple and practical approach to classify neurologic outcome in survivors of cardiac arrest.

Location of cardiac arrests in the public access defibrillation trial.

BACKGROUND: The Public Access Defibrillation (PAD) Trial found an overall doubling in the number of out-of-hospital cardiac arrest (CA) survivors when a lay responder team was equipped with an automated external defibrillator (AED), compared with cardiopulmonary resuscitation (CPR) alone. OBJECTIVES: To describe the types of facilities that participated in the trial and to report the incidence of CA and survival in these different types of facilities. METHODS: In this post-hoc analysis of PAD Trial data, the physical characteristics of the participating facilities and the numbers of presumed CAs, treatable CAs, and survivors are reported for each category of facilities. RESULTS: There were 625 presumed CAs at 1,260 participating facilities. Just under half (n = 291) of the presumed CAs were classified as treatable CAs. Treatable CAs occurred at a rate of 2.9 per 1,000 person-years of exposure; rates were highest in fitness centers (5.1) and golf courses (4.8) and lowest in office complexes (0.7) and hotels (0.7). Survival from treatable CA was highest in recreational complexes (0.5), public transportation sites (0.4), and fitness centers (0.4) and lowest in office complexes (0.1) and residential facilities (0.0). CONCLUSIONS: During the PAD Trial, the exposure-adjusted rate of treatable CA was highest in fitness centers and golf courses, but the incidence per facility was low to moderate. Survival from treatable cardiac arrest was highest in recreational complexes, public transportation facilities, and fitness centers.

Implementation of community-based public access defibrillation in the PAD trial.

BACKGROUND: The Public Access Defibrillation (PAD) Trial was a randomized, controlled trial designed to measure survival to hospital discharge following out-of-hospital cardiac arrest (OOH-CA) in community facilities trained and equipped to provide PAD, compared with community facilities trained to provide cardiopulmonary resuscitation (CPR) without any capacity for defibrillation. OBJECTIVES: To report the implementation of community-based lay responder emergency response programs in 1,260 participating facilities recruited for the PAD Trial in the United States and Canada. METHODS: This was a descriptive study of the characteristics of participating facilities, volunteers, and automated external defibrillator (AED) placements compiled by the PAD Trial, and a qualitative study of factors that facilitated or impeded implementation of emergency lay responder programs using focus groups of PAD Trial site coordinators. RESULTS: The PAD Trial enrolled 1,260 community facilities (14.8% residential), with 20,400 lay volunteers (mean +/- standard deviation = 13.4 +/- 10.7 per facility) trained to respond to OOH-CA. The 598 locations randomized to receive AEDs required 2.7 +/- 1.8 AEDs per facility. Volunteer attrition was high, 36% after two years. Barriers to recruitment and implementation included identification of appropriate "at-risk" facilities, lack of interest or fear of litigation by a facility key decision maker, lack of motivated potential volunteer responders, training and retraining resource requirements, and lack of an existing communication/response infrastructure. CONCLUSIONS: These data indicate that implementation of community-based lay responder programs is feasible in many types of facilities, although these programs require substantial resources and commitment, and many barriers to implementation of effective PAD programs exist.

Public defibrillation: increased survival from a structured response system.

The Public Access Defibrillation (PAD) trial was a prospective, randomized, controlled study designed to compare the number of persons surviving to hospital discharge after experiencing an out-of-hospital cardiac arrest (OOH-CA) among "community units" randomized to receive cardiopulmonary resuscitation (CPR) only or CPR plus an automated external defibrillator (AED). In 24 centers across the United States and Canada, 993 community units, composed of 1260 individual facilities, trained more than 19,000 layperson responders in CPR-only or CPR+AED. Survival to hospital discharge in the CPR+AED arm was double that of the CPR-only arm (30 vs 15, P = .03; RR = 2.0, 95% CI [1.07-3.77]). Intense focus on facility infrastructure, including responder recruitment and training, communication, evaluation, and oversight, was necessary for implementing the emergency response systems for the trial. Use of an AED within this structured response system can increase the number of survivors to hospital discharge after OOH-CA. Trained nonmedical responders can use AEDs safely and effectively.