Temporal trends in sudden cardiac arrest: a 25-year emergency medical services perspective.

BACKGROUND: Little is known about temporal trends in survival and prognostic characteristics of patients with out-of-hospital cardiac arrest treated by emergency medical services (EMS). We hypothesized that an evolving combination of beneficial and adverse factors may contribute to temporal patterns of survival. METHODS AND RESULTS: We evaluated a population-based cohort of EMS-treated adult patients with cardiac arrest (n=12 591) from 1977 to 2001 in King County, Washington. Time was grouped into an initial 5-year period and 5 successive 4-year periods. We sought to determine the potential impact of temporal changes in prognostic factors typically beyond EMS control termed "fate" factors (for example, patient age) and factors implemented by EMS termed "program" factors (programs of dispatcher-assisted cardiopulmonary resuscitation and basic life support defibrillation). Several characteristics associated with survival changed over time. Observed survival did not change over time among all patients with cardiac arrest (OR=0.98 [0.95, 1.01], trend for each successive time period) and improved over time among patients with witnessed ventricular fibrillation (OR=1.05 [1.01, 1.09]). In models that included all patients with cardiac arrest and controlled for fate factors, advancing time period was associated with an increase in survival (OR=1.08 [1.05, 1.11]). Conversely, in models that controlled for program factors, advancing time period was associated with a decrease in survival (OR=0.95 [0.93, 0.98]). Results were similar among patients with witnessed ventricular fibrillation. CONCLUSIONS: The static temporal pattern of survival from cardiac arrest appeared to result from an evolving balance of prognostic factors. Programs implemented by EMS appeared to counter adverse temporal trends in prognostic factors typically beyond EMS control.

Public access defibrillation in out-of-hospital cardiac arrest: a community-based study.

BACKGROUND: The dissemination and use of automated external defibrillators (AEDs) beyond traditional emergency medical services (EMS) into the community has not been fully evaluated. We evaluated the frequency and outcome of non-EMS AED use in a community experience. METHODS AND RESULTS: The investigation was a cohort study of out-of-hospital cardiac arrest cases due to underlying heart disease treated by public access defibrillation (PAD) between January 1, 1999, and December 31, 2002, in Seattle and surrounding King County, Washington. Public access defibrillation was defined as out-of-hospital cardiac arrest treated with AED application by persons outside traditional emergency medical services. The EMS of Seattle and King County developed a voluntary Community Responder AED Program and registry of PAD AEDs. During the 4 years, 475 AEDs were placed in a variety of settings, and more than 4000 persons were trained in cardiopulmonary resuscitation and AED operation. A total of 50 cases of out-of-hospital cardiac arrest were treated by PAD before EMS arrival, which represented 1.33% (50/3754) of all EMS-treated cardiac arrests. The proportion treated by PAD AED increased each year, from 0.82% in 1999 to 1.12% in 2000, 1.41% in 2001, and 2.05% in 2002 (P=0.019, test for trend). Half of the 50 persons treated with PAD survived to hospital discharge, with similar survival for nonmedical settings (45% [14/31]) and out-of-hospital medical settings (58% [11/19]). CONCLUSIONS: PAD was involved in only a small but increasing proportion of out-of-hospital cardiac arrests.

Defibrillation waveform and post-shock rhythm in out-of-hospital ventricular fibrillation cardiac arrest.

BACKGROUND: The importance of the defibrillation waveform on the evolving post-shock cardiac rhythm is uncertain. The primary objective of this study was to evaluate cardiac rhythms following the first defibrillation shock, comparing biphasic truncated exponential (BTE), monophasic damped sinusoidal (MDS), and monophasic truncated exponential (MTE) waveforms in patients experiencing out-of-hospital ventricular fibrillation cardiac arrest (OHCA). METHODS: We reviewed the automated external defibrillator (AED) and emergency medical services (EMS) records of 366 patients who suffered OHCA and were treated with defibrillation shocks by first-tier emergency responders between 1 January 1999 and 31 August 2002 in King County, Washington. The post first shock rhythms were determined at 5, 10, 20, 30, and 60 s and compared according to defibrillation waveform. RESULTS: The MDS and BTE waveforms were associated with significantly higher frequency of defibrillation than the MTE waveform, though only the BTE association persisted to 30 and 60 s. No difference in defibrillation rates was detected between MDS and BTE waveforms. By 60 s, an organized rhythm was present in a greater proportion for BTE (40.0%) compared with MDS (25.4%, P=0.01) or MTE (26.5%, P=0.07). CONCLUSION: In this retrospective cohort investigation, MDS and BTE waveforms had higher first shock defibrillation rates than the MTE waveform, while patients treated with the BTE waveform were more likely to develop an organized rhythm within 60 s of the initial shock. The results of this investigation, however, do not provide evidence that these surrogate advantages are important for improving survival. Additional investigation is needed to improve the understanding of the role of waveform and its potential interaction with other clinical factors in order to optimize survival in OHCA.

Epinephrine use by emergency medical technicians for presumed anaphylaxis.

OBJECTIVE: The use of epinephrine for the treatment of anaphylaxis by emergency medical technicians (EMTs) has not been rigorously evaluated. The aim of this study was to determine whether first-tier EMTs use epinephrine safely and appropriately for anaphylactic reactions. METHODS: The study used a case-control design. Cases were persons treated by EMTs with epinephrine for presumed anaphylaxis from January 1, 2000, through January 31, 2003, in King County, Washington (n = 22). Controls were emergency medical services (EMS)-treated persons matched to cases by diagnosis category, patient age, fire department, and year, but who had not been administered epinephrine by EMTs (n = 44). Cases and controls were compared with regard to history, symptoms, and examination characteristics. In a second assessment, physicians blinded to treatment (case/control) status reviewed events to determine whether they would have treated the patient with epinephrine RESULTS: When cases were compared with controls, cases were more likely to report a history of anaphylaxis (27% vs. 2%), upper airway symptoms (59% vs. 18%), and shortness of breath (77% vs. 27%). Cases were also more likely to have tachypnea (32% vs. 5%), hypotension (41% vs. 9%), decreased level of consciousness (32% vs. 2%), abnormal breath sounds (46% vs. 16%), and rash (50% vs. 23%) (p < or = 0.01 for all comparisons). The physicians agreed with the EMTs' decisions regarding epinephrine use (or nonuse) in 86% (57/66) of events: 86% (19/22) in which the EMTs used epinephrine and 86% (38/44) in which the EMTs did not use epinephrine. CONCLUSION: In this EMS system, the EMTs used epinephrine for presumed anaphylaxis in a discriminating manner that typically agreed with physician review.

Time to first shock by emergency medical technicians with automated external defibrillators.

UNLABELLED: The interval from collapse to electrical rescue shock is a critical determinant of successful defibrillation in cardiac arrest. In order to achieve the earliest possible defibrillation, many emergency medical services (EMS) systems equip first-responding units with an automated external defibrillator (AED). OBJECTIVE: To measure the time from on-scene emergency medical technician (EMT) recognition of cardiac arrest to AED application and shock in ventricular fibrillation (VF) arrest. In addition, the authors sought to understand the reasons for delays. METHODS: Using the AED recordings and written EMS reports, the authors conducted a retrospective cohort study of all persons who experienced an EMS-attended VF cardiac arrest in which an AED was applied and a shock delivered by an EMT, from January 1999 through December 2000 (n = 177). Based on the bimodal distribution of times, two groups were assembled: no delay (time to shock < or = 90 seconds) and delayed (time to shock > 90 seconds). Patient and event characteristics associated with delay status were determined using Mantel-Haenszel methods. RESULTS: The median (25th, 75th percentile) time from cardiac arrest recognition to shock was 51 (43, 64) seconds. Ninety-four percent (n = 166) of the cohort received a shock within 90 seconds. Delayed shock was associated with unwitnessed arrest status (odds ratio = 9.3, 95% confidence interval = 2.3, 36.8) and nursing home location (odds ratio = 10.0, 95% confidence interval = 2.1, 47.5). CONCLUSION: The findings suggest that a 1-minute goal and a 90-second minimum standard for time to first shock are appropriate for EMT AED defibrillation in the field.

An emergency medical services program of alternate destination of patient care.

OBJECTIVE: The emergency department (ED) is ideally reserved for urgent health needs. The ED, however, is often the site of care for nonurgent conditions. The authors investigated whether emergency medical technicians could decrease ED use by patients with nonurgent concerns who use 911 by appropriately identifying and triaging them to alternate care destinations. METHODS: From August 2000 through January 2001, two King County fire-based emergency medical services (EMS) agencies participated in an alternate care destination program for patients with specific low-acuity diagnosis codes (intervention group). Eligible patients were offered care at a clinic-based destination as an alternate to the ED (n = 1,016). The frequency of the destination of care (ED, clinic, or home) for the intervention group was compared with a matched control group that was comprised of a preintervention historical cohort of EMS encounters from the same two fire-based agencies and with the same acuity and diagnosis criteria and seasonal interval (n = 2,617). RESULTS: Compared with the preintervention group, a smaller proportion of patients in the intervention group received care in the ED (44.6% vs. 51.8%, p = 0.001), while a greater proportion of patients in the intervention group received clinic care (8.0% vs. 4.5%, p = 0.001) or home care (no transport) (47.4 vs. 43.7%, p = 0.043). Results were comparable when adjusted for other patient characteristics. Similar relationships were not evident among nonparticipating King County EMS agencies. Based on physician review and patient interview, the alternate care intervention appeared to be safe and satisfactory. CONCLUSION: An EMS-based program may represent one approach to limiting nonurgent ED use.