| Defibrillation probability and impedance change between shocks during resuscitation from out-of-hospital cardiac arrest. | |
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MedLine Citation:
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PMID: 19423211 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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OBJECTIVE: Technical data now gathered by automated external defibrillators (AEDs) allows closer evaluation of the behavior of defibrillation shocks administered during out-of-hospital cardiac arrest. We analyzed technical data from a large case series to evaluate the change in transthoracic impedance between shocks, and to assess the heterogeneity of the probability of successful defibrillation across the population. METHODS: We analyzed a series of consecutive cases where AEDs delivered shocks to treat ventricular fibrillation (VF) during out-of-hospital cardiac arrest. Impedance measurements and VF termination efficacy were extracted from electronic records downloaded from biphasic AEDs deployed in three EMS systems. All patients received 200J first shocks; second shocks were 200J or 300J, depending on local protocols. Results presented are median (25th, 75th percentiles). RESULTS: Of 863 cases with defibrillation shocks, 467 contained multiple shocks because the first shock failed to terminate VF (n=61) or VF recurred (n=406). Defibrillation efficacy of subsequent shocks was significantly lower in patients that failed to defibrillate on first shock than in patients that did defibrillate on first shock (162/234=69% vs. 955/1027=93%; p<0.0001). The failed VF terminations were distributed heterogeneously across the population; 5% of patients accounted for 71% of failed shocks. Shock impedance decreased by 1% [0%, 4%] and peak current increased by 1% [0%, 4%] between 200J first and 200J second shocks. Shock impedance decreased 4% [2%, 6%] and current increased 27% [25%, 29%] between 200J first and 300J second shocks. In all 499 pairs of same-energy consecutive shocks, impedance changed by less than 1% in 226 (45%), increased >1% in 124 (25%) and decreased >1% in 149 (30%). CONCLUSIONS: Impedance change between consecutive shocks is minimal and inconsistent. Therefore, to increase current of a subsequent shock requires an increase of the energy setting. Distribution of failed shocks is far from random. First shock defibrillation failure is often predictive of low efficacy for subsequent shocks. |
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Authors:
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Robert G Walker; Rudolph W Koster; Charles Sun; George Moffat; Joseph Barger; Pamela P Dodson; Fred W Chapman |
Publication Detail:
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Type: Journal Article Date: 2009-05-06 |
Journal Detail:
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Title: Resuscitation Volume: 80 ISSN: 1873-1570 ISO Abbreviation: Resuscitation Publication Date: 2009 Jul |
Date Detail:
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Created Date: 2009-06-15 Completed Date: 2009-09-29 Revised Date: 2009-12-02 |
Medline Journal Info:
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Nlm Unique ID: 0332173 Medline TA: Resuscitation Country: Ireland |
Other Details:
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Languages: eng Pagination: 773-7 Citation Subset: IM |
Affiliation:
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Physio-Control Inc. A Division of Medtronic, Redmond, WA 98052, USA. rob.walker@medtronic.com |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Clinical Protocols Cohort Studies Defibrillators Electric Countershock* Electric Impedance Heart Arrest / complications, therapy* Humans Resuscitation* Retrospective Studies Treatment Outcome Ventricular Fibrillation / complications, therapy* |
| Comments/Corrections | |
Comment In:
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Resuscitation. 2009 Dec;80(12):1438; author reply 1438-40
[PMID:
19837502
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Resuscitation. 2009 Dec;80(12):1440; author reply 1440-1 [PMID: 19942082 ] |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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