title: Patient outcomes following defibrillation with a low energy biphasic truncated exponential waveform in out-of-hospital cardiac arrest.
abstract: OBJECTIVE
  To determine the outcome of patients with out-of-hospital cardiac arrest and ventricular fibrillation as the presenting rhythm while using automated external defibrillators (AEDs) that delivered non-escalating, impedance-compensated low-energy (150 J) shocks.
  
  
  METHODS
  AEDs delivering low-energy biphasic truncated exponential (BTE) shocks were employed in an emergency medical services (EMS) system in which first-arriving personnel - police, firefighters or paramedics - delivered the initial shocks. Patients were classified according to their response to shocks: restoration of sustained spontaneous circulation (ROSC) without need for epinephrine and other advanced life support (ALS) interventions; and ALS, those requiring epinephrine in all instances. The primary end-point was neurologically-intact discharge survival. Secondary end-points were ROSC with shocks only and the call-to-shock time interval.
  
  
  RESULTS
  Of 42 patients with VF arrest treated with BTE shocks, 35 were bystander-witnessed. Of these 35, 14 (38%) regained a sustained ROSC on-scene with shocks only, needing no epinephrine for ROSC. All 14 survived to discharge home. Of the remaining 21 patients needing ALS intervention, only two (9.5%) survived to discharge. Overall, 16/35 patients (46%) survived to discharge home, an outcome comparable to our experience with patients treated with escalating high-energy monophasic waveform shocks.
  
  
  CONCLUSIONS
  Low-energy (150 J) non-escalating biphasic truncated exponential waveform shocks terminate VF in out-of-hospital cardiac arrest with high efficacy; patient outcome is comparable with that observed with escalating high-energy monophasic shocks. Low-energy shocks, in addition to high efficacy, may confer the advantage of less shock-induced myocardial dysfunction, though this will be difficult to define in the clinical circumstance of long-duration VF provoked by a pre-existing diseased myocardial substrate.
authors.affiliation: Department of Anesthesiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA. white.roger@mayo.edu
authors.forename: R D
authors.initials: RD
authors.lastname: White
authors.forename: D G
authors.initials: DG
authors.lastname: Hankins
authors.forename: E J
authors.initials: EJ
authors.lastname: Atkinson
mesh_terms: D000368:Aged; D004554:Electric Countershock / Q000379:methods; D004632:Emergency Medical Services; D005260:Female; D006323:Heart Arrest / Q000401:mortality / Q000628:therapy*; D006801:Humans; D008297:Male; D012151:Resuscitation; D015996:Survival Rate; D013997:Time Factors; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000401:mortality / Q000628:therapy