Cardiac Arrest: 175 J defibrillation shocks were not clearly better than 320 J.

Clinical bottom line (level 2b-)

  1. Patients in the community who were in cardiac arrest due to ventricular fibrillation who were given a 320 J shock had no clear difference in resuscitation or discharge from hospital than those given a 175 J shock.
Weaver et al: N Engl J Med 1982; 307: 1101-1106
Expires October 2003

The study

Double-blinded ?concealed quasi-randomised trial with intention-to-treat
Setting: city, USA

249 patients (aged mean 65, ?% male) out-of-hospital cardiac arrest due to ventricular fibrillation

Excluded if
  • initial rhythms of ventricular tachycardia, asystole, electrical mechanical dissociation even if after drug therapy they were converted to VF
  • treated with unmodified defibrillator whenever the modified device was not functioning correctly or being repaired


    • Control Group: (n = 122, 122 analysed): 175 J shock administered by defibrillators (Physio-Control Corp., LifePak models 4 and 5), modified by manufacturer to provide continuous magnetic recording of the ECG and a voice channel on which time, level of energy, type and dosage of drugs were recorded.
    Experimental Group: (n = 127, 127 analysed): 320 J shock, given as control
    A single paddle-skin conductive gel (Dermagel) was used throughout the trial and stainless steel paddles were 8.5 cm in diameter. Sodium bicarbonate (mean 161 mmol) was administered as soon as an i.v. line was established. Lidocaine and epinephrine were not administered until VF had reverted to another rhythm or two shocks had been given.
    100% followed for ? resuscitation and discharge from hospital

    The evidence

    Outcome Time to outcome CEREERRRR
    (95% CI)    		ARR
    (95% CI)    		NNT
    (95% CI)
    resuscitation unknown 96
    (78.7%)    		 94
    (74.0%)    		 -6%
    (-18% to 8%)    		 -4.67%
    (-15.2% to 5.86%)    		 -21
    (NNT = 17 to infinity;
    NNH = 7 to infinity)
    survival to discharge unknown 46
    (37.7%)    		 51
    (40.2%)    		 7%
    (-22% to 45%)    		 2.65%
    (-14.6% to 9.66%)    		 41
    (NNT = 7 to infinity;
    NNH = 10 to infinity)

    Comments

    1. No information on adverse effects was provided.
    2. There was no clear difference between the 2 groups for the number of shocks required to resuscitate the patient.
    3. The trial was too small to show any clear differences in resuscitation or discharge from hospital.
    4. Basic life support initiated by bystanders or trained firefighters until paramedics arrived.

    Citation

    1. Weaver WD, Cobb LA, Copass MK, et al: Ventricular fibrillation- a comparative trial using 175-J and 320-J shocks.. N Engl J Med 1982; 307: 1101-1106
    Contributor: Clare Wotton and Chris Ball, October 1999
    Reviewer: -

    Clinical Question.
    Patient cardiac arrest
    Intervention or Exposure 320 J shock
    Comparison 175 J shock
    Outcome discharge from hospital