Cardiac arrest: the polarity of external defibrillator electrode had no clear effect on the success of resuscitation.

Clinical bottom line (level 1b)

  1. Patients who had a cardiac arrest in the community and were defibrillated with a negative electrode as compared with a positive electrode were not more likely to be resuscitated.
  2. There was no clear effect on discharge from hospital.
Weaver et al: PACE 1993; 16: 285-290
Expires October 2003

The study

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

289 patients (aged mean 66, 75% male) cardiac arrest
Note:
  • Patients unconscious and unresponsive when found by firefighters


    • Control Group: (n = 163, 163 analysed): positive apex electrode
    Experimental Group: (n = 126, 126 analysed): negative apex electrode
    electrode shock given using Lifepak 200 Automatic Advisory Defibrillator used with self-adhesive monitoring defibrillator electrodes to the upper right sternal chest areas.
    100% followed for 2 weeks resuscitation or discharge

    The evidence

    Outcome Time to outcome CEREERRRR
    (95% CI)    		ARR
    (95% CI)    		NNT
    (95% CI)
    resuscitation minutes 91
    (55.8%)    		 75
    (59.5%)    		 7%
    (-30% to 13%)    		 3.70%
    (-7.78% to 15.2%)    		 27
    (NNT = 13 to infinity;
    NNH = 7 to infinity)
    discharge from hospital weeks 24
    (14.7%)    		 20
    (15.9%)    		 8%
    (-38% to 86%)    		 1.15%
    (-7.24% to 9.53%)    		 87
    (NNT = 10 to infinity;
    NNH = 14 to infinity)

    Comments

    1. Amount of energy delivered through electrodes not taken into account.
    2. A study in a calf model has suggested that the polarity of the electrodes used for defibrillation could effect survival rates - this is not clearly the case in humans.

    Citation

    1. Weaver WD, et al: Influence of External Defibrillator Electrode Polarity on Cardiac Resuscitation. PACE 1993; 16: 285-290
    Contributor: Clare Wotton and Chris Ball, October 1999
    Reviewer: Kenneth Ballew

    Clinical Question.
    Patient suspected out of hospital cardiac arrest
    Intervention or Exposure external defibrillator electrode with negative polarity versus positive polarity
    Outcome cardiac resuscitation