Intended for healthcare professionals


Spurious asystole with use of manual defibrillators

BMJ 1999; 319 doi: (Published 11 December 1999) Cite this as: BMJ 1999;319:1574

Users should not rely on monitoring through paddles, using any type of gel pad, once shocks have been delivered

  1. Douglas Chamberlain, honorary professor, University of Wales College of Medicine (chambda{at}
  1. Hove, East Sussex BN3 6DH
  2. 3M Medical-Surgical Division, 3M Health Care, 3M Center, St Paul, MN 55144-1000, USA

    EDITOR—Many readers will be aware that in 1998 a problem was identified in the United Kingdom that is highly relevant to some users of manual defibrillators. The original report (which led to a safety notice from the UK Medical Devices Agency1) related to the use of the Hewlett Packard Codemaster defibrillator in conjunction with gel pads. After one or more defibrillatory shocks an electrical “offset” could influence the monitor on the defibrillator to show a straight line (either continuous or broken), even when ventricular fibrillation was still present or had recurred This spurious asystole could last long enough to delay further shocks and could thereby hinder the prospects of a successful resuscitation. As far as I am aware, no definitive studies have yet been published to determine how widespread the problem might be, and how far other equipment may also be implicated.

    At the Royal Sussex County Hospital we have recently identified an exactly similar problem with a defibrillator from a different manufacturer used in conjunction with gel pads. Further investigation showed that periods of spurious asystole may last for, at worst, three or four minutes.

    Rescuers relying on monitoring through defibrillating paddles during an emergency may have no reason to suspect that they are being misled unless conventional electrocardiographic monitoring is conducted simultaneously through independent electrodes. The phenomenon may therefore have escaped attention on numerous occasions. It is nevertheless of considerable clinical importance.

    Until the extent of the problem has been fully identified, we recommend that users of manual defibrillators should not rely on monitoring through paddles, using any type of gel pad, once shocks have been delivered It seems wise to establish independent monitoring as quickly as possible. I believe that all conventional monitoring electrodes that are currently available are of the silver/silver chloride type that should not be subject to polarisation for more than a very brief period.

    I hope that readers may take any opportunity of identifying instances when spurious asystole is shown on defibrillator monitors so that they can inform manufacturers and regulatory bodies. Formal studies would have the advantage of quantifying the risk, bearing in mind that some equipment or combinations of equipment may give reliable information.

    I understand that 3M, the leading manufacturer of gel pads, has included advice in its packs that they should not be used for monitoring purposes. Unfortunately, many users may not yet have seen the warning because the packs have a commendably long shelf life, and older stock will still be in widespread use. 3M has pointed out that gel pads were not designed for, nor intended as, a coupling medium for reading electrocardiograms, but this fact is not widely known.

    I know of no instances of the problem occurring with stick-on pads of the type used with automated defibrillators.


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    Manufacturer's comment

    1. Kenneth W Bartelt, technical director
    1. Hove, East Sussex BN3 6DH
    2. 3M Medical-Surgical Division, 3M Health Care, 3M Center, St Paul, MN 55144-1000, USA

      EDITOR—We welcome Professor Chamberlain's action in bringing this information to the notice of people likely to use a defibrillator and are grateful for the opportunity to add the following comments.

      The potential for excessive time delay between the administration of a shock and display of an electrocardiographic trace is not unique to 3M defibrillation pads. Any defibrillation gel pad/paddle combination or defibrillation paste/paddle combination in which the offset potential after a shock exceeds the input saturation limit of the defibrillation system will result in an excessive time delay between the administration of that shock and the display of an electrocardiogram.

      After receiving a few reports of customers using the product for monitoring electrocardiograms 3M added a warning to the 3M Defib-Pad packaging at the beginning of this year to clarify how not to use the product Because patient safety is of utmost importance to 3M, a clear warning was included as follows:

      “Do not monitor heart rhythm through a defibrillator paddle/3M Defib-Pad combination because there may be an excessive time delay between the administration of a shock and an ECG trace display.”

      The 3M Defib-Pad has never been intended for monitoring electrocardiograms The product is clearly described as a conductive gel pad for defibrillation and cardioversion, and the instructions for use clearly set out how to use the pads for these procedures. 3M believes that there is no safety issue regarding the use of the 3M Defib-Pad when used for its intended purpose—that is, as a conductive pad for defibrillation and cardioversion.

      Users should refer to instructions for use provided by the manufacturers of the defibrillation pads or paste and the defibrillators in all cases and should consult the manufacturers of these products for their advice on their suitability for trace monitoring.

      To ensure that you have a display of a trace after a shock, use silver/silver chloride electrocardiographic monitoring electrodes.

      If you have any questions or comments about this matter please contact Derek J Wright, technical service specialist (dwright{at}; tel: 01509 613151 in the United Kingdom or +44 1509 613151 from outside the United Kingdom).

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