Without evidence of benefit, an intervention should not be presumed to be beneficial or safe.

- Rogue Medic

AEDs and Water

In an earlier post, Off Duty CPR in the Middle of the Road, I wrote about the perceived problem of moisture on the ground when shocking a patient. I do not recall what led me to post that now, but I have found some research on the topic. None of these studies found any problems with defibrillating wet patients. They found that the current delivered to the patient was adequate for defibrillation and that it was safe for rescuers to defibrillate the wet patient. Some of these were addressing the conditions that would affect defibrillation of a patient during therapeutic hypothermia with ice water and with saline. The one bit of advice was to dry the chest before applying pads, but that should be obvious. 🙂

Click on each study for it’s abstract. The one without an abstract is an editorial about the study below it.

Klock-Frézot JC, Ohley WJ, Schock RB, Cote M, Schofield L.
Successful defibrillation in water: a preliminary study.
Conf Proc IEEE Eng Med Biol Soc. 2006;1:4028-30.
PMID: 17945819 [PubMed – indexed for MEDLINE]

Only a small difference was measured in the overall defibrillation voltage and current as applied to the electrodes for the different cases. Thus, underwater defibrillation is safe and can be performed effectively.

de Vries W, Bierens JJ, Maas MW.
Moderate sea states do not influence the application of an AED in rigid inflatable boats.
Resuscitation. 2006 Aug;70(2):247-53. Epub 2006 Jun 27.
PMID: 16806638 [PubMed – indexed for MEDLINE]

Our study demonstrated that all the AEDs involved are robust enough to be used on RIBs (Rigid Inflatable Boats); none of them gave problems with monitoring or defibrillation,

Lyster T, Jorgenson D, Morgan C.
The safe use of automated external defibrillators in a wet environment.
Prehosp Emerg Care. 2003 Jul-Sep;7(3):307-11.
PMID: 12879378 [PubMed – indexed for MEDLINE]

CONCLUSIONS: Thirty volts may result in some minor sensation by the operator or bystander, but is considered unlikely to be hazardous under these circumstances. The maximum currents were lower than allowed by safety standards. Although defibrillation in a wet environment is not recommended practice, our simulation of a patient and a rescuer/bystander in a wet environment did not show significant risk should circumstances demand it.

Varon J.
Therapeutic hypothermia and the need for defibrillation: wet or dry?
Am J Emerg Med. 2007 May;25(4):479-80. No abstract available.
PMID: 17499671 [PubMed – indexed for MEDLINE]

Comments positively on the study below, from the same publication.

Schratter A, Weihs W, Holzer M, Janata A, Behringer W, Losert UM, Ohley WJ, Schock RB, Sterz F.
External cardiac defibrillation during wet-surface cooling in pigs.
Am J Emerg Med. 2007 May;25(4):420-4.
PMID: 17499660 [PubMed – indexed for MEDLINE]

Transthoracic defibrillation via AED pads is safe and effective in a wet condition after cooling with ice-cold water in a pig VF cardiac arrest model because ROSC could be achieved in all animals. Thus, this new cooling device needs further exploration in cases of cardiac arrest
in humans.

Comments

  1. In the system that I work in, there is one reported incident of a firefighter receiving a conducted shock from defibrillation. This occurred while they were working the arrest on a wet dock in a marina. Every surface they were working on was wet and the firefighter received a mild shock (nothing debilitating but defiantly startling) when the patient was shocked.

  2. In the discussion of the results the authors of the Lyster study state:”The maximum voltage recorded occurred at a distance of approximately 15 cm from the simulated patient and was 14 V peak in the case of pool water, and 30 V peak in the case of salt water. Thirty volts may result in some minor sensation (e.g., tingling) by the operator or bystander, but is considered unlikely to be hazardous under these circumstances. Similar voltages in other environments have not proved to be hazardous. For example, aircraft and helicopter batteries are 28 V, and routinely are handled in wet or marine environments without incident.””The measured voltages dropped off quickly as the distance between the sense probe and the patient increased. At a distance of approximately 60 cm (2 ft) from the patient, the maximum voltage was 0.28 V peak (current 0.28 mA peak) in the case of pool water, and11 V peak (current 11 mA peak) in the case of salt water. Eleven volts is unlikely to cause any operator or bystander sensation or risk in this environment.””The maximum voltage recorded when the sense probe was touching the AED, simulating touching the shock button, was 0.4 V peak (current 0.4 mA peak) or less, resulting in no sensation or risk.””Defibrillators are designed expressly to deliver currents electrically isolated from the earth. As a result, currents entering the chest through one electrode pad exit the chest and return to the defibrillator through the other electrode pad and do not seek to escape to earth.”

  3. We can Always count on you to dig up more facts that we can swallow. Our local VFD had an incident where a bystander received a conducted shock from the defib. The bystander was apparently leaning on a flag pole in that was at the edge of a puddle that the AED was touching. Who woulda thunk!

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