Automated External Defibrillators in the Wilderness

A friend of mine who manages a fishing camp in British Columbia recently asked me whether or not he should purchase an automated external debrillator (AED) for the camp. An AED is a device that is attached to a person in the event of an apparent cardiac arrest. Its circuitry automatically detects whether the victim is suffering from ventricular fibrillation (VF), in which the heart is not beating, but rather, is quivering and therefore not effectively pumping blood. If VF is detected, it delivers a shock designed to restore an instrinsic and effective cardiac rhythm. If it is successful in accomplishing this, the victim might survive. If an effective life-sustaining rhythm cannot be restored, the victim dies. My friend asked my advice because a fair number of fishermen who use the camp are senior citizens. The base camp is located a good two hours drive from the nearest medical assistance (including the arrival of an ambulance with paramedics or emergency medical technicians [EMTs]), and the remote fishing sites are even further out, adding at least an hour to any hypothesized response time.

The same question comes up from time to time with regard to expeditions, usually persons climbing mountains where they will be far from sophisticated medical care or on ocean-going vessels out at sea. My answer is more often related to the finances of the inquiring party than to any expectation that the device might actually save a life in a remote setting, where it couldn’t immediately be followed by advanced life support techniques (e.g., airway management, intravenous access, administration of anti-arrhythmic drugs) and other adjuncts to manage the primary cause of the cardiac arrest (specifically, ventricular fibrillation). But I usually conclude, as my grandmother was fond of saying, “It couldn’t hurt.”

In the New England Journal of Medicine, Volume 358, pages 1793-1804, April 1, 2008 (10.1056/NEJM0oa08011651), Gust Bardy, M.D. and colleagues published an article entitled “Home Use of Automated External Defibrillators for Sudden Cardiac Arrest,” in which 7001 patients residing at home with previous anterior-wall (of the heart) heart attacks (myocardial infarction) who were not candidates for an implantable cardioverter-defibrillator were assigned to two different response groups should they suffer a sudden cardiac arrest at home. The first group was assigned to call emergency medical services (EMS) and perform CPR, while the second group was assigned to use an AED, then call EMS and perform CPR. The conclusion of the study was that being in possession of an AED in a home setting did not improve overall survival, as compared with reliance on conventional resuscitation methods. Notably, of the group of patients who had access to AEDs, they were used in 32 patients, of which 14 received an appropriate shock. Of the persons who received a shock, 4 survived. The conclusion of the investigators was that access to a home AED did not significantly improve overall survival, as compared with reliance on conventional resuscitation measures.

So, what can we learn from this study of the use of AEDs in the home as it might relate to their use in a remote setting? Without question, the device sometimes works to convert VF to a life-sustaining heart rhythm. Prompt (generally accepted to be within 4 minutes of the onset of VF) deployment of an AED can save someone’s life. Therefore, the question now becomes, is it practical or cost-effective to have one with you on an expedition? The answer depends on your finances, ability to carry the device, which weighs pounds, keep it charged with electricity, have it withstand the environmental conditions in which you will travel, train participants how to promptly access the device and use it properly, rapidity with which it can be deployed, and so forth. Furthermore, you must be aware that even if one is able to convert VF to a stable heart rhythm, the victim may be suffering a heart attack or have other problems (such as congestive heart failure) that require advanced medical care. On the other hand, sometimes a person will suffer a single episode of VF that when terminated by an AED, results in no further deterioration and, thus, survival. So, would I carry an AED with me to fishing camp? I cannot offer a definitive answer, because it depends…

If you have thoughts about this matter, please feel free to share them.

Preview the 25th Anniversary & Annual Meeting of the Wilderness Medical Society, which will be held in Snowmass, Colorado July 25-30, 2008.

Tags: AED, automated external defibrillator, wilderness medicine, outdoor medicine, healthline

Labels: AED, automated external defibrillator, cardiac arrest

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