Take it for what it's worth! This time I was able to copy the text from the PDF.
Snakebite Suction Devices Don’t Remove
Venom: They Just Suck
Sean P. Bush, MD
From the Department of Emergency Medicine, Loma Linda
University School of Medicine, Medical Center and Children’s
Hospital, Loma Linda, CA.
It was only a few decades ago that incision and suction
were recommended snakebite first aid. However, concerns
arose about injuries and infections caused when
laypersons made incisions across fang marks and
applied mouth suction. Meanwhile, several snakebite
suction devices (eg, Cutter’s Snakebite Kit, Venom Ex)
were evaluated, and it was determined that they were
neither safe nor effective.1 So, recommendations
changed, and mechanical suction without incision was
advocated instead.2-5 It seemed intuitive that suction
alone would probably remove venom and should not
cause harm. However, when the techniques were studied
rigorously, quite the opposite was discovered.
One of the most popular suction devices, the Sawyer
Extractor pump (Sawyer Products, Safety Harbor, FL),
operates by applying approximately 1 atm of negative
pressure directly over a fang puncture wound (or
wounds) without making incisions. The manufacturer
instructs that the device be applied within 3 minutes of
the snakebite and left in place for 30 to 60 minutes. For
many years, most agreed (including the Wilderness
Medical Society and the American Medical Association)
that the Extractor might be beneficial and would probably
cause no harm.2-5 Others suggested that it could
exacerbate tissue damage, adding insult to injury after
viper envenomation.6-9 In this issue of Annals, the
Extractor’s inefficacy has been further confirmed with a
well-designed study and fully detailed manuscript.10
In their prospective experimental trial, a human
model was used to test the amount of radioactively
labeled mock venom that could be removed by an
Extractor after subcutaneous injection with a 16-gauge
hypodermic needle. The investigators measured radioactive
count as an approximation of the amount of
venom removed. The bottom line: the Extractor removed
0.04% to 2.0% of the envenomation load. The
authors conclude that this is a clinically insignificant
amount and that the Extractor is essentially useless.
The main limitation of their study is that they could not
use real venom.
The study by Alberts et al10 corroborates other studies
that have tested the efficacy and safety of the Extractor.
Using a porcine model and real rattlesnake venom in a
randomized, controlled trial, Bush et al11 measured
swelling and local effects as outcome variables after
application of an Extractor to artificially envenomated
extremities. The conclusion of the study was that the
Extractor did not reduce swelling, but resulted in further
injury in some subjects. Specifically, circular
lesions identical in size and shape to the Extractor suction
cups developed where the devices had been applied.
These lesions subsequently necrosed, sloughed, and
resulted in tissue loss that prolonged healing by weeks.
Similar injuries after Extractor use have been noted in
human patients.1,12
In another study, Extractors were applied to 2 human
patients immediately after rattlesnake envenomations,
and the device was left in place until its cup filled with
serosanguinous fluid 5 times, although the authors do
not specify the volume(s) of fluid obtained. The concentration
of venom was measured in the fluid removed
using an enzyme-linked immunosorbent
assay.13 There were no control subjects, and this study
has only been published in abstract form. Ironically,
this abstract is cited amongst the main supporting evidence
for the Extractor.4,14 However, a closer review of
the results reveals that the concentration of venom in
the serosanguinous fluid removed was only about
1/10,000th the concentration of rattlesnake venom.
Alberts et al10 similarly noted that although a relatively
large volume of bloody fluid was pulled from the puncture
site, it contained virtually no venom. Most interestingly,
Alberts et al found that the amount of venomin the fluid that spontaneously oozed from the wound
was greater than the amount of venom in the Extractor
aspirate. It is possible in these 2 experiments that the
fluid obtained came from superficial tissues, and that
the strong suction exerted by the device collapses the
distal portion of the fang tract where the venom is deposited,
thereby reducing the amount of venom that
would spontaneously ooze out. This suggests, like the
study by Bush et al,11 that the Extractor might make
the envenomation worse by paradoxically increasing
the amount of venom left in the wound.
Although each of these 3 studies was done independently
of each other and using different methodology,
they arrive at the same conclusion: the Extractor does
not work, and it could make things worse. The only
study that suggests the Extractor removes a clinically
important amount of venom is an uncontrolled experiment
using a rabbit model.15 Unfortunately, this study
was only published as an abstract, and the methodology
is not described in detail. Furthermore, its results are
suspect for many reasons. Rabbits have a very thin subcutaneous
layer, unlike humans (and pigs).16 Most
snake envenomations are thought to occur in the subcutaneous
layer.17 It is possible that in Bronstein et
al’s15 investigation the injected venom collected just
under the rabbit’s skin, where it was easily suctioned
back out by the device. Because this inadequately documented
single abstract reports a finding that is vastly
different from all the other studies that follow, its conclusions
are questionable and may be erroneous.
If there was controversy before, the study by Alberts
et al10 adds to the growing pile of evidence against the
Extractor. This study should change our practice. We
should stop recommending Extractors for pit viper bites,
and the manufacturer should certainly stop advertising
that they are recommended medically as the only acceptable
first aid device for snakebites.
Because it is becoming clear that this gadget does not
work, future investigations should focus on other first
aid techniques, such as pressure-immobilization or
others yet to be discovered. Meanwhile, the best first aid
for snakebite is a cell phone and a helicopter.
The author reports this study did not receive any outside funding
1. Hardy DL. A review of first aid measures for pitviper bite in North America with an
appraisal of Extractor suction and stun gun electroshock. In: Campbell JA, Brodie ED
Jr., eds. Biology of the Pitvipers. Tyler, TX: Selva Publishing; 1992:405-414.
2. Forgey WW, ed. Wilderness Medical Society Practice Guidelines for Wilderness
Emergency Care. Merrillville, IN: ICS Books; 1995.
3. Forgey WW. More on snake-venom and insect-venom extractors [letter]. N Engl J
Med. 1993;328:516.
4. Gold BS. Snake venom extractors: a valuable first aid tool [letter]. Vet Hum Toxicol.
1993;35:255.
5. Forgey W, Norris RL, Blackman J, et al. Viewpoints: response. J Wild Med.
1994;5:216-221.
6. Gellert GA. Snake-venom and insect-venom extractors: an unproved therapy [letter].
N Engl J Med. 1992;327:1322.
7. Gellert GA. More on snake-venom and insect-venom extractors [letter]. N Engl J
Med. 1993;328:516-517.
8. Winkel KD, Hawdon GM, Levick N. Pressure immobilization for neurotoxic snake
bites. Ann Emerg Med. 1999;34:294-295.
9. Warrell DA. Snake bite and snake venoms. Quart J Med. 1993;86:351-353.
10. Alberts MB, Shalit M, LoGalbo F. Suction for venomous snakebite: a study of
“mock venom” extraction in a human model. Ann Emerg Med. 2004;43:181-186.
11. Bush SP, Hegewald K, Green SM, et al. Effects of a negative-pressure venom
extraction device (Extractor) on local tissue injury after artificial rattlesnake envenomation
in a porcine model. Wilderness Environ Med. 2000;11:180-188.
12. Bush SP, Hardy Sr DL. Immediate removal of Extractor is recommended [letter].
Ann Emerg Med. 2001;38:607-608.
13. Bronstein AC, Russell FE, Sullivan JB. Negative pressure suction in the field treatment
of rattlesnake bite victims [abstract]. Vet Hum Toxicol. 1986;28:485.
14. Norris RL. A call for snakebite research. Wilderness Environ Med. 2000;11:149-151.
15. Bronstein AC, Russell FE, Sullivan JB, et al. Negative pressure suction in the field
treatment of rattlesnake bite [abstract]. Vet Hum Toxicol. 1985;28:297.
16. Hobbs GD. Brown recluse spider envenomation: is hyperbaric oxygen the answer?
Acad Emerg Med. 1997;4:165-166.
17. Gold BS, Barish RA, Dart RC, et al. Resolution of compartment syndrome after rattlesnake
envenomation utilizing non-invasive measures. J Emerg Med. 2003;24:285-288.
Statistics: Posted by Kent VanSooy — August 14th, 2012, 1:38 pm