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Snakebite suction devices don't remove venom: they just suck

March 2004
Annals of Emergency Medicine 43(2):187-8

DOI:10.1016/S0196064403011041

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PubMed

Authors:

Sean P Bush

East Carolina University

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FEBRUARY 2004 43:2 ANNALS OF EMERGENCY MEDICINE 187

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.

See related article, p. 181.

[Ann Emerg Med. 2004;43:187-188.]

It was only a few decades ago that incision and suction

were recommended snakebite first aid. However, con-

cerns 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.

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 stud-

ied 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 Extractormight be beneficial and would proba-

bly 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.

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 radio-

active count as an approximation of the amount of

venom removed. The bottom line: the Extractor re-

moved 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 al

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 al

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 fur-

ther injury in some subjects. Specifically, circular

lesions identical in size and shape to the Extractor suc-

tion 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 con-

centration of venom was measured in the fluid re-

moved using an enzyme-linked immunosorbent

assay.

There were no control subjects, and this study

has only been published in abstract form. Ironically,

this abstract is cited amongst the main supporting evi-

dence 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 al

similarly noted that although a relatively

large volume of bloody fluid was pulled from the punc-

ture site, it contained virtually no venom. Most inter-

estingly, Alberts et al found that the amount of venom

TOXICOLOGY/BRIEF COMMENTARY

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doi:10.1016/j.annemergmed.2003.10.031

SNAKEBITE SUCTION DEVICES Bush

in 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 de-

posited, thereby reducing the amount of venom that

would spontaneously ooze out. This suggests, like the

study by Bush et al,

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 indepen-

dently 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 experi-

ment using a rabbit model.

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 sub-

cutaneous layer, unlike humans (and pigs).

Most

snake envenomations are thought to occur in the sub-

cutaneous layer.

It is possible that in Bronstein et

al’s

investigation the injected venom collected just

under the rabbit’s skin, where it was easily suctioned

back out by the device. Because this inadequately docu-

mented single abstract reports a finding that is vastly

different from all the other studies that follow, its con-

clusions are questionable and may be erroneous.

If there was controversy before, the study by Alberts

et al

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 ac-

ceptable 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 or

support.

Address for reprints: Sean P. Bush, MD, 11234 Anderson Street, PO

Box 2000, Room A108, Loma Linda, CA 92354; 909-558-4344, fax 909-

558-0121; E-mail sbush@ahs.llumc.edu.

188 ANNALS OF EMERGENCY MEDICINE 43:2 FEBRUARY 2004

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extraction device (Extractor) on local tissue injury after artificial rattlesnake envenoma-

tion 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 treat-

ment 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.

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