Reprieve for snakebite victims
When a poisonous snake’s fangs sink into someone, the victim needs anti-venom treatment as soon as possible. The snake toxin travels from the bite’s location to the lymphatic system and then to the bloodstream, where it can, for example, cause respiratory failure and death. It might buy time when you put pressure on the bite with a bandage, slowing the venom’s journey through the body. But there is bitter disagreement among snakebite experts about whether pressure bandages help or harm.
A team of researchers at John Hunter Hospital, the University of Newcastle, and the Royal Brisbane and Women’s Hospital in Australia has tested a gel that slows the voyage of venom in a snakebite victim’s body. The gel could also heighten the effects of pressure bandages, increasing the need for consensus on this type of snakebite treatment.
Publishing their findings in the July issue of Nature Medicine, the scientists tested a commercially available gel on 15 male and female volunteers. Instead of using real snake venom on their subjects, they used a stand-in for the venom. The non-toxic substance travels just like venom from the point of injection to the lymph nodes.
Travel time
The team injected the substance into the feet of their volunteers, tracking in each case the time the molecule took to travel from foot to groin lymph nodes. To be able to compare results, they smeared the ointment on the injection sites of some, but not all of their test subjects.
The gel led to a “marked slowing” of the molecule’s transit from simulated bite site to the lymph nodes. Without the ointment, the venom substitute took between 4 to 81 minutes. With the ointment it took between 6.5 to 162 minutes for it to go from foot to lymph nodes. The tested individuals show a wide range of transit times, an aspect on which the scientists do not comment in their paper.
The team also performed animal experiments using a venom replacement on the hind legs of anesthetized rats. In these cases, adding the gel increased transit time to the lymph nodes three-fold.
The gel, normally used to treat hemorrhoids, releases nitric oxide (NO), which is a chemical that is also a signaling molecule in the body. The scientists believe that NO-release brakes the spread of venom after a snake bite by stopping smooth muscle contractions that are a part of the body’s lymphatic pump. These contractions push the toxin onward in the body. The authors write that delaying venom transportation also lowers venom effects because it lowers the peak venom concentration in blood.
Photo by Peter Woodard. Eastern Brown Snake in Tamban Forest near Kempsey, New South Wales, Australia.
The scientists also applied real venom, from the Eastern Brown snake, on anesthetized rats. The Eastern Brown snake has “extremely potent venom” and causes more snakebites in Australia than any other, according to a snake site at the University of Sydney.
The researchers found that the gel “significantly” increased the lymph transit time by 6 minutes and staved off respiratory system collapse by around half an hour. As the results sicker through the scientific community, it is sure to stir up plenty of disagreement about pressure bandages.
Speed is the first priority with snakebites. The University of Sydney site has the tale of Theodore the dog who died after being bitten by the Eastern Brown snake. His owner is upset to not have recognized the symptoms quick enough. The symptoms include vomiting green bile, frothing at the mouth, swollen gums, and rapid heartbeat.
Pressure bandages must be placed skillfully to work well. The University of Melbourne’s department of pharmacology website has an explanation and illustration.
Here is a Youtube video of someone bandaging a cat’s leg to illustrate a firm bandage. (I do not think the kittie has been hurt, it is just calm enough to be a bandage show-kitty.)
Some bites are unlike others
The World Health Organization’s Regional Office for South-East Asia also mentions pressure bandages on its site about snakebites in Southeast Asia. It states that pressure immobilization is “recommended for bites by neurotoxic elapid snakes, including sea snakes but should not be used for viper bites because of the danger of increasing the local effects of the necrotic venom.” For those kinds of bites, a local compression pad is better, according to the site.
New York Search and Rescue, a private group that works in search and rescue missions, highlights the difference of opinion about pressure bandages for snakebites by the elapid snakes such as cobras, mambas and many Australian species. According to the site, pressure bandaging is a method that “remains controversial in the U.S,” and the authors note it can increase the risk of local tissue damage, which can be disfiguring and require rehabilitation or plastic surgery.
The authors of the Nature Medicine paper point out that pressure bandaging is recommended in Australia but not in other countries. According to the researchers, while pressure bandages may risk increasing damage to local tissue, they believe these bandages “need to be considered for use against a wider range of snakes.”
One drawback of the pressure bandage is that when a victim moves, the bandage loses its effect at hindering venom movement. The University of Melbourne’s site explicitly states that it is “very important to keep the bitten limb still.”
Although the Nature Medicine study does not end the debate, it adds a new perspective to the pressure bandage discussion. When ointment is applied, venom movement is slowed even if the victim moves.
The scientists write that their NO-ointment approach offers a new type of snakebite first aid and could be used in combination with the pressure bandage. Foes of the pressure bandage will not agree, but the ointment might offer common ground for both sides.
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References and links: Saul, Megan et. al. A pharmacological approach to first aid treatment for snakebite. Nature Medicine (17) 7, p. 809-811. DOI: http://dx.doi.org/10.1038/nm.2382
University of Melbourne, Department of Pharmacology, Australian Venom Research Unit
University of Sydney, Discipline of Anaesthesia
World Health Organization’s Regional Office for South-East Asia
Image: Peter Woodard, photographer.
Posted on October 10, 2011, in First aid, Medicine, Snakes and tagged John Hunter Hospital, nitric oxide, Royal Brisbane and Women’s Hospital, snakebites, snakes, University of Newcastle. Bookmark the permalink. 4 Comments.
à propos 
Being bitten by a snake is definitely not a joke. Been there once.. got bitten by a non-venomous snake. The feeling? During the pain attacks, I was wishing that I could had preferred being bitten by a black mamba to end that suffering right away! Source: venomoussnakes.net/snakebite.htm
Oh my, sounds excruciating. Lucky it was a non-venomous snake. I don’t know if the pressure bandage helps with pain or just with venom spread. I must check in with these researchers some time to see how this first aid technique progresses. Thanks for your comment.
“But there is bitter disagreement among snakebite experts about whether pressure bandages help or harm.”
Where is this bitter disagreement coming from? I’ve never heard of anyone suggesting against using the pressure–immobilisation technique on an elapid bite, apart from some misinformation relating to South African elapids (see http://www.sareptiles.co.za/forum/viewtopic.php?f=45&t=31223).
Thanks. Groovy photos on your blog, wow. I corresponded with Dr. van Helden on his work published in Nature Medicine. He mentioned the jury is still out on whether to use pressure bandages for cytotoxic snakes. I should follow up with him and check the literature and see how the jury sense is now. He had mentioned he had some ongoing research, which may have been published by now.
He and his colleagues note in the paper on the subject of pressure bandage with immobilization (PBI): “PBI is currently recommended in Australia but not in other countries, as snakes in Australia tend to cause minimal local tissue damage compared to the cytotoxic venoms of many other snakes, for which delaying systemic entry of the venom toxin using PBI would increase local tissue damage.” That seemed intriguing.
When I dug around a bit, I came across a 2010 paper in Clinical Toxicology ((2010) 48, 61–63 DOI: 10.3109/15563650903376071) in which William Meggs and colleagues at East Carolina University pointed out that pressure-immobilization bandages are recommended for field treatment of elapid bites. “They are problematic for bites with local toxicity,” the team noted.
Any suggestions about other papers/research to look at are welcome. Maybe there is a geographic disparity on this subject? It seemed to me there was a difference of opinion.