Category Archives: injury

Komodo dragons: Myth vs Reality

The Komodo dragon is a creature that inspires fear and mysticism in many. It’s got all the characteristics of a good monster movie: only found on rare tropical islands, large, and possessing magical saliva that can kill. First identified by the west in 1910 by Dutch sailors, they reported the lizards could spit fire and reached 7m in length. In reality the lizard can only get up to 3m and can weigh 70kg, and none have been identified as either breathing or spitting fire.

Komodo dragon (Varanus komodoensis), Komodo National Park, Indonesia

This review comes after a zoo worker was bitten on the hand by a small Komodo dragon. She had transient hypotension, and a retained tooth on xray. This was not removed, and after loose approximation (Ed. note: never do this), she was discharged on antibiotics. Thankfully the tooth came out on its own, and she did not develop a deep space infection. After this case report, the authors decided to do a literature review, knowing that it would help them get published.

Many of us are taught in school that Komodo dragon saliva is a possibly venomous, potentially fatal concoction of particularly virulent bacteria, including E. Coli, Staphylococcus, Streptococcus, and Pasteurella. These bacteria live in the rotting flesh that they leave in their mouth. But what is that based on?

It turns out, not much. The “facts” we have in textbooks, zoos, and medical literature are based on one guy’s book written in 1981. While Walter Auffenberg was the Jane Goodall of Komodo dragons, moving to the island and studying them in their natural habitat, his results haven’t been widely reproducible. And, more importantly, komodos don’t carry rotting flesh in their mouth. They fastidiously clean their teeth and gums. Now, perhaps the water buffalo does die of sepsis after being bitten, but if it does, it’s because it runs into murky water with fresh wounds, and not from bacteria in the mouth of the lizard. So, the “bacteria as venom” concept is just as dead in the water as the buffaloes.

So what about the venom aspect? The author of that study (Fry) was able to identify glands in the lower jaw that could potentially be venom glands. Furthermore, the extract of those glands does in fact contain proteins that inhibit blood clotting similar to snake venom. However, there isn’t any evidence that the venom actually affects the prey or is secreted in any significant amount during bites. The teeth lack venom grooves present in every other venomous animal (including the shrew). On the plus side, the author did come up with the “grip, rip, and drip” model of lethality from komodos.

Then why do animals die after being bitten by a large, reptilian predator? For the same reasons they die after being bitten by any large animal. Direct trauma, blood loss, and hypovolemic shock (and by eating).

Our findings are also in accord with the view that the killing technique of V. komodoensis is broadly similar to that of some sharks and Smilodon fatalis (saber cat). Despite obvious anatomical differences, these unrelated predators kill or are thought to have killed (respectively) large prey by using relatively weak bite forces amplified by sharp teeth and postcranial input.

They have strong neck muscles and serrated teeth, so after they bite they pull away, tearing holes in the prey that then bleeds to death. Is it possible that venom can increase this bleeding? Sure, but it’s also possible that it doesn’t.

So then why did this patient become hypotensive? Likely a vasovagal response. And given that the bite was on the hand, it’s appropriate to put the patient on antibiotics. But maybe we can finally stop propagating the magical thinking associated with komodo dragons.

Bitten by a Dragon
http://www.wemjournal.org/article/S1080-6032(16)00100-9/abstract

Further enjoyable reading
National Geographic
http://phenomena.nationalgeographic.com/2013/06/27/the-myth-of-the-komodo-dragons-dirty-mouth/
A central role for venom in predation by Varanus komodoensis (Komodo Dragon) and the extinct giant Varanus (Megalania) priscus
http://www.pnas.org/content/106/22/8969.full

Is there anything a SAM splint can’t do?

Deciding what to carry in your medical kit on an expedition is hard. You don’t want to leave anything out, but you can’t carry an entire hospital on your back. I mean, the wheels on the slit lamp really suck at crossing rough terrain. So you have to decide what goes and what doesn’t. Thus the reason for much of the improvisation inherent in wilderness medicine. An item that only does one job had better be the only item that can do that job, or it is extra weight.

C collars are one of those items. Now, ignoring the fact that many of them aren’t good at their job to begin with, they really aren’t good for much else. Sure, you could maybe improvise a pressure dressing out of it, but what else are you going to do? And while some of them do lay flat, they’re still pretty long and take up space that could be used for something else.

Enter the SAM splint®*. Waterproof, moldable, and able to be cut to size, it can be used pretty much anywhere on the body. And everyone has seen the picture of one being used to immobilize the cervical spine. But does it work well in that role?

Improvised C Collar in Auckland

These authors put it to the test against a Philadelphia collar using 13 EM resident “volunteers”. I’m sure they were paid well for their time. Using a goniometer they measured maximal extension, rotation, and lateral flexion. They found that no statistically significant difference in any one measurement, but looking at the results the SAM does appear to allow slightly more rotation and extension, while doing a better job of limiting lateral flexion. This likely is due to the bulkiness of the SAM laterally.

While the method of measuring falls short of a radiographic gold standards, and the number of subjects is low (but powered to an 11° difference per the authors), it looks like the SAM splint, in fact, is just as good as a Philly collar at immobilizing the C spine. I am OK with it in an awake patient, but would add more reinforcement to an unconscious patient.

Comparison of a SAM Splint-Molded Cervical Collar with a Philadelphia Cervical Collar
http://www.ncbi.nlm.nih.gov/pubmed/19594206

*I’m using SAM splint to cover all the moldable splints out there, similar to how Xerox is used to cover all photocopiers. I do not receive any money from SAM Medical Products® for using their name here. You are welcome to use other splints, but this article only used the SAM.