Monthly Archives: June 2016

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

Further enjoyable reading
National Geographic
A central role for venom in predation by Varanus komodoensis (Komodo Dragon) and the extinct giant Varanus (Megalania) priscus

Don’t use compression-only CPR for drowning victims

Vasily Perov: The drowned, 1867

Compression-only CPR has improved bystander participation and patient survival for OOCA. Advertisements on television and in print media have done a good job of increasing layperson awareness of this modality. And for many patients, it’s the right thing to do. But only if the etiology of their cardiac arrest is cardiac in nature. As is explained in this short little “article in press” that’s actually a letter to the editor, this can ignore the true cause of arrest in drowning victims and decrease their chance of survival.

In drowning victims, it’s primarily respiratory in nature, and they absolutely need ventilations. But how many of the ads for CCPR are that nuanced? I certainly haven’t seen any, and I would imagine many of the rest of you haven’t either. The major societies (ECR and AHA) are certainly aware of it, as their guidelines strongly urge proper use of respiratory support.

European Resuscitation Council Guidelines for Resuscitation 2015. Section 2 and 4.

“Most cardiac arrests of non-cardiac origin have respiratory causes, such as drowning (among them many children) and asphyxia. Rescue breaths as well as chest compressions are critical for successful resuscitation of these victims.”

“Most drowning victims will have sustained cardiac arrest secondary to hypoxia. In these patients, compression-only CPR is likely to be ineffective and should be avoided.”

American Heart Association (AHA) 2010

“CPR for drowning victims should use the traditional A-B-C approach in view of the hypoxic nature of the arrest”

“The first and most important treatment of the drowning victim is the immediate provision of ventilation.”

And since preventable drowning deaths can be due to improperly or not-at-all performed bystander CPR, this gap between the guidelines and the layperson needs to be closed by education. Anticipatory guidance for parents with pools, people who take part in watersports, and lifeguards can help, but really there needs to be a public campaign for CPR for drowning that’s similar to that of cardiac arrest of coronary artery disease. Specifically, any instructional materials need to address the dreaded mouth foam that can appear during resuscitation, as this is a major deterrent for anyone performing mouth to mouth.

So yeah, maybe we can dial back on the CCPR a bit, and focus on getting patients the best care available specific to their process.

A call for the proper action on drowning resuscitation