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<< Diagnosis And Management Of North American Snake And Scorpion Envenomations

Identification

Identification of the snake that produced the bite can be extremely helpful. Accurate information about the identity of a snake can provide information on the potency of the venom (rattlesnake venom being the most potent among native US snakes) and the patient's expected clinical course and response to antivenom. Often, well-meaning patients or bystanders will bring in the snake for identification; it goes without saying that unless you have significant experience handling snakes it is best not to handle specimens that are brought in...alive or dead! If the animal is brought in dead or in parts, keep in mind that snakes retain the ability to strike, bite, and potentially cause a significant envenomation for several minutes after death or decapitation. If you have been provided a specimen that is fairly intact and is in an appropriate container to allow for safe inspection (and you don't develop profound cataplexy at the thought of handling a snake), then knowing a few good resources can be helpful in accurate identification; see Table 5.



Figure 1 shows some of the characteristic features that help distinguish the venomous pit vipers from the thousands of non-venomous species of snakes in the US. In general, pit vipers will have a triangular shaped head, elliptical pupils, and a heat sensing pit in front of the eye. These snakes will also have a set of retractable fangs and may or may not have a rattle on the tail. The body markings on the Crotalids are widely variable and can be helpful in identifying the specific species of snake. The fourth species of native venomous snake, the coral snake, is in a totally different subfamily of snakes and does not have any of this characteristic set of pit viper features despite possessing very potent venom. The clinically important feature to know with coral snakes is the difference in the markings between a coral snake (venomous) and a king snake (non-venomous) which has evolved very similar markings to the coral snake in order to fool its prey. The old saying, "red on yellow kills a fellow; yellow on black, venom lack," works well to differentiate the corals from the king snakes in North America ONLY. Both species are found throughout the geographical distribution of the coral snake.



Generally speaking, if you see more than two or three snakebites a year or if you are the regional referral center for snake envenomations (like we are), you may also want to keep a field guide specific to your region in your ED reference library. Peterson Field Guides publishes two titles on reptiles and amphibians, one for Eastern and Central North America and one for the Western US.24-25 These guides are recommended by several herpetology sources and are inexpensive (approximately $15 each) references to keep handy. Other potentially useful resources are poison control centers, medical toxicology divisions of large hospitals, state agriculture departments, university veterinary programs, and local zoos that keep and care for reptiles.

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Last Modified: 06/27/2017
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