ACMT Toxicology Visual Pearls: Snake Bite

Answer: Difficulty swallowing and muscle weakness (3)

North American Coral Snake Bites

The photo depicts a Texas coral snake, Micrurus tener. North America is also home to the Arizona or Sonoran coral snake (Micruroides euryxanthus) and the Eastern coral snake (Micrurus fulvius).^1,2 Of the 3, envenomation by the Eastern coral snake is most severe, followed by the Texas coral snake. The Arizona or Sonoran coral snake does not produce medically significant envenomation. In the Eastern and Southern United States, the presence of red-on-yellow bands implies a venomous snake, as opposed to the non-venomous banded snakes such as the milk snake or the king snake. This follows the rhyme “Red on yellow, kill a fellow; red on black, venom lack”; however, this does not necessarily hold true outside of the United States.²

Coral snakes have small, fixed fangs and are often observed to “chew” on the victim for a period of time before envenomation can occur. After envenomation, fang marks may be absent, and local effects may not occur, even after a venomous bite.^1,2 While rare, death from coral snake envenomation has been reported.³

Coral snake envenomation causes neurologic symptoms. The initial signs of toxicity may include double vision, slurred speech, and difficulty swallowing (bulbar paralysis). Generalized muscle weakness may progress to paralysis, and respiratory depression may occur. The onset of neurotoxicity may be delayed up to 12 hours, and the progression may be rapid. Early endotracheal intubation should be considered in symptomatic patients.²

The mechanism of toxicity is competitive inhibition of the nicotinic acetylcholine receptors at the neuromuscular junction.¹ Tissue damage and coagulopathy are not noted with typical coral snake envenomation, although they may occur after envenomation in related species from Central and South America.

Treatment in symptomatic coral snake envenomation requires supportive care and mechanical ventilation as needed. North American Coral Snake Antivenin is available but is currently in short supply.^1,2,4 Your local poison center can assist in obtaining this scarce antidote and further addressing indications for administration.^2,4,5

Bedside Pearls for North American Coral Snake Envenomation

• Coral snake envenomation can cause a descending flaccid paralysis that may occur more than 12 hours after the bite.
• The bite site may show no fang marks and no swelling.
• Admit patients with suspected coral snake bite to a unit where resuscitation, including endotracheal intubation, is readily available for at least 24 hours.
• Continuous capnography may be utilized to assess for respiratory depression.
• Call the poison center to locate antivenin, if needed.