History and exam
Key diagnostic factors
common
identification of the snake
Can help determine whether the snake responsible was a crotaline, an elapid, or a nonvenomous snake. If a coral snakebite is suspected, geography can help determine the species.
A good photograph taken from a safe distance (equal to more than the length of the snake) can be transmitted to an expert by smartphone to assist identification.[20]
Crotalines (pit vipers) in the US include rattlesnakes, sidewinders, copperheads, cottonmouths, and water moccasins. All have a pit organ located between the nostril and the eye, and a triangular head. Rattlesnakes have a distinctive rattle at the end of their tail that they shake when threatened.
Elapids in the US include 3 species of coral snakes. A mnemonic to help differentiate venomous coral snakes from nonvenomous snakes on the basis of skin color is: "Red next to yellow will kill a fellow. Red next to black, venom lack."
The Eastern coral snake (Micrurus fulvius fulvius) is found east of the Mississippi river in Louisiana, Mississippi, Alabama, Georgia, Florida, South Carolina, and the southeastern tip of North Carolina.
The Texas coral snake (Micrurus tener) is found west of the Mississippi river in Louisiana, Texas, the southwestern tip of Arkansas, and Mexico.[2]
The Sonoran coral snake (Micruroides euryxanthus) is found in Arizona and New Mexico, but is rarely responsible for human envenomation.[3]
local redness, swelling, tenderness, and pain at wound site
Developing within 12 hours of the bite suggests Crotalinae envenomation. The leading edge of the affected area should be serially marked every 15 to 30 minutes to assess for symptom progression. The circumference of the bitten limb should be measured above and below the snakebite for later comparison and determination of subsequent swelling.[20]
Evaluation for compartment syndrome should be performed in patients with significant local effects.
Elapidae envenomation rarely causes local effects.
Local redness, swelling, tenderness, and pain developing more than 12 hours after the bite is suggestive of wound infection.
blurred or double vision
When developing minutes to hours after the snakebite, suggests Elapidae envenomation, and may signal impending respiratory collapse.
shortness of breath
When developing minutes to hours after the snakebite, suggests Elapidae envenomation, and may signal impending respiratory collapse.
If it develops very rapidly after snakebite, it may signal an anaphylactic reaction.
difficulty swallowing
When developing minutes to hours after the snakebite, suggests Elapidae envenomation, and may signal impending respiratory collapse.
hypotension
Suggests Crotalinae envenomation with increased capillary permeability, third-spacing, and shock.
May also signal an anaphylactic reaction to snake venom.
tachypnea
Tachypnea and hypoxemia can occur with Crotalinae envenomation with metabolic acidosis.
tachycardia
Nonspecific.
puncture marks, fang marks
Puncture marks are common following snakebite. However, absence of fang marks does not preclude envenomation, especially in coral snake bites.
Fang marks are only visible in 85% of victims.[26] One case has been reported of symptomatic coral snake envenomation without visible fang marks, despite examination under magnification.[27]
bulbar weakness/paralysis
Bulbar paralysis with dysarthria, ptosis, dysphagia, drooling, and fixed pupils is highly suggestive of Elapidae envenomation, and may signal impending respiratory collapse.
uncommon
stridor
May be present in an anaphylactic reaction to snake venom.
hemorrhage
Petechiae, ecchymosis, hemorrhage, and hemorrhagic bullae may occur following Crotalinae envenomation.
quadriplegia/locked-in syndrome
Quadriplegia/locked-in syndrome has been rarely reported following nondomestic elapid envenomation.[21]
Other diagnostic factors
common
nausea and vomiting
When developing minutes to hours after the snakebite, suggests Crotalinae envenomation.
malaise, generalized weakness or dizziness
When developing minutes to hours after the snakebite, suggests Crotalinae envenomation.
perioral tingling or numbness
When developing minutes to hours after the snakebite, suggests Crotalinae envenomation.
uncommon
urticaria
May signal a systemic immunoglobulin E-mediated allergic reaction to the snake venom and can herald a developing anaphylactic reaction.
tremors
Suggestive of Elapidae envenomation.
Risk factors
strong
male sex
Men account for 72% of snakebite casualties treated in emergency departments.[4] This may be a result of a greater degree of risk-taking among men.
alcohol consumption
Around 40% of snakebite casualties consume alcohol prior to sustaining the bite.[14] Alcohol intoxication may predispose people to aggravate or act less conservatively around snakes, and slows response time to threats.
intentional snake encounter
Around 67% of snakebites occur during intentional exposure to snakes such as professional snake handling, snake hunts, and aggravating snakes in the wild.[14]
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