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death is greatest in the very young, the very old, those with medical problems involving the cardiovascular
and respiratory systems and those who sustain multiple bites. Only about 1/5 of snake bites in the U.S. are
inflicted by venomous snakes and not all bites by poisonous snakes result in envenomation. Rattlesnakes fail
to inject venom in up to 20% of bites. The typical victim of a pit viper is a young male 11 - 19 years of
age who is bitten on the hand while trying to handle the snake. Alcohol use is often a contributing factor.
Because snakes either hibernate or are inactive during winter, the peak snakebite season in temperate
climates is April-October. In the United States the great majority of poisonous snakebites are caused by
pit vipers (Crotalidae), specifically rattlesnakes, copperheads and cottonmouth snakes. Eastern and western
diamondback rattlesnakes, although causing only about 10% of all snakebites in the U.S., are responsible
for 95% of all snakebite deaths in the U.S. The other poisonous species of snakes in North America (not pit
vipers) are the Eastern and Texas coral snakes. They are members of the Elapidae family, along with cobras,
kraits, and mambas. Sea snakes belong to the Hydrophidae family.
Subjective: Symptoms
Variable depending on type of snake, amount of venom injected, age of victim and other factors.
Acute (2 hr) Sub-acute (2-48 hr) Chronic (>48 hr)
Constitutional Crotalidae: Rapid onset Crotalidae: Persistent severe Either improving or organ
of severe pain at bite site, pain, HA, thirst, dizziness, system failure (renal,
severe HA, marked thirst. chills, nausea. Elapidae: respiratory, cardiovascular),
Elapidae/Hydrophidae: Excessive perspiration disseminated hemorrhage,
Little/no immediate pain Hydrophidae: Muscle aches/ Pruritus, fever, myalgia,
at bite site pains/stiffness and pain on arthritis suggests serum
passive movement of arm, sickness secondary to
thigh, neck, trunk muscles antivenin admin.
Respiratory If anaphylaxis: Difficulty Onset of anaphylaxis may be Elapidae/Hydrophidae:
breathing, shortness of delayed > 2 hr. so consider if Respiratory paralysis may be
breath. Elapidae/ SOB/ bronchospasm occur. prolonged (up to 7 days)
Hydrophidae: Severe Elapidae/Hydrophidae:
envenomation may cause Respiratory paralysis/arrest
respiratory paralysis/arrest possible
Cardiovascular If anaphylaxis: Fainting/ Palpitations, shock symptoms Usually no long term effects
near fainting, shock
symptoms, severe
envenomation may cause
arrest
GI Nausea/Vomiting Nausea/Vomiting Usually no long term effects
Neuro Elapidae/Hydrophidae:
Blurred vision Elapidae/Hydrophidae: Elapidae/Hydrophidae:
Paresthesias (numbness of Recovery or possible
lips/soles of feet) long-term numbness, burning/
tingling sensation
Focused History: Can you identify the snake? (give appropriate antivenin) When was your last tetanus
immunization? (need for current tetanus protection) Do you have allergies to horses/horse serum? (check
before giving serum derived from horses)
Objective: Signs
Rapid onset suggests a more severe envenomation.
Using Basic Tools:
Acute (2 hr) Sub-acute (2-48 hr) Chronic (>48 hr)