History
History usually can be obtained from the patient, although some patients do not see the snake and many patients cannot correctly identify the snake. Patients are encouraged to take a picture of the snake if it is safe to do so and it does not delay transport to the hospital. Identifying the species of snake can be helpful if it expedites treatment, facilitates crotaline antivenom selection where relevant, or enables experts to tailor therapy. Victims and emergency medical service providers should be discouraged from bringing in the snake because even a dead snake can envenomate. [18, 19]
Determine the time of the bite and what signs and symptoms have developed. Inquire about local effects as well as systemic symptoms such as nausea, dyspnea, and lightheadedness. Some snakebite victims describe experiencing a metallic taste.
Ascertain what treatments what have already been attempted and by whom.
Obtain a thorough medical history, including medications and allergies. Ask if the patient has had a previous snakebite and if he or she has had antivenom in the past.
Physical Examination
Assess the patency of the patient's airway and the adequacy of oxygenation and ventilation. Ensure the patient has adequate perfusion.
Document a complete set of vital signs and reassess frequently.
Assess for local damage. Crotalid envenomations are characterized by swelling, tenderness, and bruising. Hemorrhagic blebs may develop over several hours. Fang marks may be obscured by swelling, or there may be one, two, or more punctures. A larger distance between fang puncture wounds suggest a bite by a larger snake. However, smaller distances between fang marks may not represent smaller snakes because crotalid fangs are highly mobile. Patients generally report significant pain, which is often described as "being struck by a hammer". It is important to assess the progression of the damage serially; snakebites are a dynamic process and patients with minimal findings initially may have significant swelling within a few hours.
The local findings from coral snake envenomation are much more subtle. Fang marks may or may not be visible. Some swelling and erythema may be present, but significant bruising is conspicuously absent. Patients may report a "burning" or "electric" pain.
Systemic toxicity following crotalid envenomation may include nonspecific signs and symptoms such as nausea, headache, and lightheadedness. More significant features include hypotension, airway swelling, and refractory vomiting. [20, 21, 22, 23] Hematologic laboratory abnormalities are common, and bleeding is seen in approximately 0.9% of patients. [24, 25, 26, 27] Examine the patient for petechiae, epistaxis, gingival bleeding, and other mucosal bleeding.
Neurological toxicity is not associated with most crotalid envenomations, but envenomations from some species (eg, Mojave rattlesnake [C scutulatus], Southern Pacific rattlesnake [C o halleri]) may result in significant weakness and other neurological abnormalities. [28, 29, 30, 31]
Coral snake envenomation may also be associated with nonspecific systemic symptoms, but the hallmark of coral snake envenomation is neurological toxicity, which may be as subtle as local paresthesias and myokymia or as severe as skeletal and respiratory muscle paralysis. Other signs and symptoms may include diplopia, hyperacusis, odontalgia, ageusia, ptosis, ophthalmoplegia, hypersalivation, and dysphagia. [32, 33]
A typical presentation of crotalid envenomation to foot is shown in the image below.
Swelling and bruising after crotalid envenomation. Courtesy of Spencer Greene, MD.
A hemorrhagic bleb following copperhead envenomation is shown in the image below.
Hemorrhagic bleb following Eastern copperhead (Agkistrodon contortrix) envenomation. Courtesy of Spencer Greene, MD.
The image below shows local effects in a toddler following rattlesnake envenomation.
Moderate rattlesnake envenomation in a toddler after treatment with antivenom. Courtesy of Sean Bush, MD.
The three images below show effects from a severe copperhead bite.
Complications
Crotalid envenomation can cause local, systemic, and hematologic toxicity. Antivenom can minimize the local tissue damage but cannot reverse tissue death. Fortunately, many of the local effects are superficial and heal over time.
In the image below is an example of superficial tissue necrosis following copperhead envenomation. The patient improved completely within 1 week.
Superficial necrosis following copperhead envenomation. Courtesy of Spencer Greene, MD.
Infection is uncommon, so antibiotics should not be administered prophylactically. [34] Infection is seen in less than 5% of snake envenomations, and typically only in patients with significant tissue necrosis. [35, 36] Broad-spectrum antibiotics should be administered in these cases.
The biggest local complication of crotalid envenomation is prolonged, and sometimes permanent, swelling and loss of limb function, particularly following exertion. Timely administration of antivenom can significantly reduce the incidence of this disability. In a study of patients with crotalid envenomations in Kentucky, patients who did not receive antivenom lost an average of 14 days from work. [37] Patients with bites to the hand or finger had reduced strength that persisted for a mean of 22 days. Poorly healing wounds took an average of 45 days to heal, with some wounds persisting for 77 days. Additionally, many patients developed recurrent pain and swelling in their hands after normal usage for an average of 1 month. In a study conducted in the Carolinas, the mean duration of disability following mild copperhead envenomation was 42 days, and some subjects had persistent disability at 1 year at the conclusion of the study. [38] Anecdotally, many patients with envenomations that were not treated with antivenom have reported significant postexertional pain and swelling that interferes with activities of daily living.
Delayed and recurrent hematotoxicity is a frequent complication of pit viper snakebite. The mechanism(s) responsible for these phenomena has been debated, but some patients may develop coagulopathy and/or thrombocytopenia up to 2 weeks after envenomation. In a study of rattlesnake bite patients, 24% had late hematotoxicity. In a study of high-risk snakebite victims, late coagulopathy was present in 32% of subjects.
Below is a image of petechiae that developed 1 week after a black-tailed rattlesnake envenomation that was treated with FabAV.
Petechiae 1 week after being treated for black-tailed rattlesnake (Crotalus molossus) envenomation; platelet count = 2,000 (reference range 150,000-450,000). Courtesy of Daniel Jarvis.
Prolonged neuromuscular blockade may occur following coral snake envenomation in which antivenom is not administered in a timely fashion.
Also see Complications in the Treatment section.
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Eastern copperhead, Agkistrodon contortrix. Courtesy of Spencer Greene, MD.
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Broad-banded copperhead, Agkistrodon laticinctus. Courtesy of Kimberly Wyatt.
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Western cottonmouth, Agkistrodon piscivorus leucostoma. Courtesy of Kimberly Wyatt.
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Western diamondback rattlesnake, Crotalus atrox.
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Texas coral snake, Micrurus tener. Courtesy of Chip St. John.
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Comparison of the harmless Mexican milksnake, Lampropeltis triangulum annulata (top) with the Texas coral snake, Micrurus tener (bottom). Courtesy of Charles Alfaro.
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Aberrant Texas coral snake, Micrurus tener. Courtesy of Reece Hammock.
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Juvenile southern Pacific rattlesnake, Crotalus oreganus helleri. Courtesy of Sean Bush, MD.
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Copperhead bite day 3; initial wounds were to finger.
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Moderate rattlesnake envenomation in a toddler after treatment with antivenom. Courtesy of Sean Bush, MD.
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Hemorrhagic bleb following Eastern copperhead (Agkistrodon contortrix) envenomation. Courtesy of Spencer Greene, MD.
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Proper elevation of upper extremity bite. Courtesy of Spencer Greene, MD.
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Swelling and bruising after crotalid envenomation. Courtesy of Spencer Greene, MD.
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Copperhead bite day 3; initial wounds were to finger.
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Copperhead bite day 3; initial wounds were to finger.
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Superficial necrosis following copperhead envenomation. Courtesy of Spencer Greene, MD.
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Petechiae 1 week after being treated for black-tailed rattlesnake (Crotalus molossus) envenomation; platelet count = 2,000 (reference range 150,000-450,000). Courtesy of Daniel Jarvis.
