Coral snake bites are relatively rare but potentially serious envenomations caused by the bites of venomous coral snakes, belonging to the Elapidae family. The most prevalent coral snake species in North America is the Eastern Coral Snake (Micrurus fulvius). They are the classic “red touch yellow, kill a fellow.” Here is a summary of key aspects related to coral snake bites:
Mechanism of Toxin: Coral snake venom primarily consists of neurotoxins that affect the nervous system. These neurotoxins which include micrurotoxin and micruroidin, target the neuromuscular junction at acetylcholine receptors, to which they inhibit. This can lead to respiratory depression.
Clinical Features of Coral Snake Bites:
Local Symptoms: Coral snake bites often do not cause significant local symptoms, such as pain or swelling, unlike many other venomous snake bites.
Neurological Symptoms: The primary clinical manifestation is neurotoxicity, characterized by weakness, difficulty swallowing, slurred speech, and respiratory failure. Patients can develop cranial nerve palsies.
Respiratory Distress: Resulting from respiratory muscle paralysis. This is the primary concern after a coral snake bite.
Evaluation and Lab Abnormalities:
Clinical Assessment: Diagnosis is primarily clinical, based on the characteristic neurological symptoms and a history of coral snake bite.
Laboratory Tests: Laboratory abnormalities may include an elevated creatine kinase (CK) level due to muscle breakdown, reflecting the neurotoxic effects of the venom.
Coagulation Studies: Unlike some other venomous snake bites, coral snake envenomation usually does not cause coagulopathy. There are rare reported cases of DIC in coral snake bites, and given that patients may not remember the type of snake that bit them, it is not unreasonable to send DIC labs.
Medical Management:
Supportive Care: Normal wound care, clean the wound, update tetanus, watch for cellulitis. Do not attempt to “suck out” the venom. No indication for using a tourniquet. Extremities should be monitored for compartment syndrome.
Antivenom: The only specific treatment for coral snake envenomation is the administration of coral snake antivenom (Micrurus fulvius antivenom). However, this has been out of production and current stock is expected to end this year.
Ventilatory Support: Patients with respiratory failure may require mechanical ventilation until the effects of the venom wear off. This should be handled aggressively. If the patient shows any signs of respiratory failure, promptly intubate them.
It's important to note that coral snake bites are uncommon, and the severity of envenomation can vary. These patients often require admission for monitoring.
Crotaline bites, commonly referred to as snakebites from pit vipers such as rattlesnakes, copperheads, and cottonmouths, are the other clinically significant snakes in NA. Here's a summary covering the mechanism of toxin, clinical features, evaluation, and medical management:
Mechanism of Toxin: Crotaline venom primarily consists of enzymes and peptides that exert cytotoxic, hemotoxic, and proteolytic effects. Metalloproteinases and serine proteinases in the venom contribute to swelling and damage to capillaries. They also lead to coagulation abnormalities.
Clinical Features of Crotaline Bites:
1. Local Effects: Immediate pain, swelling, and ecchymosis at the bite site. Local tissue necrosis may occur, especially with rattlesnake bites.
2. Systemic Effects: Hematologic abnormalities, such as thrombocytopenia and coagulopathy, due to venom-induced consumption coagulopathy. Systemic symptoms like nausea, vomiting, weakness, dizziness, and diaphoresis also occur. Severe envenomation can lead to shock, respiratory distress, and organ failure.
Evaluation, Including Lab Abnormalities:
1. Clinical Assessment: Assess local and systemic signs of envenomation. Evaluate for signs of compartment syndrome in the affected limb. Patients can develop hypotension from significant third spacing.
2. Laboratory Studies: Complete blood count (CBC) to assess for thrombocytopenia and coagulopathy. Coagulation studies, including prothrombin time (PT), activated partial thromboplastin time (aPTT), and fibrinogen levels. Blood chemistry to assess organ function.
Medical Management:
1. Supportive Care: Normal wound care, clean the wound, update tetanus, watch for cellulitis. Do not attempt to “suck out” the venom. No indication for using a tourniquet. Extremities should be monitored for compartment syndrome. Limbs should be measured. Patients should receive IVF and may need pressors.
2. Respiratory support: Patients with bites to the head and neck are at risk for airway compromise due to edema. Early intubation should be considered in these patients.
3. Antivenom Therapy: There are two antivenoms approved, Crofab and Anavip. Crofab is the original, Anavip was just approved in 2015.
Criteria for administration of Crofab or Anavip– significant progression of swelling, abnormal test results (plt less than 100k or fibrinogen less than 100), altered vital signs or altered mental status.
Crofab is given as 6 vials, usually diluted into 1 L of NS and run over an hour. Repeat doses (2 vials) may be given if symptoms persist at 6, 12, and 18 hours. Patients should be monitored for allergic reactions.
Anavip is a newer antivenom. It is given as 10 vials, repeated Q1H PRN for initial control of local signs of envenomation. 4 vials are given as maintenance for symptom recurrence.
Both antivenoms are quite expensive. Crofab is $3400 per vial and Anavip is $1200 a vial. Patients with systemic symptoms and receiving antivenom should go to the ICU.
Buchanan JT, Thurman J. Crotalidae Envenomation. [Updated 2022 Oct 3]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK551615/
Hessel MM, McAninch SA. Coral Snake Toxicity. [Updated 2023 Mar 13]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK519031/