AUTHOR AND EDITOR INFORMATION

Section 1 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

INTRODUCTION

Section 2 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Background

Approximately 40-50 species of venomous coral snakes exist in North and South America, with the greatest variety from Mexico to northern South America. A number of African and Asian coral snake species also exist. All coral snakes belong to the family Elapidae; Micrurus fulvius (eastern coral snake) and Micrurus tener (Texas coral snake) are the most important species in the United States.

Another US coral snake is Micruroides euryxanthus (Sonoran or Arizona coral snake); but this is a relatively innocuous snake, and no deaths have been attributed to its bite.

Coral snakes tend to be relatively shy creatures, and bites are uncommon. Coral snakes account for fewer than 1% of venomous snakebites in the United States. Most people bitten by coral snakes are handling them intentionally. Most bites occur in the spring or fall.

Pathophysiology

The coral snake venom apparatus is composed of a pair of small, fixed, hollow fangs in the anterior aspect of the upper jaw through which the snake conducts venom via a chewing motion (see Image 2). Unlike pit vipers, such as rattlesnakes, copperheads, and cottonmouths, which strike quickly, coral snakes must hang on for a brief period to achieve significant envenomation in humans.

Coral snake venoms tend to have significant neurotoxicity, inducing neuromuscular dysfunction. They have little enzymatic activity or necrotic potential compared to most vipers and pit vipers. These venoms tend to be some of the most potent found in snakes, yet the venom yield per animal is less than that of most vipers or pit vipers. Because of the relatively primitive venom delivery apparatus, as many as 60% of those bitten by North American coral snakes are not envenomed.

Frequency

United States

Probably fewer than 20 bites per year (though 99 alleged bites were reported to the American Association of Poison Control Centers in 2004)

International

No accurate information available

Mortality/Morbidity

No deaths related to coral snake bites have been reported in the United States since coral snake antivenom became available. Before that time, the estimated case fatality rate was 10%, and the cause of death was respiratory or cardiovascular failure. Patients who survive the bite may require respiratory support for up to a week and may suffer persistent weakness for weeks to months.

CLINICAL

Section 3 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

History

• The vast majority of patients bitten by coral snakes report that a brightly colored snake bit them.
• North of Mexico City, including the United States, the color pattern of the snake can be helpful in differentiating a coral snake from a harmless mimic (eg, nonvenomous milk snake).
• • In this region, all coral snakes have a red, yellow, black, yellow, red banding pattern (red and yellow touching, see Image 1); most harmless mimics have a red, black, yellow, black, red pattern (red and yellow separated by black).
  • South of Mexico City, the banding patterns are much more difficult to differentiate, and bicolor (red and black) species are also present.
• Onset of symptoms may be delayed up to 10-12 hours but may then be rapidly progressive.
• Paucity of local complaints
• Local paresthesias (may be painful)
• Soft tissue swelling (usually very mild)
• Alteration of mental status
• Complaints related to cranial nerve dysfunction (eg, diplopia, ptosis, difficulty swallowing)

Physical

• Impending respiratory failure
• • Respiratory distress
  • Pharyngeal spasm
  • Hypersalivation
  • Cyanosis
  • Trismus
• Neurologic dysfunction
• • Altered mental status
  • Ptosis
  • Generalized weakness
  • Muscle fasciculations
• Cardiovascular collapse
• • Hypotension
  • Tachycardia

DIFFERENTIALS

Section 4 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

WORKUP

Section 5 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Lab Studies

• No laboratory studies are of diagnostic benefit. Baseline labs (eg, complete blood count [CBC], electrolyte tests, renal function studies) may be obtained in severe bite cases or if the patient has significant underlying medical problems. Coagulation studies are not indicated.
• An arterial blood gas (ABG) determination may be helpful if the patient's respiratory status is of concern.

Imaging Studies

• A chest radiograph is beneficial in patients who have severe envenomations, require intubation, or show evidence of cardiopulmonary failure.

TREATMENT

Section 6 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Prehospital Care

Of utmost importance is prompt movement of the victim to a medical facility capable of rendering advanced care, including possible antivenom administration and airway support.

• Briefly attempt to identify the snake (especially, note the color pattern). If possible, take a digital photo of the snake from a safe distance. Efforts to catch or kill the animal can result in wasted time and further bites.
• Rapidly apply a compressive bandage (eg, elastic bandage, crepe bandage, torn clothing) to the bitten extremity, starting distally and progressing to encompass the entire limb. Wrap it as tightly as one would wrap a severe sprained ankle. Then, splint the extremity and, if possible, keep it at approximately heart level. This technique may significantly delay systemic absorption of elapid venoms, including coral snake venom. Research suggests that, in a simulated snakebite scenario, people tend to underestimate the application tension required for the technique to be effective.
• No incisions are indicated.
• Suction is of no benefit and may be harmful.
• Avoid applying ice or initiating any other cooling measures.

Emergency Department Care

• Aggressively manage any signs of impending respiratory failure with endotracheal intubation to prevent aspiration.
• Immediately institute cardiac and pulse oximetry monitoring.
• Monitor vital signs closely.
• Start at least one large bore intravenous line of normal saline or Ringer's lactate at a maintenance rate. If evidence of hypotension or hypoperfusion is present, select an appropriate, faster rate.
• Although numerous recommended grading scales are available for judging the severity of pit viper bites, these scales rely heavily on local findings, which are often minimal in coral snake bites.
• • Do not use such scales for coral snake bites.
  • Because of the lack of early signs and symptoms, the severity of coral snake bites may be underestimated at presentation. Maintain a high index of concern.
• If the snake is positively identified as an eastern or Texas coral snake, or if signs and symptoms of envenomation are already present, obtain and immediately administer appropriate antivenom.
• • Specialized agencies (eg, poison control centers, zoos, research laboratories) can assist in obtaining antivenom.
  • If the patient has definitely been bitten by an eastern or Texas coral snake, and if the snake was able to hang on and chew for any length of time, antivenom should be administered even if signs of envenomation are lacking. These may be delayed and are difficult to reverse once they begin.
  • Bites by Sonoran coral snakes tend to be very mild (there has never been a documented fatality). Treat them with supportive measures alone.

Consultations

• Toxicologist or expert in snakebite management
• The University of Arizona Poison and Drug Information Center maintains a consultant on call who can be reached any hour of the day at 520-626-6016.

MEDICATION

Section 7 of 11  

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• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Definitive therapy for coral snake envenomation is antivenom administration. Antivenom (usually derived from horses or sheep) is generally specific for closely related species of snakes, and no advantage exists to giving antivenom developed for unrelated snakes. Administering antivenom of unrelated snakes may add complications of acute allergic reaction (eg, anaphylactoid reactions, delayed serum sickness) to an already serious situation. If specific antivenom is unavailable, compression and immobilization should be maintained and the airway and respiratory status supported as necessary. An appropriately applied compression/immobilization device should be removed only after supportive measures are in place and antivenom is obtained (if available).

In the United States, the current available product is Wyeth's Micrurus fulvius Antivenin. It is the DOC for bites by the eastern and Texas coral snakes. Other antivenoms are produced in other countries (eg, Brazil, Costa Rica) for non-North American coral snakes. Mexico produces an antivenom that is likely effective for coral snake bites in the United States. Care for persons bitten by Sonoran coral snakes is entirely supportive because no specific antivenom is available for this species. It is unclear whether Wyeth's Micrurus fulvius Antivenin would be of any benefit in the unlikely scenario of a life-threatening bite by a Sonoran coral snake.

Antivenom should be administered according to the manufacturer's instructions. Experimental work has been done with a new fragment antigen binding (Fab)–based ovine antivenom for Micrurus fulvius fulvius, which could prove safer to use with less risk of allergic phenomena. This product is not yet commercially available.

As with any form of bite, tetanus status should be updated as necessary.

Antibiotic prophylaxis is not indicated. Because of the relative paucity of enzymatic necrotic components in their venoms, coral snake bites tend to cause little local tissue damage, and secondary infections are rare.

Drug Category: Antivenom

Imparts passive immunity to the patient against the venom components of the snake(s) for which it is manufactured. Heterologous antibodies administered bind with venom antigens and block their deleterious effects.

Drug Category: Antihistamines

H1 and H2 blockers may blunt or prevent acute allergic reaction when given before the administration of antivenom. If an anaphylactoid reaction occurs despite pretreatment, further antihistamine dosing may be required. They are also useful in managing pruritus in cases of delayed serum sickness, which may appear days to weeks following antivenom treatment.

Drug Category: Cardiovascular agents

Useful in treating acute allergic reactions that may occur with antivenom administration and in supporting the blood pressure and tissue perfusion of hypotensive patients with shock unresponsive to IV fluids and antivenom.

Drug Category: Corticosteroids

Essential for management of acute and delayed allergic phenomena following antivenom administration. Steroids have no primary role in the management of snake envenomation.

Drug Category: Immune globulins

Bind toxoids, stimulate an immune response, and offer transient protection while the host immune system develops antibodies.

Drug Category: Tetanus toxoid

Used to induce active immunity against tetanus.

FOLLOW-UP

Section 8 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Further Inpatient Care

• Admit all persons bitten by coral snakes to a closely monitored facility, whether or not antivenom is given.
• Observe asymptomatic patients for at least 24 hours because delayed signs and symptoms may occur.
• If signs or symptoms of envenomation progress after initial administration of antivenom, further antivenom may be required. It is rare for antivenom to be required after 24 hours.
• Continue to administer systemic antihistamines and steroids to patients who have experienced an acute allergic reaction to antivenom until stable.
• Generally, little or no risk of tissue necrosis is present following coral snake bites.
• Inform patients who have received antivenom of the signs and symptoms of delayed serum sickness. If symptoms of serum sickness develop after discharge, promptly evaluate the patient for initiation of systemic steroids and diphenhydramine (see Medications).

Deterrence/Prevention

• Avoid handling venomous or unidentified snakes.

Complications

• Respiratory failure
• Cardiovascular collapse
• Prolonged neuromuscular weakness
• Antivenom-related complications
• • Anaphylactoid reactions
  • Delayed serum sickness

Prognosis

• With sound supportive care (eg, prevention of aspiration) and appropriate antivenom administration, prognosis following coral snake envenomation is excellent; expect a full recovery. However, the case fatality rate in untreated cases has been estimated to approach 10%.

Patient Education

• For excellent patient education resources, visit eMedicine's Bites and Stings Center. Also, see eMedicine's patient education article Snakebite.

MISCELLANEOUS

Section 9 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Medical/Legal Pitfalls

• Considering the potential delay in onset of signs and symptoms, it is unwise to discharge asymptomatic patients with possible coral snake bites.
• Some risk of acute or delayed allergic reaction associated with antivenom use always exists. If possible, obtain patient consent before use and be immediately available throughout the administration to intervene if necessary.
• Failure to aggressively manage a patient's airway in the face of impending respiratory failure may lead to aspiration, with its attendant complications.

Special Concerns

• Treatment of a patient with significant coral snake envenomation and evidence of acute allergy to antivenom (positive skin test or reaction on administration of antivenom) is difficult. The risks and benefits of proceeding with antivenom administration must be weighed. Alternative approaches include the following:
• • Maximally premedicate the patient with drugs that may blunt or prevent anaphylaxis (eg, H1 and H2 blockers, steroids), and begin the infusion very slowly and in a very dilute state.
  • Admit the patient to an intensive care facility, establish invasive hemodynamic monitoring (arterial line), maximally premedicate the patient, establish an additional line with an epinephrine infusion, and administer very dilute antivenom at a slow rate. The epinephrine infusion can be titrated with the antivenom to prevent an anaphylactoid reaction. This technique should be used only in consultation with an intensivist, a toxicologist, or an expert in snakebite management.
  • Rely on supportive care measures only, including aggressive airway and respiratory management.

MULTIMEDIA

Section 10 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Media file 1:  Snake envenomations, coral. Comparison of the harmless Lampropeltis triangulum annulata (Mexican milksnake) (top) with Micrurus tener (Texas coral snake) (bottom). Photo by Charles Alfaro.
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Media type:  Photo

Media file 2:  Coral snake skull.
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Media type:  Image

Media file 3:  The Australian pressure-immobilization technique for field management of elapid snakebite. This technique may be useful in coral snake bites, but it has never been formally evaluated. See Image 4 for Figures 4-6. Figure 1: Apply a broad-pressure bandage over the bite site as soon as possible. Do not take off jeans because the movement of doing so assists venom to enter the bloodstream. Keep the bitten leg still. Figure 2: The bandage should be as tight as it would be when applied to a sprained ankle. Figure 3: Extend the bandage as high as possible.
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Media type:  Image

Media file 4:  The Australian pressure-immobilization technique for field management of elapid snakebite. This technique may be useful in coral snake bites, but it has never been formally evaluated. See Image 3 for Figures 1-3. Figure 4: Apply a splint to the leg. Figure 5: Bind the splint firmly to as much of the leg as possible. If the bandages and splint are applied correctly, they will be comfortable and may be left on for several hours. They should not be taken off until the patient has reached medical care. The doctor will decide when to remove the bandages. If venom has been injected, it will move into the bloodstream quickly once the bandages are removed. The doctor should leave the bandages and splint in position until he or she has assembled appropriate antivenom and drugs that may need to be used when the dressings and splint are removed. Figure 6: For bites on a hand or forearm, bind to the elbow with bandages, use a splint to the elbow, and use a sling.
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Media type:  Image

REFERENCES

Section 11 of 11

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

• Davidson TM, Eisner J. United States coral snakes. Wilderness Environ Med. 1996;1:38-45.
• German BT, Hack JB, Brewer K. Pressure-immobilization bandages delay toxicity in a porcine model of eastern coral snake (Micrurus fulvius fulvius) envenomation. Ann Emerg Med. Jun 2005;45(6):603-8. [Medline].
• Gray S. Pressure immobilization of snakebite. Wilderness Environ Med. 2003;14(1):70-1. [Medline].
• Kitchens CS, Van Mierop LH. Envenomation by the Eastern coral snake (Micrurus fulvius fulvius). A study of 39 victims. JAMA. Sep 25 1987;258(12):1615-8. [Medline].
• Norris RL, Dart RC. Apparent coral snake envenomation in a patient without visible fang marks. Am J Emerg Med. Jul 1989;7(4):402-5. [Medline].
• Norris RL, Bush SP. North American venomous reptile bites. In: Auerbach PS, ed. Wilderness Medicine. 4th ed. St. Louis, Mosby;2001:896-926.
• Norris RL, Ngo J, Nolan K. Physicians and lay people are unable to apply pressure immobilization properly in a simulated snakebite scenario. Wilderness Environ Med. 2005;16(1):16-21. [Medline].
• Parrish HM, Khan MS. Bites by coral snakes: report of 11 representative cases. Am J Med Sci. May 1967;253(5):561-8. [Medline].
• Watson WA, Litovitz TL, Rodgers GC. 2004 Annual report of the American Association of Poison Control Centers Toxic Exposure Surveillance System. Am J Emerg Med. Sep 2005;23(5):589-666. [Medline].

Article Last Updated: Jan 4, 2007