AUTHOR INFORMATION

Section 1 of 12

Authored by Robert Norris, MD, Chief, Associate Professor, Department of Surgery, Division of Emergency Medicine, Stanford University Medical Center

Robert Norris, MD, is a member of the following medical societies: American College of Emergency Physicians, American Medical Association, California Medical Association, and Wilderness Medical Society

Edited by Edmond Hooker, MD, Assistant Clinical Professor, Department of Emergency Medicine, University of Louisville, Wright State University; John T VanDeVoort, PharmD, Clinical Assistant Professor, College of Pharmacy, University of Minnesota; David Eitel, MD, MBA, Associate Professor, Department of Emergency Medicine, York Hospital; John Halamka, MD, Chief Information Officer, CareGroup Healthcare System, Assistant Professor of Medicine, Department of Emergency Medicine, Beth Israel Deaconess Medical Center; Assistant Professor of Medicine, Harvard Medical School; and Jonathan Adler, MD, Attending Physician, Department of Emergency Medicine, Massachusetts General Hospital; Division of Emergency Medicine, Harvard Medical School

Author's Email:	Robert Norris, MD
Editor's Email:	Edmond Hooker, MD

eMedicine Journal, January 4 2007, VOLUME 8, Number 1

INTRODUCTION

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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:

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

• Internationally: 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

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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

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Snake Envenomations, Brown
Snake Envenomations, Cobra
Snake Envenomations, Moccasins
Snake Envenomations, Mohave Rattle
Snake Envenomations, Rattle
Snake Envenomations, Sea

WORKUP

Section 5 of 12

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

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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

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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 Name	Micrurus fulvius Antivenin -- DOC for significant bites by M fulvius (eastern coral snake) and M tener (Texas coral snake). Manufacturer generally recommends skin testing for potential acute sensitivity. However, such testing is not a reliable predictor of anaphylactoid reactions. If the patient is in extremis, antivenom should be started while closely monitoring for adverse reactions. Before administration, the patient's IV volume should be expanded using crystalloid solutions (eg, NS) unless contraindication exists (eg, presence of congestive heart failure). Pretreat with antihistamines (H1 and H2 blockers, see antihistamines below). Epinephrine should be immediately available for treatment of an allergic response to heterologous serum. Wyeth-Ayerst product comes in a lyophilized state and must be reconstituted before administration. This is best accomplished by instilling 10 mL warm diluent (NS) into each vial and gently agitating under warm running tap water. Then, the starting dose is diluted in 500-1000 mL of crystalloid (this volume may need to be reduced in children) and should be initiated at a slow rate with physician in immediate attendance. If no reaction occurs, rate should be increased gradually to administer full starting dose in 1-2 h. If acute reaction occurs, antivenom should be halted and the patient treated prn with epinephrine, antihistamines, and steroids. Then, antivenom can usually be restarted at a slower rate or in a more dilute form. If reaction persists or is severe, the physician may need to rely solely on sound supportive care for the patient.
Adult Dose	Initial: 3-6 vials IV over 1-2 h; if signs or symptoms continue to progress, administer an additional 3-5 vials over 1-2 h; rarely are more than 10 vials required
Pediatric Dose	Administer as in adults; total volume of diluent should be appropriately reduced depending on child's size and hemodynamic status
Contraindications	Documented hypersensitivity; may be indicated for severe envenomation despite allergy
Interactions	None reported
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Anaphylactic/anaphylactoid reactions and delayed serum sickness are a concern; appropriate therapeutic agents for anaphylaxis treatment should be ready for immediate use; while use in pregnancy has not been well studied, it is generally felt that the benefits of antivenom administration outweigh the risks

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 Name	Diphenhydramine (Benadryl) -- Administered parenterally and often is the H1 blocker of choice in treating or preventing anaphylactic/anaphylactoid reactions. Also effective in oral form for treating itching associated with serum sickness.
Adult Dose	Pretreatment for antivenom: 1 mg/kg/dose IV; not to exceed 100 mg/dose; if acute allergic reaction subsequently occurs, additional doses may be required; not to exceed 300 mg/d Serum sickness: 1 mg/kg PO q6h prn itching; not to exceed 400 mg/d
Pediatric Dose	Pretreatment for antivenom: Administer as in adults Serum sickness: 1 mg/kg PO q6h prn itching; not to exceed 300 mg/d
Contraindications	Documented hypersensitivity; MAOIs
Interactions	Potentiates effect of CNS depressants; because of alcohol content, do not give syrup dosage form to patient taking medications that can cause disulfiramlike reactions
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	May exacerbate angle closure glaucoma, hyperthyroidism, peptic ulcer, and urinary tract obstruction

Drug Name	Cimetidine (Tagamet) -- Administered parenterally and often is the H2 blocker of choice in treating or preventing anaphylactoid reactions. Use this medication in addition to H1 antihistamines.
Adult Dose	300 mg IV q6h prn
Pediatric Dose	5-10 mg/kg IV q6h prn; not to exceed 300 mg/dose
Contraindications	Documented hypersensitivity
Interactions	Can increase blood levels of theophylline, warfarin, tricyclic antidepressants, triamterene, phenytoin, quinidine, propranolol, metronidazole, procainamide, and lidocaine
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Elderly persons may experience confusional states; may cause impotence and gynecomastia in young males; may increase levels of many drugs; adjust dose or discontinue treatment if changes in renal function occur

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 Name	Epinephrine (EpiPen, Adrenaline) -- DOC for treating anaphylactoid reactions. Has alpha-agonist effects that increase peripheral vascular resistance and reverse peripheral vasodilatation, systemic hypotension, and vascular permeability. Conversely, beta-agonist activity of epinephrine produces bronchodilatation, chronotropic cardiac activity, and positive inotropic effects.
Adult Dose	0.01 mL/kg of 1:1000 (1 mg/mL) IM/SC; not to exceed 0.5 mL
Pediatric Dose	0.01 mL/kg of 1:1000 (1 mg/mL) IM/SC; not to exceed 0.3 mL; may be repeated q10-20min prn For severe hypotension: 0.05 mcg/kg/min IV initially (ie, 1 mg in 500 mL isotonic saline, starting at 0.025 mL/kg/min); titrate to effect
Contraindications	Documented hypersensitivity; cardiac dysrhythmias or angle-closure glaucoma; do not use during labor (may delay second stage of labor)
Interactions	Concurrent use with alpha- or beta-blockers is not recommended; nonselective beta blockade allows alpha-receptor effects to predominate; increasing vascular resistance leads to increased BP and reflex bradycardia; closely monitor vital signs if the patient is taking a beta-blocker; pressor action is increased when coadministered with alpha agonists; increases toxicity of halogenated inhalational anesthetics
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Caution in elderly persons, prostatic hypertrophy, hypertension, cardiovascular disease, diabetes mellitus, hyperthyroidism, and cerebrovascular insufficiency; rapid IV infusions may cause death from cerebrovascular hemorrhage or cardiac dysrhythmias

Drug Name	Dopamine (Intropin) -- May be required to support BP with hypotension caused by anaphylactoid reaction that is unresponsive to fluids and epinephrine or by direct coral snake venom effects that are unresponsive to fluids and antivenom.
Adult Dose	5-20 mcg/kg/min IV; titrate to effect
Pediatric Dose	Administer as in adults
Contraindications	Documented hypersensitivity; pheochromocytoma; ventricular fibrillation
Interactions	Phenytoin, alpha-adrenergic and beta-adrenergic blockers, general anesthesia, and MAOIs increase and prolong the effects
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Monitor closely urine flow, cardiac output, pulmonary wedge pressure, and BP during infusion; prior to infusion, correct hypovolemia as indicated; monitoring central venous pressure or left ventricular filling pressure may be helpful in detecting and treating hypovolemia

Drug Name	Norepinephrine (Levophed) -- May be used as alternative to dopamine to support BP in the face of hypotension caused by anaphylactoid reaction unresponsive to fluids and epinephrine.
Adult Dose	0.5-1 mcg/min IV; titrate to effect
Pediatric Dose	0.1 mcg/kg/min IV; titrate to effect
Contraindications	Documented hypersensitivity; peripheral or mesenteric vascular thrombosis because ischemia may be increased and area of infarct extended
Interactions	Atropine may enhance pressor response by blocking reflex bradycardia
Pregnancy	D - Unsafe in pregnancy
Precautions	If possible, correct intravascular volume depletion before therapy; extravasation may cause severe tissue necrosis and, thus, should be administered into a large vein; caution in occlusive vascular disease

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 Name	Methylprednisolone (Solu-Medrol, Adlone) -- Ameliorates the delayed effects of anaphylactoid reactions and may prevent biphasic anaphylaxis. In severe cases of serum sickness, parenteral steroids may reduce the inflammatory effects of this immune-complex mediated disease.
Adult Dose	125 mg IV q6-8h
Pediatric Dose	1-2 mg/kg IV q6-8h
Contraindications	Documented hypersensitivity; viral, fungal, or tubercular skin infections
Interactions	Coadministration with digoxin may increase digitalis toxicity secondary to hypokalemia; estrogens may increase levels; phenobarbital, phenytoin, and rifampin may decrease levels (adjust dose); monitor patients for hypokalemia when taking medication concurrently with diuretics
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Hyperglycemia, edema, osteonecrosis, peptic ulcer disease, hypokalemia, osteoporosis, euphoria, psychosis, growth suppression, myopathy, and infections are possible complications of glucocorticoid use

Drug Name	Prednisone (Deltasone) -- This or other PO forms of corticosteroids (eg, prednisolone) are useful in managing mild-to-moderate serum sickness on an outpatient basis.
Adult Dose	1 mg/kg PO qd until symptoms resolve; taper over 1-2 wk
Pediatric Dose	Administer as in adults
Contraindications	Documented hypersensitivity; viral infection; peptic ulcer disease; hepatic dysfunction; connective tissue infections; fungal or tubercular skin infections
Interactions	Coadministration with estrogens may decrease clearance; concurrent use with digoxin may cause digitalis toxicity secondary to hypokalemia; phenobarbital, phenytoin, and rifampin may increase metabolism of glucocorticoids (consider increasing maintenance dose); monitor for hypokalemia with coadministration of diuretics
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Abrupt discontinuation of glucocorticoids after long-term therapy may cause adrenal crisis; hyperglycemia, edema, osteonecrosis, myopathy, peptic ulcer disease, hypokalemia, osteoporosis, euphoria, psychosis, myasthenia gravis, growth suppression, and infections may occur with glucocorticoid use

Drug Category: Immune globulins -- Bind toxoids, stimulate an immune response, and offer transient protection while the host immune system develops antibodies.

Drug Name	Tetanus immune globulin (Hyper-Tet) -- Used for passive immunization if wound might be contaminated with tetanus spores when the patient has no history of completing a primary tetanus immunization series.
Adult Dose	Prophylaxis: 250-500 U IM in different anatomical site than tetanus toxoid administration Clinical tetanus: 3000-10,000 U IM
Pediatric Dose	Prophylaxis: 250 U IM in different anatomical site than tetanus toxoid administration Clinical tetanus: Administer as in adults
Contraindications	Since antibodies in globulin preparation may interfere with immune response to vaccination, do not administer within 3 mo of live virus immune globulin administration; may be necessary to revaccinate persons who received immune globulin shortly after live virus vaccination
Interactions	None reported
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Persons with isolated immunoglobulin A (IgA) deficiency have potential for developing antibodies to IgA and could have anaphylactic reactions to subsequent administration of blood products that contain IgA; do not perform skin testing since intradermal injection of concentrated gamma globulin may cause localized area of inflammation and can be misinterpreted, causing the medication to be withheld from a patient not allergic to this material; true allergic responses to human gamma globulin given in prescribed IM manner are extremely rare; do not admix with other medications since usually incompatible

Drug Category: Tetanus toxoid -- Used to induce active immunity against tetanus.

Drug Name	Tetanus toxoid -- The immunizing agent of choice for most adults and children > 7 y is tetanus and diphtheria toxoids. Necessary to administer booster doses to maintain tetanus immunity throughout life. Pregnant patients should receive only tetanus toxoid, not a diphtheria antigen-containing product. In children and adults, may administer into deltoid or midlateral thigh muscles. In infants, preferred site of administration is the mid-thigh laterally.
Adult Dose	Suggested dosing: Primary immunization: 0.5 mL IM, give 2 injections 4-8 wk apart and a third dose 6-12 mo after second injection Booster dose: 0.5 mL q 10 y
Pediatric Dose	Administer as in adults
Contraindications	Documented hypersensitivity; a history of any type of neurological symptoms or signs following administration of this product; FDA recommends that elective tetanus immunization be deferred during any outbreak of poliomyelitis because tetanus toxoid injections are an important cause of provocative poliomyelitis
Interactions	Patients receiving immunosuppressants, including corticosteroids or radiation therapy, may remain susceptible despite immunization due to poor immune response; cimetidine may enhance or augment delayed-hypersensitivity responses to skin-test antigens; avoid concurrent use of medication with systemic chloramphenicol since it may impair amnestic response to tetanus toxoid; concurrent use of tetanus immune globulin may delay development of active immunity by several days (interaction is nevertheless clinically insignificant and does not preclude its concurrent use)
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Do not use to treat actual tetanus infections, or for immediate prophylaxis of unimmunized individuals (use instead tetanus antitoxin, preferably human tetanus immune globulin) diminished antibody response to active immunization may be seen in patients receiving immunosuppressive therapy; better to defer primary diphtheria immunization until immunosuppressive therapy discontinued; routine immunization of symptomatic and asymptomatic HIV-infected persons is recommended

FOLLOW-UP

Section 8 of 12

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 12

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.

TEST QUESTIONS

Section 10 of 12

CME Question 1: Which of the following statements regarding coral snakes is true?

A: They can be reliably identified throughout their range by a contiguous red and yellow banding pattern.
B: Most bites occur in individuals who are unaware of a nearby snake.
C: They tend to be shy and reclusive.
D: They have a sophisticated venom delivery apparatus with long, retractable, anterior fangs.
E: None of the above

The correct answer is C: Coral snakes are generally shy and reclusive creatures, which explains the small number of bites reported in the United States each year. South of Mexico City, the color pattern can be misleading as a guide to identification. Because of their relatively inefficient venom delivery apparatus (ie, small fixed anterior fangs), coral snakes generally have difficulty envenomating unless they are touched or handled.

CME Question 2: Which of the following statements regarding the management of coral snake bites is true?

A: Asymptomatic patients can be safely discharged after 4 hours of observation.
B: Pit viper antivenom can effectively neutralize the venom of most coral snakes.
C: Patients should be administered sedative agents liberally.
D: Prophylactic antibiotics generally are unnecessary.
E: None of the above

The correct answer is D: 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. Admit all persons bitten by a coral snake in order to watch for delayed onset of signs and symptoms. Pit viper antivenom is of no benefit in coral snake bites. Sedatives must be used cautiously in these patients because of the risk of respiratory depression.

Pearl Question 1 (T/F): Respiratory arrest is the most significant risk to life following coral snake envenomation.

The correct answer is True: Historically, death related to coral snake bite has been related to respiratory and cardiovascular failure.

Pearl Question 2 (T/F): In the United States, a red-on-yellow band color pattern is reliable in identifying a snake as a coral snake.

The correct answer is True: A pattern of red, yellow, black, yellow, red bands (red and yellow bands contiguous) reliably identifies coral snakes in the United States. A helpful hint is to remember the warning colors on a traffic light: red and yellow. When these two colors touch on a snake in the United States, a strong possibility exists that it is a dangerous coral snake.

Pearl Question 3 (T/F): Pressure immobilization may be a worthwhile first aid technique following a coral snake bite.

The correct answer is True: The pressure immobilization technique (starting distally, wrapping with materials, such as an elastic bandage or long strip of cloth, and working up the entire limb), combined with a splint, has been demonstrated to significantly limit and delay the spread of elapid snake venoms, including coral snake venom. Wrap the extremity as tightly as for a severely sprained ankle.

Pearl Question 4 (T/F): Antivenin (Micrurus fulvius), produced by Wyeth-Ayerst Labs, is indicated for bites by all coral snake species native to the United States.

The correct answer is False: Antivenin (M fulvius) provides coverage for the eastern and the Texas coral snakes. Its value in treating Sonoran coral snake bites is uncertain, but these bites tend to be very mild and can be managed with supportive care alone.

PICTURES

Section 11 of 12

Caption: Picture 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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Caption: Picture 2. Coral snake skull.
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Caption: Picture 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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Caption: Picture 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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BIBLIOGRAPHY

Section 12 of 12

• 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 2005 Jun; 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 1987 Sep 25; 258(12): 1615-8[Medline].
• Norris RL, Dart RC: Apparent coral snake envenomation in a patient without visible fang marks. Am J Emerg Med 1989 Jul; 7(4): 402-5[Medline].
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