DESCRIPTION

Coral snakes are small, multicolored (black, red, yellow) venomous snakes.

FORMS AND USES

North American coral snakes include the following species and subspecies:

• Eastern coral snake (Micrurus fulvius fulvius)
• Texas coral snake (Micrurus fulvius tenere)
• Western coral snake (Micruroides euryxanthus)

Snake Identification

In North America only, coral snakes have colored bands that encircle their bodies in the following arrangements: if red and yellow bands are adjacent, the snake is venomous; if red and black bands are adjacent, the snake is nonvenomous.

TOXIC DOSE

One bite is potentially fatal; however, the coral snake usually has to hold on and chew to produce envenomation.

PATHOPHYSIOLOGY

• The venom produces an irreversible inhibition of neuromuscular transmission.
• Recovery takes weeks or months because receptors must regenerate.
• Unlike the pit vipers (e.g., rattlesnakes), coral snakes have fangs that are toothlike, fixed in erect position, and all of the same size.
• The bite deposits venom in subcutaneous tissues, but produces minimal local effects.

EPIDEMIOLOGY

• Coral snake bites are rare.
• Because prolonged contact is needed for envenomation to occur, nearly all coral snake bites occur during handling of snakes.
• Death may occur in patients who do not receive appropriate airway management.

CAUSES

Nearly all cases are associated with intentional handling of coral snakes.

Section Outline:

• DESCRIPTION
• FORMS AND USES
  • Snake Identification
• TOXIC DOSE
• PATHOPHYSIOLOGY
• EPIDEMIOLOGY
• CAUSES

DIFFERENTIAL DIAGNOSIS

• Fang marks may have the appearance of puncture wounds from inanimate objects (thorns, etc.) or the bite of a nonvenomous snake.
• Systemic effects may appear similar to any cause of bulbar palsy or progressive diffuse muscle paralysis.

SIGNS AND SYMPTOMS

• Venom effects may be delayed; however, if no effects occur over a period of 12 hours, it is likely a "dry bite."
• Reports of the snake holding on, being shaken or pulled to remove, or a history of drops of fluid coming through the puncture wound indicate bites with a high probability of envenomation.

Vital Signs

Tachycardia may develop, especially if hypotension is present.

HEENT

Difficult or slurred speech, or ptosis, may develop due to cranial nerve palsy.

Dermatologic

• The bite site will exhibit several puncture wounds, but these may be difficult to identify; the use of a magnifying glass is helpful.
• Injection of lidocaine or 0.9% saline beneath the suspected bite site may show exudation of fluid through unseen puncture wounds.
• Serious envenomation without fang marks has been reported.

Pulmonary

Dyspnea and respiratory insufficiency may develop.

Gastrointestinal

Nausea and vomiting may occur.

Musculoskeletal

Muscle tenderness may develop.

Neurologic

• Paresthesia, nausea, vomiting, lightheadedness, dizziness, and weakness are the most common effects; they may not appear immediately, but usually develop within hours.
• Fasciculation, diplopia, ptosis, or confusion may develop in serious envenomation cases.

PROCEDURES AND LABORATORY TESTS

Essential Tests

There are no diagnostic laboratory tests.

Recommended Tests

• Arterial blood gases may show evidence of hypoventilation.
• Serum electrolytes, glucose, BUN, creatinine, magnesium, calcium, and phosphate may be useful to evaluate causes of weakness.
• Serial evaluation of tidal volume or negative inspiratory force may be useful to monitor venom effects on ventilation.

Section Outline:

• DIFFERENTIAL DIAGNOSIS
• SIGNS AND SYMPTOMS
  • Vital Signs
  • HEENT
  • Dermatologic
  • Pulmonary
  • Gastrointestinal
  • Musculoskeletal
  • Neurologic
• PROCEDURES AND LABORATORY TESTS
  • Essential Tests
  • Recommended Tests

• Supportive care with appropriate airway management is vital.
• Time of bite and first aid measures that were performed should be determined.
• The principle of management is to use antivenom to neutralize the venom before serious toxicity develops.

DIRECTING PATIENT COURSE

The health-care provider should call the poison control center when:

• A known coral snake bite has occurred, even if without apparent envenomation.
• Signs and symptoms are not consistent with coral snake envenomation.
• Underlying disease presents an unusual or difficult problem.

The patient should be referred to a health-care facility whenever a known coral snake bite has occurred.

Admission Considerations

Inpatient management is warranted if there is a high probability that a coral snake bite has occurred, or if any signs of envenomation develop.

DECONTAMINATION

Out of Hospital

• The bitten limb should be immobilized in functional position at or below heart level.
• Aspiration of the bite site may remove some venom, but should not involve incision of the bite marks; a venom extractor is marketed for this purpose.
• Intravenous access should be established, if possible, and the patient should be transported to the emergency department.

In Hospital

• The bitten limb should be immobilized and maintained at heart level or above.
• Decontamination is not useful by the time the patient reaches the hospital.
• If the hospital does not have antivenom, the limb should be immobilized until antivenom is obtained, or the patient should be transferred to a facility with antivenom available.

ANTIDOTES

• Coral snake antivenom (Antivenin, Micrurus fulvius) is commercially available and is the specific antidote for envenomation by this species of snake. The health-care worker should contact a regional poison center if antivenom is not available (see SECTION III, Antivenom chapter, for further details).
• Antivenin (Crotalidae) Polyvalent is not effective for coral snake bites.

Indications

• The determination of whether a bite has occurred is key to treatment; if bite marks are seen with the naked eye, through a magnifying glass, or by exudation of fluid through the puncture wounds, antivenom should be administered.
• Any confirmed bite (even if no effects are apparent) by the eastern or Texas coral snake should be treated.
• Bites by the western coral snake do not require antivenom treatment.

Contraindications

Severe allergy to horse serum or to coral snake antivenom is a relative contraindication.

Method of Administration

• Antivenom should be administered in a monitored critical care setting, and the clinician should be prepared to manage the airway and treat anaphylaxis.
• A skin test should be conducted once the decision to administer antivenom has been made.
  • The skin test dose is 0.02 ml of test solution provided with the antivenom, injected intradermally, and observed for wheal and flare reaction.
  • A negative skin test does not rule out hypersensitivity reaction to antivenom.
• Four to six vials of antivenom diluted in 250 ml of crystalloid should be administered intravenously over 1 hour.
• Antivenom should be administered as soon as possible after envenomation is confirmed.
• If symptoms develop or worsen, another four to five vials should be administered.

Potential Adverse Effects

• Localized phlebitis, rash, wheezing, or anaphylaxis may occur during infusion.
• Serum sickness may develop within 1 to 2 weeks of administration.

ADJUNCTIVE TREATMENT

• Electric shock therapy of the bite site is not recommended.
• The patient should be assessed repeatedly for development of complications of muscle weakness or respiratory insufficiency.
• Endotracheal intubation should be performed as soon as evidence of respiratory insufficiency develops (elevated pCO₂, declining negative inspiratory force).

Section Outline:

• DIRECTING PATIENT COURSE
  • Admission Considerations
• DECONTAMINATION
  • Out of Hospital
  • In Hospital
• ANTIDOTES
  • Indications
  • Contraindications
  • Method of Administration
  • Potential Adverse Effects
• ADJUNCTIVE TREATMENT

PATIENT MONITORING

• Negative inspiratory force or tidal volume should be performed frequently for the first several hours to determine whether deterioration will occur.
• Respiratory function monitoring should continue until the patient recovers.
• Antivenom will likely stop progression of signs, but will not reverse effects that are present at time of administration.

EXPECTED COURSE AND PROGNOSIS

• If the bite did not penetrate the skin or no venom was injected, no effects will develop.
• If the patient is envenomated, but antivenom is administered early, venom effects should stabilize and then resolve over a period of weeks.
• Severe effects (muscle weakness, respiratory insufficiency) may take weeks to resolve despite the use of antivenom.

DISCHARGE CRITERIA/INSTRUCTIONS

• From the emergency department. Patient may be discharged after several hours of observation if it appears that the bite did not penetrate the skin, no venom was injected, and no toxic effects are developing.
• From the hospital. Patient may be discharged if symptoms and signs of envenomation do not develop or have resolved following treatment with antivenom.

PATIENT EDUCATION

Venomous snakes should not be handled.

Section Outline:

• PATIENT MONITORING
• EXPECTED COURSE AND PROGNOSIS
• DISCHARGE CRITERIA/INSTRUCTIONS
• PATIENT EDUCATION

DIAGNOSIS

Serious envenomation without apparent fang marks has been reported.

TREATMENT

Delay in the administration of antivenom allows irreversible venom effects to develop.

FOLLOW-UP

Serum sickness may occur 3 to 14 days following antivenom infusion (see SECTION III, Snake Antivenom chapter, for details of treatment).

Section Outline:

• DIAGNOSIS
• TREATMENT
• FOLLOW-UP

Toxic effect of: venom.

See Also: SECTION III, Snake Antivenom—Crotalid and Elapid Snakes chapter.

RECOMMENDED READING

Kitchens CS, Van Mierop LHS. Envenomation by the eastern coral snake (Micrurus fulvius fulvius). JAMA 1987;258:1615-1618.

Author: Richard C. Dart

Reviewer: Rivka S. Horowitz