Prehospital Care
Focus prehospital care on maintenance of vital functions and prevention of toxin transport from the injection site.
Remove the individual from the water to prevent drowning. Airway maintenance and ventilation may prove lifesaving. Systemic symptoms can occur within 30 minutes, and death has been reported within an hour.
Transport the patient appropriately, as the patient may have oropharyngeal muscle paralysis, and the risk of aspirating vomitus is real.
Keep the stung extremity in a dependent position, and keep the patient still. Careful, knowledgeable use of the lymphatic-occlusion pressure immobilization bandage suggested for Australian snakebites may be effective (for information on the immobilization technique, see Coral Snake Envenomation). Tourniquet use is not recommended because it may result in significant iatrogenic injury.
No role exists for attempted suctioning of conotoxin from the wound.
Emergency Department Care
For initial management of suspected cone shell envenomation, place emphasis on immediate resuscitation and treatment of respiratory failure.
No antivenom is available for cone shell envenomation.
Examine the wound for the presence of a radular tooth and cleanse it. Typical points of entry include the hands and feet and occasionally waist if a collection bag has been used. There is no role for excision of the sting site. The wound should be regarded as potentially contaminated with marine organisms, and prophylaxis with ceftriaxone or doxycycline have been suggested. Determine the patient's tetanus status and update as appropriate.
Placing the affected limb in hot (not scalding) water to tolerance may be tried, with pain relief as the goal. Patients who have experienced a significant envenomation may not obtain adequate pain relief with hot-water immersion and may require additional local anesthesia (1-2% lidocaine without epinephrine) and/or oral or intravenous analgesia.
A lymphatic-occlusive pressure immobilization bandage may have been placed proximal to an extremity wound site in the prehospital setting. Do not jeopardize arterial circulation distal to this bandage. This bandage may be applied for 4-6 hours; do not remove until the provider is prepared for potential patient deterioration following distribution of conotoxins to the systemic circulation.
Cardiovascular and respiratory supports are the keystones of management; therefore, the provider must be prepared to support the patient systemically. Prioritize the airway. Mechanical ventilation may need to be provided for more than 24 hours; paralysis usually resolves within 12-36 hours. Case reports suggest that edrophonium 10 mg IV may be used as empiric therapy for paralysis. A 2-mg test-dose should first be administered and, if effective, followed by an additional 8-mg dose. Atropine 0.6 mg should be immediately available for intravenous administration in case of an adverse reaction to the edrophonium occurs. A 2- to 4-mg dose of intravenous naloxone may help treat severe hypotension because it blocks the beta-endorphin vasodepressor response. Consider central venous access for fluid resuscitation in cases of severe envenomation.
Seizures are unlikely but may occur secondary to hypoxia.
Coagulopathy is rare. Further study may provide guidelines for the use of blood products, fresh-frozen plasma, cryoprecipitate, desmopressin, and fibrinolytic/antifibrinolytic agents.
Mild envenomations should resolve within 6-8 hours, and the patient can be discharged.
Inpatient care
Intensive care unit monitoring is indicated for patients with conidae envenomation who are experiencing cardiopulmonary arrest and requiring mechanical ventilation.
Admit patients to a monitored bed for further observation if they exhibit hypoxia, significant muscular weakness, and/or cardiac ectopy.
Carefully monitor patients with persistent paresthesias and muscular weakness for signs of respiratory compromise.
Consider inpatient observation for patients with underlying cardiac, pulmonary, or neurologic disease.
Consultations
Upon encountering a cone shell envenomation, consult the appropriate local poison control center or medical toxicologist.
Prevention
Properly identify cone shells and handle them only with protective gloves.
Never carry a live cone in net bags next to skin, wet suits, or buoyancy control vests. If a live cone must be carried, lift it at the large posterior end of the shell with protective gloves. This is not always adequate protection as the proboscis can extend the entire length of the shell. If the proboscis protrudes, immediately drop the cone.
Walk in intertidal areas wearing appropriate footwear. Do not reach blindly under corals or rocks.
Long-Term Monitoring
Monitor the wound for evidence of infection. Patients whose wounds show any evidence of infection should return for evaluation and should inform the examining health care provider that the wound occurred in the marine environment because antibiotic choice will vary accordingly. The wound should be re-examined for foreign body.
The patient may require oral analgesics for pain control.
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Cone snail ingesting a small fish. Cone snails incapacitate their prey by injecting a cocktail of neurotoxins, which can be dangerous to humans. Courtesy of Wikimedia Commons and David Burdick.
