Cnidaria Envenomation Treatment & Management

Updated: Mar 16, 2022
  • Author: Spencer Greene, MD, MS, FACEP, FACMT, FAAEM; Chief Editor: Joe Alcock, MD, MS  more...
  • Print

Prehospital Care

Prehospital personnel and rescuers on scene need to protect themselves from injury and protect the patient from further injury. When entering the water, protective clothing with wet suits and gloves is ideal. “Stinger suits” are highly recommended when available. On very rare occasion, it may be helpful if rescuers can safely identify the species of jellyfish, but in general it is not necessary to identify the animal to guide treatment. Risking injury in an attempt to capture the animal is discouraged.

To prevent further injury to the patient, the following decontamination steps are important:

  • Inactivate nematocysts: Vinegar or acetic acid in solutions of 4-6% is the most widely accepted treatment of initial stings. Pour vinegar over adhering tentacles for at least 30 seconds. Although a randomized controlled trial supports the use of vinegar in Physalia stings, controversy exists because vinegar stimulated the discharge of nematocysts from Australian Physalia tentacles in the laboratory. [23] Application of hot water (42-45°C) for 20 minutes is likely beneficial for reducing pain in envenomation by C. barnesi and Physalia species. Methylated spirits, ethanol, and urine should not be used. Commercial products containing aluminum sulfate have not been shown to be better than vinegar or sea water in the inactivation of nematocysts or resolution of pain.

  • Seawater rinsing has been found to increase venom load from Cyanea capillata (lion's mane jellyfish) in in vitro models. Instead, rinsing with vinegar is recommended, and 40 min application of heat packs at 45° C reduced venom activity. [24]

  • Removal of tentacles: Vinegar-treated tentacles may be removed easily and safely, preferably using gloved hands. If vinegar is not available, forceps or similar instruments are recommended. Detached live tentacles should be treated with caution as envenomation may still occur for several hours.

No animal studies have been performed to demonstrate a beneficial effect of pressure immobilization bandaging. In vitro models suggest additional venom release from naturally discharged nematocysts. It is not currently recommended by the Australian Resuscitation Council. Pressure immobilization bandaging remains controversial and cannot be routinely recommended at this time.

In an incident occurring in Brazil, a 3-year-old girl experienced anaphylaxis after being stung by Chrysaora lactea, a sea nettle common to Brazilian waters. The patient was supported with oxygen at 15 L/min and treated with subcutaneous adrenaline (0.1 mg/kg) and intravenous hydrocortisone (10 mg/kg) with complete resolution of anaphylaxis. [25]


Emergency Department Care

General care of Cnidaria envenomation

Treatment of Cnidaria envenomation is directed by the severity of the injury. Severe systemic symptoms may require respiratory and cardiovascular support.

Inactivate and remove tentacles as directed in Prehospital Care.

Treat anaphylaxis with airway support, supplemental oxygen, intravascular volume resuscitation, and epinephrine.

Wound care is paramount because both freshwater and saltwater contain numerous microbes. Infected wounds should be cultured for both aerobes and anaerobes. Antibiotics should be reserved for evidence of true infection and should not be given prophylactically.

Baking soda (sodium bicarbonate) may be effective for stings caused by sea nettle (Chrysaora quinquecirrha).

Tetanus prophylaxis should be given if indicated.

Pruritus typically responds to antihistamines. Topical anesthetics and corticosteroids may also relieve pain. The majority of mildly painful stings respond to the application of ice after the application of vinegar.

A delayed recurrent reaction may occur after 1-2 months at the contact site and should be treated with corticosteroids.

Hwang et al demonstrated that a common polyphenol, epigallocatechin-3-gallate (EGCG), inhibits the toxic proteases found in the venom of Nomura's jellyfish (Nemopilema nomurai), a member of the Scyphozoa class native to the seas of East Asia. [26]

Treatment of box jellyfish (C. fleckeri) envenomation  [27, 28, 29]

Most stings are not life threatening and require only basic wound care and pain relief. Tentacles should be inactivated with vinegar.

Box jellyfish antivenom, manufactured by Commonwealth Serum Laboratory in Melbourne, Australia, is ovine-derived concentrated immunoglobulins. Each ampule contains sufficient activity to neutralize 20,000 intravenous mouse doses (amount of toxin lethal in a 20-g mouse) of C. fleckeri venom. Chironex antivenom cross-reacts with Chiropsalmus species venom to prevent neurotoxic and myotoxic effects. However, it has not prevented cardiovascular effects in vivo. Antivenom is indicated in the following situations: cardiopulmonary arrest, hypotension, dysrhythmia, coma, or difficulty with breathing, swallowing, or speaking. It is also recommended in cases of severe pain that are refractory to more conservative treatment. Its use may be considered when the possibility of severe scarring is high.

The recommended dose is 3 ampules diluted 1:10 with normal saline and given intravenously. Six ampules can be administered in the setting of cardiac arrest. Antivenom can be given intramuscularly if no intravenous access is established.

The use of verapamil has been advocated in the management of severe Chironex envenomations based on in vitro models. However, its use in clinical management remains controversial and cannot be recommended at this time.

Magnesium has been demonstrated to improve the effectiveness of antivenom in rats from 40% to 100%. However, prophylactic administration alone did not prevent cardiovascular collapse.

Treatment of Irukandji syndrome

Evidence as to the best management of Irukandji syndrome remains predominantly anecdotal. Supportive care, with an emphasis on airway, breathing, and circulation, is the mainstay of treatment. Nitroglycerin and phentolamine have both been used successfully in the treatment of hypertension. Magnesium has also been reported to improve the hyperadrenergic state and relieve pain, although opioid analgesia is frequently required. Benzodiazepines may also mitigate the adrenergic toxicity as well as relieve some of the associated anxiety. There is no available antivenom.

Further inpatient care

Patients with significant Cnidaria envenomation may need inpatient treatment for pain relief and further supportive care. Generally, only severe Portuguese man-of-war, C. barnesi, or box jellyfish stings result in rapid clinical decompensation.

In addition to cardiopulmonary supportive care, management should include treatment of renal consequences of rhabdomyolysis. Continuous monitoring for wound infection should take place because antibiotics are not always initially indicated.