Stingrays and Such

This is the next post based upon my presentation given at the Wilderness Medical Society Annual Meeting held in Snowmass, Colorado from July 24-29, 2009. The presentation was entitled “Just When You Thought It Was Safe to Go Back in the Water.” The topic was an overview of hazardous marine animals and it was delivered by me. In the previous post, there was information about shark attacks. In this post, there is information about envenomations incurred in the marine environment.

Marine venoms, similar to other toxins and poisons that originate in the animal and plant kingdoms, may cause a wide range of human physiological derangements. It is very important to remember that certain of these venoms, such as that elaborated by jellyfish, may invoke a serious allergic reaction.

Stingrays are a commonly incriminated group of envenoming animals. There are more than 10 species found in U.S. coastal waters, with from 1 to 4 venomous “stings” found on the top of the caudal appendage (“tail’). The spine is a serrated cartilaginous structure that houses venom glands covered by a fragile tissue sheath. Thus, when the spine enters a human victim, most commonly on the lower limb (ray is stepped upon) or upper limb (ray is handled), the tissue sheath is disrupted and venom enters the wound. Thus the injury is just a puncture/cut and an envenomation.

The clinical aspects of a stingray envenomation are:

1. Immediate intense pain
2. Spine or fragments embedded in the wound
3. Chest or abdomen may be punctured
4. Dusky, swollen and bruised wound, with or without severe bleeding
5. Muscle and fatty tissue may be affected in such a manner as to become severely inflamed or eventually destroyed
6. Varying presence of systemic symptoms, including nausea, vomiting, diarrhea, sweating, dizziness, headache, seizures, unconsciousness, muscle twitching, paralysis, low blood pressure, abnormal heart rhythms

Stingrays may also bite humans with their grinding plate-type mechanism, with a force sufficient to sever a digit. This occurs when a person offers up a body part to a stingray, usually when handling or attempting to feed the animal.

The treatment for stingray envenomation is:

1. Extract the spine or spine and tissue fragments, unless the spine is felt to possibly have penetrated a large blood vessel or other vital structure. In such a case, the spine should be managed as would be an impaled knife or other foreign object, and secured in place until advanced medical attention can be reached. This would be to allow the spine to be removed in a setting where rapid bleeding initiated upon its removal could be best managed.
2. Immerse the wound into nonscalding hot (113 degrees Fahrenheit or 45 degrees Centigrade – “to tolerance”) water for 30 to 90 minutes or until there is significant pain relief. If this is successful in relieving pain, but pain recurs upon exit from the water, repeat the immersion. Do not immerse the affected part in ice water – this may actually cause a frostbite injury.
3. Pain control may not be sufficiently obtained with hot water immersion, so the administration of pain medications, and/or the application of an anesthetic nerve block (local or regional) may be required.
4. The wound should be explored and cleaned, then thoroughly rinsed.
5. Imaging methods (such as x-ray, computed tomography [CT], magnetic resonance imaging [MRI}, etc.) should be deployed as needed to identify any suspected retained foreign bodies.
6. Surgery may be necessary to remove spines or spine fragments.
7. In the field, if possible, do not tightly close the wound. In other words, allow drainage of any possible fluid or pus collected without significant inhibition of such drainage.
8. If the wound is significant (deep puncture or cut) or the victim has any reason to be immunosuppressed, consider administering antibiotics (a fluoroquinolone, tetracycline or doxycycline, or trimethoprim-sulfamethoxazole) as noted in my previous post about shark attacks.

Moving on to stonefish, scorpionfish and lionfish, these animals have 12 or 13 (of 18) dorsal venomous spines, as well as pelvic and anal venomous spines. As with the stingray, the spines are associated with venom glands. Some of these fishes can be very well camouflaged and difficult to locate against their native backgrounds, even for experienced divers. The clinical aspects vary a bit from stingray envenomations but the approach to treatment is precisely the same, with the notation that there is an antivenom available to treat stings of the Indo-Pacific species of stonefishes.

Other marine vertebrates that sting and cause injuries similar to scorpionfishes are weeverfishes, catfishes, dragonfishes, horned sharks, ratfishes, toadfishes, rabbitfishes, stargazers, squirrelfishes, sea robins, flying gurnards, and goosefishes.