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UCSF School of Medicine
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My first encounter with marine envenomations was in 9th grade. Wading out into the ocean to catch a wave, I felt a sharp pain in my left foot that shot up my leg. Thinking I’d stepped on some broken glass, I hobbled out of the ocean – arm slung around a friend’s shoulder. After I sat down, we saw that it wasn’t glass I’d stepped on, but rather the raised, sharp barb of an unsuspecting stingray.
My friends gathered around me. “I think you can get poisoned to death like the crocodile guy! Let’s call 911!” one exclaimed. “Can I pee on your foot?” another “friend” suggested.
Soon the lifeguard arrived and took a look at my foot. “Do NOT pull it out – let’s soak it in warm water and go see a doctor.” Soon enough, after a quick visit to urgent care and a couple weeks of healing, my foot was completely back to normal.
This review briefly covers the epidemiology, presentation, and management of these types of injuries in the emergency department or acute care clinic.
Stingrays are flattened fish that like to bury themselves under soft sands of the ocean floor or muddy river bottoms, waiting surreptitiously for prey to swim by. Stingrays often rely on the pointed barb at the proximal ends of their tails, which can inject an amino-acid toxin into its prey. When disturbed or threatened, these animals reflexively whip their tails sideways or backwards over their bodies to ward off potential predators.
Unsuspecting river and beachgoers – unaware of what hides beneath the sand – can trigger this stingray defense mechanism. An estimated 750-2,000 people each year are victims of stingray injuries in the United States, with the vast majority of them being minor superficial wounds of the lower extremities. However, penetration of more central areas of the body (e.g., chest) have been reported to lead to fatalities, infamously in Australian wildlife expert Steve Irwin.
Patients who have encountered stingrays usually report immediate and intense pain that radiates up the injured limb. This pain usually peaks 30-90 minutes after the sting and can last for up to 48 hours. At first, local swelling and erythema mark the site of injury. However, in most cases, the barb of the spine is retained within the skin, leaking out a vasoconstrictive toxin that can lead to cyanosis, infection, and necrosis.
Systemic symptoms following a stingray injury include anxiety, nausea, vomiting, diarrhea, and hypotension. Stingray toxin can be directly cardiotoxic, though arrhythmias following stings have been only rarely reported. While most stingray injuries occur in the extremities, deeper penetration of bigger blood vessels, the heart, or the lungs can lead to fatal traumatic complications such as exsanguination or pneumothorax.
Initial wound care is key to treating patients who come in after being injured by stingrays. If the spine is superficial, it should be removed as quickly as possible to minimize toxin exposure. However, providers should perform a careful assessment of cardiopulmonary stability before removing deeper barbs or those that embedded in neck, chest, or abdomen.
As the amino-acid toxin is heat-labile, immersing the site of injury in hot, though not scalding, water (43-45oC) has been shown to denature the toxin and facilitate pain relief. For patients whose pain persists following hot water immersion alone, adding a single dose of an oral analgesic has been shown to help the pain subside. If pain is still not relieved, local injections of lidocaine or performing nerve blocks can further alleviate the pain.
After barb removal, thorough wound cleansing should be performed to minimize the chance of infection. Deeper injuries of the chest, abdomen, or neck may require further imaging such as ultrasound, MRI, or CT and possible surgical consultation to remove the barbs.
Prophylaxis against tetanus is important in all stingray injuries, no matter how superficial. Immunization status of the patient should be reviewed and updated appropriately. Prophylactic antibiotics should be considered in deeper injuries to prevent the development of wound necrosis, botulism, or gangrene. Some experts recommend empiric antibiotic coverage with a quinolone (levofloxacin or ciprofloxacin) or a cephalosporin (e.g., cephalexin or cefazolin) plus doxycycline to cover for Vibrio species. Any prescribed antibiotics should be followed up with culture and sensitivity testing of wound aspirates, if possible.
Importantly, there is no evidence to support the application of urine to stingray wounds, or to any marine envenomation for that matter.
Stingrays are known to be skittish, avoidant creatures. When they happen to injure humans, it is out of self-defense. Thus, simple patient education during a visit after a stingray injury can help prevent future similar encounters.
During my visit to the urgent care center, my doctor advised that the next time I wade through shallow, sandy waters at the beach, I shuffle my feet to kick the sand up and scare away any hiding stingrays before I step on them. I’ve followed that advice religiously and have warned many of my friends to do the same. Thankfully, none of us has encountered a stingray since, outside of an aquarium!
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