Class: Chondrichthyes

Order: Myliobatiformes

Suborder: Myliobatoidei

Stingrays

Location: Worldwide

Appearance: Flat and cartilaginous with a stinger containing a retroserrate barb and venom glands located on the ventral aspect of the tail.

Pathophysiology and Symptoms: There are two phases to injury. Phase one is due to traumatic injury from the barb and is characterized by significant pain, usually peaking around 60 minutes post-exposure, but which can persist for up to 48 hours.² This phase accounts for most of the morbidity and mortality due to hemorrhage, injury to vital organs (as was the case with wildlife expert and television personality Steve Irwin), or subsequent infection. Additional symptoms include nausea, vomiting, diarrhea, muscle cramps, and wound necrosis. Phase two is due to venom release, which causes vasospasm and other significant sequelae, including limb ischemia, cardiotoxicity (eg, dysrhythmias, heart block, non-ST segment elevation myocardial infarction, etc.) seizures, coma, and death.

Management: Pain control is best achieved with hot-water immersion and/or local lidocaine administration. Patients should be brought to the operating room for removal of any barbs in the chest or abdomen. Infusion of prostaglandin E1 has resulted in successful salvage of an ischemic leg, but insufficient data exists to recommend this as routine therapy. There is no antivenom available.^2,7

Family: Synanceiidae (*Also classified in the family Scorpaenidae)

Stonefish

Location: Indo-Pacific Ocean

Appearance: Grey, mottled, and often covered with algae that allow for camouflage. These fish possess multiple spines that release venom in response to external pressure.

Pathophysiology and Symptoms: These are the most venomous fishes known, with venom likened to that of a cobra. The venom blocks cardiac calcium channels, increases systemic catecholamine release, simultaneously causing diffuse vasodilation, and increased tissue destruction which propagates uptake of its own venom. Initial effects include rapid onset of severe pain, edema, necrosis, and ulceration. Pain tends to peak at 60 minutes but can persist for several days. Additional symptoms include fatigue, weakness, hyper-/hypotension, syncope, dyspnea, delirium, seizures, and limb paralysis. Severe complications include dysrhythmias, heart failure, heart block, cardiogenic pulmonary edema, hemolysis, and compartment syndrome. Death can occur in as few as six hours from the time of envenomation. Venom remains stable for up to 48 hours after the fish has died, and delayed wound healing for weeks to several months is common.⁸

Management: Pain control and venom neutralization is achieved with hot-water immersion. Heating the site of a stonefish venom injury to 122 degrees F (50 degrees C) for five minutes prevents wound necrosis and hypotension in animal models.⁹ Local lidocaine can also be used for pain management. Patients should be observed for 6 to 12 hours.