The Tragic Death of Steve Irwin

4/20/2009 5:06:51 PM
By Paul S. Auerbach, M.D.

We are all saddened by the untimely death of naturalist and television personality Steve Irwin, who was killed by a stingray on September 4, 2006. Steve was filming a segment for a series entitled “Ocean’s Deadliest” at Batt reef off the coast of northeastern Queensland, Australia.

While in the water, Irwin closely approached a stingray, which struck him in the left side of his chest with the venomous barb attached to its tail. He was witnessed to have pulled the detached barb from his chest, and then to have died.

According to what has been reported about the autopsy, the wound likely penetrated Steve’s heart. It is not determined at the time of this writing whether the cause of death was bleeding (blood loss), compression of the heart by blood trapped within the fibrous lining around his heart (pericardium) – a condition known as pericardial tamponade – a heart attack, fatal disruption of the heart’s rhythm from the shock of penetration and effects of the venom, or some combination of these.

I have been asked whether Steve would have had a better chance for survival had he not pulled the spine from his chest. The classic teaching for treatment of impalement (e.g., by a knife or arrow) is to leave the object in place undisturbed until one has been brought to a controlled medical (surgical) environment before attempting removal. The reason for this is that the object may act as a “finger in the dike” if it has punctured a large blood vessel or, in Steve’s case, the heart. When it is removed, the plug is removed, and bleeding can be torrential through the now-opened hole.

In addition, the removal process itself can worsen the internal tissue damage. On its way out, the spine may have torn more heart muscle, widened the hole in the heart and damaged an essential heart valve or other internal structure.

If the removal occurs where (a) surgeon(s) can rapidly expose the complete path of the wound, stop the bleeding and undertake other essential repairs, then the victim may survive. However, Steve was not a trained medical professional, and what he did was a normal response to what was, in all likelihood, a very painful predicament. He had a stingray spine sticking into his chest, and it was likely a very painful and visually distressing situation. He sought to relieve his suffering and pulled out the spine. Anyone in this situation would have probably done the same thing, and absent a trauma surgeon or emergency physician present to guide the immediate rescue, what happened is understandable.

So, might he have had a better chance if the spine was left in place? Perhaps, if his heart or a great vessel was penetrated and he could tolerate the presence of a venom-bearing spine until he could be taken to the operating room.

Stingrays are wild animals, and while they usually make every effort to flee encounters with perceived predators, they will sometimes act in defense, by striking out with the caudal appendage (“tail”) in order to cause injury with the attached stinger(s).

Under no circumstances should anyone assume that a stingray approached in the wild is “tame,” even if it has been habituated to the presence of humans. What follows is a brief medical tutorial on stingrays, adapted from a chapter about hazardous marine animals in the forthcoming 5th edition of the textbook Wilderness Medicine (Mosby-Elsevier, 2007).

The stingrays are the most commonly incriminated group of fish involved in human envenomations. They have been recognized as venomous since ancient times, known as “demons of the deep” and “devil fish.” Aristotle (384-322 B.C.) made reference to their stinging ability.

Stingrays are members of the class Chondrichthyes (cartilaginous fish), subclass Elasmobranchii (plates and gills; with sharks and chimaeras), order Rajiformes (which contains stingrays [Dasyatidae], guitarfish [Rhinobatidae], skates [Rajidae], electric rays [Torpedinidae], eagle rays [Myliobatidae], mantas [Mobulidae], and freshwater rays [Potamotrygonidae]).

There are at least 22 species of stingrays found in U.S. coastal waters, 14 in the Atlantic and 8 in the Pacific. The family Dasyatidae includes most of the species that cause human envenomation. Skates are harmless. It is likely that at least 2,000 stingray injuries take place each year in the United States.

On the west coast of the United States, the round stingray (Urolophus halleri) is a frequent stinger; along the southeastern coast, it is the southern stingray (Dasyatis americana). Most attacks occur during the summer and autumn months, as vacationers venture into the surf that may be laden with congregating (for spawning purposes) rays. Freshwater species do not inhabit U.S. waters. They are found in South America, Africa and Southeast Asia.

Stingrays are usually found in tropical, subtropical and warm temperate oceans, generally in shallow (intertidal) water areas, such as sheltered bays, shoal lagoons, river mouths, and sandy areas between patch reefs. Although rays are generally found above moderate depths, at least one deep sea species has been discovered. Rays can enter brackish and fresh waters. For instance, freshwater stingrays are common in rivers and tributaries in South America.

Rays are small (several inches; one inch = 2.54 cm) to large (up to 12 feet by 6 ft [3.66 meters by 1.83 m]) creatures observed lying on top of the sand and mud or partially submerged, with only the eyes, spiracles, and part of the tail exposed. Their flattened bodies are round , diamond , or kite shaped, with wide pectoral fins that look like wings.

Rays are nonaggressive scavengers and bottom feeders that burrow into the sand or mud to feed on worms, mollusks and crustaceans. The mouth and gill plates are located on the under surface of the animal. The flattened shape is largely configured by the modified pectoral fins, or “wings,” of the animal. These ripple or flap to propel the animal through the water.

The venom organ of stingrays consists of one to four venomous stings on the top of an elongate, whiplike caudal appendage (“tail”). There are four different anatomic types of stingray venom organs, based on their adaptability as a defense organ. Thus, the stinging ability of rays may be divided into four categories:

  • the gymnurid type (butterfly rays, or Gymnuridae), with a poorly developed sting of up 1.1 inches (2.8 cm) placed at the base of a short tail;
  • the myliobatid type (eagle and bat rays, or Myliobatidae), with a sting of up to 5.5 inches (14 cm) placed at the base of a cylindrical caudal appendage that terminates in a long whiplike tail;
  • the dasyatid type (stingrays and whiprays, or Dasyatidae), with a sting of up to more than 12 inches (30.5 cm) placed at the base or further out on the caudal appendage that terminates in a long whiplike tail; and
  • the urolophid type (round stingrays, or Urolophidae), with a sting of up to nearly 2 inches (5.1 cm) located at the base of a short, muscular, well-developed caudal appendage.

The efficiency of the apparatus is related to the length and musculature of the tail and to the location and length of the sting.

Eagle rays and some mantas (Atlantic Mobular mobular and Pacific Mobula japanica) have a stinging apparatus, but it is less of a threat because the spine is located at the base of the tail and is not well adapted as a striking organ.

Although the manta (Manta birostrisi) may grow to a width (“wingspan”) of 20 feet (6 m) and weight of 4,000 pounds (1,800 kg), it dines on small fish, crustaceans and microorganisms. Many divers have “hitched” a ride on the wings of a manta; there are no reports of envenomation. However, manta skin is rough and can abrade unprotected human skin.

A stingray “hickey” is a mouth bite, created by powerful grinding plates, that produces superficial erosions and bruising in an oral pattern. Persons who hand-feed stingrays may incur this type of injury. The suction force generated by a stingray is sufficient to pull in a large amount of soft tissue, say, from a thigh. This may result in a large and painful contusion and/or hematoma.

In all cases, the venom apparatus of stingrays consists of a bilaterally retroserrate spine or spines and the enveloping integumentary (“skin“) sheath or sheaths. The elongate and tapered cartilaginous spine is firmly attached to the dorsum of the tail (whip) by dense collagenous (connective) tissue and is edged on either side by rear-facing (toward the base of the spine) serrations, which create a formidable cutting surface. Along either edge on the underside of the spine are the two grooves, which house the soft venom glands.

The entire spine is encased by the integumentary sheath, which also contains some glandular cells. The sting is often covered with a film of venom and mucus. The spine is replaced if detached.

The venom contains various toxic fractions, including serotonin, 5' nucleotidase, and phosphodiesterase. Findlay Russell investigated the pharmacologic properties of stingray venoms. In animal studies he demonstrated significant venom- induced peripheral blood vessel constriction, slow heart rate, severe abnormal heart rhythms and electrocardiogram changes, respiratory depression, seizure activity, neurologic abnormalities, coma and death.

Research on stingray venom from the 1950s observed that heating the venom to a temperature above 122° F (50° C) diminished some biologic effects. More recently, Haddad analyzed proteins from freshwater stingray (Pomatotrygon falkneri) venom and identified components with enzymatic activities that may contribute to the tissue injuries seen following an envenomation.

Stingray “attacks” are purely defensive gestures that occur when a human handles, too closely approaches, corners, startles or steps on a creature, which may be nestled into and “camouflaged” on the ocean bottom. The injuries are most often incurred while a person is wading in shallow waters, but as we all are now very much aware, can occur in open water if a stingray is disturbed. The tail of the ray reflexively whips upward and accurately thrusts a spine or spines into the victim, producing a puncture wound or jagged cut. The sheath covering the spine is ruptured and venom is released into the wound, along with mucus, pieces of the sheath and fragments of the spine. On occasion, the entire spine tip is broken off and remains in the wound.

“Domesticated stingrays,” such as those that congregate at “Sting Ray City” in the waters of Grand Cayman Island, are habituated to the presence of humans and apparently pose less hazard for a spine puncture, but may still be induced to bite and presumably, to sting.

A stingray wound from a spine puncture is both a traumatic injury and an envenomation. The former involves the physical damage caused by the sting itself. Because of the rear-facing serrations of the rigid cartilage within the spine and powerful strikes, significant lacerations can result. Secondary bacterial infection is common. Bone infection may occur.

Most injuries occur when the victim steps on a ray; another common cause is handling a ray during its extraction from a fishing net or hook. The lower limbs, particularly the ankle and foot, are involved most often, followed by the upper limbs, abdomen and thorax. In a rare case, the heart may be directly injured. There have been two reported cases of survival following cardiac injury. Deaths have occurred after abdominal or chest (heart) penetration, and from bleeding to death from a torn femoral artery. One death has been attributed to tetanus infection complicating a leg wound. A spine partially or totally stripped of its sheath and venom glands may not necessarily cause an envenomation.

When envenomation occurs, it classically causes immediate intense pain, edema and variable bleeding at the site of the wound. The pain may radiate centrally (towards the chest), peaks at 30 to 60 minutes, and may last for up to 48 hours. The wound is initially dusky or bluish and rapidly progresses to redness and bruising, with rapid onset of bleeding into fat and muscle, followed by tissue death and destruction. If discoloration around the wound edge is not immediately apparent, within two hours it often extends a few inches from the wound.

Bloody blisters resembling a severe thermal burn or frostbite may occur, and may be worsened by overzealous therapeutic hot-water immersion (see below). Delayed healing seen following stingray injuries is usually attributed to direct venom toxicity and infections. It is possible that the immune system is involved in the tissue reaction. If this is the case, it might contribute to the delayed healing of stingray injuries.

System-wide manifestations of envenomation include weakness, nausea, vomiting, diarrhea, sweating, dizziness, rapid heart rate, headache, fainting, seizures, groin or armpit pain, muscle cramps and twitching, generalized swelling (with wounds involving the trunk), paralysis, low blood pressure, serious abnormal heart rhythms and death. Paralysis may represent spastic muscle contractions induced by pain, which are a tremendous hazard for a diver or swimmer.

When handled, a stingray may place its underside adjacent to a human limb, or even “wrap” itself around a leg. The stingray may then bite the victim with a powerful crushing force sufficient to sever a finger or to create a substantial bruise.

The success of therapy is largely related to the rapidity with which it is undertaken. Treatment is directed at combating the effects of the venom, alleviating pain and preventing infection. If hot water for immersion and wound rinsing (see below) is not immediately available, the wound should be rinsed immediately with nonheated water or sterile saline. If sterile saline or water is not available, tap water may be used. This removes some venom and mucus and may provide minimal pain relief.

As soon as possible, the wound should be soaked in nonscalding hot water to tolerance (upper limit 113° F [45° C]) for 30 to 90 minutes. This might attenuate some of the temperature-sensitive components of the protein venom (although this has never been proven) and/or interrupt nerve impulse transmission, and, in some envenomations, relieves pain.

Hot water immersion likely has minimal or no effect on the ultimate degree of soft tissue destruction. There is no indication for the addition of ammonia, magnesium sulfate, potassium permanganate, or formalin to the soaking solution. Under these circumstances they are toxic to tissue and may obscure visualization of the wound. During the hot-water soak (or at any time, if soaking is not an option), the wound should be inspected in order to remove any readily visible pieces of the sting or its sheath, which would continue to envenom the victim.

Although the standard recommendation is to remove the spine and fragments as soon as possible (to limit the extent of envenomation and pain), if a spine is seen to be lodged in the victim and has acted as a dagger deeply into the chest, abdomen or neck (this is extremely rare) and may have penetrated a critical blood vessel or the heart, it should be managed as would be a weapon of impalement (e.g., like a knife). In this case, the spine should be left in place (if possible) and secured from motion until the victim is brought to a controlled operating room environment where emergency surgery can be performed to guide its extraction and control bleeding that may occur upon its removal.

Immersion into a bath of ice water can be disastrous (because of the risk for frostbite injury), and no data yet support the use of antihistamines or steroids. One local remedy, application of the cut surface of half a bulb of onion directly to the wound, has been reported to decrease the pain and perhaps inhibit infection after a sting from the blue-spotted stingray Dasyatis kuhlii. The person making this recommendation noted that this approach is used in the Northern Territory of Australia for other fish spine stings, and that the medicinal use of the Liliaceae plant family has been recorded in many cultures. No other folk remedy, such as the application of macerated cockroaches, cactus juice, “mile a minute” leaves, fresh human urine, or tobacco juice, has been proven effective.

Pain control should be initiated during the first wound inspection or soaking period. The pain may be of a severity to require administration of a narcotic analgesic. Injection of the wound with a local anesthetic may be necessary, as might a nerve block.

Along with properly cleaning, repairing and dressing the wound, a physician may prescribe antibiotics because of the high incidence of ulceration, tissue death, and secondary infection. These antibiotics will anticipate contamination with marine germs, such as Vibrio species, that may have entered the wound.

Wounds that are not properly cleansed of foreign material may fester for weeks or months. Such wounds may appear infected, when what really exists is a chronic draining ulcer initiated by persistent retained organic matter. Within the first few weeks after an envenomation, a foreign body (e.g., retained spine or spine fragment) can sometimes be observed by soft tissue radiograph, ultrasound or magnetic resonance imaging (MRI).

Prevention is key. A stingray spine can penetrate a wetsuit, leather or rubber boot, and even the side of a wooden boat; therefore a wetsuit or pair of athletic sneakers is not adequate protection. Persons walking through shallow waters known to be frequented by stingrays should shuffle along and create enough disturbance to frighten off any nearby animals. The same precautions hold true for other animals, such as horses.

Under no circumstance should a person knowingly approach a stingray within striking distance of its tail. Photographers and divers should keep their distance. Petting stingrays, even those that appear tame, is flirting with disaster.

See the related story "'Crocodile Hunter' Steve Irwin Dies in Rare Accident," or click here.