Pathophysiology

Crocodilians survived the Ice Age and are the dominant predators in many of the world’s tropical waterways. The American alligator may be found in the southeastern United States, from North Carolina to Louisiana. The saltwater crocodile is found in Southeast Asia and Australia, with males reaching lengths of up to 23 feet (7 m). Victims of crocodilian attacks sustain trauma from a combination of penetrating, blunt, and sheer force. The saltwater crocodile can generate 2000 psi when it bites. The sheer magnitude of the jaw muscle force sustained with extensive penetrating injuries devitalizes large areas of tissue, thereby making such injuries slow to heal and susceptible to infection. Bites must be considered to be heavily contaminated with multiple bacteria, including Aeromonas hydrophila, Pseudomonas, and Proteus (Fig. 141.1).

Fig. 141.1 Crocodile.

(Courtesy Hogle Zoo, Salt Lake City, UT.)

Presenting Signs and Symptoms

Crocodilian bites are characterized by punctures and tears. Their teeth are conical and not designed for chewing but for grasping their prey. Among survivors, the extremities were the most commonly injured site, with less than 10% sustaining torso trauma.^3,6 Crocodilians may also roll their entire body (known as the “death roll”) to disorient and drown the victim, as well as to tear pieces from the victim’s body.³ The force of the massive jaws may lead to extensive internal injury, but even when bite wounds are not present, the force of the animal’s movement—or even blunt trauma from its tail—may also inflict significant internal trauma. Initial survivors of severe attacks may exhibit hypotension from massive hemorrhage, in addition to respiratory distress from submersion injury.

Differential Diagnosis and Medical Decision Making

Victims of crocodilian bites often have injuries comparable with those sustained in a severe motor vehicle collision. Prehospital care should start with movement of the patient to a safe environment well away from water’s edge. The provider should make sure that airway control, breathing, and circulatory support are adequate with use of the advanced trauma life support (ATLS) protocols. External hemorrhage should be controlled with direct pressure or packing, and chest wounds should be dressed to prevent the development of tension physiology. Extremity fractures should be splinted and suspected major pelvic deformities bound or sheeted. Resuscitation in the hospital should continue according to ATLS protocols, including a focused assessment with sonography for trauma.

A secondary evaluation should be done to determine the extent of tendon, neurologic, and vascular injuries and possible internal organ damage. Underlying fractures and dislocations should be considered, particularly in light of the force and sheering mechanism of the animal’s bite. Depending on the nature and location of the bite, radiographs can aid in evaluation for bony injury. Computed tomography may be useful to evaluate for internal injury.

Treatment

Specialists should be consulted to evaluate and treat internal injuries, nerve and tendon damage, fractures, and major lacerations. Local wound care techniques are mandated to cleanse what are typically very contaminated wounds. Because of the high incidence of infection, all significant wounds need exploration, preferably in the operating room, where débridement of devitalized tissue and thorough decontamination can be accomplished. Prophylactic broad-spectrum antibiotic therapy may be necessary to prevent wound infection. The patient’s tetanus status should be checked and brought up to date.

Follow-Up, Next Steps in Care, and Patient Education

Disposition is based on the extent of the injuries, but admission should be considered for all patients except those with minor cutaneous extremity trauma. If the patient is discharged, close follow-up is advisable for wound care and to evaluate for wound infection. Prolonged rehabilitation is frequently needed because of the extent of injuries. The public should be advised to contact local wildlife managers about crocodilian activity before recreating in crocodilian-inhabited environments. Care should be taken when swimming, wading in, or approaching water. If attacked, the best defense appears to be to “fight back” by gouging the crocodile’s eyes with thumbs and fingers. If a hand or arm is within the reptile’s mouth, reaching caudally may displace the palatal valve, causing the crocodile to aspirate water and open its mouth.

Pathophysiology

The Gila monster (Heloderma suspectum) and the closely related beaded lizard (Heloderma horridum) are native to the southwestern United States and Mexico but may be found throughout the world in zoos and as illegal pets. They are characterized by black beadlike scales mixed with bandlike patterns of yellow, white, or pink scales (Fig. 141.2). These reptiles typically range in length from 9 to 32 inches (22 to 81 cm); the beaded lizard is the larger of the two species.

Fig. 141.2 Gila monster.

(Courtesy Hogle Zoo, Salt Lake City, UT.)

Unlike pit vipers, which inject their venom through fangs, Heloderma species have a very rudimentary venom delivery mechanism. The animal has individual vertical grooves in its lancet-shaped teeth to deliver venom by capillary-type action from anterior mandibular venom glands. The lizards tend to stay attached to their victims by using mastication to augment the delivery of venom.^5,6 Their venom is similar in some respects to rattlesnake venom and can stimulate the release of vasoactive kinin, which leads to hypotension.⁵

Presenting Signs and Symptoms

Patients may arrive at the emergency department (ED) with the lizard still attached. Bite wounds are classically indurated and erythematous. Significant edema may develop at the site of the wound. Patients often describe excruciating pain associated with the bites. In envenomated patients, weakness, hypotension, and tachycardia are commonly seen as a result of systemic effects of the reptile’s venom.^4,5

Differential Diagnosis and Medical Decision Making

In addition to local pain and swelling, laboratory evaluation assists in determining the severity of envenomation. The most common reported laboratory abnormality in Gila monster bite envenomations is leukocytosis, although coagulopathy has also been reported. Minimum laboratory work-up should include a complete blood count with platelets, basic metabolic panel, and coagulation panel. An electrocardiogram and cardiacenzymes should be considered, especially in symptomatic patients with cardiac risk factors.

Radiographs may be obtained to rule out associated fractures. However, retained teeth do not show up radiographically, and local wound exploration should be performed to rule out this possibility.

Treatment

If still attached, the lizard must be removed from the patient. Increased time of mastication can increase the severity of envenomation. A flame placed under the animal’s jaw will usually result in release within 3 to 5 seconds and decreases the possibility of leaving teeth in the wound. Other techniques, such as immersion in cold water, may also be used. Special care should always be taken to prevent reattachment of the animal to the victim or subsequent attachment to the person removing the reptile.

Envenomation may cause hypotension, tachycardia, and generalized weakness. These symptoms generally respond well to intravenous crystalloid administration. Refractory hypotension may require treatment with vasopressors such as dopamine. No antivenom is commercially available for Gila monster or beaded lizard envenomation.^4,6

The most important aspect of evaluation of the wound is physical examination for evidence of vascular or tendon injury and local wound exploration for retained teeth from the animal. The pain typically requires large amounts of opiate analgesics; the few patients who have experienced both rattlesnake and Gila monster bites report much greater pain associated with a Gila monster bite. The pain generally peaks between 15 and 45 minutes following the bite and may last for days.^4,7

Although the use of prophylactic antibiotics for animal bites remains somewhat controversial, patients may benefit from treatment with broad-spectrum antibiotics, such as amoxicillin-clavulanate (Augmentin) for 3 to 5 days, with specific instructions to watch for signs of infection. Delayed or loose wound closure should be considered to prevent early infection, and the patient should be instructed about local wound care techniques.

Follow-Up, Next Steps in Care, and Patient Education

All symptomatic and potentially envenomated patients should be admitted for monitoring, supportive care, and pain management. Patients who remain asymptomatic and have normal laboratory values may be discharged after a period of 8 hours of observation. Tetanus prophylaxis is necessary if the patient’s immunization status is not up to date. All patients should be reevaluated in 24 to 48 hours for evidence of the development of infection.

Pathophysiology

Native to the islands of Indonesia, the Komodo dragon (Varanus komodoensis) is the largest lizard in the world; it can reach lengths greater than 10 feet (3 m) and weigh as much as 300 lb (136 kg) (Fig. 141.3). These lizards can move as fast as 13 mph (20 km/hr) over short distances and take down prey as large as water buffalo. Komodo dragons’ teeth are sharklike, with posterior serrations that create deep open wounds to facilitate envenomation. Its venom is known to cause coagulopathy, increased vascular permeability, and vasodilation.⁸ Victims bleed profusely from large wounds. hypotension and shock develop rapidly and lead to death. If the initial attack does not kill the victim, infections from multiple pathogenic bacteria in the Komodo’s saliva can lead to sepsis and death.⁹

Fig. 141.3 Komodo dragon.

(Courtesy Hogle Zoo, Salt Lake City, UT.)

Presenting Signs and Symptoms

Most evaluations of Komodo dragon bites in the United States would expectedly come from exposure at zoos or zoologic parks. These bites typically occur on the extremities and produce puncture wounds and lacerations of the skin, along with the potential for local tendon, bone, and neurovascular damage. Bleeding from the wounds may be significant because of envenomation and subsequent coagulopathy. patients who delay medical evaluation of their wounds will most likely show signs of local and/or systemic bacterial infection. Komodo dragon attacks in the wild may result in multiple large lacerations and areas of tissue loss, not unlike victims of shark attacks. The combination of extensive tissue loss and venom toxicity can lead to hypotension, exsanguination, and sudden death.⁸

Differential Diagnosis and Medical Decision Making

For victims of significant attacks, laboratory and radiologic studies should be ordered as directed by ATLS protocols for major penetrating trauma with associated coagulopathy. Blood and local wound cultures may be useful in the evaluation of hypotension and infection in patients whose arrival for initial medical care is delayed. Radiography can identify underlying damage to bony structures.

Treatment

Victims of Komodo dragon attacks may experience trauma comparable with that sustained in a severe motor vehicle collision. Prehospital care should start with movement of the patient to a safe environment. The provider should make sure that airway control, breathing, and circulatory support are adequate with use of the ATLS protocols. External hemorrhage should be controlled with direct pressure or packing, and chest wounds should be dressed to prevent the development of tension physiology. Extremity fractures should be splinted. Resuscitation in the hospital should continue according to ATLS protocols, with immediate attention to large open wounds, control of hemorrhage, and potential coagulopathy. Because of possible significant blood loss, blood products, including packed red blood cells, platelets, and coagulation factors, should be started early. With the additional vasodilation from envenomation, vasopressors may be needed for refractory hypotension. A broad-spectrum intravenous antibiotic should also be started immediately. No antivenom is commercially available for treatment of komodo dragon enveromation.

Follow-Up, Next Steps in Care, and Patient Education

Survivors of significant Komodo dragon attacks should be admitted to an intensive care unit. Victims of domestic attacks have required admission and speciality care as a result of underlying tendon and neurovascular injury from extremity wounds. As with all bite wounds, delayed closure of the wound may be required.

Outpatient treatment of simple lacerations or puncture wounds includes tetanus prophylaxis, broad-spectrum antibiotics, and close follow-up to monitor for signs of wound infection. Hospitalization for intravenous antibiotics should be considered because of the high risk for significant infection in these wounds.

Pathophysiology

The green iguana (Iguana iguana) is native to Central and South America. It is the most common lizard sold as a pet in the United States (Fig. 141.4). Feral iguana populations can now be found in Florida, Hawaii, and southern Texas. Iguanas are usually docile but can cause injuries with their teeth, claws, and tail. They can also be a source of Salmonella infection.¹⁰ No specific venom is associated with iguana bites.

Fig. 141.4 Iguana.

(Courtesy Hogle Zoo, Salt Lake City, UT.)

Presenting Signs and Symptoms

Most trauma from iguana bites is superficial soft tissue injury, although tendon injuries have been reported.¹¹ The majority of bites (80%) occur on the upper extremities, particularly the fingers, with 19% occurring on the face.¹⁰ As with any bite, patients may have infectious complications, particularly those with delayed care or immunosuppression.

Differential Diagnosis and Medical Decision Making

Extensive diagnostic testing is not generally necessary in cases of iguana bites. Blood and local wound cultures may be useful for patients with established wound infections and systemic signs and symptoms. During physical examination the physician should look for underlying tendon and neurovascular injury. Associated bone damage is rare with iguana bites.¹¹

Treatment

As with any animal bite wounds, delayed closure should be considered and any underlying neurovascular or tendon injuries treated as appropriate. Prophylactic antibiotics remain somewhat controversial, but a 3- to 5-day course of ciprofloxacin should be considered in light of the Salmonella typically carried by the green iguana. In patients with wound infections, treatment with intravenous ceftriaxone may be beneficial. Tetanus prophylaxis is important.

Pathophysiology

Both the common and the alligator snapping turtles have powerful beaklike jaws without teeth but with sharp occlusal surfaces adapted for cutting and holding prey. They are not aggressive but curious about activity occurring around them. Snapping turtles will bite out of self-defense when cornered or cut off from their aquatic environment. Most bites tend to occur when victims put their fingers near the turtle’s head. These turtles may be as long as 20 inches (50 cm) and have a long neck that may extend up to two thirds the length of their body. These freshwater turtles live in habitats ranging from southeastern Canada to Mexico and Ecuador.

Presenting Signs and Symptoms

A snapping turtle’s bite typically causes only soft tissue injury; however, the force of its bite may lead to digit amputation, fractures, or damage to underlying neurovascular structures. Patients with delayed arrival at the ED may show signs of infection.

Differential Diagnosis and Medical Decision Making

When performing the physical examination, the physician should be aware of the potential for damage to nerve, tendon, vascular, and bony structures because of the force of a snapping turtle’s bite. Edema may be present and bleeding should be controlled with local wound pressure. Plain radiography may be helpful to evaluate for injury to bones.

Treatment

Attempts to remove a turtle still attached to a patient will cause it to exert greater bite pressure and result in further injury. Although they rarely remain attached, they will typically release their bite if placed in water. The bite wound should be thoroughly irrigated and débrided. Management of tendon, neurovascular, and bony trauma may require specialty consultation. Delayed closure of wounds may be necessary. Because snapping turtles may carry Salmonella, antibiotic prophylaxis with ciprofloxacin is advisable; in patients with significant wound infections, treatment with intravenous ceftriaxone is recommended.

Follow-Up, Next Steps in Care, and Patient Education

All patients should be educated on the signs of infection and the need for elevation of any injured extremity. Reevaluation of the patient should be scheduled for 24 to 48 hours after discharge.