Cobra Envenomation Treatment & Management

Prompt movement of the victim to a medical facility capable of rendering advanced care, including airway support and antivenom administration, is critical.

Make every effort to specifically identify the envenoming species; this will aid further management and is vital in determining the proper antivenom to be administered.

If the patient is bitten by a wild snake, the snake should be killed and brought to the admitting institution if it is possible to do so safely. Knowledge of the snake fauna of an area and habits of the various species may help in identification. Fairly accurate ELISA tests for identification of snake venoms in wound aspirate, serum, urine, and other body fluids have been developed but are not generally available in regions where cobras live.

If the bite occurs in a research or zoo setting, the cage identification card should be brought to the hospital. If available, species-specific antivenom should be sent with the patient.

If a captive cobra in a private collection inflicts the bite, identification may be more straightforward. Unfortunately, tremendous controversy exists among experts regarding taxonomy of cobra species and becomes amplified in the lay herpetoculturist community. A private collector who presents after being bitten by his or her captive "Thai cobra" may have been envenomed by any 1 of at least 3 different species, each with different clinical consequences. Thus, expect a variety of physiologic abnormalities and enlist professional help (eg, from a local zoo) to obtain prompt, accurate identification of the snake.

In some regions of the world, clothing is wrapped around a bitten extremity proximal to the bite site. However, prolonged use of arterial tourniquets is unwise and has caused loss of limb function. A completely occlusive tourniquet is reasonable when a victim has been bitten by a highly toxic snake, such as a cobra, and is a short distance from medical care.

An alternative first aid procedure is the Australian pressure immobilization technique (see the images below). This technique has been shown to be helpful in delaying systemic absorption of some elapid venoms, but its use in cobra bites remains controversial.

An elastic compress (eg, Ace wrap, clothing, crepe bandage) is wrapped rapidly around the bitten extremity, beginning distally and progressing proximally to encompass the entire limb. The compress is as tight as one used for immobilization of a severe ligamentous sprain. Then, the extremity is splinted and kept at heart level while the victim is carried from the scene. Research shows, however, that, in simulated snakebite scenarios, individuals usually underestimate the degree of tension required for the wrap to be effective, and, even with intensive training, are usually unable to apply the technique correctly.

This technique should not be used in any situation in which the snake responsible for the bite is known to cause local necrosis, as local tissue damage may be increased with its use.

Incisions are not helpful. Using a mechanical suction device is unlikely to return any significant amount of venom, and it could increase local tissue damage when a necrotizing venom is involved. Suction should, therefore, be avoided.

Avoid cooling measures and ice application. They have been associated with increased necrotic complications.

If venom is spit into the eyes, immediately and copiously irrigate them with any bland fluid, such as water, saline solution, or milk.

Assess the patient's airway and breathing. Aggressively manage any signs of impending respiratory failure with endotracheal intubation to prevent aspiration.

Immediately institute cardiac and pulse oximetry monitoring and closely monitor the patient's vital signs.

Start, at an appropriate rate, at least 1 large-bore line with normal saline or Ringer's lactate.

Grading scales for judging the severity of viper venom poisoning rely heavily on local findings, which are variable in cobra bites; they should not be used. All persons who have been bitten by a cobra should be treated as if a severe envenomation has occurred.

Antivenom is the only proven therapy for significant snakebites. About 20 laboratories in Africa, Asia, and Europe produce cobra antivenoms. Some are monovalent, but most are polyvalent against venoms of all the important snakes of a nation or region. However, the quality varies, and no international standards of purity or effectiveness exist. In the United States, no cobra antivenom has FDA approval. All are considered experimental drugs. Antivenoms are largely ineffective in preventing or ameliorating the necrosis caused by many cobra venoms.

If the envenomating species has been determined, a resource, such as the Antivenom Index (published and maintained by the American Association of Zoological Parks and Aquariums and the American Association of Poison Control Centers), can be accessed by calling a regional poison control center or the Arizona Poison and Drug Information Center (from outside Arizona, 520-626-6016; from Arizona only, 800-362-0101). This document lists the preferred antivenoms available for most medically important venomous snakes around the world and has information about where these sera can be obtained in the United States (usually zoos or serpentariums). Once the antivenom is located, the physician may need assistance from the police or military to facilitate its rapid transport.

If possible, the antivenom should have antibodies against venom of the cobra species that inflicted the bite. However, shared venom antigens among cobra species exist, and heterologous antivenoms may be effective. Venoms of the African spitting cobras are among the most difficult to neutralize by nonspecific antivenoms. Notechis (Australian tiger snake) antivenom proved effective in animal experiments against 9 of 11 cobra venoms, exceptions being ringhals and Chinese cobra venoms. Apparent effectiveness of tiger snake antivenom in clinically treating cobra bites has been shown in a few cases.

If the patient arrives with some device applied in an attempt to limit spread of the venom, such as a tourniquet, constriction band, or pressure device, quickly assess the patient to determine if any evidence of systemic toxicity is present.

Assess the presence of distal pulses below the ligature. If symptoms are present and antivenom is available, start the antivenom before removing the tourniquet device. If symptoms are absent and antivenom is available, remove the device and observe the patient closely for symptoms or signs of toxicity. If signs of envenoming occur, administer antivenom promptly.

If the tourniquet is totally occluding arterial flow, apply a more loosely fitting device, such as a proximal constriction band, as tightly as one would for a phlebotomy. A pressure immobilization device may also be used (see Prehospital Care). A more loosely fitting device is appropriate to prevent the release of an acidotic, hyperkalemic blood into the central circulation as the tourniquet is released.

When applicable, initiate and continue irrigation of the eyes with saline. Applying several drops of a topical ophthalmic anesthetic agent may reduce pain and aid in irrigation. The topical use of 1:1000 epinephrine solution is reported to relieve pain promptly. A fluorescein-aided slit lamp examination helps to find evidence of corneal damage. A brief course of topical ophthalmic antibiotics may be prescribed.

• Toxicologist or expert in snake envenomation
• Regional poison control center
• A local zoo or museum may be able to assist in species identification and may have appropriate antivenom in stock.
• An ophthalmologist should evaluate any patient who has suffered eye exposure to spitting cobra venom.
• General surgeon or plastic surgeon for follow-up care of necrotic wounds