Injected Poisons: Stinging Insects, Snake Bites - Environmental Emergencies

INJECTED POISONS: STINGING INSECTS

A person may have an extreme sensitivity to the venoms of the Hymenoptera (bees, hornets, yellow jackets, fire ants, and wasps). Venom allergy is thought to be an IgE-mediated reaction, and it constitutes an acute emergency. Although stings in any area of the body can trigger anaphylaxis, stings of the head and neck are especially serious.

Clinical manifestations range from generalized urticaria, itching, malaise, and anxiety due to laryngeal edema to severe bronchospasm, shock, and death. Generally, the shorter the time between the sting and the onset of severe symptoms, the worse the prognosis.

Management

Management includes stinger removal if the bite is from a bee, because the venom is associated with sacs around the barb of the stinger itself. Wound care with soap and water is sufficient for stings. Scratching is avoided because it results in a histamine re-sponse. Ice application reduces swelling and also decreases venom absorption. An oral antihistamine and analgesic will decrease the itching and pain.

In the case of an anaphylactic or severe allergic response, epi-nephrine (aqueous) is injected subcutaneously (not intravenously), and the injection site is massaged to hasten absorption. The patient is assessed for signs and symptoms of anaphylactic reaction and treated as necessary. Desensitization therapy should be given to people who have had systemic or significant local reactions.

Patient and family education is an important measure in pre-venting exposure to stinging insects.

SNAKE BITES

Venomous (poisonous) snakes cause 7000 to 8000 bites in the United States each year and result in 12 to 15 deaths. Children between the ages of 1 and 9 years are the most likely victims. The greatest number of bites occur through the daylight hours into early evening during summer months. The most frequent poiso-nous snakebite occurs from pit vipers. The most common site is the upper extremity. Of these bites, only 20% to 25% result in envenomation (injection of a poisonous material by sting, spine,bite, or other means). Venomous snake bites are medical emer-gencies (Moon & Galvan, 2000).

Nineteen different species of venomous snakes are found in every part of the United States, with different parts of the coun-try and the world having different types of snakes. Because snake bites are medical emergencies, nurses should be familiar with the types of snakes that are common to the geographic region in which they practice. Snake venom consists primarily of proteins with a broad range of physiologic effects. Multiple organ systems, especially the neurologic, cardiovascular, and respiratory systems, may be affected.

Management

Initial first aid at the site of the snake bite includes having the vic-tim lie down, removing constrictive items such as rings, provid-ing warmth, cleansing the wound, covering the wound with a light sterile dressing, and immobilizing the injured body part below the level of the heart. Ice or a tourniquet is not applied. Initial evaluation in the ED is performed quickly and includes in-formation about the following:

Whether the snake was venomous or nonvenomous; if the snake is dead, it should be transported to the ED with the patient for identification

·      Where and when the bite occurred and the circumstances of the bite

·       Sequence of events, signs and symptoms (fang punctures, pain, edema, and erythema of the bite and nearby tissues)

·      Severity of poisonous effects

·       Vital signs

·       Circumference of the bitten extremity or area at several points; the circumference of the extremity that was bitten is compared with the circumference of the opposite extremity

·      Laboratory data (complete blood count, urinalysis, and clot-ting studies)

The course and prognosis of snake bite injuries depend on the kind and amount of venom injected, where on the body the bite occurred, and the general health, age, and size of the victim. There is no one specific protocol for treatment of snake bites. Generally, ice, tourniquets, heparin, and corticosteroids are not used during the acute stage. Corticosteroids are contraindicated in the first 6 to 8 hours after the bite, because they may depress antibody production and hinder the action of antivenin (antitoxin manu-factured from the snake venom and used to treat snake bites).

Parenteral fluids may be used to treat hypotension. If vasopres-sors are used to treat hypotension, their use should be short-term. Surgical exploration of the bite is rarely indicated. Typically, the patient is observed closely for at least 6 hours. The patient is never left unattended.

ADMINISTRATION OF ANTIVENIN (ANTITOXIN)

Although envenomation is rare, it can occur with snake bites. An assessment of progressive signs and symptoms is essential before considering administration of antivenin, which is most effective if administered within 12 hours after the snake bite. The dosage depends on the type of snake and the estimated severity of the bite. Children may require more antivenin than adults because their smaller bodies are more susceptible to toxic effects of venom. A skin or eye test should be performed before the initial dose to detect allergy to the antivenin. However, because even the skin test can cause an anaphylactic reaction, patients should not be tested unless antivenin is to be given.

Before administering antivenin and every 15 minutes there-after, the circumference of the affected part is measured proxi-mally. Premedication with diphenhydramine and cimetidine decreases the allergic response to antivenin. Antivenin is admin-istered as an intravenous infusion whenever possible, although intramuscular administration can be used. Depending on the severity of the bite, the antivenin is diluted in 500 to 1000 mL of normal saline solution; the fluid volume may be reduced for chil-dren. The infusion is started slowly, and the rate is increased after 10 minutes if there is no reaction. The total dose should be in-fused during the first 4 to 6 hours after poisoning. The initial dose is repeated until symptoms decrease. After the symptoms de-crease, the circumference of the affected part should be measured every 30 to 60 minutes for the next 48 hours to detect symptoms of compartment syndrome (swelling, loss of pulse, increased pain, and paresthesias).

The most common cause of allergic reaction to the antivenin is its too-rapid infusion, although about 3% of patients with negative skin test results develop reactions not related to infusion rate. Reactions may consist of a feeling of fullness in the face, urticaria, pruritus, malaise, and apprehension. These symptoms may be followed by tachycardia, shortness of breath, hypoten-sion, and shock. In this situation, the infusion should be stopped immediately and intravenous diphenhydramine (Benadryl) ad-ministered. Vasopressors are used for patients in shock, and re-suscitation equipment must be on standby while antivenin is infusing.