Procedures Pro - Decontamination Of The Poisoned Pet

procedures pro

TOXICOLOGY

Decontamination of the Poisoned Pet Jacqueline B. Heller, DVM, ASPCA Animal Poison Control Center, Urbana, Illinois

efore decontamination, the patient should be examined and stabilized. The decontamination plan should then be designed based on the nature and amount of the substance; whether several agents are involved; time and route of exposure; and the patient’s condition, signalment, and species

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(Table). Ultimately, the goal of decontamination is to limit continued exposure to the toxic substance. Dermal, ocular, and oral decontamination procedures are discussed here. If the condition of the patient allows, appropriate samples of the toxicant should be obtained before decontamination. This may include col-

lection of blood, urine, topical contaminants, and stomach contents (via vomitus or gastric lavage). Samples should be collected and set aside for toxicologic testing and, if warranted, for legal considerations. A diagnostic laboratory should be consulted for appropriate sample handling and storage. c o n t i n u e s

Decontamination Contraindications Procedures Dermal Bath

Ocular Eye flush

Oral Emetics

Activated charcoal

Contraindications

Rationale

Solvents (e.g., acetone, paint thinner, turpentine), automatic dishwasher detergent, laundry detergent

Can alter skin permeability, resulting in dermal irritation or chemical burns

Neutralizing agents

Risk for ocular tissue damage

Rabbits, rodents, reptiles, birds

Species do not readily vomit; cannot safely and consistently induce emesis

Acids, alkalis, caustic agents Hydrocarbons Previously vomited Exhibiting significant signs Preexisting health condition (e.g., seizure disorder, dyspnea)

Corrosive damage to alimentary tract Increased risk for aspiration Redundant; risk for chronic gastritis Increased risk for aspiration Increased risk for aspiration

Caustic agents

Delayed healing; ineffectively adsorbed Not effectively adsorbed

Alcohols, hydrocarbons, heavy metals, inorganic minerals, fertilizers, salts

Cathartics

Animals with diarrhea, dehydration, or ileus

Increased risk for dehydration and intussusception

Gastric/crop lavage

Caustic substances

Corrosive damage to alimentary and gastrointestinal tract Increased risk for aspiration

Hydrocarbons

Decontaminant Dosages Agent

Dose

3% hydrogen peroxide

2 ml/kg BWT PO, not to exceed 45 ml/dose

Apomorphine

0.04 mg/kg IV or SQ

Activated charcoal

1–3 g/kg BWT

Sorbitol cathartic

3 ml/kg BWT

Saline cathartics

250 mg/kg BWT in water or activated charcoal

Psyllium

1 tsp in food Q 12–24 H (dogs and cats) 1/2 tsp in 60 ml baby food (birds)

Other bulking agents

1–3 tbsp Q 6–8 H

Gastric lavage fluid

5–10 ml/kg BWT

Atropine (preanesthetic)

0.02 mg/kg BWT

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procedures pro STEP-BY-STEP

CONTINUED

1. Dermal Decontamination Bathing is usually the method of choice for decontaminating skin that has been exposed to toxic substances. Appropriate measures should be taken to prevent human exposure to the toxicant during the bathing process.1 This includes use of protective eyewear, water-impermeable aprons, and gloves. Bathing is often necessary to prevent the animal from ingesting a potentially harmful substance and not necessarily because of associated dermal risk. Thus, protective gear can be used at the clinician’s discretion. Patient evaluation is necessary to determine how well the animal will tolerate the bath. Sedation, if deemed appropriate, may minimize stress to both the patient and the practitioner. Severely depressed or otherwise compromised patients should be monitored closely to avoid hypothermia, extreme stress, or aspiration.

Bathing with mild, liquid, hand dish detergent, such as Dawn or Joy, is generally effective in removing most agents, especially oil-based compounds. Wet the animal thoroughly with warm water, apply detergent, and lather. Repeated washing may be required for complete removal.

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Dry compounds are best removed via brushing or vacuuming. Water or shampoo may alter skin surface tensions and enhance dermal absorption of the chemical across the skin.

PROCEDURE PEARL Appropriate measures should be taken to prevent human exposure to the toxicant during the bathing process.

After being bathed, the patient should be rinsed thoroughly then wiped with a towel and kept in a warm area until dry.

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When attempting to remove sticky substances (e.g., gum, tacky glue, glue from glue traps, tar), vegetable or mineral oil can be used to soften or break up these agents. Work into the exposed area; let sit for 5 minutes; then bathe with mild, liquid, hand dish detergent. Heavily exposed areas of fur may require clipping to remove as much of the substance as possible. Afterward, bathe with the mild dish detergent and rinse thoroughly. With birds, feathers should not be trimmed to avoid nicking a blood feather—pretreat with the vegetable or mineral oil; then mist as described previously.

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Light dermal exposures in very small animals, such as birds, reptiles, or pocket pets, can be treated by misting the animal with room-temperature water. If necessary, a mild, liquid, hand dish detergent can be diluted in the spray bottle and applied. Avoid spraying near the eyes. Rinse by misting with plain water until soap residue is gone.

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3. Oral Decontamination The goals of gastrointestinal decontamination are to prevent or limit absorption of ingested toxicants and minimize mucosal exposure to irritating or corrosive agents. One or more procedures may be necessary, and the techniques used should be based on individual exposure history and assessment.

2. Ocular Decontamination Ocular injury from exposure to toxicants can range from mild irritation of the conjunctiva and cornea to corrosive injury with subsequent blindness. Solvents, such as alcohols, detergents, and hydrocarbons, usually cause only superficial injury to the eye, while strong acid and alkaline corrosive agents may cause more extensive damage.1 The degree of ocular impairment depends on the duration of exposure and the type and amount of contaminant. As with dermal decontamination, sedation may be used before ocular decontamination if the animal is stable.

Immediately irrigate with tepid water or sterile saline solution to limit corneal damage and decrease systemic absorption. Continue to gently flush the eyes with copious amounts of liquid for 20 to 30 minutes, taking short breaks at as-needed intervals to minimize stress. For smaller patients, an eyedropper can be used.

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PROCEDURE PEARL Solvents, such as alcohols, detergents, and hydrocarbons, usually cause only superficial injury to the eye, while strong acid and alkaline corrosive agents may cause more extensive damage.

Most commonly, gastric evacuation involves inducing emesis. Depending on the success of emesis (i.e., whether the toxicant is observed in the vomitus), activated charcoal, with or without a cathartic, may be indicated as the next step in the decontamination process. In certain circumstances, gastric lavage can be used when evacuation is indicated but administration of an emetic is contraindicated (i.e., presence of seizures or in a species unable to vomit).

Dilution

Small amounts of water or milk may help minimize irritation to the alimentary tract associated with ingestion of corrosive substances (e.g., anionic detergents, acids, alkalis), hydrocarbons, or products that cause taste reactions (e.g., topically applied insecticides). Dilution with a demulcent such as milk or yogurt may also help relieve oral irritation, which is commonly associated with chewing plant leaves containing insoluble calcium oxalate crystals (e.g., Philodendron species).

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With larger animals use a syringe, plastic bottle, or cup.

3B After flushing, stain the eyes with fluorescein dye to check for any corneal ulceration. Apply appropriate ophthalmic ointments as required, and repeat staining in follow-up examinations 12 to 24 hours after exposure.

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For birds, reptiles, and small mammals, juicy fruits such as melon and pineapple can be offered. c o n t i n u e s

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Emesis On average, emesis removes 40% to 70% of the chyme from the stomach. Thus, additional decontamination may be required if the actual amount of toxicant ingested is not observed in the vomitus.1,2,3

In general, emetics may be beneficial if given within 2 to 3 hours after ingestion. In certain cases, emesis may be effective after 2 to 3 hours when formation of boluses (chocolate, large numbers of sugar-coated tablets) or delay in gastric emptying (grain-based rodenticides or plant matter) occurs in the stomach. Sufficient mass must be present in the stomach for productive emesis to occur.4 Thus, offering a small amount of food, such as a slice of bread, before induction often achieves better results.

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Three percent hydrogen peroxide is the preferred emetic since it is inexpensive, readily available, and generally easy to administer.1 It acts locally by inducing a mild gastric irritation with no significant risks.5 Vomiting usually occurs within

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Activated Charcoal 10 to 15 minutes. The dose may be repeated once if no vomiting occurs within 20 minutes. Overdosing may cause persistent gastritis.

PROCEDURE PEARL To ensure peroxide is fresh, a few drops may be poured into the hand or a sink—fizzing or foaming assures activity.

In a clinical setting, apomorphine is often used as an emetic. However, recent availability has been limited, requiring compounding by a pharmacist. A centrally acting emetic, apomorphine stimulates dopaminergic receptors in the chemoreceptor-trigger zone. Apomorphine can be administered by the intravenous, intramuscular, or conjunctival route. Emesis usually occurs almost immediately after intravenous injection and lasts for 1 to 2 minutes. Intramuscular injection usually induces emesis within approximately 5 minutes, and emesis can be prolonged. Apomorphine can also be administered via instillation in the conjunctival sac. Vomiting can be regulated in part by washing the conjunctival sac free of unabsorbed apomorphine once sufficient emesis has occurred. Use of apomorphine in some species, such as cats, is controversial because emesis can be less effective than other options and may be less safe. Side effects include CNS depression and protracted vomiting. Naloxone may reverse CNS depression but does not inhibit emetic effects.1,2,3,6

Activated charcoal is a nonspecific adsorbent that binds many organic compounds and facilitates excretion of the toxicants via the feces. The liquid or powder form is usually recommended for decontamination because of the large surface area. Commercial formulations provide the recommended amount of charcoal when dosed per label. Surface binding area of these activated charcoal formulations range from 900 to 1500 m2/g. Activated charcoal tablets or capsule products bind much less surface area (approximately 2 to 4 m2/g), making them unsuitable for toxic decontamination. Severe vomiting should be controlled before activated charcoal administration.1

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Other emetics that have been used in small animals include salt, liquid dish soap, dry mustard, syrup of ipecac, and xylazine. These substances are not routinely recommended because of their questionable efficacy and potential for serious side effects.

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Administer activated charcoal orally using a syringe.

If the animal is symptomatic or uncooperative, charcoal administration should be done under anesthesia using a stomach tube with cuffed endotracheal tube in place to prevent aspiration.1,2 Repeated doses every 4 to 12 hours at half the initial amount may be indicated when dealing with toxicants known to undergo enterohepatic recirculation or with sustainedrelease medications.

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Cathartics

Lavage

Cathartics enhance the movement of substances through the gastrointestinal tract. They are often administered along with activated charcoal to hasten elimination of the charcoalbound toxicants.3 When treating smaller patients such as birds and reptiles, cathartics should be used cautiously as they can lead to or increase dehydration.7

Gastric lavage is generally considered less effective than emesis, but may be necessary if emesis is unsuccessful or contraindicated.2 Crop lavage is a similar and relatively simple procedure in birds.

When removing the tube, occlude the outside end to reduce risk for aspiration. Check body temperature because hypothermia may occur.

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Sorbitol is a nonabsorbable sugar that works as an osmotic cathartic by drawing electrolyte-free water into the gastrointestinal tract. It is often combined with activated charcoal in ready-made products and can be used in mammals, birds, and reptiles. Saline cathartics, such as magnesium sulfate (Epsom salt) and sodium sulfate (Glauber’s salt), also act as osmotic cathartics. Because magnesium is excreted by the kidneys, caution is advised when administering magnesium sulfate cathartics to an animal with renal compromise.6

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Psyllium (Metamucil) is a bulk cathartic that may be used in birds or mammals. This hydrophilic laxative is used to enhance passage of toxicants or mechanically disruptive agents through the gastrointestinal tract (e.g., lead paint chips, fiberglass insulation). Other bulking agents include bread, canned pumpkin, and other high-fiber vegetables. When using osmotic cathartics, pay particular attention to the frequency of administration— excessive use has been associated with electrolyte disturbances (most notably hypernatremia) due to loss of excess free body water into the gut. Although such electrolyte disturbances can occasionally occur when added to a single dose of activated charcoal, they are more likely to happen when multiple doses are given. Therefore, if several doses of activated charcoal are necessary, cathartics should only be used with the initial charcoal dose.1

Before gastric lavage, the patient should be anesthetized with a cuffed endotracheal tube in place to protect the airway. Using a large-bore gastric tube, measure from the tip of the nose to the xiphoid process to estimate stomach location. A piece of tape can be applied to the tube to mark the correct length.

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In birds, crop lavage is done in a similar manner. Use intubation and anesthesia to facilitate administration of warm saline into the crop. Aspirate the fluid three to four times.7

Enterogastric lavage is recommended when both gastric and intestinal decontamination are indicated. For example, when life-threatening toxicant doses have been ingested and emesis is contraindicated, enterogastric lavage may remove a greater portion of the gastrointestinal contents than afforded by gastric lavage alone.2 In this procedure, gastric lavage is performed and the orogastric tube and cuffed endotracheal tube are left in place. The rectum is evacuated using tepid water. The enema tube is then attached to a continuously running, low-pressure faucet. It may be necessary to hold the tube in place while the intestines fill with water. Ultimately, the fluid will exit the gastric tube via the mouth. Continue until fluid is clear. A preanesthetic dose of atropine, if not contraindicated or previously administered, may be given to relax the gastrointestinal smooth muscles.1 As with gastric lavage, monitor body temperature. ■

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Pass the tube, fenestrated end down, into the stomach. Instill tepid water or normal saline. Both instillation and draining of fluid should be done with gravity flow only—in dogs and cats, keep the patient’s head lower than the chest to facilitate this process. Several flushes may be needed to rinse the stomach completely. Rinse until the fluid is clear. Reserve the initial lavage sample for toxicologic analysis.1–3,5

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PROCEDURE PEARL Excessive use of osmotic cathartics has been associated with electrolyte disturbances (most notably hypernatremia).

PHOTO CREDITS Figures 1B, 1C, 2A, 3B, 4B, and 5B. Reprinted with permission from Managing Ferret Toxicoses. Richardson JA, Murphy LA, Khan SA, Means C. Exotic DVM 2:2326, 2000 and Managing Pet Bird Toxicoses. Richardson JA, Balabuszko RA. Exotic DVM 3:23-27, 2001.

See Aids & Resources, back page, for references, contacts, and appendices.

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