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Veterinarian Technician September 2009 (Vol 30, No 9)

Emesis — Is It for Your Patient?

by Jo Marshall

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    Rapid induction of emesis may be the best method of limiting absorption and preventing continued exposure in potentially harmful or life-threatening ingestion situations. Veterinary staff need to respond quickly in these situations and be able to evaluate and recognize instances where induction of emesis may be contraindicated or pose additional health concerns to the animal, staff, and owners. This article is a primer on what concerns need to be evaluated before reaching for an emetic agent.

    Breed and Species Concerns

    Most cats, dogs, ferrets, and potbelly pigs can be safely induced to vomit.1,2 Brachycephalic breeds that may have anatomical concerns, such as an elongated soft palate, are candidates for sedation and gastric lavage rather than emesis. Rabbits, ruminants (e.g., sheep, cattle, llamas, goats), horses, and birds cannot safely have emesis induced, and rodents (e.g., chinchillas, rats, gerbils) are anatomically unable to vomit.3

    Risk vs. Benefit

    Does the risk of inducing emesis outweigh the benefits? Inducing emesis can result in the aspiration of gastric content and potential injury to the stomach and esophagus. If the ingested substance poses in minimal to no risk when left to pass through the digestive tract, the benefit of inducing emesis would be limited and, therefore, not recommended. Altered mentation or underlying medical conditions may prevent safe induction of emesis. Animals that are unconscious, seizing, or laterally recumbent pose a greatly increased risk of aspiration with emesis. Animals in a state of agitation or extreme excitability can become further stimulated when attempts are made to induce emesis, and this may potentiate seizures.

    Animals with underlying medical conditions or seizure history require careful evaluation of the risk associated with exacerbation and worsening preexisting concerns with induced emesis. Patients that are already vomiting should never be given an emetic agent without veterinary guidance.

    What Was Ingested

    Caustic or corrosive substances such as undiluted drain cleaners, toilet bowl cleaners, hydrochloric acid, concentrated sodium hypochlorite, and lye products can result in further burns and corrosive injury to the stomach, esophagus, and mouth when vomiting occurs after ingestion. Gastric lavage also is contraindicated in these ingestions because of the increased risk of perforation to the already damaged and weakened digestive tract. Keep in mind that if damage occurred going down, it will occur on the way back up.

    When ingested, fragrance oils and liquid potpourri can cause burns to the oral cavity, pharynx, and esophagus. Fragrance oils are cationic detergents in various concentrations. The more concentrated the product, the greater the burns and corrosive damage. Burns can be seen with concentrations of 7.5% and higher, but with cats, concentrations as low as 2% have resulted in corrosive ulcerations.4 Pets can walk through spilled fragrance oil, getting it on their feet and hair. These instances of dermal exposure quickly become oral exposures as the animal begins to self groom to remove the oily substance. Cats tend to be at the greatest risk for exposure to these products. Many of the essential oil products contain terpenes. Once absorbed, terpenes are metabolized in the liver by glucuronidation. Cats are unable to eliminate compounds through glucuronidation because they lack the glucuronyl transferase enzyme.2

    Contraindications to Emesis Induction

    Hydrocarbons and petroleum distillates, such as gasoline, mineral spirits, and furniture polish oils, are of products that can pose an aspiration risk when ingested. The very thin viscosity of this type of liquid enables them to be easily aspirated when a patient vomits. The aspiration risk outweighs the benefits of emesis and, therefore, emesis is not recommended.

    Zinc, calcium, and aluminum phosphides are the active ingredients in many of the commercially available mole and gopher baits. Induction of emesis needs to occur quickly because of the rapid onset of symptoms. Ingestion of phosphides produces a toxic phosphine gas in the moist, acid environment of the stomach.1 Phosphine gas exposure poses significant health risks for staff and owners. Dogs being transported to the clinic after ingestion of this rodenticide often vomit in the car and owners may be exposed to the gas. Owners should be advised to transport their pet in a ventilated car after administration of an aluminum hydroxide or calcium carbonate antacid preparation.1 Induction of emesis and a physical examination need to be performed in a well ventilated area or outdoors to prevent inhalation of phosphine gas by staff. Vomitus generally has a telltale garlic or rotten fish odor to it.

    Xylitol is a sweetener frequently used in low-sugar or no-sugar products and may be used in combination with aspartame or other sugar/alcohols. Common products that contain xylitol are sugar-free gums, sugar-free mints and numerous dental hygiene products. Xylitol ingestions in dogs need to have emesis immediately induced because of the rapid onset of signs. Dogs ingesting concentrated xylitol-containing products experience a rapid rise in serum insulin levels and subsequent drop in blood glucose. This drop in blood glucose is dose-dependent and may occur within 15 minutes of ingestion. Clinical signs often occur very quickly and include vomiting, diarrhea, lethargy, ataxia and seizures as well as potential long-term effects on the liver.

    Pharmaceutical ingestions (especially ingestions of large quantities of medications) that do or do not have typical veterinary use, can result in significant, rapidly occurring life-threatening signs. Examples of these signs are central nervous system (CNS) excitability, changes in blood pressure and heart rate, respiratory depression, sedation, and seizure activity. Many of the pharmaceutical ingestions need to have emesis induced within 10 minutes to prevent significant signs from occurring simultaneously with vomiting. After an emetic agent has been administered, there is generally a 10 to 15 minute period before emesis is actually achieved, and the status of the patient may rapidly deteriorate during that time.

    Considerations in Choosing an Emetic Agent

    The list of methods used to induce emesis in animals is broad and varying. Many home remedies are used without success and have the potential of causing further concerns. Emetics can work by causing local gastric irritation, stimulation of the CNS or a combination of irritation and CNS stimulation.5 Regardless of the emetic used, all work best if there is food in the patient's stomach. If the animal has not eaten within the last 2 hours, a small snack is recommended before administration of the emetic agent.2 Emetic agents often are not effective if an antiemetic (e.g., ondansetron) has been previously administered.

    Methods that are not recommended to induce emesis include digital induction of emesis, syrup of ipecac, liquid soaps, dry mustard powders, and salt. Digital induction of emesis or forcing a foreign object down a pet's throat often results in physical injury to the throat and soft palate, and a high likelihood of the individual being bitten in the process. Historically, syrup of ipecac has been recommended for use in rapid induction of emesis. However, its cardiotoxic potential and tendency to result in prolonged vomiting, lethargy and diarrhea, have caused syrup of ipecac to fall out of favor in routine management of poisoned patients.7,8 Soaps, mustard powders, and table salt are not reliable as induction agents and in addition, salt may result in hypernatremia in the patient.

    Recommended emetic agents include hydrogen peroxide, apomorphine hydrochloride and xylazine hydrochloride.4 Hydrogen peroxide (H2O2) works by local irritation of the oropharynx and gastric lining, which results in a gag reflex. It is usually recommended for oral administration by the pet owner when timely transportation to a veterinary clinic is not possible. A 3% hydrogen peroxide solution is recommended. It is dosed at a rate of 1-5 ml/kg and is administered orally. The maximum dose should not exceed 10 ml for a cat and 50 ml for a dog.6 Use of hydrogen peroxide from an unopened bottle is recommended. Hydrogen peroxide deteriorates after it has been opened and can lose efficacy as an emetic over time. Once H2O2 is administered, the pet should be gently walked. If emesis does not occur within a 10 to 15 minute time frame, the dose may be repeated once. Adverse effects associated with the use of H2O2 as an emetic agent include irritation to gastrointestinal tract, gastric dilatation-volvulus in dogs, and aspiration risk.

    Hydrogen peroxide solutions with concentrations of greater than 3% have the potential of being corrosive to the gastrointestinal mucosa and should never be used. Cats have reportedly developed gastrointestinal ulcerations with administration of 3% concentrations and judicious use, if at all, of H2O2 is recommended in cats.

    Apomorphine hydrochloride is a centrally acting emetic agent and in many circumstances is considered the emetic agent of choice for dogs in a clinical setting. Administration results in stimulation of the chemoreceptor trigger zone, quickly followed by emesis. Apomorphine may be administered IV, IM or subconjunctivally. Dosing for IV administration is 0.03-0.04 mg/kg, for IM administration is 0.04-0.08 mg/kg and subconjunctival dosing is 0.25 mg/kg.6 When using apomorphine tablets for subconjunctival administration, tablets or portions of the tablet are crushed and added to a few drops of water in a syringe. This solution is then instilled directly into the conjuctival sac.

    Once emesis is achieved, the conjunctival sac should be flushed well with water or saline to remove apomorphine residue. Adverse effects associated with apomorphine administration are prolonged emesis and ocular irritation. These may be limited with subconjunctival administration and subsequent flushing of the conjunctival sac. Overdose of the drug results in prolonged emesis, respiratory and cardiac depression, CNS depression or excitement. Reversal of CNS and respiratory concerns may be done with naloxone, but reversal will not have an effect on prolonged emesis.6 Apomorphine should not be used with ingestions of medications that result in compounding of respiratory or CNS depression symptoms or with antidopaminergic drugs that prevent emesis from occurring. Apomorphine hydrochloride has at times been difficult to obtain but can generally be obtained from compounding pharmacies.

    Xylazine hydrochloride is a reliable, centrally acting emetic agent used primarily in cats. A dose of 0.44 mg/kg is administered intramuscularly to cats with anticipated emesis occurring in 3 to 5 minutes.6 Xylazine does not reliably produce an emetic response when used in dogs. Adverse effects associated with xylazine use include bradycardia, sedation, tremors, and respiratory depression. Overdoses of xylazine result in hypotension, cardiac arrhythmias, respiratory depression, and CNS depression. Clinical signs can be reversed with yohimbine or atipamezole.6 Xylazine hydrochloride should not be used in cats that have ingested medications or products that may result in compounding of bradycardia, respiratory depression, sedation, or CNS depression symptoms.

    Induction of emesis can be a valuable tool in limiting and preventing continued exposure to ingestion of potentially harmful substances. However, emesis needs to be performed only after a thorough physical evaluation of the pet and appropriate evaluation of time of exposure and potential risks involved are considered. Once this evaluation has been completed, the veterinary team can confidently move forward with the safest course of treatment and potential decontamination method.

    Pet Poison Helpline (PPH) is an animal poison control center that provides treatment advice and recommendations relating to exposures to potential dangerous plants, products, medications, and substances, to veterinarians, veterinary staff and pet owners 24 hours a day, 7 days a week. There is a $35.00 per case consultation fee. PPH is located in Bloomington, Minn. The PPH number is 800-213-6680. For further information regarding services, visit the PPH website at www.petpoisonhelpline.com.

    Acknowledgments

    The author wishes to thank Lynn Hovda, RPh, DVM, MS, DACVIM, Director of Veterinary Services at Pet Poison Helpline, for her input and review of this article and Justine Lee, DVM, DACVECC, for her editing expertise and input.

    1. Pet Poison Helpline Case Database: Unpublished data, Bloomington, MN, 2004 - 2009.

    2. Gupta R. Veterinary Toxicology, Basic and Clinical Principles. New York: Elsevier;2007.

    3. Bihun C, Bauck L. Basic anatomy, physiology, husbandry, and clinical techniques. In: Quesenberry K, Carpenter JW, eds. Ferrets, Rabbits, and Rodents, ed 2. St Louis: Saunders; 2004:289-290.

    4. Plumlee KH. Clinical Veterinary Toxicology, St Louis: Mosby, 2004.

    5. Battaglia, AM. Small Animal Emergency and Critical Care for Veterinary Technicians, ed 2. St Louis, MO, Saunders, 2007, pp 356-367.

    6. Plumb, DC. Plumb's Veterinary Drug Handbook, ed 6. Ames, IA, Blackwell Publishing, 2008.

    7. Rosendale, ME. Decontamination Strategies, in: Poppenga RH, Volmer PA, eds. The Veterinary Clinics of North America, Philadelphia: WB Saunders Co, 2002; 311-316.

    8. Krenzelok EP, Vale JA. Gastrointestinal Decontamination, in Brent J, Wallace KL, et al, eds. Critical Care Toxicology: Diagnosis and Management of the Critically Poisoned Patient, Philadelphia: Elsevier Mosby, 2005; 53-59.

    References »

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