Approach to Poisoning and Drug Overdose

Chapter 77 Approach to Poisoning and Drug Overdose



Julie C. Schildt, DVM, L. Ari Jutkowitz, VMD, DACVECC



KEY POINTS



• The initial approach to the poisoned patient includes major organ system assessment and stabilization.

• Gastric evacuation can be achieved by induction of emesis, gastric lavage, or whole bowel irrigation.

• Activated charcoal is an adsorbent that binds toxins and facilitates excretion through the gastrointestinal (GI) tract.

• Cathartics often are used in combination with activated charcoal and decrease the absorption of toxins by shortening GI transit time.

• Other methods exist to enhance elimination of toxins but are not widely recommended because of their potential harmful effects or limited availability.


INTRODUCTION


Most animals with suspected poisoning or drug overdose may be treated successfully by adhering to general principles for assessment and decontamination. Initially, a brief medical history should be obtained from the owner with questions focusing on the suspected toxic agent, amount and time of ingestion, clinical signs noted, any preexisting medical conditions, and current medications. A more extensive history can be taken following triage and initial interventions.


Immediate assessment of the patient should be performed to evaluate vital signs and major body systems. Appropriate therapy should be initiated to stabilize the cardiovascular, respiratory, and neurologic systems. In the event of a witnessed ingestion, it may be appropriate to administer an antidote immediately. However, in many cases an antidote does not exist or the exact toxic agent is not known. Therefore, when treating the poisoned patient, decontamination often becomes the most effective means of therapy. Depending on the route of exposure, several methods of decontamination may be used to eliminate the toxin and prevent continued absorption. Further symptomatic and supportive care should be tailored to the needs of the individual patient.



OCULAR DECONTAMINATION


Ocular exposure to toxic substances can damage the corneal surfaces, conjunctiva, and other external tissues. These insults may result in local irritation or permanent corneal damage and blindness. Potential irritants include acids, alkalis, organic solvents, alcohols, and detergents. Acids and alkalis tend to have the most severe effects because progressive damage may occur for some time after initial contact.


With any ocular exposure, the pet owner should immediately perform copious irrigation of the eye. Irrigation solutions that may be used include tepid tap water, saline, or distilled water. Contact lens solutions should be avoided, because they may contain agents that cause further irritation. The eye should be rinsed for 20 to 30 minutes with the patient positioned such that the eye is flushed medially to laterally to prevent contamination of the other eye. Once the eyes have been flushed, the patient should be taken to a veterinarian or veterinary ophthalmologist for further evaluation.



DERMAL DECONTAMINATION


Exposure of the skin to toxic agents may cause local effects such as irritation and allergic dermatitis, or systemic effects if the toxin is absorbed. Although the epidermal layer is relatively impermeable to water-soluble substances, lipophilic agents or those containing surfactants are more readily absorbed. As with ocular exposure, rinsing or bathing the animal with mild dish soap is the standard method of decontamination for most dermal toxin exposures. However, care should be taken in cases of debilitated or intolerant patients, because bathing may exacerbate their preexisting conditions. Automatic dishwashing detergents and insecticidal shampoos should be avoided. The animal may need repeated baths to remove the toxin completely, and thorough rinsing should be performed to remove any remaining soap. During the bathing process, protective garments and rubber gloves should be worn to prevent human exposure to the toxic agent. After bathing, the animal should be thoroughly towel dried to prevent hypothermia.



GASTROINTESTINAL DECONTAMINATION


Gastrointestinal (GI) decontamination is used extensively in human and veterinary patients to limit exposure to ingested toxins and traditionally has consisted of gastric emptying followed by the administration of agents to hasten toxin elimination. Methods of gastric evacuation include emesis induction, gastric lavage, and whole bowel irrigation. Following gastric evacuation, activated charcoal may be administered to adsorb residual toxin. Cathartics frequently are used in conjunction with activated charcoal to shorten GI transit time and hasten elimination of ingested toxins.



Gastric Evacuation



Emesis


Emetics act either locally to cause gastric irritation or centrally at the chemoreceptor trigger zone to induce vomiting. A number of factors should be considered before inducing emesis including time of ingestion, agent ingested, and clinical status of the patient. Most emetics are effective only if given within 1 to 2 hours of ingestion, and induction of emesis does not eliminate the need for additional therapies, because emetics are successful at retrieving only a fraction of the gastric contents.1 Emesis is contraindicated with ingestion of petroleum distillates, acids, and alkalis because of the risk of aspiration and chemical burns to the esophagus. Emesis should not be induced in animals with altered mentation or seizures because of the possibility of aspiration, in animals that are already vomiting, and in animals with preexisting health conditions such as significant cardiac disease, epilepsy, or recent abdominal surgery.


Three-percent hydrogen peroxide administered orally is used frequently to induce vomiting in cats and dogs. Because of its availability and low cost, hydrogen peroxide is often recommended to pet owners for use at home to promote rapid removal of ingested toxins. The dosage is 1 to 2 ml/kg, administered with a syringe or turkey baster.2 Administration of hydrogen peroxide results in vomiting by triggering gastric irritation and is usually effective within minutes. The dose may be repeated once if emesis is not achieved. The use of more concentrated or higher doses of hydrogen peroxide is not advised, because it may lead to severe vomiting, mucosal irritation or ulceration, and salivation.


Apomorphine hydrochloride is a synthetic opiate that stimulates dopamine receptors in the chemoreceptor trigger zone to induce vomiting.3 Apomorphine is considered by many veterinarians to be the emetic of choice in dogs, but its use in cats is unreliable. The recommended dosage in dogs is 0.03 mg/kg IV and 0.04 mg/kg IM.2 Apomorphine may also be administered conjunctivally by crushing a portion of a tablet and dissolving it in a few drops of water. The conjunctival sac is then rinsed after emesis has occurred to prevent ongoing vomiting.2 Adverse effects associated with apomorphine include protracted vomiting, restlessness, excitement, and central nervous system (CNS) depression. Naloxone may be used to the reverse the central nervous system depression but does not inhibit the emetic effects.3


Another emetic that can be used is xylazine hydrochloride, an α2-adrenergic agonist. The recommended dosage for emesis in cats is 0.44 to 1.1 mg/kg IM or SC.4 Adverse effects include sedation, bradycardia, arrhythmias, and muscle tremors. Once emesis has been achieved, the effects of the drug can be reversed with yohimbine hydrochloride at a dosage of 0.25 to 0.5 mg/kg IM.4 Xylazine does not reliably produce emesis in dogs.


Syrup of ipecac is a nonprescription emetic that has been used in animals and is considered the emetic of choice in human patients. Ipecac is prepared from the roots of certain plants and contains two pharmacologically active compounds, the alkaloids emetine and cephaeline.5 Ipecac functions as a local gastric irritant and also stimulates the chemoreceptor trigger zone in the brain to induce vomiting. Four studies have been performed in dogs to determine the value of ipecac-induced emesis using various compounds as markers. When ipecac was administered within 30 minutes of dosing, recovery rates varied from 17.5% to 45.6%.6-9 Syrup of ipecac has been used at dosages of 1 to 2.2 ml/kg in dogs6 and 3.3 ml/kg diluted in an equal volume of water in cats.10 Reported adverse effects in humans associated with ipecac include diarrhea, drowsiness, prolonged vomiting, and cardiotoxicity at high dosages.11 Ipecac has been shown to critically delay the administration of activated charcoal in poisoned human patients, and it is therefore no longer routinely recommended in their treatment.11-13 Safer and more reliable emetics are available in veterinary patients.


The administration of liquid dishwashing detergents and table salt (sodium chloride) or mechanical stimulation of the pharynx to induce emesis are also not recommended. Excessive quantities of salt may result in hypernatremia and seizures. Attempts by pet owners to “gag” their pets are unreliable and may be dangerous to both the patient and the pet owner.

Related posts:

  1. Deteriorating Mental Status
  2. Hyperthermia and Fever
  3. Ventilator-Associated Lung Injury
  4. Allergic Airway Disease in Dogs and Cats and Feline Bronchopulmonary Disease

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Sep 10, 2016 | Posted by in SMALL ANIMAL | Comments Off on Approach to Poisoning and Drug Overdose

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