Management of common household toxins (Proceedings)
Key therapeutic points
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.Gastrointestinal decontamination is used 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 and gastric lavage. Following gastric evacuation, activated charcoal may be administered to adsorb residual toxin. Cathartics such as sorbitol are commonly used in conjunction with activated charcoal to shorten gastrointestinal transit time and hasten elimination of ingested toxins.
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. Emesis is contraindicated with ingestion of petroleum distillates, corrosive agents, or sharp objects because of the risk of aspiration and damage 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.
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, (not to exceed 3 tbsp even in large dogs), administered with a syringe or turkey baster. 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. 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 0.03-0.04 mg/kg intravenously or intramuscularly. Apomorphine may also be administered conjunctivally by crushing a portion of a tablet (approximately 0.25 mg/kg) and dissolving it in a few drops of water. The conjunctival sac is then rinsed after emesis has occurred to prevent ongoing vomiting. Adverse effects associated with apomorphine include protracted vomiting, restlessness, excitement, and central nervous system depression. Naloxone may be used to the reverse the central nervous system depression but does not inhibit the emetic effects.
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 administered intramuscularly or subcutaneously. 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 intramuscularly. Xylazine does not reliably produce emesis in dogs.
The administration of syrup of ipecac, liquid dishwashing detergents, and table salt (sodium chloride) are not recommended. Syrup of ipecac has a narrow therapeutic index in dogs and safer options are available. Excessive quantities of salt may result in hypernatremia and seizures. Attempts by pet owners to "gag" their pets are also unreliable and may be dangerous to both the patient and the pet owner.