Your step-by-step guide to treat a poisoned pet

Shutterstock/bsdAnimals are often indiscriminate eaters, and accidental poisonings are a relatively common occurrence. Treating intoxicated patients is largely supportive and symptomatic, but some general principles apply. In an effort to help you keep things simple yet still provide high-quality patient care, I have outlined a step-by-step approach to treating a poisoned patient. Follow this guide to know what to do when a poisoned pet comes through your clinic's doors.

Extracorporeal therapies

Step-by-step guidance to performing extracorporeal therapies is beyond the scope of this article, but you should be aware of them. These therapies (e.g. intermittent hemodialysis, continuous renal replacement therapy, charcoal hemoperfusion) may be helpful in treating patients that have ingested certain medications or toxicants.

Acetaminophen

Acetylsalicylic acid

Aminoglycosides

Amphetamines

Atenolol

Azathioprine

Barbiturates

Chloramphenicol

Cyclophosphamide

Digoxin

Diltiazem

Ethylene glycol

Ibuprofen

Monoamine oxidase inhibitors

Penicillin

Tricyclics

1. Assess the patient

At presentation, all patients should be assessed for stability with particular focus on the respiratory, cardiovascular, neurologic and urinary systems.

• Respiratory signs include tachypnea, dyspnea, an orthopneic posture (extended head and neck, abducted elbows), audible upper airway noises or cyanosis.

• Cardiovascular signs include hyperemia, pale or white mucous membranes, tachycardia or severe bradycardia, dysrhythmia, or poor or variable pulse quality.

• Neurologic signs include altered mentation, loss of consciousness, ataxia, altered or absent cranial nerve reflexes or postural or gait abnormalities.

• Urinary signs include bladder obstruction.

If your assessment reveals compromise in any of these major body systems, stabilize the patient as necessary.

2. Talk to the owners

Once the patient is stable, talk to the owners. First, obtain the patient's history and find out about any medications the patient receives. Then if the toxicant is unknown, ask the owners if the patient is allowed outside and what cleaning products and medications or illicit drugs are in the home that the patient might have had access to.

If the toxicant is known, ask when the patient was exposed. If the patient is exhibiting clinical signs, ask when they began. Also, try to find out what the maximum amount of toxicant the animal might have been exposed to by asking, “Do you remember if the pill bottle was full or almost empty?” or “Had you just opened the bottle?”

When possible, I encourage owners to bring the medication bottle or product container to the hospital so that we can get detailed product information.

3. Initiate decontamination

Once the patient is stable, if possible, perform decontamination to inhibit or minimize further systemic absorption of the toxicant. The decontamination method you perform depends on the toxicant, the type of exposure, and whether the patient is symptomatic.

Flush the eyes: For ocular decontamination, flush the eyes for 20 minutes with either physiologic saline solution or tepid tap water. Ideally, owners would perform this flush at home before presentation. After flushing, place an Elizabethan collar on the patient to keep it from pawing at its eyes.

Bathe the patient: For dermal decontamination, gently wash the patient's skin with tepid water and liquid dish soap. Be sure to wear gloves while bathing the patient to prevent skin exposure to the toxic agent. Closely monitor the patient's temperature as hypothermia may develop during the bathing process.

Cats suffering from pyrethrin toxicosis may have moderate or severe muscle tremors and can be given methocarbamol (50 mg/kg intramuscularly) just before bathing.

Induce emesis: If the toxicant was ingested less than two hours previously, the patient is asymptomatic, and there are no contraindications, induce emesis.

For dogs: Administer 3% hydrogen peroxide (1 to 5 ml/kg orally [maximum dose = 50 ml]) or apomorphine (0.03 mg/kg intravenously or place a tablet in the subconjunctival sac). A second dose of hydrogen peroxide can be given if the dog has not vomited within 10 to 15 minutes. With apomorphine, dogs will generally vomit within several minutes. If the dog becomes sedate after apomorphine administration, reverse it by administering naloxone (0.02 mg/kg intramuscularly or intravenously). Naloxone will not affect the emetic action of apomorphine.

For cats: Emesis occurs less reliably in cats than in dogs. The mainstay emetic of choice in cats is xylazine (0.44 mg/kg intramuscularly). However, a recent retrospective study conducted at our facility found that dexmedetomidine is an effective alternative to xylazine and may be a superior agent for inducing emesis.1 Further research is needed to identify the most effective route for and dose of dexmedetomidine, but we typically administer 7 µg/kg intramuscularly.

When emesis is successfully induced with xylazine or dexmedetomidine, it typically occurs within 15 minutes. Both of these drugs may cause sedation and peripheral vasoconstriction, so a reversal drug should be given after emesis is induced or within 15 minutes of the drug being given if emesis is not successfully induced. To reverse xylazine, administer yohimbine (0.1 mg/kg intramuscularly or intravenously). To reverse dexmedetomidine, give atipamezole (50 µg/kg or a volume equal on a per ml basis to the amount of dexmedetomidine administered, intramuscularly or intravenously).

Syrup of ipecac, table salt and liquid dish soap are no longer recommended as emetic agents.

Contraindications: Emesis is contraindicated following the ingestion of caustic substances, which may further injure the esophagus during vomiting, or the ingestion of hydrocarbon liquids, which may be easily aspirated into the airway. Patient anatomy and comorbid disease processes should also be taken into consideration. Emesis is not recommended for patients that are predisposed to aspiration pneumonia (e.g. patients with brachycephalic obstructive airway syndrome, upper airway or laryngeal dysfunction, neuromuscular disease, megaesophagus).

4. Perform gastric lavage

After an unsuccessful emesis attempt or when emesis is contraindicated, gastric lavage can be considered if the toxicant was recently ingested. Gastric lavage can be considered in symptomatic patients, for example if a patients is too sedate to induce emesis safely. Gastric lavage should not be performed after ingestion of caustic substances or hydrocarbons.

To begin, place the patient under general anesthesia and intubate, so that the patient's airway is protected. Place a roll of white tape in the patient's mouth to help keep it open during the procedure. Measure an orogastric tube from the patient's mouth to just beyond its last rib. Lubricate the tube, feed it through the hole in the tape roll, and gently advance it into the stomach to the previously measured length.

Slowly infuse warm water (60 ml/kg) into the stomach while palpating the stomach to monitor for gastric overdistention. The fluid is recovered by gravity.

The cycle should be repeated until the retrieved fluid is relatively clear. You can save the recovered fluid for toxicology testing.

Contraindications and complications: Gastric lavage is contraindicated if the patient has ingested caustic agents or hydrocarbons. Complications of gastric lavage can include aspiration pneumonia and injury to the mouth, esophagus or stomach during placement of the tube.

Perform endoscopy or surgery: In some cases, endoscopy or surgery is required for decontamination (e.g. the ingestion of corrosive caustic substances, transdermal patches or metals like zinc, which are not removable through emesis or gastric lavage). Gorilla glue is an adhesive that rapidly expands within the stomach and often forms a cast of the inside of the stomach, obstructing gastric outflow. When that occurs, gastrotomy is typically required for removal.

Table 1: Select toxicants for which intravenous lipid emulsion might be considered

Baclofen

Bupivacaine

Carprofen

Clomipramine

Cyclosporine

Diazepam

Digoxin

Ditiazem

Itraconazole

Ivermectin

Lidocaine

Moxidectin

Naproxen

Permethrin

Trazodone

Vinblastine

5. Administer activated charcoal

After decontamination, if patients are asymptomatic and have no contraindications, activated charcoal (1 to 2 g/kg orally) may be administered to help diminish systemic absorption of certain ingested toxicants. Activated charcoal should be avoided in patients that are experiencing clinical signs such as seizures or excessive sedation that might predispose the patient to aspiration.

For patients that have ingested toxicants that undergo enterohepatic recirculation (bromethalin, for example) giving multiple doses (every six to eight hours) may be warranted. However, only administer activated charcoal with sorbitol (a cathartic) on the first dose. Activated charcoal without a cathartic should be given for the second and subsequent doses because of the potential for hypernatremia.

Many dogs will eat activated charcoal if it is mixed into canned food-and some indiscriminate eaters will eat it by itself. For other patients, administer it carefully by syringe.

For patients undergoing gastric lavage, activated charcoal can be administered through the orogastric tube before tube removal.

Contraindications: Activated charcoal administration is contraindicated in patients that will undergo gastrointestinal surgery or with gastrointestinal perforation because of the risk of leakage. Other contraindications include hypernatremia, ileus and comorbidities that increase the risk for aspiration pneumonia. Activated charcoal does not adsorb reliably to alcohol, xylitol or heavy metals, so its administration is not recommended in patients ingesting these toxicants.

6. Start fluid therapy

If patients have ingested toxicants that undergo renal elimination, start fluid therapy for forced diuresis. For healthy patients, I recommend an intravenous (IV) fluid rate of 3 to 5 ml/kg using an isotonic crystalloid.

Considerations: Administer fluids judiciously in patients with preexisting cardiovascular or pulmonary disease to avoid volume overload.

7. Initiate ILE therapy

If patients have ingested lipophilic toxicants (Table 1), intravenous lipid emulsion (ILE) therapy could be considered initially as a bolus (1.5 ml/kg) followed by a constant rate infusion of 0.25 ml/kg/min for 30 to 60 minutes. Additional boluses (1.5 ml/kg) may be administered every four to six hours for the first 24 hours as needed, provided the patient's serum has not become significantly lipemic.

Log on to the lipophilicity of drugs

The lipophilicity of a drug can be estimated somewhat by its log P value (P representing the parturition coefficient of the drug). If the log P is greater than 1, the drug is lipophilic, and the higher the log P value, the more lipophilic. You can often find this information online via a browser search such as “ibuprofen log P.”

Complications: Complications of ILE therapy are thought to be uncommon but may include microbial contamination, leading to thrombophlebitis, fever, hypersensitivity reaction to the emulsion, hyperlipidemia, hypertriglyceridemia or pancreatitis. ILE therapy should be used cautiously in patients that are septic or suffering from acute respiratory distress syndrome as administration has been associated with increased venous admixture and decreased partial pressure of oxygen in critically ill people.

8. Monitor the patient

Monitor patients for clinical signs of toxicosis and treat accordingly.

Reference

1. Thawley VJ, Drobatz KJ. Assessment of dexmedetomidine and other agents for emesis induction in cats: 43 cases (2009-2014). J Am Vet Met Assoc 2015;247(12):1415-1418.