Monday, April 25, 2011

Common Household Hazards for Dogs and Cats- Part 2

Sharon Gwaltney-Brant DVM, PhD Jill A. Richardson, DVM

Continued - items to watch out for that could harm our pets!

6. Chocolate

There are a wide variety of chocolate and cocoa products to which pets may be exposed, including candies, cakes, cookies, brownies, and cocoa bean mulches. Not surprisingly, the incidence of accidental chocolate exposures in pets occurs around holidays, especially Easter, Halloween and Christmas. The active (toxic) agents in chocolate are methylxanthines, specifically theobromine andcaffeine. Methylxanthines stimulate the CNS, act on the kidney to stimulate diuresis, and increase the contractility of cardiac and skeletal muscle. The relative amounts of theobromine and caffeine will vary with the form of the chocolate (see table).

Cocoa beans may contain up to 255 mg theobromine per ounce of beans, although the exact amount will vary due to natural variation of the cocoa beans. The LD50's of theobromine and caffeine are 100-300 mg/kg, but severe and life threatening clinical signs may be seen at levels far below these doses. Based on NAPCC experience, mild

signs have been seen with theobromine levels of 20 mg/kg, severe signs have been seen at 40-50 mg/kg, and seizures have occurred at 60 mg/kg. Accordingly, less than 2 ounces of milk chocolate per kg is potentially lethal to dogs.

Clinical signs occur within 6-12 hours of ingestion. Initial signs include polydypsia, bloating, vomiting, diarrhea, and restlessness. Signs progress to hyperactivity, polyuria, ataxia, tremors, seizures, tachycardia, PVC's, tachypnea, cyanosis, hypertension, hyperthermia, and coma. Death is generally due to cardiac arrhythmias or respiratory failure. Hypokalemia may occur later in the course of the toxicosis. Because of the high fat content of many chocolate products, pancreatitis is a potential sequela.

Management of chocolate ingestion includes decontamination via emesis followed by gastric lavage. Because methylxanthines undergo enterohepatic recirculation, repeated doses of activated charcoal are usually of benefit in symptomatic animals (vomiting may need to be controlled with metaclopramide). Intravenous fluids at twice maintenance levels will help maintain diuresis and enhance urinary excretion. Because caffeine can be reabsorbed from the bladder, placement of a urinary catheter is recommended. Cardiac status should be monitored via EKG and arrhythmias treated as needed; propranolol reportedly delays renal excretion of methylxanthines, so metoprolol is the beta-blocker of choice. Seizures may be controlled with diazepam or a barbiturate. In severe cases, clinical signs may persist up to 72 hours.

7. Cigarettes

Tobacco products contain varying amounts of nicotine with cigarettes containing 13-30 mg and cigars containing 15-40 mg. Butts contain about 25% of the total nicotine content. The oral LD50 in dogs is 9.2 mg/kg.

Signs often develop quickly (usually within 15-45 minutes) and include excitation, tachypnea, salivation, emesis, and diarrhea. Muscle weakness, twitching, depression, tachycardia, shallow respiration, collapse, coma, and cardiac arrest can follow the period of excitation. Death occurs secondary to respiratory paralysis.

Table of nicotine content of common sources of nicotine.

8. Pennies

Ingestion of coins by pets, especially dogs, is not uncommon. Of the existing US coins currently in circulation, only pennies pose a significant toxicity hazard. Pennies minted since 1983 contain 99.2% zinc and 0.8% copper, making ingested pennies a rich source of zinc. Other potential sources of zinc include hardware such as screws, bolts, nuts, etc., all of which may contain varying amounts of zinc. In the stomach, gastric acids leach the zinc from its source, and the ionized zinc is readily absorbed into the circulation, where it causes intravascular hemolysis.

The most common clinical signs of penny ingestion are vomiting, depression, anorexia, hemoglobinuria, diarrhea, weakness, collapse and icterus. Secondarily, acute renal failure may develop. Clinical laboratory abnormalities will be suggestive of hemolysis (elevated bilirubin, hemoglobinemia, hemoglobinuria, regenerative anemia) and may also indicate the development of kidney failure. Serum zinc levels may be obtained—blood should be collected in all plastic syringes (no rubber grommets) and shipped in Royal blue top vaccutainers to minimize contamination with exogenous zinc. Radiography of the abdomen may reveal the presence of coins or other “hardware” within the stomach.

Treatment for recently ingested pennies would include induction of vomiting. Activated charcoal is not indicated, as it is of little benefit in binding metals. Removal of zinc-containing foreign bodies via endoscopy or gastrotomy/enterotomy may be required. Treatment for symptomatic animals should include blood replacement therapy as needed, intravenous fluids, and other supportive care. The use of chelators may not be necessary in cases where prompt removal of the zinc source is accomplished. If chelation therapy is instituted, careful monitoring of renal parameters is important for the duration of therapy.

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