Eric K. Dunayer,     Grand Cayman, Cayman Islands

Alcohol (Ethanol)

Ethanol, the type of alcohol found in beer, wine, and distilled spirits, is frequently ingested by dogs and occasionally ingested by cats. Dogs and cats may more readily consume alcoholic beverages if they contain sweet fruit juices or milk. Other products, such as mouthwashes and waterless hand sanitizers, may also contain ethanol. Because the growing yeast in rising bread produces ethanol and carbon dioxide, ingestion of raw bread dough can lead to both ethanol toxicosis and gastric distention.

Ethanol content greatly varies with the type of beverage: generally, it is 4% to 7% in beer, about 12% in wine, and from 40% to about 100% in distilled spirits. The reported proof of an alcoholic beverage is twice the percentage of ethanol (e.g., “80 proof” signifies 40% ethanol). In dogs, the minimum lethal ingested dose for ethanol is about 5500 mg/kg, but significant signs of toxicosis can develop with smaller exposures.

Following ethanol ingestion, onset of signs is rapid; initial signs appear within 15 to 30 minutes. Ataxia is usually observed first. Following ataxia, signs can rapidly progress to vomiting, central nervous system (CNS) depression, hypothermia, hypoglycemia, and coma. Ethanol is metabolized via alcohol dehydrogenase and aldehyde dehydrogenase. Both enzymes cause the release of numerous hydrogen ions, so significant metabolic acidosis can develop. Death is usually associated with CNS and respiratory depression, metabolic acidosis, and/or aspiration pneumonia.

Treatment is symptomatic and supportive. Emesis can be attempted but should not be used if signs have already appeared. Activated charcoal adsorbs small molecules, such as ethanol molecules, poorly and is not considered useful. Additionally, because of the high incidence of vomiting, its use can increase the risk of aspiration pneumonia. Intravenous fluids containing added dextrose and B vitamins should be started to correct any dehydration and hypoglycemia. Blood gases should be monitored, and significant acidosis should be corrected with sodium bicarbonate. If respiration is severely depressed, assisted ventilation through a cuffed endotracheal tube should be initiated (see Chapter 11). Yohimbine at 0.1 to 0.2 mg/kg IV has been reported to reverse some of the CNS depression. However, the effect is short-lived; the yohimbine may need to be repeated frequently. Dialysis (either hemodialysis or peritoneal dialysis) has been shown to rapidly clear ethanol and may be considered in the case of potentially lethal ingestions. Prognosis is good with small ingestions but can be guarded, especially in patients who are comatose or severely acidotic.

When a dog ingests yeasted bread dough, the warmth and low oxygen tension of the stomach environment augment the yeast’s production of ethanol and carbon dioxide. In addition to ethanol toxicosis, expanding dough mass can lead to gastric distention with poor venous return and dyspnea secondary to diaphragmatic impingement. Therapy addresses both problems. In asymptomatic dogs, emesis can be attempted, but it often has little effect due to the weight and consistency of the dough mass. Gastric lavage with cold water can be used to chill or kill the yeast and reduce ethanol production. In severe cases, gastrotomy may be necessary to remove the dough mass.

Allium Plants Such as Onions and Garlic

Onions, garlic, scallions, and leeks belong to the genus Allium. The disulfides and thiosulfates in Allium spp. are metabolized to compounds that can cause oxidative damage to erythrocytes, with the resultant production of Heinz bodies and methemoglobinemia. Cats are particularly sensitive to the toxic effects of Allium spp. because feline hemoglobin contains many exposed sulfhydryl groups and because methemoglobin reductase is relatively inactive in cats. Allium spp. are toxic whether fresh, dried, or cooked and may be ingredients in other foods.

In dogs the minimum toxic dose of ingested onions is considered to be more than 0.5% body weight (>5 g/kg); garlic is more toxic than onions. Like cats, certain breeds of dogs such as the Japanese breeds (e.g., Akita, Shiba Inu) or those with hereditary red-blood-cell (RBC) enzyme deficiencies may be more sensitive to Allium spp. toxicosis. Because the damage to the RBCs is cumulative, the dose can be ingested over a period of days to weeks. Hours or days after ingestion, Heinz bodies appear, followed by hemolysis. The patient may show weakness (secondary to anemia), pale mucous membranes, and hemoglobinuria (often reported by the owner as bloody urine). With methemoglobinemia the mucous membranes, the blood, and possibly the urine become brownish due to methemoglobinuria from hemolyzed RBC. The patient may show variable degrees of dyspnea.

With recent ingestions, emesis may be useful; administration of activated charcoal should also be considered in significant ingestions. The dog or cat should be monitored for several days for the appearance of hemolysis or declining hematocrit. In severely anemic dogs or cats, RBC transfusions may be needed as support until increased hematopoieses replaces the lost RBCs. Patients with severe methemoglobinemia may need oxygen supplementation and blood transfusion. In cats, methylene blue is contraindicated as a treatment for methemoglobinemia. With control of signs, prognosis is generally good.

Hops

Hops, the female cones harvested from Humulus spp., are used in the brewing of beer and also are present in some herbal preparations. Canine exposure generally occurs when dogs ingest spent hops that have been discarded after being used for home production of beer. Canine ingestion of herbal products has also been associated with signs of toxicity. The toxic principle and doses are unknown.

Following ingestion, onset of signs is rapid; death can occur within 6 hours. The dogs develop malignant hyperthermia; body temperatures commonly exceed 42.2° C (108° F). Vomiting, tachypnea, and tachycardia are also common.

Prior to onset of signs, induction of emesis should be attempted. In symptomatic dogs, gastric lavage may be effective. Activated charcoal can be given; enemas may accelerate gastrointestinal passage. Intravenous fluids and thermoregulation should be instituted. Dantrolene, a peripheral muscle relaxant, has been used to treat malignant hyperthermia. Doses of either 2 to 3 mg/kg IV or 3.5 mg/kg PO q8-12h (canine dose) should be started immediately. Anecdotal reports have indicated that cyproheptadine at 1.1 mg/kg PO or rectally PRN may help control hyperthermia until dantrolene can be obtained. Prognosis is guarded, especially once hyperthermia has developed.

Macadamia Nuts

Macadamia nuts are harvested from Macadamia integrifolia or M. tetraphylla trees. They are consumed as nuts (sometimes chocolate-covered) or included in baked goods such as cookies. The toxic principle has not been identified. Dogs that ingest more than 2 g/kg of macadamia nuts may develop weakness and muscle tremors. Also, because the nuts are high in fat, pancreatitis is a possible sequela. Other nuts, such as almonds and walnuts, are not considered toxic in dogs.

After a dog ingests macadamia nuts, signs of toxicity usually develop within 12 hours. Vomiting is common. Weakness (especially in the hind limbs), tremors, and hyperthermia are frequently seen. Signs are generally mild and, in most cases, can be managed at home.

In cases of heavy ingestion of macadamia nuts, emesis and activated charcoal should be considered. Severe tremors can be controlled with methocarbamol (55 to 220 mg/kg slow IV PRN). Intravenous fluids may be useful in controlling hyperthermia. Prognosis is generally good.