Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.
Issue link: http://todaysveterinarypractice.epubxp.com/i/840151
75 JULY/AUGUST 2017 ■ TVPJOURNAL.COM PRACTICAL TOXICOLOGY to 90% is absorbed within 30 to 60 minutes. 3 Ethanol can also be absorbed dermally, especially if the skin is not intact. 2 Peak plasma levels occur 30 minutes to 2 hours after ingestion but can be delayed after larger doses or in the presence of food. 3 Although the time to reach peak plasma levels in these situations is increased, there is little difference in the amount absorbed. 4 Most ingested ethanol (95%) is metabolized in the liver by alcohol dehydrogenase to acetaldehyde and then to acetic acid. 3 About 5% to 10% is excreted unchanged in the breath, urine, sweat, and feces. 3,5,6 The elimination half-life is not meaningful because it is affected by saturation of the metabolizing enzymes. 5 At lower concentrations, the elimination rate may be nonlinear (first-order reaction), but it becomes linear (zero-order reaction) at high concentrations when all the available alcohol dehydrogenase is occupied. 5 In the average human adult, the blood level of ethanol decreases by 15 to 20 mg/dL per hour. 6 In animals, the onset of action is typically within 1 hour of exposure; most animals recover within 12 to 24 hours. 7–9 The amount of ethanol needed to cause intoxication varies depending on its concentration in the substance ingested ( Table 1 ). The published oral lethal dose in dogs is 5.5 to 7.9 g/kg of 100% ethanol. 11 One milliliter of ethanol is equal to 0.789 g. Kammerer et al reported a case of lethal ethanol toxicosis in a dog caused by the massive ingestion of rotten apples. 12 CLINICAL SIGNS The most common clinical signs of ethanol toxicosis are ataxia, lethargy, vomiting, and recumbency. In more severe cases, hypothermia, disorientation, vocalization, hypotension, tremors, tachycardia, acidosis, diarrhea, respiratory depression, coma, seizures, and death may occur. 4 Alcohol is directly irritating to the stomach and causes vomiting. High ethanol blood levels also stimulate emesis. The concern with vomiting during intoxication is that at high blood ethanol concentrations, the muscles that control the epiglottis become slow to react or even paralyzed. This increases the risk for aspiration. 13 Ethanol intoxication reduces peripheral oxygen delivery and metabolism and causes mitochondrial oxidative dysfunction, potentially resulting in shock or hypoxia in an acutely intoxicated patient. 14 Hypothermia may result from multiple mechanisms. Peripheral vasodilation, CNS depression, ethanol interference with the thermoregulator mechanism, and/or impaired behavioral responses to a cold environment all lead to a lowered body temperature. 3 MANAGEMENT • Induce emesis only in asymptomatic animals. Activated charcoal is not indicated because it binds poorly to ethanol. 15 In addition, because ethanol toxicosis is characterized by vomiting, the risk for charcoal aspiration is high. • In cases of dermal exposure, bathe the animal to reduce both dermal absorption and ingestion resulting from grooming behaviors. • Monitor heart rate and rhythm, blood pressure, and body temperature. Monitor for acidosis and calculate anion gap if possible. The normal anion gap for dogs and cats is 10 to 15 mEq/L. Values greater than 25 mEq/L are considered acidotic. 16 Although there TABLE 1 Ethanol Concentrations in Alcoholic Beverages and Other Household Products 5,10 SUBSTANCE PROOF a % ETHANOL BY VOLUME Light beer 5–7 2.5–3.5 Beer 8–12 4–6 Ale 10–16 5–8 Wine 20–40 10–20 Mouthwash 14–27 Amaretto 34–56 17–28 Aftershave 19–90 Schnapps 40–100 20–50 Coffee liqueurs 42–53 21–26.5 Brandy 70–80 35–40 Bourbon 80–90 40–45 Rum 80–82 40–41 Cognac 80–82 40–41 Vodka 80–82 40–41 Whiskey 80–90 40–45 Tequila 80–92 40–46 Gin 80–94 40–47 Cologne/perfume 50 Hand sanitizers 60–95 a For alcoholic beverages, the proof is double the percentage of alcohol present.