Today's Veterinary Practice

NOV-DEC 2017

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.

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20 PRACTICAL TOXICOLOGY PEER REVIEWED Although long-term ingestion by livestock causes reproductive losses and concentrated essential oils and extracts can cause central nervous system signs, such as seizures, the amount of essential oil a pet is likely to ingest is minimal. The most common clinical signs of ingestion include vomiting, anorexia, abdominal pain, and depression. Some trees have sharp needles, which can cause mechanical irritation and trauma to the mucosa of the alimentary tract. Signs are generally mild and self-limiting. Typical signs of a foreign body (abdominal distension, persistent vomiting) may occur. Most cases are managed at home by withholding food and water for several hours. For severe or protracted vomiting, antiemetics may be indicated. Gastrointestinal protectants (sucralfate slurries for mucosal irritation) may be helpful for large ingestions or protracted vomiting. If dehydration is present, replace fluids and correct any electrolyte abnormalities. If a foreign-body obstruction develops, surgical or endoscopic removal of the plant material may be required. In most cases, prognosis is good. HOLLY (ILEX AQUIFOLIUM) Holly has shiny green leaves with sharp spines and bright red drupes (generally referred to as berries). It is used in wreaths and other decorative trimming. Holly is also planted in gardens. The sharp leaves can cause mechanical damage. Several potentially toxic substances are found in holly, including methylxanthines and cyanogens, as well as saponins. Significant intoxication usually involves ingestion of concentrated extracts. In plant ingestions, the primary toxic effect in dogs and cats is gastrointestinal irritation from the saponins. Some animals may ingest enough leaf material to cause a foreign-body obstruction, but this is rare. Typical clinical signs include hypersalivation, vomiting, diarrhea, head shaking, lip smacking, and potential mechanical injury resulting in mild oral ulceration or laceration. Most holly ingestions can be managed at home. If large quantities of plant material were ingested, bulk up the diet (eg, with bread). Emesis may be attempted for significant ingestions. Mild vomiting can be treated by withholding food and water. Prolonged or significant vomiting can be treated with antiemetics. If oral discomfort is present (head shaking, lip smacking), rinse the mouth with water and administer sucralfate slurries. Evaluate and treat as needed for a foreign-body obstruction if vomiting is protracted. Prognosis is good. Most cases resolve in a few hours. KALANCHOE (KALANCHOE BLOSSFELDIANA) Kalanchoe has only recently been associated with Christmas. These plants can be forced to bloom during winter, and red kalanchoes are popular Christmas gifts. Because this is a year-round houseplant, ingestions can occur at any time. Dwarf varieties are used as houseplants. Kalanchoe is a cardiotoxic plant; other cardiotoxic agents are listed in Box 1 . The toxic principle is bufadienolides, which are found in all parts of the plant, but are concentrated in the flowers. Bufadienolides inhibit the Na-K adenosine triphosphatase in the myocardial cell membrane. This causes an increase in intracellular sodium and a decrease in intracellular potassium. The net result is a reduction in the normal membrane resting potential, which reduces the myocardium's ability to act as pacemaker. The loss of the normal myocardial electrical function can result in asystole. Hyperkalemia is seen in severe toxicosis. Dogs are reported to be especially sensitive to the cardiotoxic effects of bufadienolides. However, most of the potted dwarf varieties of kalanchoe cause only mild gastrointestinal effects; cardiovascular signs are uncommon. The most common clinical signs in dogs and cats are vomiting, depression, lethargy, and diarrhea. Other reported signs include weakness, dyspnea, anorexia, tachycardia, and vocalization. Neurologic BOX 1. Diagnostic Differentials for Kalanchoe Ingestion Ingestion of any of the following may cause cardiotoxic clinical signs. • Digoxin • Digitoxin • Lily of the valley (Convallaria majalis) • Oleander (Nerium oleander) • Foxglove (Digitalis purpurea) • Cane toad (Rhinella marina; formerly Bufo marinus) secretions • Fireflies (Photinus species)

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