Keeping cats safe: introduction to toxicology. This article introduces our series. Key point

Transcription

1 Keeping cats safe: introduction to toxicology Toxicology is a broad and interesting area, which often provides challenging cases for veterinary nurses and technicians to care for. Cases of toxicity are not uncommon in general veterinary practice and the practice nurse or technician should understand the triage and initial management of such cases. Taking an accurate history from the owner is important along with an initial examination of the patient. Decontamination techniques vary according to the toxin and method of exposure and advice should always be taken from experts in toxicology such as the Veterinary Poisons Information Service. Common toxicities seen in cats include ethylene glycol, lilies, paracetamol, permethrin and cleaners/solvents. This article introduces our series of articles on toxicity as part of International Cat Care s Keep cats safe initiative launched this month. The following information provides a brief overview of general considerations regarding potential toxins veterinary nurses and technicians may encounter in practice, as well as an overview of the most common toxins reported to the Veterinary Poisons Information Service (VPIS: com/). It is not a detailed guide but aims to provide the basic knowledge that is necessary to triage these Key point Cats are vulnerable to toxins due to their lifestyle and habits as well as their metabolism. Laura George DipHECVN DipAVN (small animal) NCertA&CC RVN Laura has worked in both general and referral practice qualifying as a registered veterinary nurse in 2010 and gaining her RCVS Advanced Diploma in Veterinary Nursing in She currently works in the internal medicine department at Dick White Referrals and has a keen interest in feline medicine. She is currently studying for her VN Certificate in Emergency and Critical Care. cases and provide initial nursing care. In this edition we also feature our first article in the series on benzalkonium chloride, next month we consider foreign bodies in detail, with other articles on toxicities and causes of accidental injury to follow over the next year. Why are cats affected more than other species by specific toxins? Cats are notoriously curious creatures and although less likely to voluntarily ingest many toxic compounds, their drive to keep their coat clean often results in ingestion of toxins from their feet and fur. Our feline patients have different hepatic metabolic pathways to dogs and 1(7) feline focus 255

2 Tip If poisoning is suspected then contact a poisons centre for specific advice to ensure the correct treatment is given as this will vary according to the toxin. lack certain hepatic enzymes, this means they are unable to effectively metabolise some chemicals and therefore more susceptible to the effects of toxins than dogs. The diagnosis, and therefore treatment, for intoxication may be delayed in our feline patients compared to their canine counterparts. Cats tend to lead an outdoor lifestyle and so exposure to toxins may go unnoticed. This lifestyle also means that a full clinical history may not be available from the owner. GENERAL CONSIDERATIONS Triage Nurses and technicians are usually the first point of contact for owners when they call the veterinary practice for advice and it is sometimes necessary for them to triage the patient over the phone. Along with gathering basic information specific questions to ask the owner include: What signs did the owner first notice? Is there a known exposure to a toxin or have they given their cat any medication? What? How much? When? Route of contamination? Is the cat a hunter/scavenger? Key point To avoid self-contamination, wear appropriate protective clothing prior to any form of decontamination. Does the cat have access to any potentially toxic substances (eg, a garage or workshop, kitchen cupboard)? Specific questions regarding potential toxins: Are there any cut flowers in the house (eg, lilies)? Has the owner used any flea products on the cat or any in contact dogs (eg, permethrin)? Has the owner administered any medication to the cat (eg, paracetamol)? Does the owner use any cleaning products that the cat may have walked through (eg, containing benzalkonium chloride or phenolics, eg, patio cleaners)? Identification of an intoxicated patient may prove difficult due to the wide range of clinical signs that can occur and the variable onset times of these signs; each toxin will act differently in an individual patient. It is also important to remember that the owner may not connect exposure to a toxin with the signs the cat is showing. Additionally, many owners are not aware of substances that are toxic to cats. Any potential toxicology case should be examined as quickly as possible as time can be a huge factor in the available treatment options and outcome. If toxicity is suspected advice may be taken from a specialist or poisons expert such as the VPIS. 256 icatcare.org/felinefocus

3 george.qxp_FF Layout1 08/07/ :56 Page 3 Keeping cats safe Methods of decontamination Before beginning any form of decontamination, remember to protect yourself by wearing appropriate protective clothing to avoid self-contamination. Tip Emesis is not recommended for certain types of poisoning such as white spirit, detergents or petrol. Skin Place an Elizabethan collar to prevent grooming (Figure 1). Ocular Flush with sterile saline or sterile water. Advise the owners to flush the eye at home with water prior to presentation after checking with a veterinary surgeon. Use a urine dipstick to check the ph of the ocular surface. Lubricate the eye once decontaminated. Provide analgesia. Figure 1: An Elizabethen collar is essential to prevent further ingestion Wash with copious amounts of water and mild detergent but monitor for hypothermia. Clip long fur. If there is a grease/paint/glue contaminant, smother the cat in vegetable fat (eg, vegetable oil) or animal fat (eg, butter) and then bathe. Solvents are not recommended as they can cause further skin irritation and spread the contaminant further. If the contaminant is an acid or alkali wash skin thoroughly and test ph of skin using urine dipstick to ensure neutral state achieved. Consider analgesia assessing each case on an individual basis. Gastrointestinal Consider emesis: following advice from a poisons advisory service or specialist; only useful 2 3 h after witnessed ingestion; xylazine can be used in cats. Exceptions: Do not induce emesis if caustic or corrosive agents, Figure 2: Activated charcoal may be considered in some cases 1(7) feline focus 257

4 volatile solvents (eg, white spirit, petrol) or detergents have been ingested or in any patient with an altered mentation due to risk of aspiration. Adsorbents: for example, activated charcoal (Figure 2); bind to some toxins creating an unabsorbable substance; repeated doses may be required depending on the substance ingested. Exceptions: Adsorbents do not work with alcohols, corrosives or metals. They should not be used in patients with ileus or obstruction as can cause impaction, or in any patient with an unsecure airway/inability to swallow. Gastric lavage: may be useful if emesis is contraindicated; general anaesthetic and intubation is required to ensure a secure airway; the patient is positioned so that the head sits lower than the chest and a gastric tube is passed into the stomach. Water is repeatedly flushed into the stomach and withdrawn, until the fluid retrieved is clear; monitor for hypothermia (which is a risk if cold water is used). Other Intravenous lipid infusion this is a fairly recent concept in veterinary toxicology; the full mechanism of intravenous lipid infusion is not fully understood but it is thought that a lipid sink is created, trapping the lipophilic toxin and preventing it from acting at the target site; intravenous lipid infusion can be used in cases of permethrin toxicity. Key point Box 1: Most common toxicities According to the VPIS the most common enquiries concerning feline toxicities are as follows: 1 Lilium species 2 Agent unknown 3 Permethrin 4 Ethylene glycol 5 Benzalkonium chloride 6 Imidocloprid 7 Paracetamol 8 Disinfectant 9 White spirit/turpentine substitute 10 Moxidectin Management of systemic clinical signs Signs will depend on the toxin involved. Management includes: control of seizure activity; provision of intravenous fluid therapy if prolonged vomiting or diarrhoea or acute kidney injury; antiemetic treatment; oxygen therapy if signs of respiratory distress; warming or cooling measures; antidote (where available and most substances do not have a specific antidote) or antivenom therapy. The most common poisonings reported to the VPIS include lilies, permethrin, ethylene glycol and benzalkonium chloride. 258 icatcare.org/felinefocus

5 george.qxp_FF Layout1 08/07/ :56 Page 5 Keeping cats safe function; it kills insects by paralysing respiratory muscles.1 Permethrin spot-on treatments for dogs are still available to buy in supermarkets in the UK, as well as online with and without a veterinary prescription (Figure 4). Figure 3: The Lilium species are nephrotoxic to cats Common feline toxins In our series of articles we will cover in detail some of the most common toxicities seen in cats (Box 1) but here is a summary of some the most dangerous substances affecting cats. Lilium (Lilies) and Hemerocallis (day Lily) The Lilium species are true lilies and, among others, include the Asiatic lily, Tiger lily and Easter lily. It is important to note there are many unrelated plants that have lily in their common name and these may or may not cause an issue. Cats are particularly sensitive to permethrin and exposure usually occurs through either accidental application of a dog product on a cat, by grooming a treated dog, or simply by the cat brushing against a recently treated dog and then grooming. Ethylene glycol Ethylene glycol (EG) toxicity is one of the most common poisonings in cats1 as it is widely used as anti-freeze in coolant, screen wash and brake fluid; potentially just a teaspoon of undiluted solution can prove fatal to cats (Figure 5). It is the toxic metabolites created after ingestion of EG that cause problems including Lilies are common garden and house plants, they are also commonly included in flower bouquets due to their beautiful appearance (Figure 3), therefore, exposure can occur in the garden, a neighbour s garden or in the home. All parts of the plant are nephrotoxic and even just brushing up against the plant followed by grooming of the pollen off contaminated fur can cause clinical signs. Acute kidney injury occurs due to necrosis of the renal tubular cells. Permethrin Permethrin is a pyrethroid insecticide that acts as a neurotoxin, disrupting normal nerve cell Figure 4: Accidental exposure to dogs treated with permethrin-containing products can be fatal for cats 1(7) feline focus 259

6 glycolic acid and oxalic acid. Glycolic acid causes a severe metabolic acidosis within hours of ingestion whilst oxalic acid combines with calcium forming calcium oxalate crystals; these accumulate in blood vessels and renal tubules leading to acute kidney injury usually 1 3 days after ingestion. 2 Benzalkonium chloride Benzalkonium chloride is found in household products such as patio cleaners. This chemical causes oral ulceration, drooling, hyperthermia and is an emerging toxicity in cats. See Nicola Bates article on pages of this issue for more detail. Paracetamol Paracetamol (acetaminophen) is an analgesic with antipyretic properties commonly used by humans and can be found in tablet and liquid form. There is no indication for use of paracetamol in cats, however owners may unwittingly give a dose prior to seeking veterinary advice if they think their cat is in pain. Paracetamol is detoxified in the liver but cats lack the metabolic capacity to detoxify paracetamol safely and suffer toxicity. A toxic metabolite is also created causing severe oxidative stress to erythrocytes and hepatocytes. 2 Haemoglobin is Figure 5: Spilt antifreeze is a common source of ethylene glycol poisoning in cats converted to methaemoglobin (by oxidation) which in turn starves the body of oxygen as methaemoglobin has a reduced ability to bind oxygen for transport to tissues. In addition to this, metabolites cause Heinz body formation resulting in anaemia. Conclusions Rapid identification of intoxicated patients is crucial to enable a suitable treatment plan to be implemented, providing the best chance of a positive outcome. The various methods of decontamination can be considered but each case should be assessed individually and appropriate management decided upon considering the time frame to presentation and current clinical signs. Consultation with a veterinary poisons advice service such as the VPIS is advised if toxicity is suspected. References 1 Poppenga, R. Chapter 19, Toxicological emergencies. In: King, L and Boag, A (eds). BSAVA manual of canine and feline emergency and critical care, 2nd ed. Quedgeley: British Small Animal Veterinary Association, 2007, p Battaglia, A. Chapter 24, Toxicologic emergencies. In: Battaglia, A (ed). Small animal emergency and critical care for veterinary technicians, 2nd ed. Missouri: Saunders Elsevier, 2010, p 364. International Cat Care is teaming up with the Veterinary Poisons Information Service and Agria Pet Insurance to launch the Keeping Cats Safe campaign. There will be advice for owners, vets and veterinary nurses and technicians on common poisons and causes of accidents and how to prevent them. For more information see: icatcare.org/felinefocus