Numerous potential toxicological hazards are present in and around the home, including in house and garden plants, fungi, household chemicals, venomous animals, pesticides and garden chemicals, and drugs.

When presented with an animal with a potentially toxic exposure, appropriate and prompt treatment – including stabilisation and decontamination – is essential.

Assessment and history taking

Stabilisation of a critically ill animal is priority, and should focus on the respiratory, neurological and cardiovascular systems. Thereafter, it is important to establish what the animal may have been exposed to and information sought on the circumstances of exposure, time since exposure occurred, and any clinical signs prior to presentation.

Estimation of the quantity involved may require examination of the packaging or material – if the owner has brought it in – counting the remaining tablets, measuring the volume left in a bottle or looking through vomitus for evidence.

After the history and exposure details have been established, the decision on the appropriateness of decontamination can be made.

Circumstances of poisoning are variable, but may involve young animals exploring their environment, boredom or dietary indiscretion. In some cases, owners may give medicines incorrectly in the wrong dose, to the wrong animal or give human medication believing it will make their pet better – for example, giving paracetamol to a cat with apparent pain.

Pets may be splashed or exposed to spilled liquids or gain access to a product while it is in use. Dogs will root through shopping bags and handbags, and eat whatever they find.

With free-roaming cats, it may be difficult to determine what they may have been exposed to while away from home.

Decontamination

Decontamination is commonly used in potentially poisoned animals in an attempt to remove the substance, reduce absorption and decrease the severity of poisoning.

The choice of method will depend on the substance ingested, time since ingestion, clinical condition of the animal, the availability of any drugs to be used, the management plan and experience of staff.

Dermal decontamination

In most cases, decontamination of skin and fur can be achieved with warm water and a detergent (for example, shampoo/washing-up liquid).

Care is required with small patients due to the risk of hypothermia if cold water is used. If the substance is oily, greasy or not very water soluble, a degreaser may be required for effective removal.

Other options for removal of sticky material – such as mouse glue traps or fly paper – are vegetable oil, margarine or butter (Bough, 2003).

Solvents, such as alcohol or white spirit, are not recommended for dermal decontamination because they are irritant and can spread the contaminant further. For heavy contamination, it may be more practical to clip the affected area.

With some substances, care may be needed to protect staff – aprons, gloves and goggles should be available (Bough, 2003).

If a strong-smelling solvent or respiratory irritant is involved, it is important to ensure the area is well ventilated and it may be more practical to decontaminate outside.

Corrosive substances, such as acids and particularly strong alkalis – for example, sodium hydroxide (caustic soda) or potassium hydroxide (which are found in oven cleaners and some drain cleaners) – can cause serious tissue damage. No attempt should be made to neutralise these compounds as this reaction generates heat, which can cause further tissue damage.

Dermal exposure to strong alkalis requires very thorough and repeated decontamination because they can cause deep penetrating burns. Rinsing the contaminated area will only remove surface alkali.

The pH of the skin should be checked about 15 minutes after the initial decontamination (use litmus paper or a urine dipstick) to allow residual alkali to diffuse up from the deeper regions of the dermis. If the pH of the affected area remains above normal (more than eight) irrigation should be repeated.

Ocular decontamination

Ocular exposure is uncommon, but can lead to severe corneal damage, depending on the chemical involved.

Alkalis can cause particularly severe damage, with deep corneal ulceration and damage to internal structures.

Ocular exposure should be managed promptly. Sedation or anaesthesia may be required to allow adequate decontamination.

Particulate matter should be removed with cotton wool buds or forceps, and contaminated eyes should be flushed with copious volumes of 0.9% saline or water for a minimum of 10 minutes to 15 minutes. If only one eye is affected, care should be taken to prevent contamination of the other during irrigation.

If the substance is alkaline it is important to check the pH of the eye and to repeat the irrigation until a pH less than 7.5 is maintained.

Gut decontamination

Gastrointestinal decontamination is the most common method of decontamination used; it generally includes partial removal of stomach contents and administration of an adsorbent.

In most cases, emptying the stomach is usually only worthwhile if ingestion was recent – within one hour to two hours. After this time, the ingested material will have been absorbed or passed beyond the stomach. The physical form of the substance ingested (large tablets versus a solution, for example) will also influence the time ingested material remains available in the stomach.

Emesis

Emesis is the most common method of emptying the stomach, but efficacy declines the longer the time between ingestion and emesis. In addition, a number of contraindications exist to the use of emetics (Lee, 2013), depending on the clinical condition of the animal and the substance ingested (Panel 1).

• is very drowsy or unconscious
• is fitting
• has reduced cough reflex
• has already vomited, since it probably has little benefit and excess vomiting may lead to dehydration

Emesis should not be induced if the substance ingested:

• is likely to cause rapid onset of drowsiness or seizures
• contains paraffin, petroleum products, or other oily or volatile organic products, which could be aspirated into the lungs
• contains detergent compounds, which could be aspirated into the lungs
• is a strong acid or alkali, which could cause further damage to the oesophagus, if regurgitated
• is likely to have passed beyond the stomach and/or been absorbed
• is of low toxicity or the dose ingested is unlikely to result in significant clinical signs

Obsolete and dangerous emetics:

• Salt (sodium chloride) should never be used. It can cause serious or fatal hypernatraemia in animals when used as an emetic (Pouzot et al, 2007; De Groot et al, 2008).
• Mustard is unreliable as an emetic and not recommended (Beasley, 1999).
• Copper sulphate is a potent emetic, but is not recommended because of copper toxicosis risks.

Apomorphine is the emetic of choice in dogs – and the only licensed drug for the induction of emesis in dogs. Vomiting typically occurs within 1 to 20 minutes of administration (depending on route of administration).

Induction of emesis in cats can be challenging. Alpha-2 adrenergic agonists – for example, xylazine, medetomidine and dexmedetomidine – are used off-label as emetics in cats, as vomiting is an adverse (and, therefore, unreliable) effect of these drugs (Flaherty, 2013; Thawley and Drobatz, 2015).

Sedation is common, but can be reversed with atipamezole. Sodium carbonate (washing soda) is sometimes used in dogs, but vomiting is more likely to occur with apomorphine (Yam et al, 2016). Where apomorphine is unavailable or not licensed, hydrogen peroxide 3% is sometimes used, but it can cause local tissue damage with haematemesis and gastritis (Niedzwecki et al, 2017; Obr et al, 2017).

A number of substances have been used as emetics in the past, but they are obsolete and potentially dangerous (Panel 1).

A common perception exists that emesis empties the stomach completely, but little evidence is available for this, and the quantity returned is generally 40% to 60% of the stomach contents (Beasley, 1999).

In a review of 147 dogs given hydrogen peroxide or apomorphine as an emetic, the mean recovery of ingested material was estimated (by visual inspection of the vomitus and the amount known to have been ingested) as 48% for hydrogen peroxide and 52% for apomorphine (Khan et al, 2012).

It is also worth noting, although emetics were once used routinely in the management of poisoning in human medicine, this is no longer the case.

The American Academy of Clinical Toxicology (AACT) and European Association of Poison Centres and Clinical Toxicologists (EAPCCT) position statement on the use of syrup of ipecacuanha (ipecac) as an emetic in human poisoning concluded limited good quality data exists; no convincing evidence is available from clinical studies that ipecac “improves the outcome of poisoned patients” (Höjer et al, 2013). This is also the case in veterinary medicine; emetics produce vomiting, but no evidence suggests vomiting improves the clinical outcome in poisoned animals.

Gastric lavage

Gastric lavage is generally used in potentially severe cases of poisoning, particularly where there is rapid onset of signs and emesis is contraindicated.

Adsorbents

Activated charcoal is an adsorbent commonly used in the management of both human and veterinary poisoning. It is a finely powdered material with a huge surface area (approximately 1,000m2/g), capable of binding a variety of drugs and chemicals.

The charcoal is given orally and passes through the gut, taking the adsorbed substance with it and, therefore, reducing or preventing systemic toxicity of the ingested substance.

The use of activated charcoal in a particular case will depend on the substance ingested (Panel 2).

• Petroleum distillates (white spirit, petrol and kerosene).
• Alcohols (ethanol, isopropanol and methanol).
• Glycols (ethylene glycol).
• Acids.
• Alkalis (sodium hydroxide and potassium hydroxide).
• Metals (iron, lead and mercury).
• Essential oils (tea tree oil).

Single-dose activated charcoal:

• Must be given as soon as possible after ingestion when the substance ingested is still in the stomach.
• To be effective in reducing absorption, it must be in direct contact with the ingested substance.

Repeat doses activated charcoal:.

• Not used routinely.
• Acts by interrupting enterohepatic recycling of substance (for example, theobromine in chocolate) and/or by promoting drug exsorption from the systemic circulation into the gut lumen.
• May be useful for drugs formulated for sustained or modified release.

Other considerations:

• Timing needs to be considered when oral treatments are to be used, as charcoal may also adsorb these and reduce their efficacy.
• Generally, a period of at least two hours should be allowed between administration of charcoal and oral medication.

It is generally well tolerated, but it will stain faeces black, and, if given to a sedated animal without airway protection, can result in aspiration into the lungs, with subsequent pneumonitis.

Laboratory analyses

As part of the initial assessment and monitoring, laboratory analyses may be required. Depending on the substance involved this may include haematology, electrolytes, urinalysis, prothrombin time, PCV, blood glucose, renal function and liver enzymes.

Where poisoning is suspected, or laboratory confirmation is required, samples for possible analysis should be collected early. These can be sent for analysis immediately or stored for possible laboratory confirmation later, if required. Delayed collection of biological samples may lead to negative results due to elimination of the poison. Samples can include blood, vomitus, urine, the suspect material involved or postmortem samples. Specialist advice should be sought for individual cases.

Further management

After decontamination, further management will depend on the substance taken, but, in many cases, supportive care is sufficient.

Where the substance is unfamiliar, a poison information service can provide information on clinical signs, specific treatments and prognosis.

Fluid therapy is important to main cellular perfusion, correct dehydration and electrolyte imbalance, to protect the kidneys after ingestion of nephrotoxic substances (for example, grapes, raisins, sultanas and lilies), and to correct hypotension. Forced diuresis (fluid overload and a diuretic) is not recommended as this may lead to fluid overload and electrolyte imbalance, and is of questionable efficacy.

Blood products may be required for animals with toxin-induced anaemia or blood loss from anticoagulant rodenticide exposure.

A number of drugs are used for poison management – including drugs readily available in most veterinary practices, such as gastroprotectants, antiemetics, analgesics, sedatives, anticonvulsants and anaesthetics.

Methocarbamol is a skeletal muscle relaxant and can be useful in the management of poisoning with substances that cause tremors, such as permethrin, metaldehyde and tremorgenic mycotoxins. Naloxone is the specific reversal agent for opiates and opioids. Hepatoprotectants, such as acetylcysteine and S-adenosylmethionine (SAMe), are used for paracetamol and xylitol toxicosis.

Atropine is used in the management of hypersalivation, and as an antidote for carbamate and organophosphate insecticide poisoning, and some fungi (for example, those containing muscarine). Vitamin K is the specific antidote for anticoagulant rodenticide toxicosis, which are very commonly ingested by dogs. Snake bites should be managed with the appropriate antivenom.

IV lipid emulsion should also be available. This is used in the management of poisoning from cardiotoxic drugs or lipophilic compounds, such as permethrin, ivermectin, tremorgenic mycotoxins and numerous other compounds (Fernandez et al, 2011; Gwaltney-Brant and Meadows, 2012; Kaplan and Whelan, 2012).

It is worth stocking parenteral lipids as they are inexpensive, easy to administer and can be used in the treatment of poisoning with a variety of drugs and chemicals.

If rarely used drugs are not available in practice it is important to know how and where to obtain them in an emergency.

Conclusions

Initial management of a poisoned patient will involve stabilisation (if necessary), risk assessment to determine the most appropriate approach to decontamination and further treatment.

A poisons information centre can provide specific advice, if required.