SA Toxicology Flashcards
What are some routes of intoxication?
Oral
Cutaneous/topical
Inhalation
Injection
Ocular
What are the first steps to take when an owner calls suggesting there has been an intoxication?
- Take relevant history (What? When? Are there clinical signs?)
- Prevent further intoxication
- Ask them to bring a sample of the substance if available
What can you recommend owners to do if their pet has had a topical contamination?
Recommend washing:
- Water only, watch temperature
- Gloves for owner
- Do not want the toxin to become systemic through grooming
On admission, what are the first steps to take in stabilising a pateint?
- Respiration (airway patency/normal ventilation)
- Cardiovascular (arrhythmia, shock, severe haemorrhage)
- CNS signs (seizures, convulsions)
- Thermoregulation (hyper- or hypothermia)
- Severe electrolyte or acid-base derangement
How should ocular contamination me managed/treated?
- Irrigate the eye(s) with saline for 20-30mins - Use tepid water if saline unavailable
- Treat for ulceration - Fluorescein staining should be performed after flushing and again at 12–24 hours post-exposure to assess for corneal ulceration.
What is the aim of treatment when a toxin has been ingested?
Aim: to decrease absorbed dose
- Prevent further absorption
- Increase elimination
- Bind toxin in inert form
Which drug is used to induce emesis in dogs?
Apomorphine
How is apomorphine administered?
Parenteral administration can result in protracted vomiting
- 0.04mg/kg IV (rapid onset) or IM
- 0.08mg/kg SC (slow onset)
- Reverse with naloxone as necessary (this does not stop the vomiting!)
Which emesis inducing drug can be used in dogs and cats?
Xylazine
How is xylazine reversed?
Atipamezole
Why drug can be used to induce emesis in just cats?
Dexmedetomidine
What must you remember to do when you have induced emesis in a toxic ingestion pateint?
Retain a sample of vomit
When is emesis induction indicated?
Within 3h of ingestion
- As soon as possible
- Up to 6h for aspirin and 12h for chocolate
When is emesis induction contraindicated?
- Animal has been vomiting
- Absent gag reflex
- Sedation or loss of consciousness
- Seizuring
- Ingestion of corrosive substance or volatile petroleum based product
Which procedure can be performed when it is not possible to induce emesis?
Gastric lavage
Describe how gastric lavage is performed
- Must have a cuffed ET tube in place
- Lower head and neck relative to thorax
- Use an orogastric tube
- 5-10ml/kg of warmed water
- Repeat 10-15 times or until lavage is clear
- Can add activated charcoal to lavage and leave in for 10-15 minutes
- Retain a sample of the initial lavage
Name an adsorbent used in toxin ingestion cases
Activated charcoal
What are the role of cathartics in toxin ingestion?
Enhance toxin clearance i.e. Reduce the time a toxin is exposed to the gastrointestinal tract
When are cathartics contraindicted?
If the animal has diarrhoea, is dehydrated, if ileus is present, or if intestinal obstruction or perforation are possible.
Name some cathartic drugs
- Psyllium hydrophilic mucilloid
- Sorbitol
- Sodium or magnesium sulphate
- Liquid paraffin
Name another method that will enhance toxin clearance
Diuresis
Describe the process of diuresis
- IVFT (monitor urine output – normal 0.5-1mL/kg/hr)
- Diuretic therapy (furosemide 1mg/kg or mannitol 0.5g/kg for oliguric or anuric AKI non-responsive to fluid replacement (ensure the animal is hydrated first!)
- Furosemide can be used to treat hypercalcaemia secondary to cholecalciforal toxicity
What is one of the most important components of toxin treatment?
Supportive care
- Thermoregulation
- Respiratory support
- Cardiovascular support
- Analgesia
- CNS disturbances
- Nutritional support
At what temperature is an animal described as being hyperthermic?
Temperature >40.5 ACTIVE COOLING REQUIRED
How can a patient be actively cooled?
- Cold packs in axillae; luke warm to cool water (not cold or ice water) spray; IVFT
- Cool to 39.4oC within 30-60 minutes. Cooling further/faster => shivering => heat gain => increased core temp
For which toxin is 100% oxygen supplementation contraindicted?
Paraquat exposure
Name some toxins that can cause arrythmias
Foxglove, Lily of the valley, Oleander, Rhododendron, Antidepressents
When is analgesia indicated for toxic pateints?
- Ingestion of a caustic substance
- Use an opioid unless contraindicated
- Pethidine has short duration of action
- Buprenorphine – partial agonist
How should seizures due to a toxin be managed?
- Diazepam - 0.5-1.0mg/kg
- Phenobarbital - 2-5mg/kg SLOW IV: may take 20-30min to have effect
- Propofol
Care if hepatic encephalopathy is suspected - diazepam/barbiturates may have profound affect and are not recommended
Which samples can be used to identify toxins?
- Heparinised blood
- Urine
- Stomach contents
- Sample of product ingested if available
- PM tissues: liver, kidney, brain, stomach
All members of which plant spp are nephrotoxic to cats?
Lilium and Hemerocallis
- All parts of the plant are considered toxic (leaves, flowers, seeds, pollen, stem).
Describe the signs of lily toxicity
Signs of AKI occur after 24-72h:
- Often present with vomiting, salivation, or neurological signs (tremors, seizures, ataxia).
- Epithelial casts can be found in the urine as early as 12-18hr after ingestion.
- Proteinuria and glucosuria are common.
When does permethrin toxicity most commonly occur?
Toxicities occurs when products “for dog use only” are used on cats
Describe the signs of permethrin toxicity
Excessive salivation, tremors, ataxia, depression, hyperthermia/hypothermia
Describe the pathophysiology of paracetamol toxicity in cats
Oxidative injury to RBCs - Methaemoglobin formation (cats)
Hepatotoxic (>24 hrs after ingestion)
What are the clinical signs of paracetamol toxicity?
- Vomiting, abdominal pain, tachycardia, pallor, cyanosis, chocolate- coloured mucous membranes
- Occasionally facial oedema in cats
- Depression (within hours)
- Progression to hepatic failure
What is the mainstay treatment for paracetamol toxicity?
N-acetylcysteine detoxifies the toxic metabolites
What are some other methods of treating paracetamol toxicity?
- Emesis if within 2h of ingestion
- Activated charcoal (multi-dose regime)
- Cathartics
- Aggressive IVFT
- Oxygen therapy, whole blood transfusion (cats)
Name the toxin usually found in antifreeze, also found in de-icer, brake and transmission fluid, motor oils, paint, ink and industrial solvents
Ethylene glycol
Describe the pathophysiology of ethylene glycol toxicity
- Ethylene glycol is metabolised in the liver by alcohol dehydrogenase to glycolic acid (-> Severe metabolic acidosis) and oxalic acid (most important final metabolite)
- Combines with calcium in blood vessels and renal tubules => hypocalcaemia, obstructed tubules, renal epithelial damage
Describe the signs seen in phase 1 of ethylene glycol toxicity
30 minutes following ingestion- lasts 2-12h
- Ataxia (look drunk)
- Tachycardia, tachypnoea
- PU/PD in dogs
- PU in cats
- Vomiting
Describe the signs seen in phase 2 of ethylene glycol toxicity
8-24h following ingestion
- Metabolic acidosis
- Anorexia, emesis
- Depression, miosis, hypothermia
- If large doses may be fatal in this phase (severe depression, tachypnoea, coma, death)
Describe the signs seen in phase 3 of ethylene glycol toxicity
1-3 days following exposure
- Oliguric renal failure
- Large painful kidneys, oral ulceration, salivation, vomiting, seizures
How is ethylene glycol toxicity treated?
- Management depends on the time of presentation
- Animals treated in phase 1 = excellent prognosis
- EG is very rapidly absorbed so gastrointestinal decontamination is unlikely to be beneficial
- Supportive care
Which drug prevents metabolism of EG to glycolic acid by inhibiting alcohol dehydrogenase
Ethanol
Which drug is the treatment of choice for ethylene glycol toxicity?
Fomepizole
How do Anticoagulant rodenticide toxicities present?
Present as coagulopathies - very variable
Onset of clinical signs 1-3 days following ingestion - usually ~48h
Diagnosis based on history and coagulation screen (WBCT, ACT, PT, aPTT)
How are anticoagulant rodenticide toxicities treated?
Vitamin K1 orally
What is the main effect on the body of cholecalciferol toxicity?
Hypercalcaemia
Which toxin is found in slug and snail pellets?
Metaldehyde
What are the effects of Metaldehyde toxicity?
Acute neurotoxicity, then hepatotoxicity
Hyperaesthesia, anxiety, restlessness, salivation, muscle tremors, incoordination, opisthotonus, tachycardia, seizures, coma, death
How do NSAIDs cause toxicity?
Inhibit prostaglandin synthesis through COX inhibition
- GI effects
- Nephrotoxicity
How is NSAID toxicity treated?
- Emesis
- Gastric lavage, adsorbents, cathartics
- Repeat doses of activated charcoal
How is GI ulceration treated?
Sucralfate
Name the toxin found in chocolate, tea and coffee
Methylxanthines
How are Methylxanthines linked to the bladder?
Methylxanthines are absorbed across the bladder wall - keep the bladder small when treating
How do grapes and raisins cause toxicity?
Acute kidney injury secondary to acute proximal tubular necrosis
What are the toxic effects of Xylitol (sweetener)?
Massive insulin release => profound hypoglycaemia
Clinical signs can appear within 30min
What are the toxic effects of onions, garlic and leeks?
Disulfide and thiosulfates are metabolised to compounds that damage RBCs
Heinz bodies, haemolysis, methaemoglobinemia
