Wednesday, April 19, 2017

 

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If you see a pet vomiting, call emetic!

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In 2016, the Animal Poison Control Center (APCC) fielded over 12,000 calls from pet owners about insecticide poisoning and 9,800 calls about rodenticides.

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Missed Tox part 1, part 2, or part 3?


5 more of Zuku's Top Toxicoses To Know For NAVLE® Success:

  1. Toad poisoning

    Marine toads are toxic to dogs

    Marine toad showing dorsum detail

    • Classic case: Affects CNS and cardiovascular system
      • Dogs affected most, sometimes cats
      • Variable presentation
        • Oral irritation, frothing and pawing at mouth
        • Retching
        • Vomiting
        • Cyanosis
        • Cardiac arrhythmias
        • Seizures
        • DEATH
    • Dx: History of exposure
      • Toxic principles:
        • Bufagenins
          • Act like digitalis
        • Bufotoxins
          • Act like local anesthetics, catecholamines, serotonin
            • Block sodium channel in nerves
    • Rx: Thoroughly rinse mouth and ...
      • Treat any cardiac arrhythmias and give digoxin-specific antibody if refractory
      • Decrease salivation: Atropine if normal cardiac rhythm
      • CNS excitability: Benzodiazepines
      • Cyanosis: Oxygen therapy
    • Pearls:
      • See most often in warm weather
      • Rhinella marina (formerly Bufo marinus): Giant or marine toad
        • This is most toxic toad in US
        • Found mostly in Florida, Texas, and Hawaii
      • Potency and type of toxin vary with type of toad

  2. Insecticides (organophosphates, carbamates, organochlorines, pyrethrins)

    Cattle going through a tick treatment bath

    Accidental toxic-level exposure may occur when insecticides are applied to fields using crop dusters

    • Classic case: All species affected
      • Organophosphates and carbamates: Affect all systems, especially gastrointestinal, neuromuscular, CNS
        • Muscarinic: SLUD
          • Salivation
          • Lacrimation
          • Urination
          • Diarrhea
        • Nicotinic:
          • Muscle tremors
          • Weakness
        • Central:
          • Anxiety
          • Ataxia
          • Seizures
        • Respiratory failure
      • Organochlorines: Affect CNS
        • Abnormal behavior, posture
        • Vocalization
        • Neuromuscular tremors, convulsions
        • Hyperthermia
      • Pyrethrins/pyrethroids: Affect CNS
        • Tremors, seizures
        • Incoordination
        • Hunched back
        • Salivation
        • Death
    • Dx: History, clinical signs, and ...
      • Organophosphates:
        • Measure acetylcholinesterase concentration in blood and brain (usually a 70% or more decrease)
        • Measure organophosphates in stomach/rumen, blood/serum, urine
      • Carbamates:
        • Measure acetylcholinesterase concentration in blood and brain (usually a 50% or more decrease)
        • Measure carbamates in stomach/rumen, blood/serum, urine
      • Organochlorines:
        • Measure organochlorines in brain/liver/kidney/fat/stomach
        • Check blood/urine in rest of herd/flock
      • Pyrethrins/pyrethroids:
        • Measure pyrethrins/pyrethroids in tissues/fluids
    • Rx:
      • Organophosphates:
        • Decontamination (gastric emesis/lavage, activated charcoal)
        • Atropine (anti-muscarinic)
        • 2-pyridine aldoxime methochloride (2-PAM)
        • Diazepam for seizures
        • Do NOT give phenothiazines as they potentiate organophosphate
      • Carbamates:
        • Decontamination
        • Atropine (anti-muscarinic)
        • Do NOT use 2-PAM as it can also reversibly bind and inhibit acetylcholinesterase and therefore may exacerbate the clinical signs
      • Organochlorines:
        • Bathe if dermal exposure
        • Decontamination
        • Reduce stress
        • Barbiturates or diazepam
      • Pyrethrins/pyrethroids:
        • Bathe if dermal exposure
        • Activated charcoal
        • Do NOT induce emesis because the petroleum solvent may cause aspiration pneumonia
        • Barbiturates or diazepam
    • Pearls:
      • Organophosphates:
        • Pathophysiology:
          • Irreversibly inactivates acetylcholinesterase at synapses and in erythrocytes
          • Newer organophosphates are less toxic because they require hepatic activation
        • Frequent toxicosis due to narrow margin of safety
      • Carbamates:
        • Pathophysiology:
          • Reversibly inactivates acetylcholine at synapses and in erythrocytes
        • Considered safer than organophosphates so used more often
      • Organochlorines:
        • Pathophysiology: CNS stimulation
        • Rarely used because of tissue residues and chronic toxicity
      • Pyrethrins/pyrethroids:
        • Pathophysiology:
          • Affect sodium, chloride, and calcium channels
          • Affect nicotinic acetycholine receptors
        • Pyrethrins are from the plant C. cinerariaefolium
        • Pyrethroids are synthetic derivatives of pyrethrins

  3. Petroleum products

    Diesel spill

    • Classic case: Affect respiratory, GI, central nervous, and dermal systems
      • Usually dogs, cats, or ruminants, but all species are vulnerable
      • All species:
        • Excitability, incoordination
        • Shivering
        • Dyspnea
        • Aspiration pneumonia
        • DEATH
      • Small animals:
        • Salivation, cough, choking
        • Vomiting
      • Ruminants: Bloat
    • Dx:
      • Toxic principle: Volatile hydrocarbons
      • Odor of hydrocarbons from lungs/rumen contents/feces
      • Measure hydrocarbons in lung/liver/kidney/GI contents
    • Rx:
      • Small animals:
        • Activated charcoal
        • Do NOT induce emesis because of aspiration risk
        • +/- Antibiotics for pneumonia
      • Ruminants: Relieve bloat with stomach tube
    • Pearls:
      • Pathophysiology:
        • CNS dysfunction
        • Chemical aspiration pneumonia: Low viscosity and high volatility (e.g., gasoline, kerosene) increase aspiration risk
      • Prognosis for aspiration pneumonia is poor
      • Dogs and cats may ingest petroleum products when grooming
      • Cows may ingest because curious or thirsty

  4. Smoke inhalation

    Cat getting oxygen treatment after rescue from a fire

    Fire in sage approaching a barn.

    • Classic case: Affects respiratory system
      • All species can be affected, but worse in smaller animals and birds
      • 12-48 h after inhalation (compromise peaks at 12-24 h post-inhalation):
        • Coughing
        • Stridor, tachypnea, dyspnea
        • Voice change, lower respiratory noise
        • If inhaled toxicants:
          • Depression, weakness
          • Obtundation, coma
    • Dx:
      • Several toxic principles (examples):
        • Carbon monoxide
        • Cyanide gas
        • Methane
        • Sulfur trioxide
        • Pyrolysis products (cause polymer fume fever)
      • Laryngoscopy/bronchoscopy (gold standard): See edema, ulceration, subglottic injury
      • Pulse oximetry: Carboxyhemoglobin and methemoglobin will cause false high readings
      • Pulse co-oximetry is usually more accurate than pulse oximetry
      • Arterial blood gases (PaO2 is not affected by carbon monoxide poisoning)
      • Elevated carboxyhemoglobin concentration (although may be falsely decreased if recent oxygen treatment)
      • Elevated lactate concentration (especially with cyanide gas poisoning)
      • CBC: Decreased PCV and hemoglobin after 1 wk
      • Thoracic imaging: See changes (atelectasis, pulmonary edema, hyperinflation) at 24-36 h
      • ECG: Compatible with cardiac ischemia (S-T segment elevation or depression, T-wave inversion)
    • Rx:
      • Intubation or tracheostomy and administer oxygen
      • Specific Rx:
        • Methemoglobinemia: Methylene blue
        • Polymer fume fever: Acetylcysteine
      • Bronchodilators
      • +/- Antibiotics, corticosteroids
    • Pearls:
      • Pathophysiology due to thermal injury and inhaled toxicants
        • Steam produces severe lung injury

  5. Strychnine

    Strychnine is mostly used as gopher bait

    Strychnos nux-vomica plant that produces the toxic seeds

    Strychnos nux-vomica seeds

    • Classic case: Affects CNS
      • All species vulnerable, but most often in western USA in young, large-breed, intact male dogs
      • Initially:
        • Nervous
        • Stiff
        • Very rapid progression
      • Generalized rigidity
      • Tetanic spasms
      • Tonic-clonic seizures
      • Hyperthermia
      • DEATH
    • Dx:
      • Toxic principle: Indole alkaloid
      • Measure strychnine in stomach contents, liver, kidney, urine
    • Rx:
      • Decontamination
      • Control seizures: Pentobarbital, methocarbamol
      • Prevent asphyxiation: +/- Intubation and artificial respiration
    • Pearls:
      • Strychnine comes from the seeds of the Indian tree Strychnos nux-vomica
      • Pathophysiology:
        • Competitive and reversible inhibition of the inhibitory neurotransmitter glycine at postsynaptic sites in spinal cord and medulla
        • Striated muscle rigidity
      • Used in gopher bait
      • Restricted use pesticide because so highly toxic

owl    Zuku-certified bodacious websites on toxicology:



VETgirl

Outstanding podcasts and articles mostly related to emergency and critical care with several articles on toxicoses.

Check out metronidazole, Fleet enema, and ivermectin.

ASPCA Animal Poison Control Center

Not just a 24-hour hotline, but also has several nice toxicology articles.

See proper use of emetics, hypernatremia and activated charcoal, and toxic causes of megaesophagus.

Courtesy of ASPCA.


Pet Poison Helpline

Another go-to site for veterinary toxicology.

Read about when NOT to induce vomiting, cocaine, and handwarmers.

Merck Vet Manual online

Can't get enough of veterinary toxicology? Look at sorghum, fescue, and metaldehyde.


“The clever men at Oxford,

Know all that there is to be knowed.

But they none of them know one half as much as intelligent Mr Toad.”

-Kenneth Grahame (author, The Wind in the Willows)

 

Example of NAVLE®-format toxicology question:

Which one of the following medications is contraindicated with organophosphate toxicity?

   A. Diazepam

   B. Diphenhydramine

   C. Pralidoxime

   D. Acepromazine

   E. Pentobarbital

Click here for the answer and explanatory text…

 

zukureview

 

Images courtesy of Sam Fraser-Smith (top marine toad), Bernard DUPONT (bottom marine toad), Wutsje (vomiting cat), Scott Bauer (dipping cows), Airman 1st Class Kenneth Norman (cropdusters), John (diesel spill), Dragonfire1024 (cat receiving oxygen), National Park Service (sage fire), Davefoc (gopher), H. Zell (strychnine seeds), Franz Eugen Köhler (strychnine plant), and Hisashi (cat licking paw).

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