Wednesday, April 5, 2017

 

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Most of the time, when a patient is already symptomatic, it is too late to induce emesis.


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Did you know that "theobromine" is from the Greek words for god (theo) and food (brosi)?




 

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

  1. Human foods (raisins/grapes, chocolate, xylitol)

    White chocolate is the least toxic and dark chocolate is the most toxic

    • Classic case: Most commonly affect dogs
      • Raisins/grapes: Affect kidneys
        • Vomiting, diarrhea, abdominal pain
        • Weakness, tremors
        • Polydipsia
        • Anuria
      • Chocolate: Affects GI, heart, CNS
        • Cardiac arrhythmias
        • CNS dysfunction: Restlessness, ataxia, tremors, seizures
        • PU/PD
        • Vomiting, diarrhea, abdominal distention
      • Xylitol: Affects endocrine system, liver
        • Vomiting
        • Weakness, depression
        • Ataxia, seizures, coma
        • +/- Icterus
        • +/- Coagulopathy
    • Dx: History and clinical signs
      • Raisins/grapes:
        • Toxic principle: Unknown
        • Azotemia
      • Chocolate:
        • Toxic principle: Methylxanthines (theobromine & caffeine)
        • Chocolate odor on breath, in vomit
        • Arrhythmias
      • Xylitol:
        • Hypoglycemia (monitor blood glucose every 1-2 h)
        • +/- Bilirubinemia (monitor liver values every 12-24 h)
        • +/- Thrombocytopenia
        • +/- Hyperphosphatemia
    • Rx:
      • Raisins/grapes:
        • Decontamination
        • IV fluid diuresis
        • Promote urination with dopamine or furosemide
      • Chocolate:
        • Decontamination (gastric emesis/lavage, activated charcoal)
        • Methocarbamol, diazepam, barbiturates
        • Treat arrhythmias
        • Other supportive care
      • Xylitol: Activated charcoal does NOT bind it
        • Emesis only at a vet hospital
        • IV dextrose
        • Liver support:
          • N-acetylcysteine
          • S-adenosylmethionine (SAMe)
    • Pearls:
      • Raisins/grapes:
        • Unclear dose relationship (5 grapes thought to have killed an 18-lb (8.2-kg) dog)
        • Some dogs resistant, others develop acute renal failure after just a few raisins or grapes
        • Toxin damages proximal renal tubular epithelium
        • Prognosis is guarded
      • Chocolate:
        • Higher cocoa percentage is most toxic (white chocolate least toxic and dark is most toxic)
        • Methylxanthines:
          • Inhibit cellular adenosine receptors
          • Increase intracellular calcium
          • Increase cyclic AMP levels
        • Death typically due to:
          • Cardiac arrhythmias
          • Hyperthermia
          • Respiratory failure
        • Signs can persist 72 h
        • Rarely affects cats
      • Xylitol:
        • A sugar-free sweetener for human foods
        • Hiding in many products (low-sugar peanut butter, gum, breath mints, candy)
        • Xylitol stimulates a profound rapid, dose-dependent insulin release
        • Liver disease and hyperphosphatemia usually mean a poor prognosis

  2. Human medications (acetominophen, SSRIs, methylphenidate, sleep aids)

    Acetominophen (Tylenol) causes methemoglobinemia

    • Classic case:
      • Acetominophen: Affects erythropoeisis, liver, +/- kidneys
        • Muddy mucous membranes
        • Hyperpnea
        • Tachycardia
        • Weakness/depression
        • Death
      • SSRIs: Affect CNS, heart
        • Mydriasis
        • Vomiting, diarrhea
        • Lethargy, fever
        • Ataxia, seizures, hyperactivity, vocalization
        • Increased or decreased heart rate
      • Methylphenidate (Ritalin, a stimulant used to treate human ADHD): Affects CNS
        • Hyperactivity, aggression
        • Hyperthermia
        • Tremors, ataxia, circling
        • Tachycardia, hypertension
        • Mydriasis
        • Death
      • Sleep aids: Affect CNS
        • Marked sedation
        • Paradoxical excitement
    • Dx: History and clinical signs
      • Acetominophen:
        • Methemoglobinemia, then Heinz bodies
        • Abnormal liver values
      • Methylphenidate:
        • Measure levels in gastric contents, urine
        • Can use over-the-counter test kits
    • Rx:
      • Acetominophen:
        • Decontamination
        • N-acetylcysteine slowly IV
        • Ascorbic acid
        • IV fluids
        • Blood transfusion
      • SSRIs:
        • Decontamination
        • Cyproheptadine
        • Phenothiazines
        • Diazepam
        • Beta-blockers
        • Do NOT use atropine
      • Methylphenidate:
        • Phenothiazines
        • Acidify urine to increase excretion
      • Sleep aids:
        • If mild: keep quiet
        • Decontamination
        • Phenothiazines
        • Flumazenil if severe
        • Do NOT use diazepam
    • Pearls:
      • Acetominophen:
        • Pathophysiology: Oxidizing toxic metabolites lead to methemoglobinemia with Heinz bodies
        • Cats uniquely sensitive because do NOT have glucuronyl transferase
        • Dogs may get keratoconjunctivitis sicca
      • SSRIs:
        • Pathophysiology: Block presynaptic serotonin receptors
        • "Serotonin syndrome" can occur with any drug than increases free serotonin levels
      • Methylphenidate:
        • Pathophysiology: Amphetamines cause release of norepinephrine and other catecholamines
        • Many other amphetamines cause similar syndrome
        • Difficult to differentiate from cocaine toxicosis
      • Sleep aids:
        • Pathophysiology: Bind to gamma-aminobutyric acid (GABA) receptors

  3. Household hazards (alcohol, chlorine bleach, dishwasher packets)

    Bleach is a common toxin in pets

    • Classic case: Dogs most commonly affected because of indiscriminate eating habits!
      • Alcohol: Affects GI, CNS
        • Vomiting, diarrhea
        • Ataxia, disorientation
        • Tremors
        • Dyspnea, respiratory failure
        • Hypothermia
        • Death
      • Chlorine bleach: Affects GI, eyes, skin, respiratory system
        • Ingested: Vomiting, diarrhea, hypersalivation
          • Vomiting, diarrhea
          • Hypersalivation
        • Inhaled:
          • Caged birds at highest risk of respiratory exposure due to their unique respiratory anatomy
          • Gagging
          • Coughing, sneezing
        • Ocular:
          • Epiphora
          • Ulceration
        • Dermal: Ulceration
      • Dishwasher packets: Affect GI tract
        • Cats can be exposed to liquid detergents due to grooming habits
        • Vocalization
        • Hypersalivation
        • Vomiting (bloody), diarrhea
        • GI pain
    • Dx: History and clinical signs
      • Alcohol:
        • Blood alcohol level
        • Hypoglycemia
        • Metabolic acidosis
      • Chlorine bleach:
        • Metabolic acidosis
        • Radiography: Pulmonary edema if inhalation exposure
      • Dishwasher packets: Endoscopy to determine degree of necrosis
    • Rx:
      • Alcohol: Activated charcoal does NOT work
        • Induce emesis
        • Treat cardiovascular and acid-base status
        • Diazepam
        • Yohimbine
      • Chlorine bleach:
        • NO routine decontamination
        • Treat metabolic acidosis
        • Treat inhalation/pulmonary edema
        • Treat dermal exposure by bathing
        • Treat ocular exposure with irrigation
      • Dishwasher packets:
        • Do NOT induce emesis or give activated charcoal
        • Dilute with milk or water
        • Supportive care
        • +/- Esophagostomy tube
    • Pearls:
      • Alcohol:
        • Pathophysiology:
          • GI irritation
          • CNS depressant
          • Stimulates catecholamine release
          • Metabolic acidosis
        • Most commonly ethanol, methanol, isopropanol
        • Dermal exposure possible
      • Chlorine bleach:
        • Pathophysiology:
          • Irritant
          • If pH greater than 11 or less than 3.5, can cause corrosive injury
        • Risk depends on concentration, pH
        • Bleach + ammonia produces a toxic gas that causes pulmonary edema
      • Dishwasher packets:
        • Pathophysiology:
          • Alkaline corrosive (pH > 11)
          • Liquefactive penetrating necrosis

  4. Rodenticides (anticoagulant, bromethalin, cholecalciferol, zinc phosphide)

    Unlabelled bait in flavored blocks is HIGH RISK!

    Cat eats rat poison - a tragedy in five acts and one tableau. Harper's New Monthly Magazine, 1881

    • Classic case:
      • Anticoagulant: Affects coagulation cascade
        • Hemorrhage!
        • Anemia/weakness, lameness if hemorrhage in a joint
        • Hematomas, melena, hematuria, etc.
        • Signs start 5-7 d after ingestion
      • Bromethalin: Affects CNS
        • Acute:
          • Hyperexcitability
          • Muscle tremors
          • Seizures
          • Hyperthermia
          • DEATH
        • Subacute/chronic:
          • Pelvic limb weakness
          • Paralysis
          • Ataxia
      • Cholecalciferol: Affects kidneys, cardiovascular system, CNS
        • Depression, anorexia
        • PU/PD
        • Vomiting, hematemesis
        • Hypertension
      • Zinc phosphide: Affects respiratory system, liver, kidneys
        • Vomiting (+/- hematemesis)
        • Tachypnea
        • Ataxia, trembling
        • Collapse
        • Seizures
        • DEATH
    • Dx: History and clinical signs
      • Anticoagulant:
        • Measure in serum/plasma/stomach contents
        • Prolonged PT, APTT, and ACT
      • Bromethalin: Measure levels in liver, kidney, fat, and brain
      • Cholecalciferol: Hypercalcemia then hyperphosphatemia
    • Rx:
      • Anticoagulant:
        • Vitamin K PO for 3-4 weeks until PT is normal 72 h after last dose
        • Plasma or whole blood transfusion
        • Oxygen
      • Bromethalin:
        • Decontamination
        • Diazepam
      • Cholecalciferol:
        • Decontamination
        • Cholestyramine
        • Calciuresis: normal saline, furosemide, prednisolone
        • Aluminum hydroxide
        • Pamidronate
      • Zinc phosphide:
        • Decontamination
        • Decrease gastric acid
        • N-acetylcysteine
        • SAMe
        • Diazepam
    • Pearls:
      • Anticoagulant:
        • Pathophysiology:
          • Vitamin K antagonist by inhibiting vitamin K epoxide reductase causing abnormal coagulation
        • Vitamin K-dependent coagulation factors are I, II, VII, IX, and X
        • First generation (warfarin): multiple feedings required for toxicity
        • Second generation (brodifacoum): single feeding is toxic
        • Half-lives vary with type
      • Bromethalin:
        • Pathophysiology:
          • Uncouples oxidative phosphorylation causing demyelination and cerebral edema
        • Cats and young dogs especially sensitive
        • Subacute/chronic toxicity seen up to 7 d after exposure
      • Cholecalciferol:
        • Pathophysiology:
          • Vitamin D3 causes increased calcium and phosphorus
        • Calciuresis initiated BEFORE hypercalcemia will cause worse disease by stimulating osteoclasts
      • Zinc phosphide: Used in gopher/mole/ground squirrel bait
        • Pathophysiology:
          • Phosphide + low gastric pH produces a toxic phosphine gas (be careful with emesis as personnel can inhale this toxic gas which causes noncardiogenic pulmonary edema
          • After absorption: Blocks cytochrome C oxidase producing reactive oxygen compounds which cause tissue damage
        • More toxic in species that cannot vomit
        • Phosphine gas is a public health hazard (smells like fish or garlic)

  5. Ethylene glycol

    Calcium oxalate monohydrate crystals (dumbbell shaped) and calcium oxalate dihydrate crystals (envelope shaped) can be seen on urinalysis with ethylene glycol toxicity

    Antifreeze is always dyed a bright color, like yellow-green

    • Classic case: Most commonly dogs and cats, although all species are susceptible
      • Affects kidneys and causes neurologic signs: stupor, ataxia, knuckling, poor withdrawal and righting reflexes
      • Phase 1
        • Vomiting
        • PU/PD
      • Phase 2
        • Oliguric renal failure
    • Dx:
      • Normochloremic metabolic acidosis with increased anion gap and osmolar gap
      • Calcium oxalate crystalluria
      • Use commercial ethylene glycol test kit
    • Rx: Best to treat dogs within 8-12 h, cats within 2 h
      • If no neurologic signs, induce vomiting and gastric lavage
      • 4-MP, fomepizole, or ethanol to inactivate alcohol dehydrogenase
      • Sodium bicarbonate for acidosis
    • Pearls:
      • Pathophysiology: Toxic metabolites of ethylene glycol
        • Metabolic acidosis
        • Renal tubular damage
      • Prognosis is poor once in acute renal failure
      • Anti-freeze is always dyed a bright color, like yellow-green
      • Sweet flavor, small lethal dose is a bad combination

owl    Zuku-certified bodacious websites on toxicology:



Animal Poison Control

The go-to site for animal toxicology resources.

Check out toilet bowl water, azaleas, and local anesthetic toxicity.

Courtesy of ASPCA.

Veterinary Poisons Information Service

Toxicology hotline website (London) with lots of interesting articles.

See phosphorus toxicity from fireworks and common poisons.


Pet Poison Helpline: Webinars

Informative webinars! Upcoming are eye drops and nasal sprays, marijuana, and decontamination.

Courtesy of Pet Poison Helpline.

The Merck Veterinary Manual online

Can't get enough of toxicology information? Check out macadamia nuts, avocados, and 5-fluorouracil.


Dog eats breakfast

Amusing video of a dog getting ready for the day!

Courtesy of Jaime Marisa.

 

Example of NAVLE®-format toxicology question:

Which one of the following is the most common clinical pathological abnormality observed in dogs that have ingested xylitol?

   A. Hypoglycemia

   B. Increased blood creatinine levels

   C. Anemia

   D. Hypophosphatemia

   E. Hypernatremia

Click here for the answer and explanatory text…

 

zukureview

 

Images courtesy of Daniel Schultz (fox and grapes), André Karwath (chocolate), raeky (Tylenol), Adina Firestone (bleach), tanakawho (drinking cat), Nolf (rat poison bait), A. B. Frost, Harper's New Monthly Magazine, 1881 (cat and rat poison tragedy), Doruku Salancı (calcium oxalate crystals), EvelynGiggles (radiator in combo image), dno1967 (Prestone in combo image), and Takashi Hososhima (cat eating chip) .

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