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Chocolate

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Introduction

Toxicity is due to the presence of methylxanthines such as theobromine and caffeine in chocolate.[1]. The consumption of more than 20mg/kg of total methylxanthines is considered the cut-off point in deciding whether or not to treat [1]. The concentration of methylxanthines differs between products. The average methylxanthine content of milk chocolate is 2mg/g, while that of baking chocolate is 16mg/g. [1]. Therefore number of grammes required to reach this threshold vary according to the product. For example in a 10kg dog 5000g of white chocolate provides the equivalent 20mg/kg dose of methylxanthines that 12-40g of plain chocolate or 7-25g of cocoa powder does [1].

Signalment

Dog that live indoors are more likely to have access to chocolate. Also puppies and dogs that scavenge are at a greater risk of eating food that is not intended for their consumption. Small breeds of dogs may reach the toxic threshold of methylxanthine concentration per body weight more easily [1].

Diagnosis

Clinical Signs

Chocolate poisoning results in CNS, gastrointestinal, cardiovascular and urological signs.[1], [2]. These signs are observed quite quickly after ingestion of toxic amount of chocolate.[2]

  • CNS: hyperexcitability, hyperactivity, ataxia initially can evolve into muscle tremors, clonic seizures and hyperthermia.[1], [2]
  • Gastrointestinal: diarrhoea, emesis, haematemesis, colic.[1], [2]
  • Cardiorespiratory: arrhythmias,infrequently bradycardia but usually tachycardia.[1], [2]
  • Urological: polydypsia and polyuria may also be present [1]

Laboratory Tests

Diagnosis is usually on the basis of clinical signs and a known history of chocolate ingestion. The following laboratory tests are possible but not commonly used;

  • Detection of methylxanthines in bodily fluids such as plasma, urine and stomach contents [1].
  • Blood Glucose: Hypoglycaemia as a consequence of hyperactivity. not seen consistently with chocolate poisoning [1].
  • Urinalysis: Proteinuria, low specific gravity; not seen consistently with chocolate poisoning [1].

Other

  • ECG: rate and rhythm abnormalities

Pathology

The methylxanthines yield their effects through

  • Antagonism of Adenosine Receptors:[1] this antagonism results in stimulation of the central nervous system, vasoconstriction and increase in heart rate [1] and also diureses [1]
  • Inhibition of Cyclic Nucleotide Phosphodiesterase:[2] consequently there is an increase in cyclic AMP, which in turn leads to greater catecholamine release and their effects [1].
  • Modulation of Intracellular Calcium Concentrations:Enhanced uptake and decreased sequestration within the cell leads to amplification of intracellular calcium levels in cardiac and skeletal muscle, the net result of which is a positive inotropic effect on these muscles. [1].

Ventricular fibrillation, and other cardiac dysrhythmias are most frequently the ultimate cause of death.[3], [4]

Treatment

  • Of dogs presenting with clinical signs
    • Inital stabilisation of Cardiorespiratory System:
      • Tachycardia: beta-blockers, eg orally administered metoprolol at a dose of 0.5mg to 1mg per kg every 8 hours [1].
      • Premature Ventricluar Contractions: slow intravenous bolus of 2mg to 6mg per kg of lidocaine. Following this a constant rate infusion of 20ug to 70ug per kg per minute [1]
      • Bradycardia: Atropine at a dose of 0.01mg to 0.02mg per kg [1]
    • Once stable treat as outlined below
  • Of dogs with a known history of recent chocolate ingestion but who have not yet developed clinical signs

Prognosis

References

  1. 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18 1.19 1.20 BSAVA Manual of Canine and Feline Emergency and Critical CareChapter 19, Second Edition,2007 Cite error: Invalid <ref> tag; name "multiples" defined multiple times with different content Cite error: Invalid <ref> tag; name "multiples" defined multiple times with different content Cite error: Invalid <ref> tag; name "multiples" defined multiple times with different content Cite error: Invalid <ref> tag; name "multiples" defined multiple times with different content Cite error: Invalid <ref> tag; name "multiples" defined multiple times with different content Cite error: Invalid <ref> tag; name "multiples" defined multiple times with different content Cite error: Invalid <ref> tag; name "multiples" defined multiple times with different content Cite error: Invalid <ref> tag; name "multiples" defined multiple times with different content Cite error: Invalid <ref> tag; name "multiples" defined multiple times with different content Cite error: Invalid <ref> tag; name "multiples" defined multiple times with different content Cite error: Invalid <ref> tag; name "multiples" defined multiple times with different content Cite error: Invalid <ref> tag; name "multiples" defined multiple times with different content Cite error: Invalid <ref> tag; name "multiples" defined multiple times with different content Cite error: Invalid <ref> tag; name "multiples" defined multiple times with different content Cite error: Invalid <ref> tag; name "multiples" defined multiple times with different content Cite error: Invalid <ref> tag; name "multiples" defined multiple times with different content Cite error: Invalid <ref> tag; name "multiples" defined multiple times with different content Cite error: Invalid <ref> tag; name "multiples" defined multiple times with different content Cite error: Invalid <ref> tag; name "multiples" defined multiple times with different content Cite error: Invalid <ref> tag; name "multiples" defined multiple times with different content
  2. 2.0 2.1 2.2 2.3 2.4 2.5 http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/211104.htm. Cite error: Invalid <ref> tag; name "multiple" defined multiple times with different content Cite error: Invalid <ref> tag; name "multiple" defined multiple times with different content Cite error: Invalid <ref> tag; name "multiple" defined multiple times with different content Cite error: Invalid <ref> tag; name "multiple" defined multiple times with different content Cite error: Invalid <ref> tag; name "multiple" defined multiple times with different content
  3. Carson TL (2006) Methylxanthines. In: Small Animal Toxicology, ed. ME Peterson, PA Talcott, pp.845-852. Elsevier Saunders, St. Louis in BSAVA Manual of Canine and Feline Emergency Care Chapter 19, Second Edition,2007
  4. Holmgren P, Norden-Petterson L and Ahlner J (2004)Caffeine fatalaties: four case reports. Forensic Science International 139, 71-73 BSAVA Manual of Canine and Feline Emergency Care Second Edition,2007