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Questions and Answers
What is a crucial first step in managing a suspected poisoning case in animals?
Which factor does NOT influence whether toxicosis will develop in animals?
What is a key component of treatment for patients with ethylene glycol poisoning?
In small animal toxicity management, what must be done before inducing emesis?
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Which metabolic condition is primarily caused by the accumulation of glycolic acid in ethylene glycol poisoning?
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What is a common clinical feature associated with poisoning from CNS depressants?
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Which of the following statements regarding veterinary toxicology is accurate?
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Which of the following is essential for the initial assessment of a poisoned patient?
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What stage in the development of toxicity is characterized by observable clinical signs?
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In which stage of ethylene glycol poisoning does apparent intoxication and neurologic involvement typically occur?
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What is the primary toxic metabolite associated with ethylene glycol that contributes to renal toxicity?
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What additional treatment should be given alongside an antidote like ethanol in cases of ethylene glycol poisoning?
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Why should patients receiving ethanol therapy for ethylene glycol poisoning be monitored in an intensive care setting?
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Which of the following methods is NOT appropriate for oral decontamination in small animals?
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What might happen to a patient with severe CNS manifestations due to ethylene glycol poisoning?
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What is the lethal dose of ethylene glycol typically estimated to be?
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What factors are crucial in determining the toxicity of a substance?
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Which toxicants can cause neuronopathies?
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What constitutes a normal osmol gap value?
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What is one potential complication that may occur with poisonings?
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Which type of toxicity is primarily linked to the interruption of neurotransmission?
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What characteristic of a person could impact the likelihood of severe toxicity when exposed to a toxicant?
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Which substances are associated with axonopathies?
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What physiological state can result from the effects of neurotoxicants?
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Study Notes
Osmolality
- Osmolality is a measure of the concentration of solutes in a solution
- Osmolality is calculated using the formula:
Osm = 2 [Na+] + [GLU]/18 + [BUN]/2.8
- Units for calculation are:
- GLU & BUN: mg/dL
- Na: meq/L
Normal Osmol Gap
- A normal osmol gap is less than 10 mosm
Substances that Can Contribute to Osmol Gap
- Acetone
- Propylene glycol
Poisoning Complications
- Hypothermia
- Hyperthermia
- Convulsions
- Urinary retention
- Rhabdomyolysis (breakdown of muscles)
Mechanisms of Toxic Action
- The principle of the “soil and the seed” can be applied to understanding the mechanisms of toxicity
- Characteristics of the organism influence the effects of toxicity
- These characteristics may be genetic or acquired
- Upon exposure to the toxicant, there may be direct reaction with the target molecule or the toxicant may cause alteration of the biological environment that the toxicant was introduced to
Stages of Toxicity Development
- Exposure
- Absorption
- Distribution
- Metabolism
- Elimination
- Excretion
Nervous System Toxicity
- Neurotoxicity refers to the ability of an agent to adversely affect the structural or functional integrity of the nervous system
- Toxicants may cause neuronopathies, axonopathies and myelinopathies
- Toxicants may also impact neurotransmission
Examples of Nervous System Toxicants
- Neuronopathies: doxorubicin, methyl mercury, trimethyltin
- Axonopathies: organophosphate compounds and other industrial compounds
- Myelinopathies: Lead, tellurium
Neurotransmission
- Some forms of toxicity are due to interruption of the process of neurotransmission, either through blocking excitation or by excessive stimulation, rather than actual cell death
- Gastric decontamination may be performed via nasogastric aspiration; other forms of decontamination are not recommended
- Haemodialysis may be done if presentation is late with a marked metabolic acidosis
Antidotes for Neurotransmission Toxicity
- Ethanol or fomepizole
- Folinic acid should be administered in conjunction with ethanol or fomepizole to help increase the formation of non-toxic metabolites
- It is recommended that patients receiving ethanol therapy be monitored in an intensive care setting and any decline in respiratory drive be countered with hyperventilation
Ethylene Glycol
- Most commonly used as antifreeze in radiator fluids
- May be drunk accidentally or intentionally
- Has a sweet taste
- A lethal dose is about 100ml by ingestion
Ethylene Glycol Kinetics
- Absorbed rapidly by gut, rapid distribution
- Metabolism: oxidised by alcohol dehydrogenase to glycoaldehyde, aldehyde dehydrogenase converts glycoaldehyde to glycolic acid
- Glycolic acid to glyoxylic acid is slow
- Calcium ions chelate oxalic acid to form insoluble calcium oxalate crystals which can be seen in the urine
Ethylene Glycol Toxicity Pathophysiology
- The etiology and pathophysiology of the CNS, metabolic, cardiopulmonary, and renal toxicity are primarily due to the formation and accumulation of toxic intermediary metabolites
- This includes glycolic acid (produces profound acidemia, oxalosis, and renal interstitial edema) and to a lesser but histologically important extent, oxalate production and excretion.
Stages of Ethylene Glycol Poisoning
- Stage 1 (30 mins to 12h after ingestion) -GI and Neurological involvement -Apparent intoxication, as with alcohol -Nausea, vomiting -Metabolic acidosis -CNS depression
Ethylene Glycol Poisoning Clinical Features
- Those who develop severe CNS manifestations, including seizures and coma, can recover full neurologic function.
- Cranial nerve palsies may occur in nerves II, V, VII, VIII, IX and XII, typically resolving over weeks to months.
Veterinary Toxicology
- The spectrum of undesired effects of toxicants are similar between animals and humans
- In addition to likelihood of exposure, host factors such as species/ breed of animal, age, weight and general health status of animal also plays a role on whether a toxicosis will develop or not
- Animals presenting with signs that are suspected to be related to poisonings need to be fully evaluated in order to rule out the possibility of an unrelated illness
- Published data on demographics of poisonings of animals in Trinidad and Tobago are not yet available (ongoing)
- Provision of an accurate history to veterinarian is important
- In animal poisonings, the cause of the animal’s condition may not be known, particularly in cases where exposure was not witnessed
- Having a systemic approach to these patients is paramount to identifying major health issues present
- Patient stabilization is essential to keep the patient alive while the underlying problem is diagnosed and treated
Management of Exposures- Small Animals
- Oral decontamination can be done through inducing emesis with 3% hydrogen peroxide (between 1 to 3 teaspoons, given the weight of animal)
- Given after soft meal such as bread or canned meal
- Adverse effects can occur and this must be adequately supervised by a veterinarian
Lecture Learning Outcomes
- Describe the clinical features of poisoning
- Discuss the importance of making a diagnosis
- Demonstrate how the laboratory may support the management of the poisoned patient
- Describe the potential stages in the development of toxicity
- Describe the mechanism of toxic action, clinical features and management of these features associated with poisoning from CNS depressants
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Description
This quiz covers key concepts related to osmolality, including its calculation and normal osmol gaps. It also explores the mechanisms of toxicity and potential complications from poisoning. Test your understanding of these fundamental toxicology principles!
