Toxicology and Osmolality Overview

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Questions and Answers

What is a crucial first step in managing a suspected poisoning case in animals?

Administering a random antidote

Inducing immediate emesis without supervision

Waiting for symptoms to develop further

Providing an accurate history to a veterinarian (correct)

Which factor does NOT influence whether toxicosis will develop in animals?

Genetic predisposition

Age and weight of the animal

Cost of treatment (correct)

Species of animal

What is a key component of treatment for patients with ethylene glycol poisoning?

Administration of calcium carbonate

Monitoring electrolytes only

Use of an effective antidote (correct)

Intravenous hydration

In small animal toxicity management, what must be done before inducing emesis?

Feed the animal a soft meal Signup and view all the answers

Which metabolic condition is primarily caused by the accumulation of glycolic acid in ethylene glycol poisoning?

Metabolic acidosis Signup and view all the answers

What is a common clinical feature associated with poisoning from CNS depressants?

Respiratory depression Signup and view all the answers

Which of the following statements regarding veterinary toxicology is accurate?

Species and overall health status play a role in toxicity development. Signup and view all the answers

Which of the following is essential for the initial assessment of a poisoned patient?

Patient stabilization Signup and view all the answers

What stage in the development of toxicity is characterized by observable clinical signs?

Clinical stage Signup and view all the answers

In which stage of ethylene glycol poisoning does apparent intoxication and neurologic involvement typically occur?

Stage 1 (30 minutes to 12 hours after ingestion) Signup and view all the answers

What is the primary toxic metabolite associated with ethylene glycol that contributes to renal toxicity?

Oxalic acid Signup and view all the answers

What additional treatment should be given alongside an antidote like ethanol in cases of ethylene glycol poisoning?

Folinic acid Signup and view all the answers

Why should patients receiving ethanol therapy for ethylene glycol poisoning be monitored in an intensive care setting?

To manage respiratory drive effectively Signup and view all the answers

Which of the following methods is NOT appropriate for oral decontamination in small animals?

Giving large quantities of milk Signup and view all the answers

What might happen to a patient with severe CNS manifestations due to ethylene glycol poisoning?

They may completely recover neurologic function Signup and view all the answers

What is the lethal dose of ethylene glycol typically estimated to be?

100 ml Signup and view all the answers

What factors are crucial in determining the toxicity of a substance?

Both the characteristics of the toxicant and the organism Signup and view all the answers

Which toxicants can cause neuronopathies?

Doxorubicin, methyl mercury, trimethyltin Signup and view all the answers

What constitutes a normal osmol gap value?

10 mosm or less Signup and view all the answers

What is one potential complication that may occur with poisonings?

Rhabdomyolysis Signup and view all the answers

Which type of toxicity is primarily linked to the interruption of neurotransmission?

Neurotoxicity Signup and view all the answers

What characteristic of a person could impact the likelihood of severe toxicity when exposed to a toxicant?

Genetic factors and drug interactions Signup and view all the answers

Which substances are associated with axonopathies?

Organophosphorus compounds and other industrial compounds Signup and view all the answers

What physiological state can result from the effects of neurotoxicants?

Convulsions Signup and view all the answers

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!