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Questions and Answers
What is the primary mechanism by which formic acid, a metabolite of methanol, causes toxicity?
What is the primary mechanism by which formic acid, a metabolite of methanol, causes toxicity?
- Interfering with the electron transport chain by binding to cytochrome oxidase. (correct)
- Inhibiting the production of neurotransmitters in the central nervous system.
- Causing direct damage to the myelin sheath of peripheral nerves.
- Directly damaging liver cells leading to hepatic failure.
Which of the following best describes the initial signs and symptoms observed 12-24 hours post-ingestion of methanol?
Which of the following best describes the initial signs and symptoms observed 12-24 hours post-ingestion of methanol?
- Hallucinations, muscle spasms, and cardiac arrhythmias.
- Central nervous system depression, metabolic acidosis, and visual disturbances. (correct)
- Restlessness, anxiety, and dilated pupils.
- Severe abdominal cramping, hypertension, and tachycardia.
Ethylene glycol toxicity leads to the formation of calcium oxalate crystals. Which of the effects below is associated with the deposit of these crystals in the brain?
Ethylene glycol toxicity leads to the formation of calcium oxalate crystals. Which of the effects below is associated with the deposit of these crystals in the brain?
- Memory loss and cognitive decline
- Peripheral neuropathy and muscle weakness
- Parkinsonian symptoms such as tremors and rigidity
- Seizures, cerebral edema, and meningismus (correct)
During which stage of ethylene glycol toxicity is the risk of death typically highest?
During which stage of ethylene glycol toxicity is the risk of death typically highest?
What is the rationale for using fomepizole in the treatment of methanol and ethylene glycol poisoning?
What is the rationale for using fomepizole in the treatment of methanol and ethylene glycol poisoning?
What additional measures alongside fomepizole can aid in the treatment of methanol and ethylene glycol toxicity?
What additional measures alongside fomepizole can aid in the treatment of methanol and ethylene glycol toxicity?
A patient presents with profound intoxication, but does not have an anion gap acidosis. Which of the following alcohols should be suspected?
A patient presents with profound intoxication, but does not have an anion gap acidosis. Which of the following alcohols should be suspected?
What biochemical process leads to scombroid poisoning after consuming improperly stored fish?
What biochemical process leads to scombroid poisoning after consuming improperly stored fish?
How does scombroid poisoning clinically manifest, often leading to misdiagnosis?
How does scombroid poisoning clinically manifest, often leading to misdiagnosis?
Which treatment approach is most appropriate for managing severe cases of scombroid poisoning that include bronchospasm and airway edema?
Which treatment approach is most appropriate for managing severe cases of scombroid poisoning that include bronchospasm and airway edema?
A patient who recently consumed reef fish presents with gastrointestinal distress along with a sensation of 'hot-cold reversal'. Which type of seafood poisoning is most likely?
A patient who recently consumed reef fish presents with gastrointestinal distress along with a sensation of 'hot-cold reversal'. Which type of seafood poisoning is most likely?
What is the primary mechanism of action of ciguatoxins on nerve cells?
What is the primary mechanism of action of ciguatoxins on nerve cells?
Why are cooking or freezing ineffective in preventing ciguatera poisoning?
Why are cooking or freezing ineffective in preventing ciguatera poisoning?
A patient reports perioral numbness shortly after consuming pufferfish. Which toxin is most likely responsible for these symptoms?
A patient reports perioral numbness shortly after consuming pufferfish. Which toxin is most likely responsible for these symptoms?
Which of the following is the primary mechanism by which tetrodotoxin exerts its toxic effect?
Which of the following is the primary mechanism by which tetrodotoxin exerts its toxic effect?
Which factor is MOST important when managing a patient with tetrodotoxin poisoning?
Which factor is MOST important when managing a patient with tetrodotoxin poisoning?
A patient presents to the emergency department with altered mental status and metabolic acidosis after ingesting an unknown substance. Lab results reveal an elevated osmolar gap and the presence of calcium oxalate crystals in the urine. Which of the below substances is the patient most likely to have ingested?
A patient presents to the emergency department with altered mental status and metabolic acidosis after ingesting an unknown substance. Lab results reveal an elevated osmolar gap and the presence of calcium oxalate crystals in the urine. Which of the below substances is the patient most likely to have ingested?
A group of diners at a restaurant develop facial flushing, headache, and palpitations shortly after consuming grilled tuna. Which of the below is the mostly likely cause?
A group of diners at a restaurant develop facial flushing, headache, and palpitations shortly after consuming grilled tuna. Which of the below is the mostly likely cause?
A fisherman develops perioral numbness, muscle weakness, and dizziness. He reports eating pufferfish the previous evening. What is the most appropriate management strategy for this patient?
A fisherman develops perioral numbness, muscle weakness, and dizziness. He reports eating pufferfish the previous evening. What is the most appropriate management strategy for this patient?
Which of the following mechanisms explains why prompt treatment with fomepizole is more effective than intravenous ethanol in cases of ethylene glycol poisoning?
Which of the following mechanisms explains why prompt treatment with fomepizole is more effective than intravenous ethanol in cases of ethylene glycol poisoning?
A patient is diagnosed with ciguatera poisoning after consuming barracuda. Besides supportive care, what dietary advice should the patient receive to prevent recurrence or exacerbation of symptoms?
A patient is diagnosed with ciguatera poisoning after consuming barracuda. Besides supportive care, what dietary advice should the patient receive to prevent recurrence or exacerbation of symptoms?
What differentiates the symptoms of isopropyl alcohol intoxication from those of methanol or ethylene glycol poisoning, aiding in differential diagnosis?
What differentiates the symptoms of isopropyl alcohol intoxication from those of methanol or ethylene glycol poisoning, aiding in differential diagnosis?
Which of the following is a key difference in the toxicokinetics of methanol compared to ethylene glycol?
Which of the following is a key difference in the toxicokinetics of methanol compared to ethylene glycol?
A chemist is investigating the stability of ciguatoxins extracted from reef fish under various conditions. Which treatment would be MOST effective at neutralizing the toxins?
A chemist is investigating the stability of ciguatoxins extracted from reef fish under various conditions. Which treatment would be MOST effective at neutralizing the toxins?
Following consumption of poorly refrigerated mackerel a patient presents with flushing, throbbing headache, and periorbital edema. The patient's symptoms began approximately 30 minutes after eating. What is the next best step in the management of this patient?
Following consumption of poorly refrigerated mackerel a patient presents with flushing, throbbing headache, and periorbital edema. The patient's symptoms began approximately 30 minutes after eating. What is the next best step in the management of this patient?
A marine biologist is studying the presence of tetrodotoxin in various species of pufferfish. Which strategy would MOST effectively reduce the risk of tetrodotoxin exposure via consumption of pufferfish?
A marine biologist is studying the presence of tetrodotoxin in various species of pufferfish. Which strategy would MOST effectively reduce the risk of tetrodotoxin exposure via consumption of pufferfish?
A 42-year-old male presents to the emergency department complaining of nausea, diarrhea, and a tingling sensation around his mouth. He reports that he recently returned from a fishing trip in the Caribbean, where he consumed a large barracuda. Physical examination reveals circumoral paresthesias and decreased sensation to temperature in his lower extremities. Which intervention is MOST appropriate?
A 42-year-old male presents to the emergency department complaining of nausea, diarrhea, and a tingling sensation around his mouth. He reports that he recently returned from a fishing trip in the Caribbean, where he consumed a large barracuda. Physical examination reveals circumoral paresthesias and decreased sensation to temperature in his lower extremities. Which intervention is MOST appropriate?
Which of the following is least likely to cause a recurrence of symptoms in patients recovering from ciguatera poisoning?
Which of the following is least likely to cause a recurrence of symptoms in patients recovering from ciguatera poisoning?
Which of the following is the MOST typical symptom of tetrodotoxin poisoning?
Which of the following is the MOST typical symptom of tetrodotoxin poisoning?
Flashcards
Methanol Toxicity
Methanol Toxicity
Methanol's toxicity is due to its metabolites, especially formic acid, which damages the optic nerve.
Ethylene Glycol Toxicity
Ethylene Glycol Toxicity
Ethylene glycol poisoning leads to oxalic acid production, forming calcium oxalate crystals that damage organs.
Fomepizole
Fomepizole
Fomepizole inhibits alcohol dehydrogenase, preventing toxic metabolite production in methanol and ethylene glycol poisoning.
Scombroid Poisoning
Scombroid Poisoning
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Ciguatera Poisoning
Ciguatera Poisoning
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Ciguatera's Allodynia
Ciguatera's Allodynia
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Tetrodotoxin Mechanism
Tetrodotoxin Mechanism
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Tetrodotoxin Symptoms
Tetrodotoxin Symptoms
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Study Notes
Alcohols
- Methanol is a competitive substrate for alcohol dehydrogenase (ADH).
- Formic acid, a toxic metabolite of methanol, harms the optic nerve.
- Early formic acid toxicity presents as metabolic acidosis, which is mainly due to lactic acidosis.
- Formic acid inhibits cytochrome oxidase, disrupting oxidative phosphorylation causing lactic acidosis.
Methanol Poisoning
- Methanol can be found in windshield washer fluid and counterfeit alcohol.
- Signs and symptoms of methanol poisoning appear within 12-24 hours after ingestion.
- Impacts of poisoning includes CNS depression, metabolic acidosis, and visual changes
- Blindness can result from the ingestion of 30 mL of methanol, with 100 mL being potentially fatal.
Ethylene Glycol
- Ethylene glycol is a colorless, odorless, sweet-tasting liquid and a competitive substrate for ADH.
- Ethylene glycol is degraded by same pathway as methanol.
- The toxicity of ethylene glycol arises from its hepatic oxidation into oxalic acid.
- Glycolic acid, produced by aldehyde dehydrogenase, is converted into oxalic acid.
- Oxalic acid binds calcium to form calcium oxalate crystals, that damage the heart, brain, lungs, and kidneys.
Ethylene Glycol Toxicity Stages
- Symptoms develop in stages after ingestion.
First Stage (0.5 - 12 hours)
- Ethylene glycol is a stronger inebriant than methanol and ethanol, causing mild CNS depression, seizures, and coma.
- Patients appear intoxicated but do not smell like alcohol.
- Calcium oxalate crystals deposit in the brain, leading to CNS toxicity, cerebral edema, and meningismus within 4-12 hours.
- Hypocalcemia, resulting from oxalic acid binding to calcium, can lead to prolonged QT intervals, arrhythmias, and myocardial depression.
Second Stage (12 - 24 hours)
- Tachypnea occurs to compensate for the metabolic acidosis caused by the toxic metabolites.
- Multiorgan failure (CHF, lung injury, myositis) occur due to crystal deposition.
- Most deaths occur in the second stage.
Third Stage (24 - 72 hours)
- Acute renal failure from crystal deposition may occur, but full recovery occurs within weeks to months.
Alcohol Poisoning Treatments
- Treatments for methanol and ethylene glycol toxicity
- IV ethanol was used historically
- Is a competitive substrate for ADH, with greater affinity for ADH than methanol and ethylene glycol.
- Fomepizole is the best initial therapy.
- It inhibits ADH, preventing the further productions of toxic metabolites.
- Fomepizole treatment is usually followed by dialysis.
- Additional treatments include replenishment of folic acid (methanol poisoning) and thiamine and pyridoxine (ethylene glycol poisoning).
Isopropyl Alcohol
- Common in alcoholics when alcohol is not available.
- Found in rubbing alcohol, disinfectants, and hand sanitizers.
- Signs and symptoms includes being profoundly intoxicated (more stuporous/ataxic than ethanol)
- Also include nausea, vomiting, abdominal pain (from gastritis), and the smell of acetone
- Will also cause an osmolar gap effect
- Treatment is mainly supportive care.
Scombroid Poisoning
- Scombroid is a common pseudo-allergenic food poisoning syndrome.
- Scombroid poisoning arises from improper storage of dark-meat fish like tuna, mackerel, ski-jack, and bonito.
- Bacterial proliferation in temperatures above 32°F results in the conversion of histidine into histamine.
- Bacterial histidine decarboxylase converts histidine to histamine.
- Scombroid is frequently misdiagnosed as fish allergy.
- Symptoms onset is rapid (10 minutes - 1 hr of ingestion) and Symptoms usually resolve within 6 hrs.
- Patients may notice a 'peppery' flavor to the fish consumed.
- Scombroid mimics anaphylaxis with oral burning sensation, facial flushing, erythema, urticaria, and itching that may progress to bronchospasm, angioedema, and hypotension.
- Treatment is with Parenteral antihistamines.
- Severe cases including hypotension/bronchospasm/airway edema includes epinephrine, solumedrol, and albuterol nebulizer solution.
Ciguatera Poisoning
- Ciguatera poisoning is the most frequently reported seafood illness worldwide.
- Caused by the ingestion of fish that have accumulated ciguatoxins produced by microscopic algae called dinoflagellates.
- Including reef finfish like barracuda, amberjack, moray eel, grouper, snapper, and parrotfish
- Ciguatoxins increase sodium ion permeability and depolarize axons.
- It is heat and acid-stable, therefore it cannot be deactivated by cooking or freezing.
- Diagnosis is primarily clinical with a recent fish-eating history from the patient.
- GI symptoms are the first to appear within 2 - 12hrs of consumption and resolve within 1 - 4 days.
- Neurologic symptoms arise within 2 days of ingestion.
- Classic symptoms includes cold allodynia (hot-cold reversal), paresthesia (stocking-glove & perioral), headache, and dizziness
- Subsequent consumption of fish (especially same type that initially caused symptoms), alcohol, caffeine, and nuts may trigger recurrence of symptoms.
- Some patients develop cardiovascular complications like heart block, bradycardia, and hypotension.
- Treatment is mainly supportive.
Tetrodotoxin
- Tetrodotoxin is a heat-stable neurotoxin mainly found in the liver and skin of pufferfish (fugu) and certain angelfish.
- Bacteria that produce tetrodotoxin accumulate in high doses up the food chain.
- Tetrodotoxin binds fast voltage-gated Na+ channels in nerve tissue, preventing depolarization which can cause possible respiratory failure.
- Patients will typically complain of perioral numbness within 30-minutes of ingestion.
- Symptoms are dose-dependent which include nausea, diarrhea, paresthesia, weakness, dizziness, and loss of reflexes.
- Treatment is supportive, focusing on airway management because of possible respiratory failure.
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