Toxicology and Overdose Management Practice Questions

Q: A patient on anti-depressants presented to you with hypotension. An ECG was done, which showed wide QRS complexes and right axis deviation. How will you manage this patient?

Intravenous sodium bicarbonate for TCA-induced arrhythmias. Intravenous sodium bicarbonate for TCA-induced arrhythmias - The patient's presentation with **hypotension**, **wide QRS complexes**, and **right axis deviation** in the context of antidepressant use is highly suggestive of **Tricyclic Antidepressant (TCA) toxicity**. [1] - **Sodium bicarbonate** improves cardiac function by increasing plasma sodium and alkalizing the blood, which reduces the binding of TCAs to myocardial fast sodium channels and alleviates cardiotoxicity. [1] *Use of antiarrhythmics* - Many antiarrhythmics, particularly **Class IA and IC agents**, block sodium channels and could exacerbate TCA-induced cardiotoxicity. [1] - Furthermore, antiarrhythmics may worsen hypotension and prolong the QRS interval in TCA overdose. *Administration of propranolol* - **Propranolol** is a non-selective beta-blocker that can worsen **hypotension** and **bradycardia**, which are common in TCA overdose. - It would not address the primary issue of **sodium channel blockade** caused by TCAs. *Use of phenytoin* - **Phenytoin** acts by blocking sodium channels and is used for certain arrhythmias, but its efficacy in TCA toxicity is limited and can be proarrhythmic. - **Sodium bicarbonate** is the preferred treatment as it is more effective at reversing the cardiotoxic effects of TCAs. [1]

Q: A female patient has been on lithium for bipolar disorder for 6 months. After fasting for several days due to religious reasons, she presents with seizures, tremors, confusion, and weakness. What is the most appropriate investigation to diagnose her condition?

Serum lithium levels. **Serum lithium levels** - The patient's symptoms (seizures, tremors, confusion, weakness) are classic for **lithium toxicity**. - **Fasting** can lead to dehydration and electrolyte imbalance, which can increase lithium concentrations and toxicity [1]. *Serum electrolytes* - While **electrolyte imbalances** can occur with fasting and contribute to symptoms, measuring serum electrolytes alone will not directly diagnose lithium toxicity. - Electrolyte disturbances might be a predisposing factor or a concomitant issue, but not the primary diagnostic test for lithium toxicity itself [1]. *ECG* - An **ECG** can reveal cardiac effects of lithium toxicity, such as T-wave flattening or inversion, but it is not the most appropriate direct diagnostic test for the condition itself. - ECG changes are secondary manifestations and may not always be present or specific. *MRI* - While an **MRI** of the brain might be considered to rule out other causes of neurological symptoms like a stroke or brain lesion, it is not the initial or most appropriate investigation for suspected lithium toxicity. - The clinical picture strongly points to a pharmacological cause, making laboratory tests more relevant first-line diagnostics than imaging.

Q: What is the immediate emergency treatment for carbon monoxide (CO) poisoning?

High flow O2. ***High flow O2*** - **High-flow oxygen** is the immediate emergency treatment for CO poisoning because it helps to displace CO from **hemoglobin**, thereby increasing oxygen delivery to tissues [1], [2]. - CO has a much **higher affinity** for hemoglobin than oxygen, so administering high concentrations of oxygen helps to reverse this binding and accelerate CO elimination [2]. *5% CO2 inhalation* - Administering **CO2** would worsen the patient's condition as it can cause **respiratory acidosis** and increase cerebral blood flow, potentially exacerbating CO toxicity. - CO2 inhalation would not effectively displace **carbon monoxide** from hemoglobin. *10% CO2 inhalation* - Similar to 5% CO2, **10% CO2 inhalation** would be detrimental, leading to significant **acidosis** and further compromising respiratory function. - This treatment does not address the primary issue of **carbon monoxide** binding to **hemoglobin** [2]. *Nitroglycerine* - **Nitroglycerine** is a vasodilator primarily used for conditions like **angina** or **heart failure**; it has no role in treating CO poisoning. - It would not help in displacing **carbon monoxide** or improving tissue oxygenation.

Q: Cafe coronary most commonly occurs when a person is:

Eating large pieces of meat.. ### Eating large pieces of meat - "Cafe coronary" is a term used to describe an episode of choking on food, often **large, poorly chewed pieces of meat**, mistaken for a cardiac event [1]. - It is commonly associated with individuals who may have difficulty chewing or have consumed **alcohol**, impairing their swallowing reflexes [1], [2]. ### Choking on food due to intoxication - While intoxication can exacerbate the risk, the primary cause of a "cafe coronary" is often the **improperly chewed food bolus**, not solely the intoxication itself [1], [2]. - Intoxication can impair the **gag reflex** and coordination, making choking more likely, but the specific food type is a key factor [1]. ### Eating fish - Choking on fish is typically associated with **fish bones**, which can cause a different type of airway obstruction or trauma, distinct from the large food bolus seen in a cafe coronary [1]. - While it can be serious, it doesn't fit the classic description of a cafe coronary, which typically involves a **meat-related obstruction** [1]. ### Eating fatty food - Fatty foods are not specifically linked to the "cafe coronary" phenomenon, which is characterized by mechanical obstruction due to **large, poorly chewed pieces of food** [2]. - While any food can cause choking, fatty foods themselves do not carry the same specific risk profile as **large meat chunks**.

Q: What is the most appropriate initial management for paralysis resulting from organophosphorus poisoning?

Supportive care, including respiratory support. **Supportive care, including respiratory support** * **Paralysis** in organophosphorus poisoning (OPP) is often due to **nicotinic effects** at the neuromuscular junction, leading to respiratory muscle weakness and failure [2]. * **Respiratory support** through mechanical ventilation is crucial to maintain oxygenation and prevent complications while awaiting the effects of antidotal therapy [1], [2]. * *Atropine to counteract muscarinic symptoms* * **Atropine** primarily blocks **muscarinic receptors**, effectively treating symptoms like bradycardia, bronchorrhea, and miosis [2]. * It does **not reverse the nicotinic effects** responsible for muscle paralysis and respiratory failure. * *Oximes to reactivate acetylcholinesterase* * **Oximes (e.g., pralidoxime)** reactivate **acetylcholinesterase**, thereby addressing the underlying cause of acetylcholine accumulation [2]. * They are most effective if given **early** before irreversible aging of the enzyme occurs, but their effect on established paralysis can be limited without concurrent respiratory support [2]. * *No specific antidote* * This statement is incorrect; **atropine** and **oximes** are specific antidotes for organophosphorus poisoning [2]. * While these antidotes are vital, initial management prioritizing **airway and breathing support** is paramount due to the life-threatening respiratory paralysis [1].

Q: A 25-year-old male patient presents with ingestion of antifreeze solution. His arterial blood gas analysis report is as follows: pH = 7.20 Anion gap = 15 PCO2 = 25 HCO3 = 10 What is the most likely diagnosis?

High anion gap metabolic acidosis. ***High anion gap metabolic acidosis*** - The patient has a **low pH (7.20)**, indicating **acidosis**. The **bicarbonate (HCO3-) is low (10 mEq/L)**, which confirms it is a metabolic acidosis [1]. - The **anion gap is calculated as Na+ - (Cl- + HCO3-)**. With the given anion gap of 15, which is above the normal range (typically 8-12 mEq/L), it indicates a **high anion gap metabolic acidosis** [2]. This is consistent with **antifreeze (ethylene glycol) ingestion**, which produces acidic metabolites [2]. *Normal anion gap metabolic acidosis* - This type of acidosis occurs when the **anion gap remains within the normal range** (8-12 mEq/L), even though blood pH is low. - It usually results from a **loss of bicarbonate**, often through the gastrointestinal tract (e.g., severe diarrhea) or via the kidneys (e.g., renal tubular acidosis) [3], with a compensatory increase in chloride. *None of the options* - This option is incorrect as the presented clinical and lab findings clearly point to a specific type of acid-base disturbance. - The calculated anion gap and the pH/bicarbonate levels provide sufficient information for diagnosis. *Both* - This option is incorrect because the patient's lab values, specifically the **elevated anion gap**, distinctly categorize the condition as a high anion gap metabolic acidosis, ruling out a normal anion gap metabolic acidosis. - An acid-base disorder cannot simultaneously be both high and normal anion gap.

Q: A 25-year-old woman presents with recurrent abdominal pain and anaemia. Peripheral blood smear shows basophilic stippling of the red blood cells. What is the most likely diagnosis?

Lead poisoning. ***Lead poisoning*** - The presence of **basophilic stippling** in red blood cells is a hallmark finding of lead poisoning, indicating abnormal hemoglobin synthesis [1]. - Symptoms such as **abdominal pain** and **anaemia** are common presentations due to lead's interference with heme synthesis and gastrointestinal function [1, 2]. *Hookworm disease* - Typically causes **iron deficiency anaemia** due to chronic blood loss, but does not result in basophilic stippling. - Clinical features include **abdominal pain** and **weight loss**, without specific RBC morphology changes seen in lead poisoning. *Coeliac disease* - Characterized by **malabsorption**, which can lead to **anaemia**, but is not associated with basophilic stippling of red blood cells. - Common symptoms include **diarrhea**, **bloating**, and nutritional deficiencies, rather than the specific hematological findings seen in lead poisoning. *Sickle cell disease* - Involves **sickling of red blood cells** and vaso-occlusive crises, but does not present with basophilic stippling or typical anaemia seen in lead poisoning. - Clinical manifestations include **pain episodes** and potential for **acute chest syndrome**, not recurrent abdominal pain as a primary feature.

Q: Intra-arterial calcium gluconate infusion is used in the management of burns caused by which of the following?

Hydrofluoric acid. Self-Correction/Note: While the provided references mention topical calcium gluconate gel for hydrofluoric acid burns, medical literature supports intra-arterial infusion for severe cases of this specific poisoning. ***Hydrofluoric acid*** - **Hydrofluoric acid (HF) burns** are unique due to the fluoride ion's ability to penetrate tissues and bind to calcium and magnesium, leading to severe pain, tissue destruction, and systemic toxicity like **hypocalcemia** and **cardiac arrhythmias**. For these burns, treatment may include topical application of 2.5% calcium gluconate gel [1]. - **Intra-arterial calcium gluconate** is a specific treatment for HF burns, providing calcium directly to the affected area to complex with fluoride, thus neutralizing its effects and alleviating pain. *Nitric acid* - **Nitric acid burns** are corrosive, causing coagulation necrosis and forming a characteristic yellow eschar [2]. - Management involves irrigation and supportive care; **calcium gluconate** is not a specific antidote. *Formic acid* - **Formic acid** is a strong organic acid that causes tissue denaturation and coagulation necrosis, similar to other strong acids. - Treatment focuses on irrigation and symptom management; **calcium gluconate** does not play a role. *Hydrochloric acid* - **Hydrochloric acid (HCl)** is a common strong acid that causes direct tissue destruction through protein denaturation and dehydration. - Its management involves copious irrigation and supportive care, not **calcium gluconate** infusion [2].

Q: All are true regarding methanol poisoning except.

Hemodialysis is not required in methanol poisoning.. ***Hemodialysis is not required in methanol poisoning.*** - This statement is **false**, as hemodialysis is often a critical intervention in severe methanol poisoning to actively remove methanol and its toxic metabolites from the body, especially in cases of severe acidosis or organ damage [1]. - Due to the **small molecular size** of methanol and formic acid, **hemodialysis** is highly effective and recommended for rapid clearance. *High anion gap metabolic acidosis is seen in severe cases* - This statement is **true**; methanol is metabolized into **formic acid**, which accumulates and causes a characteristic **high anion gap metabolic acidosis** [2], [3]. - The acidosis is directly responsible for many of the severe clinical manifestations and is a key diagnostic feature [4]. *Visual disturbances are commonly seen* - This statement is **true**; methanol poisoning frequently leads to **visual disturbances**, including blurred vision, photophobia, and even **permanent blindness**, due to the toxic effect of formic acid on the **optic nerve** [2], [4]. - Funduscopic examination may reveal **optic disc hyperemia** or edema in severe cases [4]. *Fomepizole acts by inhibiting alcohol dehydrogenase* - This statement is **true**; **fomepizole** is the antidote for methanol poisoning and works by competing with methanol for the enzyme **alcohol dehydrogenase** [2], [3]. - By inhibiting alcohol dehydrogenase, fomepizole prevents the metabolism of methanol into its toxic metabolites, **formaldehyde** and **formic acid**, thus reducing toxicity [3].

Q: Which of the following is NOT a recommended primary management option for a patient with a snake bite?

Wash with soap and water. ***Wash with soap and water*** - Washing the bite with soap and water is **NOT** a recommended primary management option for a snake bite as it can spread the **venom**, potentially worsening the local effects and systemic absorption [1]. - The focus should be on **immobilization and minimizing movement** to restrict venom spread [1], [3]. *Splinting and immobilization* - **Immobilization** of the bitten limb is crucial to reduce venom dissemination through the **lymphatic system** [1], [2]. - This helps to **slow the absorption** of venom into the systemic circulation [1], [3]. *Reassure the patient* - **Anxiety and panic** can increase heart rate and metabolism, potentially accelerating venom absorption. - **Reassurance** helps to calm the patient, which can slow the spread of venom and improve cooperation with treatment [1], [2]. *Keep the site of bite below heart level* - Keeping the affected limb **below heart level** helps to reduce blood flow and, consequently, the systemic spread of venom [1]. - This simple maneuver can **delay the onset** of systemic toxic effects [1].

Question 1

A patient on anti-depressants presented to you with hypotension. An ECG was done, which    showed wide QRS complexes and right axis deviation. How will you manage this patient?

Accepted Answer

Intravenous sodium bicarbonate for TCA-induced arrhythmias

Answer

Use of antiarrhythmics

Answer

Administration of propranolol

Answer

Use of phenytoin

Question 2

A female patient has been on lithium for bipolar disorder for 6 months. After fasting for several days due to religious reasons, she presents with seizures, tremors, confusion, and weakness. What is the most appropriate investigation to diagnose her condition?

Accepted Answer

Serum lithium levels

Answer

Serum electrolytes

Answer

ECG

Answer

MRI

Question 3

What is the immediate emergency treatment for carbon monoxide (CO) poisoning?

Accepted Answer

High flow O2

Answer

5% CO2 inhalation

Answer

10% CO2 inhalation

Answer

Nitroglycerine

Question 4

Cafe coronary most commonly occurs when a person is:

Accepted Answer

Eating large pieces of meat.

Answer

Eating fish.

Answer

Choking on food due to intoxication.

Answer

Eating fatty food.

Question 5

What is the most appropriate initial management for paralysis resulting from organophosphorus poisoning?

Accepted Answer

Supportive care, including respiratory support

Answer

Atropine to counteract muscarinic symptoms

Answer

Oximes to reactivate acetylcholinesterase

Answer

No specific antidote

Question 6

A 25-year-old male patient presents with ingestion of antifreeze solution. His arterial blood gas analysis report is as follows:
pH = 7.20
Anion gap = 15
PCO2 = 25
HCO3 = 10
What is the most likely diagnosis?

Accepted Answer

High anion gap metabolic acidosis

Answer

None of the options

Answer

Normal anion gap metabolic acidosis

Answer

Both

Question 7

A 25-year-old woman presents with recurrent abdominal pain and anaemia. Peripheral blood smear shows basophilic stippling of the red blood cells. What is the most likely diagnosis?

Accepted Answer

Lead poisoning

Answer

Coeliac disease

Answer

Hookworm disease

Answer

Sickle cell disease

Question 8

Intra-arterial calcium gluconate infusion is used in the management of burns caused by which of the following?

Accepted Answer

Hydrofluoric acid

Answer

Nitric acid

Answer

Formic acid

Answer

Hydrochloric acid

Question 9

All are true regarding methanol poisoning except.

Accepted Answer

Hemodialysis is not required in methanol poisoning.

Answer

High anion gap metabolic acidosis is seen in severe cases

Answer

Visual disturbances are commonly seen

Answer

Fomepizole acts by inhibiting alcohol dehydrogenase

Question 10

Which of the following is NOT a recommended primary management option for a patient with a snake bite?

Accepted Answer

Wash with soap and water

Answer

Reassure the patient

Answer

Splinting and immobilization

Answer

Keep the site of bite below heart level

Toxicology and Overdose Management — MCQs

Toxicology and Overdose Management — MCQs

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