Toxicology and Overdose Management Practice Questions

Q: A 7-year-old girl's parents report a history of fever, for which she was treated with paracetamol, following which the fever subsided. Later, she developed seizures and altered sensorium. Urine examination revealed oxalate crystals on microscopy. Blood anion gap and osmolality were increased. The diagnosis is:

Ethylene glycol. ***Ethylene glycol*** - The presence of **calcium oxalate crystals** in urine, along with a high **anion gap metabolic acidosis** and **increased osmolality**, are classic signs of ethylene glycol poisoning [2]. - Initial symptoms can be vague, but progression to **seizures** and altered sensorium indicates severe toxicity affecting the central nervous system and kidneys [2]. *Lactic acidosis* - While lactic acidosis can cause an **increased anion gap**, it does not typically present with **oxalate crystals** in the urine [1]. - It's a common finding in many critical conditions but doesn't explain the full clinical picture, especially the specific urinary findings. *Renal tubular acidosis* - This condition involves a defect in renal acid excretion or bicarbonate reabsorption, leading to **normal anion gap metabolic acidosis**, not an elevated one. - It is not associated with **oxalate crystals** or acute neurological deterioration like seizures. *Paracetamol poisoning* - Paracetamol overdose primarily causes **hepatotoxicity** and, in severe cases, renal failure, but does not typically lead to **oxalate crystalluria** or an **increased osmolal gap** like ethylene glycol. - The patient was treated with paracetamol for fever, but the subsequent severe symptoms are inconsistent with paracetamol directly causing the described findings.

Q: A patient with salicylic acid poisoning has the following arterial blood gas analysis report: pH is 7.12 , PCO2 is 18 mm Hg HCO3– is 12 mmol/L. The resulting acid-base abnormality can be best labelled

Metabolic acidosis with respiratory alkalosis. ***Metabolic acidosis with respiratory alkalosis*** - The **low pH (7.12)** indicates academia, while the **low HCO3– (12 mmol/L)** points to a **primary metabolic acidosis** [1]. - The **low PCO2 (18 mm Hg)** suggests a **compensatory respiratory alkalosis**, as the body attempts to blow off CO2 to raise pH [1]. *Metabolic acidosis* - While there is a **primary metabolic acidosis (low HCO3–)**, this option fails to recognize the **compensatory respiratory response (low PCO2)** [1]. - In salicylic acid poisoning, both a metabolic acidosis and a respiratory alkalosis (due to direct stimulation of the respiratory center) typically occur together [2]. *Metabolic acidosis with respiratory acidosis* - This option incorrectly identifies a **respiratory acidosis**, which would be characterized by a **high PCO2** [3]. - Salicylate poisoning causes **respiratory stimulation**, leading to a **low PCO2** (respiratory alkalosis), not acidosis [2]. *Respiratory acidosis with metabolic alkalosis* - This option is incorrect because the **low pH** clearly indicates acidosis, not alkalosis [3]. - Additionally, the **low PCO2** indicates respiratory alkalosis, not acidosis, and the **low HCO3–** indicates metabolic acidosis, not alkalosis.

Q: A 50-year-old male with a history of chronic alcoholism presents with altered sensorium and signs of portal hypertension. What is the most appropriate initial management step?

Administer lactulose. ***Administer lactulose*** - The patient's presentation with altered sensorium and chronic alcoholism, coupled with signs of portal hypertension, strongly suggests **hepatic encephalopathy**. [1] - **Lactulose** is the most appropriate initial management step because it helps to reduce ammonia absorption from the gut by acidifying the colon and acting as an osmotic laxative, thereby improving neurological function. [1] *Perform upper gastrointestinal endoscopy (UGIE)* - While **portal hypertension** can lead to varices and bleeding, an UGIE is an invasive procedure and not the immediate priority for a patient presenting with altered sensorium due to suspected hepatic encephalopathy. - UGIE would be indicated if there were active **gastrointestinal bleeding** (e.g., hematemesis, melena) or hemodynamic instability, which are not explicitly mentioned as the primary concern. *Administer chlordiazepoxide* - **Chlordiazepoxide** is a benzodiazepine used to treat **alcohol withdrawal syndrome** (delirium tremens), which can also cause altered mental status. - However, given the signs of portal hypertension, **hepatic encephalopathy** is a more likely cause of altered sensorium, and benzodiazepines can worsen it by precipifying sedation. *Administer thiamine* - **Thiamine** administration is crucial in chronic alcoholics to prevent and treat **Wernicke-Korsakoff syndrome**, which can cause altered mental status, ophthalmoplegia, and ataxia. [2] - While important in all chronic alcoholics, addressing the potentially life-threatening ammonia toxicity in **hepatic encephalopathy** with lactulose takes precedence in the immediate management of altered sensorium.

Q: A 45-year-old woman presents with shortness of breath and cyanosis. Arterial blood gas shows a low oxygen saturation despite a normal PaO2. What is the most likely diagnosis?

Carbon monoxide poisoning. ***Carbon monoxide poisoning*** - **Carbon monoxide** binds to **hemoglobin** with a much higher affinity than oxygen, forming **carboxyhemoglobin (COHb)**, which prevents oxygen transport [1]. - This leads to a low-oxygen saturation reading by pulse oximetry, even when the **partial pressure of oxygen (PaO2)** in the blood is normal, because the PaO2 measures dissolved oxygen, not oxygen bound to hemoglobin [1], [2]. - Furthermore, CO causes a leftward shift of the oxyhemoglobin dissociation curve affecting the offloading of oxygen from hemoglobin to the tissue [1], [2]. *Pulmonary embolism* - A **pulmonary embolism** typically causes **hypoxemia** and a low **PaO2** due to ventilation-perfusion mismatch, which contradicts the normal PaO2 in this case. - While it can cause shortness of breath and cyanosis, the **ABG** findings of **normal PaO2** despite **low oxygen saturation** are not characteristic. *Asthma* - **Asthma** involves **bronchoconstriction** and airflow obstruction, leading to **hypoxemia** and a **low PaO2** in severe cases. - It would not typically present with a normal PaO2 alongside a significantly desaturated pulse oximeter reading, as the PaO2 directly reflects the amount of dissolved oxygen in the blood. *Pneumonia* - **Pneumonia** causes impaired gas exchange due to inflammation and fluid in the alveoli, resulting in **hypoxemia** and a **low PaO2**. - The coexistence of **normal PaO2** with **low oxygen saturation** points away from pneumonia, as the primary issue in pneumonia is usually a failure to oxygenate the blood effectively, thus lowering PaO2.

Q: Which of the following conditions is MOST characteristically associated with central cyanosis?

Methemoglobinemia. ***Methemoglobinemia*** - This condition involves the oxidation of hemoglobin to **methemoglobin**, which cannot bind oxygen effectively and gives blood a characteristic **chocolate-brown color**. [1], [3] - Even with normal oxygen levels, the presence of **deoxygenated methemoglobin** leads to a striking **central cyanosis** that is often out of proportion to oxygen saturation. [1] *Pulmonary embolism* - While a large pulmonary embolism can cause hypoxemia and peripheral cyanosis, **central cyanosis** is not its most characteristic or earliest sign. - The primary mechanism is **ventilation-perfusion mismatch**, which can lead to desaturation but often presents with dyspnea before profound cyanosis. *Severe anemia* - In severe anemia, there is a **reduced amount of hemoglobin** available to become deoxygenated, even if oxygen transport is inadequate. [2] - Patients with severe anemia are often **pale** rather than cyanotic because the absolute amount of deoxygenated hemoglobin required to produce cyanosis (typically 5 g/dL) is not met. *Congestive heart failure* - Severe heart failure can lead to **peripheral cyanosis** due to poor perfusion and increased oxygen extraction in the tissues. - **Central cyanosis** may occur in decompensated heart failure with significant pulmonary edema causing hypoxemia, but it is not the most uniquely characteristic initial sign compared to methemoglobinemia.

Q: A 40-year-old male presents with altered mental status and metabolic acidosis. His blood tests show a high anion gap and osmolar gap. Which poison would you suspect?

Methanol. ***Methanol*** - **Methanol** poisoning typically leads to a **high anion gap metabolic acidosis** due to the accumulation of formic acid, which is a toxic metabolite [1], [2]. - It also causes a **high osmolar gap** because methanol itself is an osmotically active substance in the bloodstream [1], [3]. *Ethanol* - While ethanol can cause a high osmolar gap, it generally does **not cause a high anion gap metabolic acidosis** unless consumed in extremely large quantities or in conjunction with other conditions like alcoholic ketoacidosis. - **Ethanol** metabolism primarily leads to the production of acetate, which does not contribute significantly to an elevated anion gap. *Isopropanol* - Isopropanol poisoning commonly results in a **high osmolar gap** due to the presence of isopropanol in the blood and its metabolite, acetone [1]. - However, it typically causes **ketosis without acidosis** or only a mild metabolic acidosis, as acetone is not a strong acid. *Benzene* - **Benzene** exposure is primarily associated with **bone marrow suppression** (aplastic anemia, leukemia) and neurological effects, not with significant metabolic acidosis or a high osmolar gap in acute overdose. - Its toxic effects are distinct from those seen with alcohol-based poisonings.

Q: A 40-year-old female presents to the emergency department after ingesting an unknown quantity of acetaminophen. Laboratory results show elevated ALT and AST, increased PT, and decreased glucose. Analyze and determine the most appropriate treatment.

N-acetylcysteine. ***N-acetylcysteine*** - **N-acetylcysteine (NAC)** is the antidote for **acetaminophen overdose** and is critically important when there is evidence of liver damage (elevated ALT/AST, increased PT) and metabolic derangements (decreased glucose) [1]. - NAC works by replenishing **glutathione stores**, which helps detoxify the toxic metabolite **NAPQI**, preventing further hepatocellular damage [1]. *Activated charcoal* - **Activated charcoal** can be used for initial management of acetaminophen overdose, but only if administered within **1-2 hours** of ingestion to prevent absorption [2]. - Given the presence of **liver damage** (elevated ALT/AST, abnormal PT), it is likely that significant absorption has already occurred, making activated charcoal less effective now. *Liver transplant evaluation* - **Liver transplant evaluation** is indicated in cases of **fulminant hepatic failure** due to acetaminophen overdose that is unresponsive to NAC or where irreversible damage has occurred. - While the patient shows signs of liver injury, NAC is the **first-line treatment** aimed at reversing the damage and should be initiated promptly before considering transplantation. *Gastric lavage* - **Gastric lavage** is generally not recommended for acetaminophen overdose due to the **risk of complications** (e.g., aspiration) and **limited efficacy**, especially if not performed within 1 hour of ingestion. - Current guidelines prioritize oral activated charcoal within a narrow window, and NAC for established liver toxicity.

Q: Which metal poisoning is most commonly associated with nephropathy and may also cause muscle pain?

Cadmium. ***Cadmium*** - **Cadmium** exposure is strongly linked to **renal tubular dysfunction** and nephropathy, leading to impaired kidney function [1]. - While less common than kidney effects, cadmium toxicity can also manifest as **muscle pain** (myalgia) and bone pain due to its impact on calcium metabolism [1]. *Arsenic* - **Arsenic poisoning** primarily affects the skin (hyperkeratosis, hyperpigmentation), gastrointestinal tract (nausea, vomiting, diarrhea), and nervous system (neuropathy). - Although it can cause renal damage in severe acute cases, **nephropathy** is not its most common or defining feature compared to cadmium. *Lead* - **Lead poisoning** is well-known for causing **neurotoxicity** (encephalopathy in children, peripheral neuropathy in adults), **hematological abnormalities** (anemia), and **gastrointestinal symptoms** (colic). - While lead can cause chronic nephropathy (interstitial nephritis), it is not as predominantly associated with renal tubular damage and muscle pain in the same way as cadmium [2]. *Mercury* - **Mercury poisoning** typically presents with neurological symptoms (tremors, ataxia, behavioral changes from elemental mercury; paresthesias, visual disturbances from organic mercury). - **Kidney damage** (glomerular disease, nephrotic syndrome) can occur with inorganic mercury exposure, but it is not as consistently associated with tubular nephropathy and muscle pain as cadmium.

Q: Indications for liver transplant in PCM poisoning include all of the following except?

SGPT increase. ***SGPT increase*** - An increase in **SGPT (ALT)** is an indicator of **liver damage**, but its absolute value alone is not a direct indication for **liver transplantation** in paracetamol (PCM) poisoning. More critical parameters are used for this decision. - While it signals liver injury, other factors like **coagulopathy** and **encephalopathy** are more directly linked to severe liver failure necessitating transplant consideration. *PT > 100 seconds or INR > 6.5* - A **prothrombin time (PT)** greater than 100 seconds or an **INR** greater than 6.5 indicates severe **coagulopathy**, a critical sign of **acute liver failure** and a strong indication for liver transplantation according to the **King's College Criteria**. - This reflects a profound impairment of the liver's synthetic function to produce **clotting factors**, leading to a high risk of bleeding. *High creatinine* - A **high creatinine level** indicates **renal impairment** or **acute kidney injury**, which is a common complication of severe **paracetamol poisoning** due to **hepatorenal syndrome** or direct toxicity. - Significant renal dysfunction, especially when coupled with other signs of severe liver failure, is a major component of the **King's College Criteria** for liver transplant. *Encephalopathy* - The presence of **encephalopathy** (any grade) in the setting of **acute liver failure** due to paracetamol poisoning is a crucial indicator for considering liver transplantation. - **Encephalopathy** signifies massive hepatocellular necrosis and the liver's inability to detoxify harmful substances, leading to neurological dysfunction.

Q: What type of neuropathy is most commonly associated with arsenic poisoning?

Symmetric peripheral sensory neuropathy. ***Symmetric peripheral sensory neuropathy*** - Arsenic poisoning commonly causes a **symmetric peripheral neuropathy**, primarily affecting **sensory nerves** [1]. - Patients often experience a **stocking-glove distribution** of paresthesias, numbness, and pain due to damage to longer nerve fibers [1]. *Asymmetrical peripheral motor neuropathy* - This type of neuropathy is **less characteristic** of arsenic poisoning, which predominantly affects sensory fibers symmetrically. - **Motor deficits** can occur but are typically secondary to sensory loss and not primarily asymmetric. *Symmetrical peripheral motor neuropathy* - While arsenic can affect motor nerves, it's typically a **secondary effect** and not the primary presentation. - The most prominent and initial neuropathy in arsenic poisoning is **sensory**, not purely motor. *Asymmetrical peripheral sensory neuropathy* - The sensory neuropathy in arsenic poisoning is characteristically **symmetrical**, affecting both sides of the body equally. - Asymmetrical presentation is **uncommon** for arsenic-induced neuropathy.

Question 1

A 7-year-old girl's parents report a history of fever, for which she was treated with paracetamol, following which the fever subsided. Later, she developed seizures and altered sensorium. Urine examination revealed oxalate crystals on microscopy. Blood anion gap and osmolality were increased. The diagnosis is:

Accepted Answer

Ethylene glycol

Answer

Lactic acidosis

Answer

Renal tubular acidosis

Answer

Paracetamol poisoning

Question 2

A patient with salicylic acid poisoning has the following arterial blood gas analysis report: pH is 7.12 , PCO2 is 18 mm Hg HCO3– is 12 mmol/L. The resulting acid-base abnormality can be best labelled

Accepted Answer

Metabolic acidosis with respiratory alkalosis

Answer

Metabolic acidosis

Answer

Metabolic acidosis with respiratory acidosis

Answer

Respiratory acidosis with metabolic alkalosis

Question 3

A 50-year-old male with a history of chronic alcoholism presents with altered sensorium and signs of portal hypertension. What is the most appropriate initial management step?

Accepted Answer

Administer lactulose

Answer

Perform upper gastrointestinal endoscopy (UGIE)

Answer

Administer chlordiazepoxide

Answer

Administer thiamine

Question 4

A 45-year-old woman presents with shortness of breath and cyanosis. Arterial blood gas shows a low oxygen saturation despite a normal PaO2. What is the most likely diagnosis?

Accepted Answer

Carbon monoxide poisoning

Answer

Pulmonary embolism

Answer

Asthma

Answer

Pneumonia

Question 5

Which of the following conditions is MOST characteristically associated with central cyanosis?

Accepted Answer

Methemoglobinemia

Answer

Pulmonary embolism

Answer

Severe anemia

Answer

Congestive heart failure

Question 6

A 40-year-old male presents with altered mental status and metabolic acidosis. His blood tests show a high anion gap and osmolar gap. Which poison would you suspect?

Accepted Answer

Methanol

Answer

Ethanol

Answer

Isopropanol

Answer

Benzene

Question 7

A 40-year-old female presents to the emergency department after ingesting an unknown quantity of acetaminophen. Laboratory results show elevated ALT and AST, increased PT, and decreased glucose. Analyze and determine the most appropriate treatment.

Accepted Answer

N-acetylcysteine

Answer

Activated charcoal

Answer

Liver transplant evaluation

Answer

Gastric lavage

Question 8

Which metal poisoning is most commonly associated with nephropathy and may also cause muscle pain?

Accepted Answer

Cadmium

Answer

Lead

Answer

Arsenic

Answer

Mercury

Question 9

Indications for liver transplant in PCM poisoning include all of the following except?

Accepted Answer

SGPT increase

Answer

PT > 100 seconds or INR > 6.5

Answer

High creatinine

Answer

Encephalopathy

Question 10

What type of neuropathy is most commonly associated with arsenic poisoning?

Accepted Answer

Symmetric peripheral sensory neuropathy

Answer

Asymmetrical peripheral motor neuropathy

Answer

Symmetrical peripheral motor neuropathy

Answer

Asymmetrical peripheral sensory neuropathy

Toxicology and Overdose Management — MCQs

Toxicology and Overdose Management — MCQs

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