Malignant Hyperthermia — MCQs
HR-180, BP-60/40, temp-39.5°C, ETCO2-65 post induction. Most likely diagnosis:
Which of the following statements about malignant hyperthermia is incorrect?
Drug used in treatment of malignant hyperthermia is
Which of the following is the most potent trigger of malignant hyperthermia?
Malignant hyperthermia is
All are seen in malignant hyperthermia except:
30 year old lady was on the OT and during the mastoidectomy, after having inhalational anaesthesia, suddenly developed fever, increased heart rate, raised BP, acidosis and arrythmia. What is the next best intervention?
Which of the following anesthetic agents does not trigger malignant hyperthermia?
All the following cause malignant hyperpyrexia except?
A child during anesthesia with halothane and succinylcholine develops severe stiffness of masseters. What is the most probable diagnosis?
Malignant Hyperthermia Indian Medical PG Practice Questions and MCQs
Question 1: HR-180, BP-60/40, temp-39.5°C, ETCO2-65 post induction. Most likely diagnosis:
- A. Thyroid storm
- B. Anaphylaxis
- C. Septic shock
- D. Malignant hyperthermia (Correct Answer)
Explanation: ***Malignant hyperthermia*** - The rapid onset of **tachycardia (HR-180)**, **hyperthermia (temp-39.5°C)**, and profoundly elevated **ETCO2 (65 mmHg)** immediately following anesthetic induction is the classic presentation of malignant hyperthermia. - This condition is a pharmacogenetic disorder, triggered by volatile anesthetics (e.g., isoflurane) and succinylcholine, leading to uncontrolled skeletal muscle metabolism and hypercapnia. *Thyroid storm* - While thyroid storm can cause **tachycardia** and **hyperthermia**, the sudden and dramatic rise in **ETCO2** is not a characteristic feature. - Onset is typically less abrupt and often associated with pre-existing hyperthyroidism or a precipitating event like surgery or infection, rather than immediate post-induction. *Anaphylaxis* - Anaphylaxis typically presents with **hypotension (BP-60/40)**, **tachycardia**, and often features like **bronchospasm**, **rash**, or **angioedema**. - Although it can cause **bronchospasm** leading to increased ETCO2, the extreme elevation to 65 mmHg is less typical, and **profound hyperthermia** is not a primary symptom. *Septic shock* - **Septic shock** is characterized by **hypotension** and **tachycardia**, often accompanied by **fever**, but its onset is usually prolonged over hours to days. - A sudden increase in **ETCO2** to 65 mmHg immediately post-induction is uncharacteristic for sepsis, which relates to an exaggerated, systemic inflammatory response to infection.
Question 2: Which of the following statements about malignant hyperthermia is incorrect?
- A. End tidal CO₂ is decreased during the episode. (Correct Answer)
- B. Dantrolene is the drug of choice for treatment.
- C. Most common cause is a mutation in the ryanodine receptor.
- D. Tachycardia occurs during the episode.
Explanation: ***End tidal CO₂ is decreased during the episode.*** - Malignant hyperthermia causes **increased metabolism and CO₂ production**, leading to a significant **elevation in end-tidal CO₂**, not a decrease. - The rapid rise in **end-tidal CO₂** is often one of the earliest and most sensitive signs of a malignant hyperthermia crisis. *Dantrolene is the drug of choice for treatment.* - **Dantrolene** is indeed the specific treatment for malignant hyperthermia, as it acts on the **ryanodine receptor** to reduce calcium release from the sarcoplasmic reticulum. - This statement is **correct**, and therefore not the incorrect statement sought by the question. *Most common cause is a mutation in the ryanodine receptor.* - The most common genetic defect underlying malignant hyperthermia is a mutation in the **RYR1 gene**, which codes for the **ryanodine receptor type 1** (RyR1). - This mutation leads to an uncontrolled release of **intracellular calcium** from the sarcoplasmic reticulum in muscle cells. *Tachycardia occurs during the episode.* - **Tachycardia** is a common and early sign of malignant hyperthermia due to the increased metabolic rate and sympathetic nervous system activation. - This rapid heart rate contributes to the overall physiological stress during the crisis.
Question 3: Drug used in treatment of malignant hyperthermia is
- A. Phenobarbitone
- B. Dantrolene (Correct Answer)
- C. Paracetamol
- D. Diazepam
Explanation: ***Dantrolene*** - **Dantrolene** is a direct-acting **skeletal muscle relaxant** that works by preventing calcium release from the sarcoplasmic reticulum. - This mechanism effectively counteracts the excessive calcium efflux responsible for the sustained muscle contraction and hypermetabolic state in **malignant hyperthermia**. *Phenobarbitone* - **Phenobarbitone** is a barbiturate primarily used as an **anticonvulsant** and sedative-hypnotic. - It has no direct muscle relaxant properties or specific action to address the underlying pathophysiology of **malignant hyperthermia**. *Paracetamol* - **Paracetamol** (acetaminophen) is an **analgesic** and **antipyretic**. - While it can help manage fever, it does not address the fundamental muscle rigidity, metabolic acidosis, or **calcium dysregulation** characteristic of malignant hyperthermia. *Diazepam* - **Diazepam** is a benzodiazepine primarily used for its **anxiolytic**, sedative, and **anticonvulsant** properties, acting on GABA receptors. - It would not treat the underlying **muscle rigidity** and hypermetabolism of malignant hyperthermia, though it might reduce anxiety.
Question 4: Which of the following is the most potent trigger of malignant hyperthermia?
- A. Thiopentone
- B. Isoflurane
- C. Suxamethonium
- D. Halothane (Correct Answer)
Explanation: ***Halothane*** - **Halothane** is a volatile anesthetic agent and the **most potent trigger** of malignant hyperthermia, directly acting on the **ryanodine receptor (RyR1)** to cause massive calcium release from the sarcoplasmic reticulum. - It has extensive historical documentation as the **primary MH trigger** and is used as the reference standard in MH susceptibility testing. *Suxamethonium* - **Suxamethonium** (succinylcholine) is a depolarizing neuromuscular blocking agent that can trigger malignant hyperthermia but is considered a **secondary trigger** compared to volatile anesthetics. - While it can independently cause MH episodes, volatile agents like **halothane** are recognized as more potent and primary triggers in current medical literature. *Thiopentone* - **Thiopentone** (thiopental) is an intravenous barbiturate anesthetic that is **safe** in patients susceptible to malignant hyperthermia. - It does not interact with the **ryanodine receptor (RyR1)** or cause uncontrolled calcium release, making it a preferred induction agent in MH-susceptible patients. *Isoflurane* - **Isoflurane** is a volatile anesthetic agent and a **potent trigger** of malignant hyperthermia, similar to halothane in its mechanism of action. - While equally potent as halothane, **halothane** is considered the classic reference trigger due to its historical significance and extensive research documentation.
Question 5: Malignant hyperthermia is
- A. Metabolic alkalosis and hypokalemia
- B. Calcium infusion is used for treatment.
- C. Autosomal recessive pharmacogenetic disease
- D. Succinylcholine is a triggering agent (Correct Answer)
Explanation: ***Succinylcholine is a triggering agent*** - **Succinylcholine**, a depolarizing neuromuscular blocker, is a potent trigger for malignant hyperthermia due to its interaction with the **ryanodine receptor**. - Other common triggering agents include **volatile anesthetic agents** such as halothane, isoflurane, and sevoflurane, all leading to uncontrolled calcium release. *Metabolic alkalosis and hypokalemia* - Malignant hyperthermia typically presents with a rapidly developing severe **metabolic acidosis**, not alkalosis, due to increased lactic acid production from muscle hypermetabolism. - Patients usually experience **hyperkalemia** due to muscle cell breakdown and potassium release, which can lead to cardiac arrhythmias. *Calcium infusion is used for treatment.* - The immediate treatment for malignant hyperthermia is **dantrolene sodium**, which acts by blocking calcium release from the sarcoplasmic reticulum in muscle cells. - **Calcium channel blockers** are generally contraindicated in malignant hyperthermia, especially when dantrolene has been administered, due to the risk of exacerbating hyperkalemia. *Autosomal recessive pharmacogenetic disease* - Malignant hyperthermia is inherited as an **autosomal dominant** pharmacogenetic disorder, primarily linked to mutations in the **RYR1 gene** (ryanodine receptor 1 gene). - This dominant inheritance pattern means that only one copy of the mutated gene is sufficient to predispose an individual to the condition.
Question 6: All are seen in malignant hyperthermia except:
- A. Bradycardia (Correct Answer)
- B. Hypertension
- C. Metabolic acidosis
- D. Hyperkalemia
Explanation: ***Bradycardia*** - Malignant hyperthermia is characterized by a hypermetabolic state, which typically causes **tachycardia** (increased heart rate) due to increased oxygen demand and catecholamine release, not bradycardia. - **Bradycardia** is not a hallmark sign of malignant hyperthermia; rather, it indicates an atypical or late-stage cardiac compromise. *Hypertension* - **Hypertension** is a common early sign of malignant hyperthermia due to intense **vasoconstriction** and release of catecholamines in response to the hypermetabolic state. - The elevated blood pressure reflects the body's attempt to increase oxygen delivery to tissues. *Metabolic acidosis* - The massive increase in cellular metabolism and oxygen consumption leads to an accumulation of **lactic acid**, resulting in a profound **metabolic acidosis**. - This acidotic state can significantly impair cardiac function and cellular processes. *Hyperkalemia* - Widespread **muscle rigidity** and breakdown (rhabdomyolysis) cause the release of intracellular potassium into the bloodstream, leading to **hyperkalemia**. - Severe hyperkalemia can lead to life-threatening **cardiac arrhythmias**.
Question 7: 30 year old lady was on the OT and during the mastoidectomy, after having inhalational anaesthesia, suddenly developed fever, increased heart rate, raised BP, acidosis and arrythmia. What is the next best intervention?
- A. Antipyretics
- B. Sodium bicarbonate
- C. Procainamide
- D. Dantrolene (Correct Answer)
Explanation: ***Dantrolene*** - The patient's presentation with **fever**, **tachycardia**, **hypertension**, **acidosis**, and **arrhythmia** during inhalational anesthesia is highly indicative of **malignant hyperthermia**. - **Dantrolene** is the specific and most effective treatment for malignant hyperthermia as it acts by interfering with muscle contraction by blocking calcium release from the sarcoplasmic reticulum. *Antipyretics* - While the patient has a fever, **antipyretics** like paracetamol or NSAIDs are not sufficient to manage the rapidly rising core body temperature in malignant hyperthermia. - The fever is a symptom of severe metabolic dysregulation, and simple antipyresis does not address the underlying pathology. *Sodium bicarbonate* - The patient has acidosis, but **sodium bicarbonate** is used to correct metabolic acidosis by buffering excess acid only after the primary cause is addressed. - While it may be used as supportive care, it does not treat the underlying mechanism of malignant hyperthermia. *Procainamide* - **Procainamide** is an antiarrhythmic drug used to treat various arrhythmias but does not address the fundamental cause of the arrhythmias in malignant hyperthermia. - The arrhythmias in malignant hyperthermia are a consequence of severe metabolic derangements and hyperkalemia, which require dantrolene and supportive care to resolve.
Question 8: Which of the following anesthetic agents does not trigger malignant hyperthermia?
- A. Isoflurane
- B. Suxamethonium
- C. Halothane
- D. Thiopentone (Correct Answer)
Explanation: ***Thiopentone*** - **Thiopentone** is an **intravenous anesthetic agent** that does not trigger **malignant hyperthermia** because it does not interact with the **ryanodine receptor (RyR1)** or lead to uncontrolled calcium release from the sarcoplasmic reticulum. - It is a **barbiturate** and its mechanism of action involves enhancing the effect of **GABA** at the GABA-A receptor, unrelated to the calcium dysregulation seen in malignant hyperthermia. *Isoflurane* - **Isoflurane** is a **volatile anesthetic agent** (inhaled) known to be a potent trigger of **malignant hyperthermia** in susceptible individuals. - It directly activates the **ryanodine receptor type 1 (RyR1)**, leading to a massive and uncontrolled release of calcium from the **sarcoplasmic reticulum** in skeletal muscle cells. *Suxamethonium* - **Suxamethonium** (succinylcholine) is a **depolarizing neuromuscular blocker** that can trigger or exacerbate **malignant hyperthermia**, especially when given with volatile anesthetics. - It causes muscle fasciculations and can lead to a sustained muscle contraction and metabolic derangements characteristic of the condition. *Halothane* - **Halothane** is a prototype **volatile anesthetic agent** and is one of the most well-known and potent triggers of **malignant hyperthermia**. - Its use has significantly decreased due to its association with malignant hyperthermia and hepatotoxicity, but it serves as a classic example of an agent that causes massive calcium release from the **sarcoplasmic reticulum**.
Question 9: All the following cause malignant hyperpyrexia except?
- A. Methoxyflurane
- B. N20 (Correct Answer)
- C. Isoflurane
- D. Halothane
Explanation: ***N2O*** - **Nitrous oxide (N2O)**, or laughing gas, is an inhaled anesthetic that does not trigger **malignant hyperthermia (MH)**. - It is often used as a carrier gas or adjunct during anesthesia, even in patients susceptible to MH, as it does not affect **ryanodine receptors**. *Methoxyflurane* - **Methoxyflurane** is a volatile inhaled anesthetic known to trigger **malignant hyperthermia (MH)** in susceptible individuals. - It causes an uncontrolled release of **calcium** from the sarcoplasmic reticulum in muscle cells, leading to severe hypermetabolism. *Isoflurane* - **Isoflurane** is a commonly used volatile inhaled anesthetic that can induce **malignant hyperthermia (MH)** in genetically predisposed individuals. - Like other volatile agents, it activates **ryanodine receptors** in skeletal muscle, leading to excessive muscle contraction and heat production. *Halothane* - **Halothane** is a potent volatile inhaled anesthetic historically associated with a high incidence of triggering **malignant hyperthermia (MH)**. - Its use has largely been replaced by newer agents due to concerns about MH and **hepatotoxicity**.
Question 10: A child during anesthesia with halothane and succinylcholine develops severe stiffness of masseters. What is the most probable diagnosis?
- A. Malignant hyperthermia (Correct Answer)
- B. Halothane hepatitis
- C. Neuroleptic malignant syndrome
- D. Anaphylaxis
Explanation: ***Malignant hyperthermia*** - **Masseter muscle rigidity** following exposure to **succinylcholine** and a **halogenated inhalational anesthetic** (like halothane) is a hallmark sign of malignant hyperthermia. - This inherited disorder results in uncontrolled **calcium release** from the sarcoplasmic reticulum in skeletal muscle, leading to hypermetabolism, severe muscle contraction, and a rapid rise in body temperature. *Halothane hepatitis* - This is an idiosyncratic liver injury that can occur hours to days after exposure to halothane, not an acute intraoperative event causing muscle stiffness. - Symptoms include elevated liver enzymes, jaundice, and often fever, but without the immediate muscle rigidity seen here. *Neuroleptic malignant syndrome* - This condition is associated with the use of **antipsychotic medications** and presents with muscle rigidity, fever, altered mental status, and autonomic instability. - It does not involve exposure to succinylcholine or inhalational anesthetics and has a slower onset, typically over days. *Anaphylaxis* - Anaphylaxis is a severe, acute allergic reaction characterized by **bronchospasm**, **hypotension**, **urticaria**, and angioedema. - While it can manifest rapidly during anesthesia, it does not typically cause severe, generalized muscle stiffness as the primary symptom.
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