General Anesthesia Practice Questions

Q: All of the following except one affect the minimum alveolar concentration (MAC)?

Altitude. **Explanation:** The **Minimum Alveolar Concentration (MAC)** is the concentration of an inhaled anesthetic at 1 atmosphere (760 mmHg) that prevents skeletal muscle movement in response to a noxious stimulus in 50% of patients. It is a measure of anesthetic **potency**. **Why Altitude is the Correct Answer:** Altitude (barometric pressure) does **not** affect the MAC of an inhalational agent. While the *partial pressure* required to achieve anesthesia remains constant, the *percentage* concentration (MAC) does not change with changes in ambient pressure. For example, if an agent has a MAC of 1% at sea level, it remains 1% at high altitude, even though the total barometric pressure is lower. **Analysis of Other Options:** * **Age (B):** MAC is highest at 6 months of age and decreases progressively with increasing age (decreases by ~6% per decade after age 20). * **Premedication (A) & Drugs (D):** Most CNS depressants decrease MAC. This includes opioids, benzodiazepines, alpha-2 agonists (clonidine, dexmedetomidine), and acute ethanol ingestion. Conversely, drugs that increase central neurotransmitters (like cocaine or amphetamines) increase MAC. **High-Yield Clinical Pearls for NEET-PG:** * **Factors Increasing MAC:** Hyperthermia, hypernatremia, chronic alcohol abuse, and red hair (MC1R gene mutation). * **Factors Decreasing MAC:** Hypothermia, hyponatremia, pregnancy (decreases by 30-40%), anemia (Hb <5g/dL), and metabolic acidosis. * **Factors with NO effect on MAC:** Duration of anesthesia, gender, thyroid status (hypo/hyper), and **altitude/barometric pressure**. * **MAC-awake:** Usually 0.3–0.5 MAC; **MAC-BAR** (Blunt Autonomic Response): Usually 1.5–2.0 MAC.

Q: Which anesthetic agent is known to cause bradycardia?

Morphine. **Explanation:** **Correct Option: D. Morphine** Morphine, a natural opioid agonist, primarily causes bradycardia through two mechanisms: 1. **Increased Vagal Tone:** It stimulates the vagal nucleus in the medulla, leading to increased parasympathetic outflow to the heart. 2. **Histamine Release:** Morphine triggers the release of histamine from mast cells, which can cause peripheral vasodilation. While this often leads to compensatory tachycardia, the direct central vagotonic effect usually predominates, resulting in a decrease in heart rate. **Analysis of Incorrect Options:** * **A. Gallamine:** This is a long-acting non-depolarizing neuromuscular blocker that is notorious for causing **tachycardia**. It acts as a potent muscarinic antagonist (vagolytic) at the M2 receptors of the SA node. * **B. Vecuronium:** This is an intermediate-acting neuromuscular blocker known for its **cardiovascular stability**. It lacks significant vagolytic or histamine-releasing properties, making it "heart-friendly." * **C. Ketamine:** This dissociative anesthetic is a **sympathomimetic**. It inhibits the reuptake of norepinephrine and stimulates the sympathetic nervous system, leading to an increase in heart rate, blood pressure, and cardiac output. **High-Yield Clinical Pearls for NEET-PG:** * **Opioids and Heart Rate:** Among opioids, **Fentanyl, Sufentanil, and Remifentanil** are even more potent than Morphine in causing profound bradycardia. **Meperidine (Pethidine)** is the exception; it has an atropine-like structure and can cause tachycardia. * **Drug of Choice for Bradycardia:** Atropine is the first-line management for symptomatic drug-induced bradycardia. * **Ketamine Exception:** In patients with depleted catecholamines (e.g., severe chronic shock), Ketamine can actually act as a myocardial depressant.

Q: All of the following are causes of increased heart rate except:

Halothane. **Explanation:** The correct answer is **Halothane** because, unlike modern volatile anesthetics, it does not typically cause an increase in heart rate; in fact, it often causes **bradycardia** or maintains a stable heart rate. **1. Why Halothane is the correct answer:** Halothane increases vagal (parasympathetic) tone and inhibits the baroreceptor reflex. This leads to a decrease in heart rate (bradycardia). Furthermore, Halothane is unique because it **sensitizes the myocardium to catecholamines**, which increases the risk of arrhythmias (especially ventricular) if epinephrine is administered concurrently, but the baseline effect is not tachycardia. **2. Why the other options are incorrect:** * **Isoflurane:** It is a potent vasodilator that causes a decrease in systemic vascular resistance (SVR). This triggers a **reflex tachycardia** via the baroreceptor mechanism. * **Desflurane:** Known for causing a transient but significant increase in heart rate and blood pressure, especially during a rapid increase in inspired concentration, due to **sympathetic nervous system stimulation**. * **Sevoflurane:** While it has the least effect on heart rate at low concentrations (making it ideal for pediatric induction), it can still cause increases in heart rate at deeper levels of anesthesia (concentrations >1.5 MAC). **Clinical Pearls for NEET-PG:** * **"Halothane Hepatitis":** A rare but classic boards-style complication. * **Arrhythmogenic potential:** Halothane + Adrenaline = High risk of PVCs/Ventricular Tachycardia. * **Pungency:** Isoflurane and Desflurane are pungent (irritate airways), whereas **Halothane and Sevoflurane are non-pungent**, making them suitable for inhalation induction. * **Speed of Induction:** Desflurane (lowest blood-gas solubility) is the fastest; Halothane is the slowest among the options.

Q: Presence of trifluoroacetic acid (TFA) in urine indicates that the volatile anesthetic agent used was:

Halothane. **Explanation:** The correct answer is **Halothane**. **1. Why Halothane is correct:** Halothane undergoes significant hepatic metabolism (approximately 20%). It is metabolized by the cytochrome P450 system (specifically CYP2E1) via oxidative pathways. The primary end-product of this oxidative metabolism is **Trifluoroacetic acid (TFA)**, which is excreted in the urine. TFA is clinically significant because it can covalently bind to hepatic proteins, forming "TFA-protein adducts." In susceptible individuals, these adducts act as haptens, triggering an immune response that leads to **Halothane Hepatitis**. **2. Why other options are incorrect:** * **Methoxyflurane:** Its metabolism primarily releases **inorganic fluoride ions** and oxalic acid. High levels of fluoride ions are associated with dose-dependent nephrotoxicity (high-output renal failure). * **Trichloroethylene:** It is metabolized into **Trichloroethanol** and **Trichloroacetic acid**. It is no longer used in modern anesthesia due to its potential to react with soda lime to form neurotoxic dichloroacetylene. **3. High-Yield Clinical Pearls for NEET-PG:** * **Metabolism Ranking:** Halothane (20%) > Sevoflurane (2-5%) > Isoflurane (0.2%) > Desflurane (0.02%). * **Other TFA producers:** Isoflurane and Desflurane also produce TFA, but in much smaller, negligible quantities compared to Halothane. * **Halothane Shivering:** Halothane is known to cause post-operative shivering due to its effect on the hypothalamus. * **Catecholamine Sensitivity:** Halothane sensitizes the myocardium to catecholamines, increasing the risk of arrhythmias if epinephrine is administered concurrently.

Q: All of the following are true about depolarizing agents, EXCEPT:

Pancuronium resembles noradrenaline. ### Explanation The question asks for the **incorrect** statement regarding neuromuscular blocking agents (NMBAs). **1. Why Option B is the Correct Answer (The False Statement):** Pancuronium is a long-acting non-depolarizing NMBA. While it has a steroid nucleus, it does **not** resemble noradrenaline structurally. However, it possesses **vagolytic properties** (blocks muscarinic receptors in the SA node) and inhibits the neuronal reuptake of norepinephrine, leading to tachycardia and hypertension. It is the sympathomimetic effect, not structural resemblance, that is clinically significant. **2. Analysis of Other Options:** * **Option A (Rocuronium):** Rocuronium is primarily eliminated unchanged by the liver (70%) and kidneys (30%). It undergoes **no significant metabolism**, making this statement true. * **Option C (Atracurium):** Atracurium is cleared via **Hofmann elimination** (a non-enzymatic chemical degradation) and ester hydrolysis. Hofmann elimination is highly temperature and pH-dependent; therefore, **hypothermia slows the degradation**, markedly prolonging its duration of action. * **Option D (Vecuronium):** Vecuronium is primarily excreted through bile. While a small portion is excreted renally, its clinical duration is **not significantly altered** in patients with renal failure compared to pancuronium, making it relatively safe for such patients. ### High-Yield Clinical Pearls for NEET-PG: * **Drug of Choice in Renal/Hepatic Failure:** Atracurium or Cisatracurium (due to Hofmann elimination). * **Mivacurium:** The only non-depolarizing NMBA metabolized by **pseudocholinesterase**. * **Laudanosine:** A metabolite of atracurium that can cross the blood-brain barrier and potentially cause **seizures**. * **Sugammadex:** Specifically reverses aminosteroid compounds (Rocuronium > Vecuronium > Pancuronium).

Q: Which of the following is NOT a true statement regarding sevoflurane?

It can be used safely in malignant hyperthermia.. **Explanation:** **1. Why Option C is the correct answer (The "NOT" statement):** Sevoflurane, like all potent volatile halogenated inhalational anesthetics (e.g., Halothane, Isoflurane, Desflurane) and the depolarizing muscle relaxant Succinylcholine, is a **known trigger for Malignant Hyperthermia (MH)**. In genetically susceptible individuals with a mutation in the ryanodine receptor (RYR1), sevoflurane causes an uncontrolled release of calcium from the sarcoplasmic reticulum, leading to a hypermetabolic state. Therefore, it is **absolutely contraindicated** in patients with a history of MH. **2. Analysis of Incorrect Options:** * **Option A:** Sevoflurane is the **agent of choice for pediatric induction** because it has a non-pungent odor, is non-irritating to the airway (low risk of laryngospasm), and has a low blood-gas partition coefficient (0.65), allowing for rapid induction and recovery. * **Option B:** When sevoflurane reacts with dry carbon dioxide absorbents (specifically those containing Potassium or Sodium Hydroxide like Sodalime), it undergoes degradation to form **Compound A** (fluoromethyl-2,2-difluoro-1-(trifluoromethyl) vinyl ether), which is nephrotoxic in rat models. * **Option D:** While sevoflurane is generally cardiovascularly stable, it can cause a dose-dependent decrease in blood pressure and a **reflex increase in heart rate (tachycardia)**, especially at higher concentrations (>1.5 MAC). **High-Yield NEET-PG Pearls:** * **Blood-Gas Partition Coefficient:** 0.65 (Fast induction/emergence). * **MAC (Minimum Alveolar Concentration):** ~2% in oxygen. * **Metabolism:** Approximately 5-8% (higher than Isoflurane/Desflurane), releasing inorganic fluoride ions. * **Clinical Caution:** To prevent Compound A accumulation, it is recommended to maintain a fresh gas flow of at least **1-2 Liters/min**.

Question 1

The action of intravenous thiopentone is terminated by which mechanism?

Accepted Answer

Redistribution

Answer

Rapid renal excretion

Answer

Oxidation

Answer

Conjugation

Question 2

All of the following except one affect the minimum alveolar concentration (MAC)?

Accepted Answer

Altitude

Answer

Premedication

Answer

Age

Answer

Drugs

Question 3

Which anesthetic agent is known to cause bradycardia?

Accepted Answer

Morphine

Answer

Gallamine

Answer

Vecuronium

Answer

Ketamine

Question 4

Regarding gantacurium, which of the following statements is true?

Accepted Answer

It has an oxime chloro fumarate group.

Answer

It is a depolarizing neuromuscular blocker.

Answer

L-cysteine is the reversal agent.

Answer

It has a longer duration of action than succinylcholine.

Question 5

All of the following are causes of increased heart rate except:

Accepted Answer

Halothane

Answer

Isoflurane

Answer

Sevoflurane

Answer

Desflurane

Question 6

Presence of trifluoroacetic acid (TFA) in urine indicates that the volatile anesthetic agent used was:

Accepted Answer

Halothane

Answer

Methoxyflurane

Answer

Trichloroethylene

Answer

None of the above

Question 7

What is the lowest concentration of an anesthetic agent in the alveoli that is needed to produce immobility in response to a painful stimulus in 50% of individuals?

Accepted Answer

Minimum alveolar concentration

Answer

Minimal analgesic concentration

Answer

Minimal anesthetic concentration

Answer

Maximum alveolar concentration

Question 8

All of the following are true about depolarizing agents, EXCEPT:

Accepted Answer

Pancuronium resembles noradrenaline

Answer

Rocuronium undergoes no metabolism

Answer

Atracurium's duration of action can be markedly prolonged by hypothermia

Answer

Vecuronium effect is not altered in renal failure

Question 9

During general anesthesia, shivering is abolished by suppression of which part of the brain?

Accepted Answer

Hypothalamus

Answer

Thalamus

Answer

Cerebral cortex

Answer

Medulla

Question 10

Which of the following is NOT a true statement regarding sevoflurane?

Accepted Answer

It can be used safely in malignant hyperthermia.

Answer

It is an ideal agent for pediatric anesthesia.

Answer

It can interact with sodalime and form Compound A.

Answer

It causes tachycardia.

General Anesthesia — MCQs

General Anesthesia — MCQs

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