General Anesthesia Practice Questions

Q: Which ultra-short acting beta-blocker is most commonly used in anesthesia?

Esmolol. **Explanation:** **Esmolol** is the correct answer because it is a **cardioselective (β1-selective)** antagonist characterized by its unique **ultra-short duration of action**. Its rapid onset (2–5 minutes) and short elimination half-life (approximately 9 minutes) are due to its metabolism by **red blood cell esterases**, making it independent of renal or hepatic function. In anesthesia, it is the drug of choice for attenuating the sympathetic "pressor response" during laryngoscopy, intubation, and emergence. **Analysis of Incorrect Options:** * **Nadolol:** A non-selective beta-blocker with a very long half-life (12–24 hours), primarily used for long-term management of hypertension or portal hypertension. * **Propranolol:** A prototype non-selective beta-blocker. It has a long duration of action and is lipid-soluble, allowing it to cross the blood-brain barrier, but it is not suitable for acute, minute-to-minute titration in anesthesia. * **Atenolol:** A cardioselective β1-blocker with a long half-life (6–7 hours), primarily excreted by the kidneys. It is used for chronic hypertension and perioperative cardioprotection, but not for ultra-short-term control. **High-Yield Clinical Pearls for NEET-PG:** * **Metabolism:** Unlike most beta-blockers, Esmolol is metabolized by **pseudocholinesterase/RBC esterases**, not the liver. * **Indication:** Best for treating intraoperative tachycardia and hypertension where rapid reversal is desired if side effects (like bradycardia) occur. * **Landiolol:** Even more cardioselective and shorter-acting than Esmolol (though Esmolol remains the standard answer for "most commonly used"). * **Contraindication:** Avoid in patients with bradycardia, heart block, or severe reactive airway disease.

Q: Most anesthetic agents are metabolized by the liver and eliminated by the kidneys. Which of the following anesthetic agents is not metabolized by the body?

Nitrous oxide (N2O). **Explanation:** The correct answer is **Nitrous oxide (N2O)**. **Why Nitrous Oxide is Correct:** Nitrous oxide is an inorganic, non-flammable gas that is unique among anesthetic agents because it undergoes **minimal to no metabolism** in the human body (less than 0.004%). It is absorbed through the lungs, remains chemically unchanged in the bloodstream, and is eliminated almost entirely (99.9%) via exhalation. Its low blood-gas solubility allows for rapid induction and recovery. **Why the Other Options are Incorrect:** * **Gallamine:** This is a long-acting non-depolarizing muscle relaxant. While it is not significantly metabolized by the liver, it is primarily excreted **unchanged by the kidneys**. It is not an anesthetic gas. * **Sevoflurane:** This is a volatile anesthetic agent that undergoes approximately **2–5% hepatic metabolism** via the Cytochrome P450 (CYP2E1) system, releasing inorganic fluoride ions. * **Halothane:** This agent undergoes the highest degree of hepatic metabolism among modern volatile anesthetics (up to **15–20%**). Its metabolites (trifluoroacetic acid) are linked to "Halothane Hepatitis." **High-Yield Clinical Pearls for NEET-PG:** * **Diffusion Hypoxia:** Since N2O is eliminated rapidly into the alveoli at the end of surgery, it can dilute oxygen. Prevention: Administer 100% O2 for 5–10 minutes post-procedure. * **Second Gas Effect:** N2O accelerates the uptake of a co-administered volatile anesthetic. * **Expansion of Closed Spaces:** N2O is 34 times more soluble than Nitrogen; it enters air-filled cavities faster than nitrogen can leave. **Contraindications:** Pneumothorax, intestinal obstruction, middle ear surgery, and air embolism. * **Enzyme Inhibition:** N2O inhibits **Methionine Synthase** (oxidizes Vitamin B12), which can lead to megaloblastic anemia or subacute combined degeneration of the spinal cord with chronic exposure.

Q: The potency of an inhalational anesthetic agent depends upon which of the following coefficients?

Oil-gas partition coefficient. ### Explanation The potency of an inhalational anesthetic is determined by its lipid solubility, which is represented by the **Oil-gas partition coefficient**. #### 1. Why Oil-gas partition coefficient is correct: According to the **Meyer-Overton Hypothesis**, the anesthetic potency of a gas is directly proportional to its lipid solubility. The Oil-gas partition coefficient measures how well a gas dissolves in oil (representing the lipid bilayer of neuronal membranes) compared to air. * **High Oil-gas coefficient = High lipid solubility = High potency.** * Potency is clinically expressed as **MAC (Minimum Alveolar Concentration)**. There is an inverse relationship between the two: **Potency ∝ 1/MAC**. Therefore, an agent with a high oil-gas coefficient will have a low MAC. #### 2. Why other options are incorrect: * **Blood-gas partition coefficient:** This determines the **speed of induction and recovery**, not potency. A lower blood-gas coefficient means the gas is less soluble in blood, leading to faster equilibration with the brain and quicker induction (e.g., Desflurane). * **Gas pressure:** While the partial pressure of a gas drives its movement across gradients, it is a physical property of delivery, not an intrinsic measure of the drug's potency. * **Blood pressure:** This is a physiological parameter of the patient that may be affected by anesthesia (hemodynamic side effects) but does not determine the drug's inherent potency. #### 3. High-Yield Clinical Pearls for NEET-PG: * **Most Potent Agent:** Methoxyflurane (Highest oil-gas coefficient, lowest MAC). * **Least Potent Agent:** Nitrous Oxide (Lowest oil-gas coefficient, highest MAC >100%). * **Speed of Induction:** Determined by Blood-gas solubility (Desflurane is the fastest; Halothane is slow). * **MAC Exceptions:** MAC is highest at 6 months of age and decreases with pregnancy, old age, and acute alcohol ingestion.

Q: In which of the following conditions can ketamine be used?

Hypovolemia. **Explanation:** **1. Why Hypovolemia is Correct:** Ketamine is a unique intravenous anesthetic agent that acts as a **sympathomimetic**. It stimulates the sympathetic nervous system, leading to an increase in heart rate, cardiac output, and arterial blood pressure due to the release of endogenous catecholamines. In patients with **hypovolemia** or hemorrhagic shock, these hemodynamic effects help maintain blood pressure and tissue perfusion during induction, making it the induction agent of choice in trauma and emergency settings. **2. Why the Other Options are Incorrect:** * **Myocardial Infarction (MI):** Ketamine increases myocardial oxygen demand due to tachycardia and increased afterload. In a heart already suffering from ischemia (MI), this can worsen the infarct or trigger arrhythmias. * **Hypertension:** Since ketamine directly increases systemic blood pressure, it is contraindicated in patients with uncontrolled hypertension as it may precipitate a hypertensive crisis or cerebrovascular accident. * **Head Injury:** Ketamine is traditionally avoided in head injuries because it is a potent cerebral vasodilator, which can increase cerebral blood flow and **intracranial pressure (ICP)**, potentially worsening brain herniation. **3. High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Non-competitive antagonist at **NMDA receptors**. * **Dissociative Anesthesia:** Characterized by eyes remaining open with a slow nystagmic gaze (catalepsy), profound analgesia, and amnesia. * **Airway:** It preserves laryngeal reflexes and is a potent **bronchodilator** (drug of choice for induction in status asthmaticus). * **Side Effects:** Associated with **emergence delirium** and hallucinations (minimized by pre-treatment with benzodiazepines like Midazolam). * **Secretions:** It causes hypersalivation; hence, it is often co-administered with glycopyrrolate.

Q: Which of the following fluorinated anesthetics corrodes metal in vaporizers and breathing systems?

Halothane. **Explanation:** **1. Why Halothane is the Correct Answer:** Halothane is a halogenated alkane (unlike the others, which are ethers). It is chemically unstable and has a unique property: it reacts with moisture to form **hydrobromic acid**. This acid is highly corrosive to metals commonly used in anesthesia machines, such as aluminum, brass, and lead. To prevent spontaneous decomposition, halothane must be stored in amber-colored bottles with **0.01% thymol** added as a stabilizing agent. However, thymol residue can accumulate in vaporizers, causing "sticky" dials or valves. **2. Why the Other Options are Incorrect:** * **Sevoflurane, Enflurane, and Isoflurane (Options A, B, C):** These are **fluorinated methyl-ethyl ethers**. The ether linkage provides significantly greater chemical stability compared to the alkane structure of halothane. They do not produce corrosive acids in the presence of moisture and do not require stabilizers like thymol. Therefore, they do not corrode metal components of the breathing system or vaporizers. **3. High-Yield Clinical Pearls for NEET-PG:** * **Corrosion:** Halothane is the only modern anesthetic that significantly corrodes metal (specifically in the presence of moisture). * **Storage:** Halothane is stored in **amber-colored bottles** to prevent photochemical decomposition. * **Soda Lime Interaction:** Sevoflurane is notable for reacting with dry soda lime to produce **Compound A** (nephrotoxic in rats), while Desflurane produces the most **Carbon Monoxide** when used with desiccated CO2 absorbers. * **Metabolism:** Halothane undergoes the highest degree of hepatic metabolism (~20%), which is linked to "Halothane Hepatitis."

Q: At the end of a balanced anaesthesia technique with a non-depolarizing muscle relaxant, a patient recovered spontaneously from the effect of muscle relaxant without any reversal. Which is the most probable relaxant the patient had received?

Atracurium. **Explanation:** The correct answer is **Atracurium** because of its unique metabolism, which allows for predictable recovery independent of organ function or pharmacological reversal. **Why Atracurium is correct:** Atracurium (and its isomer Cisatracurium) undergoes **Hofmann Elimination**—a non-enzymatic, spontaneous degradation that occurs at physiological pH and temperature. It also undergoes ester hydrolysis by non-specific plasma esterases. Because it does not rely on the liver for metabolism or the kidneys for excretion, the drug clears from the plasma rapidly and spontaneously. This makes it the "drug of choice" in patients with renal or hepatic failure and explains why a patient can recover fully without the need for a reversal agent like Neostigmine. **Why the other options are incorrect:** * **Pancuronium:** A long-acting muscle relaxant primarily excreted by the kidneys (80%). It has a high potential for cumulative effects and residual neuromuscular blockade, making spontaneous recovery without reversal unlikely and risky. * **Gallamine:** A long-acting relaxant excreted almost entirely (95-100%) unchanged in the urine. It is contraindicated in renal failure and strictly requires reversal. * **Vecuronium:** An intermediate-acting relaxant metabolized primarily by the liver and excreted in bile. While shorter-acting than Pancuronium, it still relies on organ clearance and typically requires reversal to ensure a safe Train-of-Four (TOF) ratio. **High-Yield Clinical Pearls for NEET-PG:** * **Hofmann Elimination** is temperature and pH-dependent; it is slowed by hypothermia and acidosis. * **Laudanosine:** A metabolite of Atracurium that can cross the blood-brain barrier and may cause seizures (though rare in clinical doses). * **Cisatracurium** is more potent than Atracurium and produces significantly less laudanosine and histamine release. * **Drug of Choice in Renal/Hepatic Failure:** Atracurium or Cisatracurium.

Q: Which anesthetic agent has the least minimum alveolar concentration (MAC)?

Isoflurane. ### Explanation **Concept: MAC and Potency** The **Minimum Alveolar Concentration (MAC)** is the concentration of an inhaled anesthetic at 1 atmosphere that prevents skeletal muscle movement in response to a noxious stimulus (surgical incision) in 50% of patients. MAC is **inversely proportional** to the potency of an anesthetic agent. Therefore, the agent with the **lowest MAC value is the most potent.** **Why Isoflurane is Correct:** Among the options provided, **Isoflurane** has the lowest MAC value, making it the most potent agent in this list. * **Isoflurane MAC:** ~1.15% **Analysis of Incorrect Options:** * **Nitrous Oxide (A):** Has the highest MAC (~104%), making it the least potent. It cannot produce surgical anesthesia alone at atmospheric pressure. * **Desflurane (C):** Has a MAC of ~6.0%. While it is fast-acting due to low blood-gas solubility, it is significantly less potent than Isoflurane. * **Xenon (D):** An inert gas with a MAC of ~63–71%. It is more potent than Nitrous Oxide but much less potent than volatile liquids like Isoflurane. **High-Yield NEET-PG Pearls:** 1. **Potency Ranking (Lowest MAC to Highest):** Halothane (0.75%) > Isoflurane (1.15%) > Sevoflurane (2.0%) > Desflurane (6.0%) > Xenon (71%) > Nitrous Oxide (104%). 2. **Meyer-Overton Hypothesis:** States that anesthetic potency correlates directly with lipid solubility (Oil:Gas partition coefficient). 3. **Factors Increasing MAC (Requiring more drug):** Hyperthermia, chronic alcohol abuse, hypernatremia, and increased central neurotransmitters (e.g., cocaine use, MAO inhibitors). 4. **Factors Decreasing MAC (Requiring less drug):** Pregnancy, old age, acute alcohol intoxication, hypothermia, and anemia.

Q: Which of the following induction agents causes the least respiratory depression?

Ketamine. **Explanation:** The correct answer is **Ketamine**. Unlike most induction agents that act as central nervous system depressants, Ketamine is a **dissociative anesthetic** that acts primarily as an NMDA receptor antagonist. **Why Ketamine is correct:** Ketamine is unique because it **preserves the upper airway muscle tone** and maintains **protective airway reflexes** (cough and swallow). Most importantly, it does not cause significant respiratory depression; instead, it may slightly increase the respiratory rate. It also acts as a potent **bronchodilator**, making it the induction agent of choice for patients with reactive airway diseases like asthma. **Why the other options are incorrect:** * **Propofol:** Known for causing significant dose-dependent respiratory depression and **apnea** (occurring in 25-35% of patients). It also reduces the ventilatory response to hypoxia and hypercapnia. * **Thiopentone:** A barbiturate that causes potent dose-dependent depression of the medullary respiratory centers, leading to a decrease in tidal volume and respiratory rate. * **Midazolam:** A benzodiazepine that causes mild to moderate respiratory depression, which can be synergistic and dangerous when combined with opioids. **High-Yield NEET-PG Pearls:** * **Ketamine** is the only induction agent that stimulates the sympathetic nervous system (increases HR, BP, and CO), making it ideal for **hypovolemic shock**. * **Contraindication:** Avoid Ketamine in patients with increased Intracranial Pressure (ICP) or Intraocular Pressure (IOP). * **Side Effect:** Watch for **emergence delirium** (vivid dreams/hallucinations), which can be mitigated by pre-treating with Midazolam. * **Drug of Choice:** Ketamine is the preferred agent for **pediatric procedures** and **burn dressing changes**.

Q: Hallucinations are commonly seen with which of the following agents?

Ketamine. **Explanation:** **Ketamine** is the correct answer because it is a phencyclidine derivative that acts as a non-competitive NMDA receptor antagonist. It induces a unique state known as **Dissociative Anesthesia**, where the patient appears awake but is detached from their surroundings. During the recovery phase, approximately 10–30% of adults experience **Emergence Reactions**, which include vivid dreams, illusions, and **hallucinations**. These occur because ketamine depresses the thalamoneocortical system while stimulating parts of the limbic system. **Analysis of Incorrect Options:** * **Halothane:** A volatile anesthetic known for causing cardiac arrhythmias (sensitizes myocardium to catecholamines) and "Halothane Hepatitis," but it does not typically cause hallucinations. * **Ether:** An irritating, flammable agent historically used for its analgesic properties. Its primary side effects are prolonged induction, postoperative nausea/vomiting (PONV), and respiratory secretions, not hallucinations. * **Cyclopropane:** An obsolete explosive gas known for causing "Cyclopropane shock" (hypotension post-op) and arrhythmias. It does not have a significant association with hallucinogenic emergence. **High-Yield Clinical Pearls for NEET-PG:** * **Prevention:** Emergence hallucinations can be minimized by pre-medicating with **Benzodiazepines** (e.g., Midazolam). * **Hemodynamics:** Ketamine is the drug of choice for **induction in shock/hypovolemia** because it increases BP, HR, and CO via sympathetic stimulation. * **Respiratory:** It is the agent of choice for **Asthmatics** due to its potent bronchodilatory properties. * **Contraindication:** Avoid in patients with head injuries as it **increases Intracranial Pressure (ICP)** and Intraocular Pressure (IOP).

Q: Which route provides the fastest reversible anesthesia?

Inhalational. **Explanation:** The correct answer is **Inhalational (Option A)**. The primary reason for this is the unique pharmacokinetic profile of inhalational agents, specifically their ability to be eliminated via the lungs. **Why Inhalational is Correct:** Inhalational anesthesia allows for the fastest **reversibility** because these agents are excreted primarily through exhalation. Once the vaporizer is turned off and the patient is ventilated with 100% oxygen, the concentration gradient reverses, drawing the anesthetic out of the blood and brain back into the lungs for elimination. This process is rapid and does not depend on hepatic metabolism or renal excretion, which are significantly slower processes. **Why Other Options are Incorrect:** * **Intravenous (IV):** While IV agents (like Propofol) have a very fast *onset*, their reversal depends on redistribution to peripheral tissues and subsequent metabolism by the liver. Once injected, they cannot be physically "removed" from the body as easily as a gas. * **Local Anesthesia:** These agents work by blocking sodium channels at a specific site. Reversal depends entirely on the rate of systemic absorption and metabolic breakdown (by plasma esterases or liver enzymes), making it much slower than the breath-by-breath elimination of gases. **NEET-PG High-Yield Pearls:** * **Blood-Gas Partition Coefficient:** This determines the speed of induction and recovery. The **lower** the coefficient (e.g., Desflurane = 0.42), the faster the recovery/reversibility. * **Desflurane** provides the fastest recovery among all inhalational agents. * **Context-Sensitive Half-Time:** This concept explains why IV infusions (like Fentanyl) take longer to reverse the longer they are administered, a phenomenon less pronounced with modern inhalational agents.

Question 1

Which ultra-short acting beta-blocker is most commonly used in anesthesia?

Accepted Answer

Esmolol

Answer

Nadolol

Answer

Propranolol

Answer

Atenolol

Question 2

Most anesthetic agents are metabolized by the liver and eliminated by the kidneys. Which of the following anesthetic agents is not metabolized by the body?

Accepted Answer

Nitrous oxide (N2O)

Answer

Gallamine

Answer

Sevoflurane

Answer

Halothane

Question 3

The potency of an inhalational anesthetic agent depends upon which of the following coefficients?

Accepted Answer

Oil-gas partition coefficient

Answer

Blood-gas partition coefficient

Answer

Gas pressure

Answer

Blood pressure

Question 4

In which of the following conditions can ketamine be used?

Accepted Answer

Hypovolemia

Answer

Myocardial infarction

Answer

Hypertension

Answer

Head injury

Question 5

Which of the following fluorinated anesthetics corrodes metal in vaporizers and breathing systems?

Accepted Answer

Halothane

Answer

Sevoflurane

Answer

Enflurane

Answer

Isoflurane

Question 6

At the end of a balanced anaesthesia technique with a non-depolarizing muscle relaxant, a patient recovered spontaneously from the effect of muscle relaxant without any reversal. Which is the most probable relaxant the patient had received?

Accepted Answer

Atracurium

Answer

Pancuronium

Answer

Gallamine

Answer

Vecuronium

Question 7

Which anesthetic agent has the least minimum alveolar concentration (MAC)?

Accepted Answer

Isoflurane

Answer

Nitrous oxide

Answer

Desflurane

Answer

Xenon

Question 8

Which of the following induction agents causes the least respiratory depression?

Accepted Answer

Ketamine

Answer

Midazolam

Answer

Propofol

Answer

Thiopentone

Question 9

Hallucinations are commonly seen with which of the following agents?

Accepted Answer

Ketamine

Answer

Halothane

Answer

Ether

Answer

Cyclopropane

Question 10

Which route provides the fastest reversible anesthesia?

Accepted Answer

Inhalational

Answer

Intravenous (IV)

Answer

Local anesthesia

Answer

None of the above

General Anesthesia — MCQs

General Anesthesia — MCQs

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