General Anesthesia — MCQs

General Anesthesia Indian Medical PG Practice Questions and MCQs

Question 331: Which day is observed as World Anaesthesia Day?

A. 16th September
B. 16th October (Correct Answer)
C. 16th November
D. 16th December

Explanation: **Explanation:** **World Anaesthesia Day** is observed annually on **16th October** to commemorate the first successful public demonstration of surgical anesthesia. On this day in **1846**, **William T.G. Morton** administered diethyl ether to a patient (Edward Gilbert Abbott) for the removal of a vascular tumor from the neck at the Massachusetts General Hospital, Boston. This event, known as the "Ether Day," revolutionized medicine by making painless surgery possible. **Analysis of Options:** * **16th October (Correct):** Marks the anniversary of the first successful public demonstration of ether anesthesia. * **16th September:** This is World Ozone Day. It has no historical significance in the field of anesthesiology. * **16th November:** This is International Day for Tolerance. * **16th December:** This is Victory Day (Vijay Diwas) in India; it is unrelated to medical history. **High-Yield Clinical Pearls for NEET-PG:** * **The "Ether Dome":** The amphitheater where the first demonstration took place is still preserved at Massachusetts General Hospital. * **The Surgeon:** The surgery was performed by **Dr. John Collins Warren**. * **The Famous Quote:** After the procedure, Dr. Warren famously remarked, *"Gentlemen, this is no humbug,"* acknowledging the success of the anesthesia. * **Terminology:** The term "Anaesthesia" was later coined by **Oliver Wendell Holmes Sr.** to describe the state of insensibility produced by ether. * **James Young Simpson:** He is credited with the first use of **Chloroform** in obstetrics (1847), which is another common historical question in NEET-PG.

Question 332: Hallucination is a major side effect of which of the following agents?

A. Nitrous oxide
B. Ketamine (Correct Answer)
C. Fentanyl
D. Chloroform

Explanation: **Explanation:** The correct answer is **Ketamine**. **Why Ketamine is correct:** Ketamine is a phencyclidine derivative that acts primarily as an **NMDA receptor antagonist**. It produces a state known as **"Dissociative Anesthesia,"** where the patient appears awake but is detached from their environment. The most characteristic side effect of Ketamine is **Emergence Delirium**, which includes vivid dreams, illusions, and **hallucinations** during recovery. These psychotomimetic effects occur because Ketamine depresses the thalamocortical system while stimulating the limbic system. These effects can be mitigated by pre-medicating the patient with benzodiazepines (e.g., Midazolam). **Why other options are incorrect:** * **Nitrous Oxide:** Known as "laughing gas," it primarily causes euphoria and mild analgesia. While it can cause diffusion hypoxia, it is not typically associated with clinical hallucinations. * **Fentanyl:** An opioid analgesic. Its major side effects include respiratory depression, miosis, and chest wall rigidity ("wooden chest syndrome"), but not hallucinations. * **Chloroform:** An obsolete anesthetic agent primarily known for its hepatotoxicity and arrhythmogenic potential (sensitizing the myocardium to catecholamines). **High-Yield Clinical Pearls for NEET-PG:** * **Ketamine** is the only intravenous anesthetic that is a **potent analgesic** and a **potent bronchodilator** (drug of choice for asthma). * It is the induction agent of choice in **hypovolemic shock** because it stimulates the sympathetic nervous system (increases HR and BP). * **Contraindications:** It increases Intraocular Pressure (IOP) and Intracranial Pressure (ICP); therefore, it is avoided in head injuries and glaucoma.

Question 333: What is commonly known as "laughing gas"?

A. N2O (Correct Answer)
B. Lewisite
C. H2S
D. CO2

Explanation: **Explanation:** **Nitrous Oxide (N2O)** is a colorless, odorless, and non-flammable inorganic gas widely used in anesthesia. It is famously known as **"laughing gas"** because it can induce a state of euphoria, giddiness, and involuntary laughter upon inhalation. In clinical practice, it is used as an adjuvant to volatile anesthetics due to its potent analgesic properties but weak anesthetic potency (MAC value of 104-105%). **Analysis of Options:** * **B. Lewisite:** This is an organoarsenic compound used as a chemical weapon (vesicant/blister agent). It is highly toxic and has no role in anesthesia. * **C. H2S (Hydrogen Sulfide):** Known as "sewer gas," it is a colorless, highly toxic, and flammable gas with a characteristic foul odor of rotten eggs. * **D. CO2 (Carbon Dioxide):** While used in laparoscopy for insufflation, it is a byproduct of metabolism. High levels lead to hypercapnia and respiratory acidosis, not euphoria. **High-Yield Clinical Pearls for NEET-PG:** 1. **Second Gas Effect:** N2O is rapidly absorbed from alveoli, increasing the concentration of the co-administered volatile anesthetic, thereby speeding up the induction of anesthesia. 2. **Diffusion Hypoxia (Fink Effect):** Post-operatively, N2O rapidly diffuses from the blood into the alveoli, diluting oxygen. This is prevented by administering **100% Oxygen** for 5–10 minutes after stopping N2O. 3. **Closed Space Expansion:** N2O is 34 times more soluble than Nitrogen. It can expand air-filled spaces, making it **contraindicated** in pneumothorax, intestinal obstruction, air embolism, and middle ear surgeries. 4. **Vitamin B12 Interaction:** It irreversibly oxidizes the cobalt atom in Vitamin B12, inhibiting methionine synthase. Chronic exposure can lead to megaloblastic anemia and peripheral neuropathy.

Question 334: Bradycardia is common after injection of which of the following agents?

A. Midazolam
B. Succinylcholine (Correct Answer)
C. Dopamine
D. Isoprenaline

Explanation: **Explanation:** **Succinylcholine (Suxamethonium)** is a depolarizing neuromuscular blocker that is structurally composed of two joined molecules of acetylcholine. Its tendency to cause bradycardia is rooted in its structural similarity to acetylcholine, which allows it to stimulate **muscarinic (M2) receptors** in the sinoatrial (SA) node. * **Why Succinylcholine is correct:** It can cause profound sinus bradycardia, especially in children (who have higher vagal tone) or after a second dose in adults. This occurs because the initial dose sensitizes the heart, and the subsequent dose triggers a strong vagal response. * **Why Midazolam is incorrect:** Midazolam is a benzodiazepine that typically causes minimal hemodynamic changes, though it may cause a slight decrease in systemic vascular resistance and a compensatory mild *increase* in heart rate. * **Why Dopamine is incorrect:** Dopamine is a sympathomimetic. At moderate to high doses, it stimulates $\beta_1$ receptors, leading to **tachycardia** and increased contractility. * **Why Isoprenaline is incorrect:** Isoprenaline is a potent non-selective $\beta$-agonist ($\beta_1$ and $\beta_2$). It is actually used to *treat* bradycardia because it significantly increases the heart rate (positive chronotropy). **High-Yield Clinical Pearls for NEET-PG:** 1. **Pre-treatment:** Atropine is often administered pre-emptively in pediatric anesthesia before giving succinylcholine to prevent severe bradycardia. 2. **Hyperkalemia:** Succinylcholine can cause a transient rise in serum potassium (approx. 0.5 mEq/L), which can lead to arrhythmias in patients with burns, crush injuries, or neuromuscular disorders. 3. **Malignant Hyperthermia:** Succinylcholine is a known triggering agent for Malignant Hyperthermia. 4. **Phase II Block:** Prolonged exposure or high doses can lead to a "Phase II block," where the depolarizing block begins to behave like a non-depolarizing block.

Question 335: Which of the following is NOT commonly used as an induction agent?

A. Midazolam (Correct Answer)
B. Etomidate
C. Ketamine
D. Propofol

Explanation: **Explanation:** The correct answer is **Midazolam**. While Midazolam is a potent benzodiazepine used extensively in anesthesia, it is primarily used for **pre-medication, conscious sedation, and maintenance** rather than as a primary induction agent. Its slow onset of action (compared to propofol) and prolonged recovery period make it less ideal for the rapid transition from consciousness to unconsciousness required during induction. **Analysis of Options:** * **Propofol:** The "Gold Standard" and most commonly used induction agent. It has a rapid onset (one arm-brain circulation time) and a short duration of action due to rapid redistribution. * **Etomidate:** A carboxylated imidazole derivative preferred for induction in **hemodynamically unstable patients** (e.g., trauma, shock) because it causes minimal cardiovascular depression. * **Ketamine:** A dissociative anesthetic used for induction, especially in patients with **bronchial asthma** (due to bronchodilation) or **hypovolemic shock** (due to sympathetic stimulation). **High-Yield Clinical Pearls for NEET-PG:** * **Propofol:** Drug of choice for Day Care Surgery; possesses anti-emetic properties. * **Etomidate:** Associated with **adrenocortical suppression** (inhibits 11-beta-hydroxylase) and a high incidence of myoclonus. * **Ketamine:** Only intravenous anesthetic with analgesic properties; contraindicated in patients with raised intracranial or intraocular pressure. * **Thiopentone:** Formerly the gold standard; stored as a yellow powder with 6% sodium carbonate to prevent precipitation by atmospheric $CO_2$.

Question 336: Administration of scoline (Sch) produces dangerous hyperkalemia in which of the following conditions?

A. Acute renal failure (ARF)
B. Raised intracranial tension (ICT)
C. Fracture of femur
D. Paraplegia (Correct Answer)

Explanation: **Explanation:** **Succinylcholine (Scoline)** is a depolarizing neuromuscular blocker that acts by mimicking acetylcholine at the nicotinic receptors. Upon binding, it causes prolonged depolarization, leading to an efflux of potassium ($K^+$) from the intracellular to the extracellular space. In a healthy individual, this typically raises serum $K^+$ by only **0.5 mEq/L**, which is clinically insignificant. **Why Paraplegia is the Correct Answer:** In conditions involving **lower motor neuron lesions, denervation, or massive muscle trauma** (like paraplegia, quadriplegia, or severe burns), there is an **upregulation of extrajunctional acetylcholine receptors**. These immature receptors are spread across the entire muscle membrane rather than being localized at the neuromuscular junction. When Scoline is administered, these widespread receptors open simultaneously, causing a massive, life-threatening efflux of potassium (hyperkalemia), which can lead to cardiac arrest. **Analysis of Incorrect Options:** * **Acute Renal Failure (ARF):** Contrary to common belief, Scoline is not contraindicated in renal failure unless the patient is *already* hyperkalemic. The $K^+$ rise remains the standard 0.5 mEq/L. * **Raised ICT:** Scoline actually *increases* intracranial tension (and intraocular pressure), but it does not cause dangerous hyperkalemia in this condition. * **Fracture of Femur:** While massive crush injuries cause hyperkalemia, a simple fracture does not lead to the receptor upregulation required for a dangerous $K^+$ surge. **High-Yield Clinical Pearls for NEET-PG:** * **Safe Window:** In denervation injuries (like paraplegia), Scoline is generally safe within the first 24–48 hours but becomes dangerous from **3 days up to 1 year** (or longer) post-injury. * **Drug of Choice for Pre-treatment:** A small dose of a non-depolarizing muscle relaxant (NDMR) can prevent fasciculations but does *not* reliably prevent hyperkalemia. * **Other Contraindications:** Muscular dystrophy (Duchenne’s), severe burns, and prolonged immobilization.

Question 337: Which anesthetic agent has epileptogenic potential?

A. Enflurane (Correct Answer)
B. Nitrous oxide
C. Desflurane
D. Isoflurane

Explanation: **Explanation:** **1. Why Enflurane is Correct:** Enflurane is uniquely associated with **epileptogenic potential**. At high concentrations (typically >3%) or in the presence of **hypocapnia** (low CO2 caused by hyperventilation), it can induce high-voltage spike-and-wave activity on an EEG, which may manifest as tonic-clonic muscle twitching. This occurs because enflurane lowers the seizure threshold, making it contraindicated in patients with a history of epilepsy or seizure disorders. **2. Why Other Options are Incorrect:** * **Nitrous Oxide (N2O):** It does not significantly alter the seizure threshold. Its primary concerns are diffusion hypoxia and inactivation of Vitamin B12 (methionine synthase). * **Desflurane:** While it can cause sympathetic stimulation (tachycardia/hypertension) during rapid induction, it does not possess epileptogenic properties. * **Isoflurane:** It is actually considered **anticonvulsant** at higher doses. It produces a dose-dependent suppression of the EEG and is often used to terminate status epilepticus. **3. High-Yield Clinical Pearls for NEET-PG:** * **Seizure-Inducing Agents:** Besides Enflurane, **Sevoflurane** (especially in children during mask induction) and **Ketamine** can also lower the seizure threshold. Among IV agents, **Methohexital** and **Etomidate** are known to trigger myoclonus/seizures. * **Drug of Choice for Epilepsy:** **Thiopentone** is the gold standard for brain protection and seizure suppression. * **Metabolism Fact:** Enflurane is metabolized to inorganic fluoride (approx. 2%), which carries a theoretical risk of nephrotoxicity, though less than Methoxyflurane.

Question 338: Which one of the following is the fastest acting inhalational agent?

A. Halothane
B. Isoflurane
C. Ether
D. Sevoflurane (Correct Answer)

Explanation: **Explanation:** The speed of induction and recovery of an inhalational anesthetic is primarily determined by its **Blood-Gas Partition Coefficient (λ)**. This coefficient represents the solubility of the gas in the blood. * **Low Solubility = Faster Action:** Agents with low blood solubility reach equilibrium between the alveoli and the blood quickly. This leads to a rapid rise in the alveolar concentration ($F_A/F_I$ ratio), resulting in faster brain uptake and quicker induction/emergence. * **High Solubility = Slower Action:** Agents that are highly soluble "dissolve" into the blood reservoir, delaying the rise in partial pressure needed to affect the brain. **Why Sevoflurane is Correct:** Among the options provided, **Sevoflurane** has the lowest blood-gas partition coefficient (~0.65). This low solubility ensures a rapid onset of anesthesia, making it the agent of choice for smooth and fast mask induction, especially in pediatric patients. **Analysis of Incorrect Options:** * **Halothane (λ ≈ 2.4):** Highly soluble in blood; therefore, induction is significantly slower than Sevoflurane. * **Isoflurane (λ ≈ 1.4):** Moderately soluble. While faster than Halothane, it is slower than Sevoflurane and is also pungent, making it unsuitable for rapid mask induction. * **Ether (λ ≈ 12.0):** Extremely high solubility and irritant properties, leading to a very prolonged and unpleasant induction period. **High-Yield Clinical Pearls for NEET-PG:** 1. **Desflurane** is actually the fastest-acting inhalational agent overall (λ ≈ 0.42), but it was not an option here. 2. **Order of Speed (Fastest to Slowest):** Desflurane > Sevoflurane > Nitrous Oxide > Isoflurane > Halothane > Ether. 3. **Second Gas Effect:** Nitrous oxide is often used to speed up the induction of a primary volatile agent (like Sevoflurane). 4. **Oil-Gas Partition Coefficient:** This determines the **potency** (MAC) of the drug, not the speed of induction.

Question 339: 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?

A. Nitrous oxide (N2O) (Correct Answer)
B. Gallamine
C. Sevoflurane
D. Halothane

Explanation: **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.

Question 340: What does the Debucain number refer to?

A. ACh cholinesterase activity derangement (Correct Answer)
B. Potency of muscle relaxants
C. Potency of general anesthetics
D. None of the above

Explanation: ### Explanation **1. Why Option A is Correct:** The **Dibucaine number** is a diagnostic test used to identify **qualitative** defects in **Pseudocholinesterase (Butyrylcholinesterase)**, the enzyme responsible for metabolizing Succinylcholine and ester-type local anesthetics. Dibucaine is an amide local anesthetic that inhibits normal pseudocholinesterase activity by approximately 80%. However, it inhibits atypical (variant) pseudocholinesterase by only about 20%. Therefore, the Dibucaine number represents the **percentage of enzyme inhibition**. A low Dibucaine number indicates an "atypical" enzyme that cannot efficiently break down Succinylcholine, leading to prolonged neuromuscular blockade (Suxamethonium apnea). **2. Why Other Options are Incorrect:** * **Option B:** The potency of muscle relaxants is typically measured by the **ED95** (the dose required to produce 95% suppression of the single twitch response). * **Option C:** The potency of inhalational general anesthetics is measured by the **MAC (Minimum Alveolar Concentration)**. **3. High-Yield Clinical Pearls for NEET-PG:** * **Normal Dibucaine Number:** ~80 (Normal genotype: $EuEu$). * **Heterozygous Genotype ($EuEa$):** Dibucaine number 40–60; clinically, Succinylcholine block is slightly prolonged (20–30 mins). * **Homozygous Atypical Genotype ($EaEa$):** Dibucaine number ~20; results in severe **Suxamethonium apnea** (block lasts 4–8 hours). * **Management of Suxamethonium Apnea:** The primary treatment is **mechanical ventilation and sedation** until the block wears off naturally. Fresh frozen plasma (FFP) contains the enzyme but is rarely used due to infection risks. * **Important Note:** The Dibucaine number measures the **quality** (efficiency) of the enzyme, not the **quantity** (concentration).

Practice by Chapter

History of Anesthesia

Practice Questions

Preoperative Evaluation

Practice Questions

Pharmacology of Inhalational Anesthetics

Practice Questions

Pharmacology of Intravenous Anesthetics

Practice Questions

Neuromuscular Blocking Agents

Practice Questions

Airway Management

Practice Questions

Endotracheal Intubation

Practice Questions

Difficult Airway Algorithms

Practice Questions

Intraoperative Monitoring

Practice Questions

Depth of Anesthesia Monitoring

Practice Questions

Emergence from Anesthesia

Practice Questions

Postoperative Care

Practice Questions

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