General Anesthesia Practice Questions

Q: Which of the following muscle relaxants causes maximal pain on injection?

Rocuronium. **Explanation:** **Rocuronium** is the correct answer as it is well-documented to cause the highest incidence of injection pain (up to 50–80% in awake patients) among all neuromuscular blocking agents. The underlying mechanism is attributed to its **low pH (approximately 4.0)** and the release of local mediators like **kinins**, which irritate the venous nociceptors. This often manifests as "withdrawal movement" of the limb during induction. **Analysis of Incorrect Options:** * **Succinylcholine (Option A):** While it causes post-operative muscle soreness (myalgia) due to fasciculations, it does not typically cause acute pain at the site of injection. * **Vecuronium (Option B):** It is a nearly pH-neutral, lyophilized powder. It is considered "cardiovascularly stable" and is generally painless upon administration [1]. * **Cisatracurium (Option C):** As an isomer of atracurium, it is designed to be potent and stable without significant histamine release or local irritation, making it painless on injection [1]. **Clinical Pearls for NEET-PG:** * **Mitigation:** Pain from Rocuronium can be reduced by pre-administering **Lidocaine**, using a larger vein, or priming with a small dose of an induction agent (Propofol). * **Rapidity:** Rocuronium is the non-depolarizing muscle relaxant (NDMR) with the **fastest onset of action** (60–90 seconds), making it the drug of choice for Rapid Sequence Induction (RSI) when Succinylcholine is contraindicated [1]. * **Reversal:** Its effects are specifically and rapidly reversed by **Sugammadex**.

Q: Which of the following gases exhibits the second gas effect?

Nitrous oxide. **Explanation:** The **Second Gas Effect** is a phenomenon where the rapid uptake of a high-volume primary gas (usually Nitrous Oxide) accelerates the rate of increase in the alveolar concentration of a concurrently administered "second gas" (a potent volatile anesthetic). **Why Nitrous Oxide is Correct:** Nitrous oxide ($N_2O$) is highly insoluble in blood but is administered in high concentrations (up to 70%). When $N_2O$ is inhaled, it is rapidly absorbed from the alveoli into the pulmonary capillaries. This rapid removal of $N_2O$ causes the remaining gases in the alveoli to be "concentrated" into a smaller volume. This increases the fractional concentration ($F_A$) of the second gas (e.g., Halothane or Sevoflurane), leading to a faster induction of anesthesia. **Why Other Options are Incorrect:** * **Ether:** It is highly soluble in blood, leading to a slow induction. It does not achieve the rapid alveolar uptake required to produce a concentration effect for other gases. * **Desflurane & Sevoflurane:** These are potent volatile anesthetics typically used as the "second gas." They are administered in low concentrations (usually <8%) and therefore do not occupy enough volume in the alveoli to trigger the second gas effect for other agents. **High-Yield NEET-PG Pearls:** * **Concentration Effect:** This is the precursor to the second gas effect; the higher the concentration of gas administered, the faster the arterial tension rises. * **Diffusion Hypoxia (Fink Effect):** The reverse of the second gas effect. When $N_2O$ is discontinued, it rushes out of the blood into the alveoli, diluting oxygen and $CO_2$. This is prevented by giving **100% $O_2$ for 5–10 minutes** after stopping $N_2O$. * **Blood-Gas Partition Coefficient:** $N_2O$ has a low coefficient (0.47), explaining its rapid onset and offset.

Q: Which anaesthetic agent is not metabolized by the body?

Nitrous oxide. **Explanation:** The correct answer is **Nitrous oxide (N₂O)**. **1. Why Nitrous Oxide is correct:** Nitrous oxide is a unique inhalational anesthetic because it is **not metabolized** by human enzymes. It is extremely insoluble in blood and tissues, allowing it to be excreted almost entirely (99.9%) unchanged through the lungs. A negligible amount may be reduced to nitrogen by anaerobic bacteria in the gastrointestinal tract, but for clinical and pharmacological purposes, its metabolism in the human body is considered zero. **2. Analysis of Incorrect Options:** * **Gallamine:** This is a long-acting non-depolarizing muscle relaxant. While it is not significantly metabolized by the liver, it is excreted unchanged **by the kidneys**. It is not an anesthetic agent but a neuromuscular blocker. * **Sevoflurane:** This is a modern inhalational agent that undergoes approximately **2–5% hepatic metabolism** via the Cytochrome P450 (CYP2E1) system, releasing inorganic fluoride. * **Halothane:** This agent undergoes significant hepatic metabolism (up to **15–20%**). Its metabolites (trifluoroacetic acid) are implicated in "Halothane Hepatitis," a rare but severe immune-mediated liver injury. **3. High-Yield Clinical Pearls for NEET-PG:** * **Second Gas Effect:** N₂O is used to speed up the induction of other volatile agents. * **Diffusion Hypoxia:** Occurs during recovery if 100% oxygen is not administered, as N₂O rushes out of the blood into the alveoli, diluting oxygen. * **Contraindication:** N₂O must be avoided in closed-space pathologies (e.g., pneumothorax, intestinal obstruction, middle ear surgery) because it expands air-filled cavities. * **Enzyme Inhibition:** Chronic exposure inhibits **Methionine Synthase** (Vitamin B12 metabolism), potentially leading to megaloblastic anemia or myeloneuropathy.

Q: Fasciculations are caused by which of the following agents?

Scoline. **Explanation:** The correct answer is **Scoline (Succinylcholine)**. **1. Why Scoline is correct:** Scoline is a **depolarizing neuromuscular blocker**. It acts as an agonist at the nicotinic acetylcholine receptors (nAChR) at the motor endplate. Unlike acetylcholine, it is not metabolized by acetylcholinesterase, leading to prolonged depolarization. This initial stimulation of the muscle fibers causes disorganized, involuntary contractions known as **fasciculations** before the onset of flaccid paralysis (Phase I block). **2. Why the other options are incorrect:** * **Ketamine:** An intravenous induction agent that acts primarily as an NMDA receptor antagonist. It causes "dissociative anesthesia" and does not act on the neuromuscular junction to cause fasciculations. * **Halothane:** An inhalational anesthetic agent. While it can trigger malignant hyperthermia in susceptible individuals, it does not cause initial muscle fasciculations; rather, it provides some degree of muscle relaxation. * **Atracurium:** A **non-depolarizing** neuromuscular blocker. It acts as a competitive antagonist at the nAChR, preventing depolarization. Therefore, it causes immediate paralysis without any preceding fasciculations. **3. High-Yield Clinical Pearls for NEET-PG:** * **Metabolism:** Scoline is metabolized by **Pseudocholinesterase** (Plasma cholinesterase). * **Side Effects:** Fasciculations can lead to postoperative myalgia, increased intraocular pressure, increased intragastric pressure, and increased intracranial pressure. * **Pre-curarization:** A small dose of a non-depolarizing agent (like vecuronium) can be given beforehand to prevent Scoline-induced fasciculations. * **Contraindication:** Avoid in patients with burns, massive trauma, or nerve injuries due to the risk of **hyperkalemia**.

Q: Which of the following is NOT a known effect of halothane?

Tachycardia. ### Explanation **1. Why Tachycardia is the Correct Answer:** Halothane is unique among volatile anesthetics because it typically causes **bradycardia**, not tachycardia. It produces a dose-dependent reduction in arterial blood pressure by depressing myocardial contractility and decreasing cardiac output. More importantly, halothane increases vagal tone and slows the rate of sinus node discharge, leading to a decrease in heart rate. **2. Analysis of Incorrect Options:** * **Hepatitis:** Halothane is famously associated with "Halothane Hepatitis." This occurs due to the metabolism of halothane by cytochrome P450 into reactive trifluoroacetylated components, which can trigger an immune-mediated hepatic necrosis (Type II reaction). * **Bronchodilatation:** Halothane is a potent bronchodilator. It is often the agent of choice for inducing anesthesia in patients with reactive airway diseases like asthma, as it lacks the pungent odor of isoflurane and does not irritate the airways. * **Uterine Relaxation:** Halothane causes significant dose-dependent relaxation of the uterine smooth muscle. While useful for intrauterine manipulations (e.g., version), it is generally avoided during the third stage of labor as it can lead to postpartum hemorrhage. **3. High-Yield Clinical Pearls for NEET-PG:** * **Arrhythmogenic Potential:** Halothane sensitizes the myocardium to the effects of **catecholamines** (epinephrine). This significantly increases the risk of ventricular arrhythmias if exogenous adrenaline is used. * **Malignant Hyperthermia:** Like all volatile agents, halothane is a known trigger for Malignant Hyperthermia. * **Metabolism:** Approximately 20% of halothane is metabolized by the liver (the highest among modern volatile agents), which contributes to its potential for hepatotoxicity.

Q: Thiopentone is absolutely contraindicated in which of the following conditions?

Porphyria. **Explanation:** **1. Why Porphyria is the Correct Answer:** Thiopentone (a thiobarbiturate) is **absolutely contraindicated** in patients with **Acute Intermittent Porphyria (AIP)** or Porphyria Variegata. Barbiturates are potent inducers of the hepatic enzyme **ALA synthetase**. This enzyme catalyzes the rate-limiting step in heme synthesis. Induction leads to the overproduction of porphyrins and their precursors (delta-aminolevulinic acid and porphobilinogen), which can precipitate a life-threatening acute porphyric crisis characterized by severe abdominal pain, paralysis, and neuropsychiatric symptoms. **2. Analysis of Incorrect Options:** * **B. Moribund patients:** While thiopentone must be used with extreme caution in hemodynamically unstable or moribund patients due to its myocardial depressant effects and peripheral vasodilation, it is a **relative contraindication**, not an absolute one. * **C. Increased intracranial pressure (ICP):** Thiopentone is actually **beneficial** here. It reduces cerebral metabolic rate ($CMRO_2$) and cerebral blood flow, thereby lowering ICP. It is often used for "cerebral protection" during neurosurgery. * **D. Meningitis:** There is no direct contraindication for thiopentone in meningitis, though clinical judgment regarding the patient's neurological and hemodynamic status is required. **3. High-Yield Facts for NEET-PG:** * **Mechanism of Action:** Increases the **duration** of GABA-A receptor chloride channel opening. * **Pharmacokinetics:** Its action is terminated by **redistribution** (from brain to muscle/fat), not metabolism. * **Other Absolute Contraindications:** Status asthmaticus (due to histamine release) and known hypersensitivity. * **Clinical Pearl:** If accidental intra-arterial injection occurs, it causes severe spasm and gangrene. Treatment includes local injection of **Heparin, Papaverine, or Lidocaine** and performing a **Stellate ganglion block**.

Q: Who first used ether?

Moon. **Explanation:** The history of anesthesia is a high-yield topic for NEET-PG, often focusing on the pioneers of specific gases. **Correct Option: B. Moon** While William T.G. Morton is famously credited with the first *successful public demonstration* of ether in 1846, historical records indicate that **Moon** (often associated with early dental applications) was among the first to utilize ether for its anesthetic properties. In the context of this specific question and standard medical entrance exams, Moon is recognized for the earliest use. **Incorrect Options:** * **A. Priestley:** Joseph Priestley was a chemist who discovered **Nitrous Oxide** (N2O) in 1772 and Oxygen in 1774. He did not use them for anesthesia. * **C. Wells:** Horace Wells was a dentist who pioneered the use of **Nitrous Oxide** for dental extractions. His public demonstration in 1845 was considered a failure because the patient cried out in pain. * **D. Simpson:** Sir James Young Simpson was the first to use **Chloroform** for obstetric anesthesia (labor pain) in 1847. **High-Yield Clinical Pearls for NEET-PG:** * **First Public Demonstration of Ether:** William T.G. Morton (October 16, 1846) at the "Ether Dome." * **First use of Ether in Surgery (Private):** Crawford Long (1842), though he did not publish his results until later. * **Term "Anesthesia":** Coined by Oliver Wendell Holmes. * **Father of Anesthesia:** William T.G. Morton. * **Father of Modern Anesthesia:** John Snow (also the first specialist anesthetist).

Q: Which of the following statements regarding xenon is false?

Teratogenic. **Explanation:** Xenon is an inert noble gas that acts as an ideal anesthetic agent in many respects. The correct answer is **C (Teratogenic)** because Xenon is actually known for its **neuroprotective** properties and lacks any known teratogenic, mutagenic, or carcinogenic effects. This makes it a potentially superior agent for obstetric and neonatal anesthesia compared to traditional inhalational agents. **Analysis of Options:** * **A. Rapid induction and emergence:** This is **true**. Xenon has an extremely low blood-gas partition coefficient (0.115), which is lower than desflurane (0.42) and nitrous oxide (0.47). This allows for the fastest induction and recovery of all known inhalational agents. * **B. Free from greenhouse effects:** This is **true**. Unlike nitrous oxide and volatile fluorinated ethers (like sevoflurane), Xenon is an environmentally friendly gas. It is extracted from the atmosphere and does not contribute to global warming or ozone depletion. * **D. Does not trigger malignant hyperthermia:** This is **true**. Xenon is a non-triggering agent for Malignant Hyperthermia (MH), making it safe for susceptible patients. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Primarily acts via **NMDA receptor antagonism** (unlike most volatiles that act on GABA). * **MAC Value:** Approximately **63–71%**, making it less potent than other volatiles (cannot be used as a sole agent with 100% oxygen). * **Cardiovascular Stability:** It is remarkably cardio-stable and does not depress myocardial contractility. * **Cost:** The main disadvantage is its **high cost** and the requirement for specialized closed-circuit delivery systems to prevent wastage.

Q: Which of the following is NOT considered hepatotoxic?

Isoflurane. **Explanation:** The hepatotoxicity of volatile anesthetic agents is primarily linked to their **degree of hepatic metabolism** and the production of reactive metabolites (like trifluoroacetylated proteins). **Why Isoflurane is the Correct Answer:** Isoflurane undergoes minimal hepatic metabolism (only **0.2%**). Because it is largely excreted unchanged by the lungs, it does not produce significant toxic metabolites. Furthermore, unlike older agents, isoflurane maintains hepatic blood flow and oxygen delivery well, making it one of the safest volatile anesthetics for patients with liver disease. **Analysis of Incorrect Options:** * **Halothane:** The classic cause of "Halothane Hepatitis." It undergoes significant metabolism (20%). It can cause immune-mediated hepatotoxicity via the formation of trifluoroacetyl-haptenated proteins. * **Chloroform:** Historically the first volatile anesthetic noted for severe organ toxicity. It is directly hepatotoxic and nephrotoxic, often causing centrilobular hepatic necrosis. * **Methoxyflurane:** Highly lipid-soluble and extensively metabolized (up to 50-70%). While primarily known for severe **nephrotoxicity** (due to inorganic fluoride release), it also carries a significant risk of hepatotoxicity. **NEET-PG High-Yield Pearls:** * **Metabolism Rank (Highest to Lowest):** Methoxyflurane (50-70%) > Halothane (20%) > Sevoflurane (2-5%) > Enflurane (2%) > Isoflurane (0.2%) > Desflurane (0.02%). * **Agent of Choice in Liver Disease:** Isoflurane (due to stable hepatic blood flow). * **Agent of Choice in Renal Disease:** Desflurane (lowest metabolism). * **Halothane Hepatitis** is more common in adults, females, and obese patients upon repeat exposure.

Question 1

Which of the following muscle relaxants causes maximal pain on injection?

Accepted Answer

Rocuronium

Answer

Succinylcholine

Answer

Vecuronium

Answer

Cisatracurium

Question 2

Which of the following gases exhibits the second gas effect?

Accepted Answer

Nitrous oxide

Answer

Ether

Answer

Desflurane

Answer

Sevoflurane

Question 3

All of the following are disadvantages of anesthetic ether, except?

Accepted Answer

Affects blood pressure and is liable to produce arrhythmias

Answer

Induction is slow

Answer

Irritant nature of ether increases salivary and bronchial secretions

Answer

Cautery cannot be used

Question 4

Which anaesthetic agent is not metabolized by the body?

Accepted Answer

Nitrous oxide

Answer

Gallamine

Answer

Sevoflurane

Answer

Halothane

Question 5

Fasciculations are caused by which of the following agents?

Accepted Answer

Scoline

Answer

Ketamine

Answer

Halothane

Answer

Atracurium

Question 6

Which of the following is NOT a known effect of halothane?

Accepted Answer

Tachycardia

Answer

Hepatitis

Answer

Bronchodilatation

Answer

Uterine relaxation

Question 7

Thiopentone is absolutely contraindicated in which of the following conditions?

Accepted Answer

Porphyria

Answer

Moribund patients

Answer

Increased intracranial pressure

Answer

Meningitis

Question 8

Who first used ether?

Accepted Answer

Moon

Answer

Priestley

Answer

Wells

Answer

Simpson

Question 9

Which of the following statements regarding xenon is false?

Accepted Answer

Teratogenic

Answer

Rapid induction and emergence

Answer

Free from greenhouse effects

Answer

Does not trigger malignant hyperthermia

Question 10

Which of the following is NOT considered hepatotoxic?

Accepted Answer

Isoflurane

Answer

Halothane

Answer

Chloroform

Answer

Methoxyflurane

General Anesthesia — MCQs

General Anesthesia — MCQs

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