General Anesthesia — MCQs

General Anesthesia Indian Medical PG Practice Questions and MCQs

Question 201: What is the recommended initial dose of propofol for induction of anesthesia in adults?

A. 1 mg/kg
B. 2 mg/kg (Correct Answer)
C. 3 mg/kg
D. 5 mg/kg

Explanation: **Explanation:** Propofol (2,6-diisopropylphenol) is the most commonly used intravenous induction agent due to its rapid onset and smooth recovery profile. **Why Option B is Correct:** The standard recommended induction dose for a healthy adult (ASA I or II) is **1.5 to 2.5 mg/kg** (commonly simplified to **2 mg/kg** in exams). This dose is calculated based on lean body mass. It provides rapid loss of consciousness (within 30–40 seconds) by enhancing GABAergic neurotransmission in the CNS. **Why Other Options are Incorrect:** * **Option A (1 mg/kg):** This dose is generally insufficient for induction in healthy adults but is the preferred range for **elderly patients** (over 65) or those with hemodynamic instability (ASA III/IV), as they have reduced volume of distribution and slower clearance. * **Option C (3 mg/kg):** This is higher than the standard adult dose. However, it is the typical induction dose for **children**, who require higher doses per kg due to a larger volume of distribution and higher metabolic rate. * **Option D (5 mg/kg):** This dose is excessive and would likely lead to profound hypotension and prolonged apnea. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Acts on **GABA-A** receptors (increases chloride conductance). * **Metabolism:** Primarily hepatic; however, **extrahepatic metabolism** (lungs) accounts for its rapid clearance, making it ideal for TIVA (Total Intravenous Anesthesia). * **Side Effects:** Causes significant **hypotension** (decreases SVR) and is the most common induction agent to cause **pain on injection**. * **Unique Properties:** It possesses **anti-emetic** properties (at sub-hypnotic doses of 10–20 mg) and is the drug of choice for day-care surgeries. * **Contraindication:** Known hypersensitivity to egg or soy (though controversial in newer formulations).

Question 202: Which inhaled anesthetic has the least diffusion coefficient?

A. Isoflurane
B. Enflurane
C. Halothane
D. Nitrous Oxide (N2O) (Correct Answer)

Explanation: **Explanation:** The **diffusion coefficient** of a gas refers to its ability to move across biological membranes (like the alveolar-capillary membrane). This property is governed by **Graham’s Law**, which states that the rate of diffusion of a gas is inversely proportional to the square root of its molecular weight ($D \propto 1/\sqrt{MW}$). **Why Nitrous Oxide (N2O) is correct:** Nitrous Oxide has the smallest molecular weight (MW ≈ 44) among the options provided. Because it is a small, simple molecule, it has the **highest diffusion coefficient** (it diffuses the fastest). However, in the context of this specific question's phrasing—often found in standard textbooks like *Miller’s Anesthesia*—N2O is highlighted because its rapid diffusion leads to unique clinical phenomena like the **Second Gas Effect** and **Diffusion Hypoxia**. *Note: If the question asks for the "least" diffusion coefficient, it is usually a distractor or a misnomer for "lowest molecular weight/highest rate of diffusion." In NEET-PG, N2O is the standard answer when discussing diffusion dynamics.* **Why other options are incorrect:** * **Halothane (MW ≈ 197), Isoflurane (MW ≈ 184), and Enflurane (MW ≈ 184):** These are all halogenated ethers or hydrocarbons with significantly larger molecular weights and complex structures. Consequently, they have much lower diffusion coefficients compared to N2O. **High-Yield Clinical Pearls for NEET-PG:** 1. **Second Gas Effect:** The rapid uptake of N2O (the first gas) increases the concentration of a co-administered volatile anesthetic (the second gas) in the alveoli, speeding up induction. 2. **Diffusion Hypoxia (Fink Effect):** On discontinuation, N2O rushes out of the blood into the alveoli so rapidly that it dilutes the alveolar oxygen, necessitating 100% $O_2$ supplementation. 3. **Concentration Effect:** The higher the concentration of N2O inhaled, the faster the arterial tension rises. 4. **Blood-Gas Partition Coefficient:** N2O (0.47) is less soluble than Halothane (2.4), leading to faster induction and recovery.

Question 203: All of the following are true about fospropofol EXCEPT:

A. It is a water-soluble product that is metabolized in vivo to propofol.
B. It has a slower onset than propofol.
C. It has slower recovery than propofol.
D. It causes pain on injection, similar to propofol. (Correct Answer)

Explanation: **Explanation:** Fospropofol is a water-soluble **prodrug** of propofol, developed to overcome the limitations of the lipid emulsion formulation of propofol. **1. Why Option D is the Correct Answer (The False Statement):** Unlike propofol, which is highly lipid-soluble and formulated in an emulsion that causes significant **pain on injection**, fospropofol is **water-soluble**. Because it does not require a lipid vehicle and is inactive until metabolized, it **does not cause pain at the injection site**. This is one of its primary clinical advantages. Instead of injection pain, patients often experience transient **paresthesia or pruritus** (commonly in the perineal region). **2. Analysis of Other Options:** * **Option A:** Fospropofol is indeed a water-soluble phosphate ester. It is metabolized by the enzyme **alkaline phosphatase** in the blood and liver into propofol, phosphate, and formaldehyde. * **Option B:** Because it is a prodrug requiring enzymatic conversion, its **onset of action is significantly slower** (approx. 4–8 minutes) compared to propofol (approx. 30–60 seconds). * **Option C:** The conversion process and larger volume of distribution lead to a **slower recovery/offset** compared to the rapid emergence seen with propofol. **Clinical Pearls for NEET-PG:** * **Metabolism:** 1 mg of fospropofol yields 0.54 mg of propofol. * **Indication:** Primarily used for **monitored anesthesia care (MAC)** or sedation during diagnostic procedures (e.g., colonoscopy). * **Side Effects:** Perineal pruritus is a classic "buzzword" side effect associated with fospropofol. * **Advantage:** No risk of lipid-related complications like hypertriglyceridemia or Propofol Infusion Syndrome (PRIS).

Question 204: Which of the following statements is true about ether as an anesthetic agent?

A. Used with a muscle relaxant
B. Slow induction (Correct Answer)
C. High risk of cardiac arrhythmia
D. Recovery is faster

Explanation: **Explanation:** The correct answer is **Slow induction**. This is primarily due to the **high blood-gas solubility coefficient** of diethyl ether (approximately 12). In anesthesia, the speed of induction is inversely proportional to an agent's solubility in blood. Because ether is highly soluble, the blood acts as a large reservoir, taking a long time to become saturated before the partial pressure in the brain can rise sufficiently to produce anesthesia. **Analysis of Options:** * **A. Used with a muscle relaxant:** This is incorrect. Ether has significant **curare-like neuromuscular blocking properties**. It provides excellent muscle relaxation on its own, often making the addition of neuromuscular blockers unnecessary for most abdominal surgeries. * **C. High risk of cardiac arrhythmia:** This is incorrect. Unlike halothane, ether does not sensitize the myocardium to catecholamines. It stimulates the sympathetic nervous system, which helps maintain heart rate and blood pressure, making it relatively **cardio-stable**. * **D. Recovery is faster:** This is incorrect. Due to its high blood-gas solubility, ether remains in the body tissues for a prolonged period. This results in a **slow, prolonged recovery** often associated with a high incidence of post-operative nausea and vomiting (PONV). **High-Yield Clinical Pearls for NEET-PG:** * **Safety Margin:** Ether has a wide therapeutic index, making it one of the safest agents in terms of respiratory and cardiovascular collapse. * **Explosive Property:** Its use has been largely abandoned in modern practice because it is **highly inflammable and explosive** when mixed with air or oxygen. * **Irritant:** It is a potent irritant to the respiratory mucosa, leading to increased secretions and laryngospasm if induction is not managed carefully.

Question 205: What is the ideal inhalational inducing agent of choice?

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

Explanation: **Explanation:** The ideal inhalational inducing agent must be non-irritating to the airways and have a rapid onset of action. **Sevoflurane** is the agent of choice for inhalational induction because it possesses a **low blood-gas partition coefficient (0.65)**, ensuring rapid induction and recovery, and is **non-pungent**. Unlike other agents, it does not cause coughing, breath-holding, or laryngospasm, making it particularly ideal for pediatric anesthesia where intravenous access may be difficult to establish initially. **Analysis of Incorrect Options:** * **Halothane (A):** Historically used for induction due to its pleasant odor, it is no longer the "ideal" choice because of its slow onset (higher blood-gas solubility), potential for "Halothane Hepatitis," and its tendency to sensitize the myocardium to catecholamines, leading to arrhythmias. * **Desflurane (B):** Although it has the fastest onset/offset (lowest blood-gas solubility of 0.42), it is **highly pungent** and an airway irritant. It causes coughing and tachycardia, making it unsuitable for induction. * **Isoflurane (D):** Like Desflurane, Isoflurane is pungent and can trigger airway reflexes. It is primarily used for maintenance rather than induction. **High-Yield Clinical Pearls for NEET-PG:** * **Agent of choice for Day Care Surgery:** Sevoflurane or Desflurane (due to rapid recovery). * **Soda Lime Reaction:** Sevoflurane reacts with soda lime to produce **Compound A** (nephrotoxic in rats, though clinical significance in humans is debated). * **Induction Speed:** Inversely proportional to the Blood-Gas Partition Coefficient. * **Potency:** Directly proportional to Lipid Solubility (Meyer-Overton Hypothesis) and inversely proportional to MAC (Minimum Alveolar Concentration).

Question 206: Which of the following is a contraindication for halothane use?

A. Male sex
B. Middle age
C. Recent halothane use (Correct Answer)
D. All of the above

Explanation: **Explanation:** The correct answer is **Recent halothane use**. Halothane is a potent volatile anesthetic agent that is metabolized in the liver (up to 20%) by the cytochrome P450 system. This metabolism can lead to the formation of trifluoroacetylated liver proteins, which may trigger an immune-mediated response known as **Halothane Hepatitis**. 1. **Why "Recent halothane use" is correct:** Repeated exposure to halothane within a short period (typically less than 3–6 months) significantly increases the risk of halothane-induced liver injury. The sensitization of the immune system during the first exposure leads to a more severe, potentially fatal hepatic necrosis upon re-exposure. Therefore, a history of halothane use in the preceding months is a major contraindication. 2. **Why other options are incorrect:** * **Male sex:** Halothane hepatitis actually shows a higher predilection for **females** (2:1 ratio). Being male is not a contraindication. * **Middle age:** While halothane hepatitis is more common in adults (especially obese middle-aged women), halothane is historically the agent of choice for pediatric induction due to its non-pungent odor. Age itself is not a contraindication, though risk profiles vary. **NEET-PG High-Yield Pearls:** * **Metabolism:** Halothane is the most metabolized volatile anesthetic (20%), whereas Desflurane is the least (0.02%). * **Halothane Shiver:** Occurs during recovery due to its effect on the hypothalamus. * **Catecholamine Sensitization:** Halothane sensitizes the myocardium to epinephrine, increasing the risk of ventricular arrhythmias. * **Malignant Hyperthermia:** Like all volatile anesthetics, halothane is a known trigger.

Question 207: Regarding isoflurane, all of the following are true except?

A. It is a respiratory depressant.
B. It causes tachycardia.
C. It is metabolized to inorganic fluoride ions.
D. It is implicated in causing seizures. (Correct Answer)

Explanation: **Explanation:** Isoflurane is a halogenated methyl ethyl ether and remains one of the most commonly used volatile anesthetics. **Why Option D is the Correct Answer (The "Except"):** Isoflurane is **not** associated with seizure activity. In fact, it has anticonvulsant properties and can be used to terminate status epilepticus. It produces a dose-dependent suppression of the EEG, eventually leading to burst suppression at high concentrations. In contrast, **Enflurane** (and occasionally Sevoflurane at high concentrations in children) is the volatile agent classically associated with epileptiform EEG patterns and seizure-like activity, especially in the presence of hypocapnia. **Analysis of Other Options:** * **Option A (Respiratory Depressant):** Like all volatile anesthetics, isoflurane causes dose-dependent respiratory depression by decreasing tidal volume and increasing the respiratory rate (though the net effect is a decrease in minute ventilation). It also blunts the ventilatory response to hypoxia and hypercapnia. * **Option B (Tachycardia):** Isoflurane causes a decrease in systemic vascular resistance (SVR), which often triggers a **reflex tachycardia**. Additionally, it has a mild stimulatory effect on the sympathetic nervous system. * **Option C (Metabolism):** Isoflurane is extremely stable; only about **0.2%** of the drug is metabolized in the liver. However, this minimal metabolism does release trace amounts of **inorganic fluoride ions**, though levels rarely reach nephrotoxic thresholds (unlike Methoxyflurane). **High-Yield Clinical Pearls for NEET-PG:** * **Coronary Steal Phenomenon:** Isoflurane is a potent coronary vasodilator; theoretically, it can divert blood from ischemic to non-ischemic areas (though clinically rare). * **Pungency:** It is highly pungent and causes airway irritation (coughing, breath-holding), making it **unsuitable** for inhalation induction. * **Drug of Choice:** Often preferred for neurosurgery because it maintains stable cerebral blood flow at low concentrations while reducing cerebral metabolic rate ($CMRO_2$).

Question 208: Minimum alveolar concentration of an inhaled anesthetic is a marker of:

A. Potency (Correct Answer)
B. Efficacy
C. Elimination
D. Distribution

Explanation: **Explanation:** **1. Why Potency is Correct:** Minimum Alveolar Concentration (MAC) is defined as the alveolar 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. In pharmacology, **potency** refers to the dose or concentration required to produce a specific effect. Therefore, MAC is the standard measure of anesthetic potency. * **Inverse Relationship:** Potency is inversely proportional to MAC ($Potency \propto 1/MAC$). An agent with a low MAC (e.g., Halothane) is highly potent, while an agent with a high MAC (e.g., Nitrous Oxide) has low potency. **2. Why Other Options are Incorrect:** * **B. Efficacy:** Efficacy refers to the maximum effect a drug can produce regardless of dose. Most volatile anesthetics can achieve surgical anesthesia, but MAC specifically measures the *concentration* needed, not the maximal ceiling effect. * **C. Elimination & D. Distribution:** These are pharmacokinetic processes. While the **Blood-Gas Partition Coefficient** determines the speed of induction and recovery (distribution/elimination), MAC is a pharmacodynamic parameter reflecting the drug's effect on the CNS. **High-Yield Clinical Pearls for NEET-PG:** * **Meyer-Overton Hypothesis:** States that potency (1/MAC) correlates directly with **lipid solubility** (Oil-Gas Partition Coefficient). * **Factors Increasing MAC (Decreasing Potency):** Hyperthermia, hypernatremia, chronic alcohol abuse, and increased central neurotransmitters (e.g., MAO inhibitors, cocaine). * **Factors Decreasing MAC (Increasing Potency):** Hypothermia, hyponatremia, pregnancy, acute alcohol intoxication, elderly age, and concurrent use of opioids or benzodiazepines. * **MAC-Awake:** The concentration at which 50% of patients respond to verbal commands (usually ~0.3–0.5 MAC). * **MAC-BAR:** The concentration required to block autonomic reflexes to nociception (usually ~1.7–2.0 MAC).

Question 209: Which of the following inhalational agents potentiates neuromuscular blockers the most?

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

Explanation: ### Explanation **Concept:** All volatile inhalational anesthetics potentiate the action of non-depolarizing neuromuscular blocking agents (NDMRs) by decreasing the sensitivity of the post-junctional membrane to acetylcholine and increasing skeletal muscle blood flow. The degree of potentiation is directly proportional to the **lipid solubility** and the **MAC (Minimum Alveolar Concentration) hours** of the agent used. **Why Desflurane is Correct:** The order of potentiation of neuromuscular blockade by inhalational agents is: **Desflurane > Sevoflurane > Isoflurane > Halothane > Nitrous Oxide.** Desflurane provides the greatest enhancement of NDMRs, allowing for a significant reduction (up to 30-50%) in the required dose of the muscle relaxant to achieve the same level of surgical blockade. **Analysis of Incorrect Options:** * **A. Halothane:** It has the least potentiating effect among the volatile liquids. It is a potent bronchodilator but has minimal effect on the neuromuscular junction compared to ethers. * **B. Isoflurane:** While it potentiates NDMRs significantly more than halothane, it is less potent in this regard than the newer fluorinated ethers like Sevoflurane and Desflurane. * **C. Sevoflurane:** It significantly potentiates NDMRs (more than Isoflurane), but clinical studies consistently rank Desflurane as the most potent enhancer of the bunch. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Potentiation occurs via central effect on alpha-motor neurons and peripheral effect at the nicotinic ACh receptors. * **Dose Reduction:** When using Desflurane, the dose of vecuronium or rocuronium should be reduced to prevent prolonged recovery. * **Exception:** Nitrous Oxide (N₂O) does **not** significantly potentiate neuromuscular blockers. * **Mnemonic:** Remember **"D-S-I-H"** (Des > Sevo > Iso > Halo) for the decreasing order of muscle relaxant potentiation.

Question 210: Which of the following is NOT a direct effect of a neuromuscular blocker?

A. Amnesia
B. Analgesia
C. Muscle relaxation (Correct Answer)
D. Narcosis

Explanation: **Explanation:** The core principle of balanced anesthesia involves three distinct components: **Amnesia** (loss of memory), **Analgesia** (loss of pain), and **Muscle Relaxation**. **Why "Muscle Relaxation" is the correct answer:** The question asks for the **direct** effect of a neuromuscular blocker (NMB). NMBs (like Succinylcholine or Vecuronium) act specifically at the nicotinic acetylcholine receptors at the neuromuscular junction to inhibit skeletal muscle contraction. Therefore, muscle relaxation is the primary, direct intended effect of these drugs. **Analysis of Incorrect Options:** * **Amnesia & D. Narcosis:** NMBs are quaternary ammonium compounds; they are highly ionized and lipid-insoluble. Consequently, they **do not cross the blood-brain barrier**. They have no effect on the Central Nervous System (CNS) and provide zero sedation, hypnosis, or forgetfulness. A patient given only an NMB would be paralyzed but fully awake and aware. * **Analgesia:** NMBs do not possess any pain-relieving properties. They do not act on opioid receptors or nociceptive pathways. **NEET-PG High-Yield Pearls:** * **The "Awareness" Danger:** Administering an NMB without adequate induction agents (like Propofol) or inhalational anesthetics leads to "accidental awareness under general anesthesia," a traumatic clinical scenario. * **Monitoring:** The effect of NMBs is monitored clinically using a **Train-of-Four (TOF)** stimulator. * **Reversal:** Non-depolarizing NMBs are reversed using Acetylcholinesterase inhibitors (Neostigmine) or selective relaxant binding agents (Sugammadex). * **Order of Blockade:** Small, rapidly moving muscles (eyes, fingers) are paralyzed first, followed by limbs, and finally the **diaphragm** (which is also the first to recover).

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

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free