General Anesthesia — MCQs

General Anesthesia Indian Medical PG Practice Questions and MCQs

Question 231: Dissociative anesthesia is characterized by which of the following agents?

A. Ether
B. Halothane
C. Enflurane
D. Ketamine (Correct Answer)

Explanation: **Explanation:** **Ketamine** is the prototype drug for **dissociative anesthesia**. This unique state is characterized by profound analgesia, amnesia, and a "trance-like" state where the patient appears awake (eyes may remain open with a slow nystagmic gaze) but is disconnected from the environment and does not respond to sensory input. **Mechanism of Action:** Ketamine works primarily as a non-competitive antagonist at the **NMDA (N-methyl-D-aspartate) receptors**. It causes "dissociation" by depressing the thalamocortical system while simultaneously stimulating parts of the limbic system. **Why the other options are incorrect:** * **Ether, Halothane, and Enflurane (Options A, B, C):** These are traditional volatile inhalational anesthetics. They produce a state of generalized CNS depression leading to unconsciousness, muscle relaxation, and loss of reflexes, rather than the specific "dissociative" state seen with ketamine. **High-Yield Clinical Pearls for NEET-PG:** * **Hemodynamics:** Unlike most anesthetics, Ketamine is **sympathomimetic**. It increases HR, BP, and CO, making it the induction agent of choice for **hypovolemic shock**. * **Airway:** It preserves airway reflexes and causes **bronchodilation**, making it ideal for asthmatic patients. * **Side Effects:** It is associated with **emergence delirium** and hallucinations (minimized by co-administration of benzodiazepines like Midazolam). * **Contraindications:** It increases Intraocular Pressure (IOP) and Intracranial Pressure (ICP), so it should be avoided in head injuries and glaucoma. * **Secretions:** It causes significant **hypersalivation**, often requiring an anticholinergic (e.g., Glycopyrrolate) as premedication.

Question 232: Which of the following drugs is least absorbed from the mucous membrane?

A. Lidocaine
B. Tetracaine
C. Procaine (Correct Answer)
D. Cocaine

Explanation: **Explanation:** The absorption of local anesthetics (LAs) through mucous membranes depends primarily on their **lipid solubility** and **vasoactive properties**. **Why Procaine is the Correct Answer:** Procaine is an ester-linked local anesthetic with **very low lipid solubility**. Because the mucous membrane barrier is lipid-rich, drugs with low lipid solubility penetrate poorly. Furthermore, Procaine is a potent **vasodilator**, which increases its systemic absorption into the bloodstream but prevents it from remaining concentrated at the site of application. Consequently, it has negligible topical (surface) anesthetic activity and is considered the least effective for mucosal application among the options. **Analysis of Incorrect Options:** * **Lidocaine (Option A):** An amide with moderate lipid solubility. It is highly effective and widely used for topical anesthesia (e.g., 2% jelly, 10% spray). * **Tetracaine (Option B):** An ester with high lipid solubility and potency. It is frequently used for surface anesthesia, particularly in ophthalmology and spinal anesthesia. * **Cocaine (Option D):** Unique among LAs because it is a potent **vasoconstrictor**. This property, combined with good lipid solubility, allows it to be rapidly and effectively absorbed through mucous membranes (e.g., nasal mucosa). **NEET-PG High-Yield Pearls:** 1. **Lipid Solubility:** Determines the **potency** and topical effectiveness of a local anesthetic. 2. **pKa:** Determines the **onset of action** (lower pKa = faster onset). 3. **Protein Binding:** Determines the **duration of action**. 4. **Vasoactivity:** Most LAs are vasodilators (except Cocaine, Ropivacaine, and Levobupivacaine). 5. **Metabolism:** Esters (like Procaine) are metabolized by **plasma pseudocholinesterase**; Amides (like Lidocaine) are metabolized by **liver microsomal enzymes**.

Question 233: The triad of general anaesthesia includes which of the following components?

A. Unconsciousness, analgesia, and muscle relaxation (Correct Answer)
B. Anxiolysis, analgesia, and unconsciousness
C. Muscle relaxation, sedation, and analgesia
D. Dissociation, analgesia, and muscle relaxation

Explanation: The **Triad of General Anaesthesia** (originally proposed by Gray and Rees) represents the three fundamental physiological states required to perform surgery safely and effectively. ### 1. Why Option A is Correct The goal of balanced anesthesia is to achieve a state where the patient is unaware, pain-free, and physically still. The components are: * **Unconsciousness (Narcosis/Hypnosis):** Ensures the patient is unaware of the surgical procedure and has no memory of it (amnesia). * **Analgesia:** Suppression of the sensory perception of pain and the autonomic responses to surgical stimuli. * **Muscle Relaxation (Areflexia):** Provides optimal operating conditions for the surgeon by paralyzing skeletal muscles and suppressing motor reflexes. ### 2. Why Other Options are Incorrect * **Option B:** **Anxiolysis** (reduction of anxiety) is a component of *pre-medication*, not a core requirement of the intraoperative triad. * **Option C:** **Sedation** is a depressed level of consciousness where the patient may still respond to stimuli; general anesthesia requires complete unconsciousness. * **Option D:** **Dissociation** is specific to "Dissociative Anesthesia" (e.g., Ketamine), where the patient appears awake but is detached from the environment. It is a type of anesthesia, not a component of the classic triad. ### 3. High-Yield NEET-PG Pearls * **Balanced Anesthesia:** This modern concept uses a combination of drugs (e.g., Propofol for induction, Opioids for analgesia, and Vecuronium for relaxation) to achieve the triad while minimizing the side effects of any single agent. * **The Fourth Component:** Modern texts often add **Amnesia** or **Autonomic Stability** as a fourth pillar, forming a "tetrad." * **Guedel’s Stages:** Remember that these stages (I-IV) specifically describe anesthesia induced by **Ether**; they are rarely seen with modern rapid-acting intravenous agents.

Question 234: Which of the following is NOT true about fospropofol?

A. It is an aqueous phosphorylated prodrug of propofol.
B. It has a more prolonged recovery profile than propofol.
C. Pain at the injection site was not reported with fospropofol.
D. It causes significantly more respiratory depression than propofol. (Correct Answer)

Explanation: **Explanation:** Fospropofol is a water-soluble, phosphorylated **prodrug** of propofol. It is metabolized by the enzyme **alkaline phosphatase** in the blood and liver to release active propofol, formaldehyde, and phosphate. **Why Option D is the Correct Answer (The False Statement):** Fospropofol actually has a **lower incidence of acute respiratory depression** and apnea compared to propofol. Because it is a prodrug, the conversion to active propofol is gradual, leading to a slower rise in plasma concentration (lower $C_{max}$). This "smoother" pharmacokinetic profile results in fewer abrupt hemodynamic and respiratory side effects. **Analysis of Other Options:** * **Option A:** Correct. Unlike propofol (which is lipid-soluble and requires an intralipid emulsion), fospropofol is **aqueous** (water-soluble), eliminating the need for lipid vehicles. * **Option B:** Correct. Due to the time required for enzymatic conversion (half-life of conversion is ~8 minutes), fospropofol has a **slower onset** (4–8 mins) and a **more prolonged recovery** profile than bolus propofol. * **Option C:** Correct. Since it is water-soluble and lacks the irritating lipid emulsion, **pain on injection is not reported**. However, it is uniquely associated with transient **perianal pruritus** or paresthesia. **NEET-PG High-Yield Pearls:** 1. **Metabolism:** 1 mmol of fospropofol yields 1 mmol of propofol. 2. **Side Effects:** The most characteristic side effect is **perianal itching/burning**, occurring in up to 70% of patients. 3. **Indication:** Primarily used for **Monitored Anesthesia Care (MAC)** during diagnostic procedures like colonoscopy. 4. **Formaldehyde:** While formaldehyde is produced during metabolism, it is rapidly converted to formate and does not reach toxic levels in clinical doses.

Question 235: Which of the following intravenous anesthetic agents interacts with tricyclic antidepressants?

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

Explanation: ### Explanation The correct answer is **Ketamine**. **1. Why Ketamine is Correct:** The interaction between Ketamine and Tricyclic Antidepressants (TCAs) is based on their shared effect on the sympathetic nervous system. * **Mechanism:** TCAs inhibit the reuptake of norepinephrine at the synaptic cleft, leading to increased levels of circulating catecholamines. Ketamine acts as a **sympathomimetic** agent by inhibiting the neuronal uptake of catecholamines and stimulating the central sympathetic outflow. * **Clinical Result:** When used together, they produce a synergistic effect, leading to **profound hypertension and cardiac arrhythmias**. This makes the combination potentially dangerous during induction. **2. Why the Other Options are Incorrect:** * **Thiopentone:** A barbiturate that primarily acts via GABA-A receptors. It typically causes peripheral vasodilation and myocardial depression, leading to a drop in blood pressure, rather than a hypertensive interaction with TCAs. * **Propofol:** Acts via GABA-A receptors. It is known for causing significant vasodilation and bradycardia (vagal dominance). It does not have a direct sympathomimetic interaction with TCAs. * **Etomidate:** An imidazole derivative used for its cardiovascular stability. It does not significantly affect catecholamine levels or interact adversely with the monoamine system. **3. High-Yield Clinical Pearls for NEET-PG:** * **Ketamine** is the induction agent of choice for patients with **bronchial asthma** (due to bronchodilation) and **hypovolemic shock** (due to sympathetic stimulation). * **Avoid Ketamine** in patients with: Ischemic heart disease, hypertension, increased intracranial pressure (ICP), and psychiatric disorders (due to emergence delirium). * **TCA Interaction:** Apart from Ketamine, avoid **Pancuronium** (vagolytic) and **indirect-acting sympathomimetics** (like ephedrine) in patients on TCAs, as they can also trigger hypertensive crises. Use direct-acting agents like Phenylephrine if needed.

Question 236: What combination of drugs causes a dual block?

A. Vecuronium and pancuronium
B. Atracurium
C. Vecuronium and rocuronium
D. Succinylcholine (Correct Answer)

Explanation: **Explanation:** **Succinylcholine** is a depolarizing neuromuscular blocker (DNMB) that uniquely causes a **Dual Block** (also known as Phase II block). Under normal circumstances, succinylcholine produces a **Phase I block** (depolarizing), characterized by muscle fasciculations followed by relaxation. However, when succinylcholine is administered in high doses, via prolonged infusions, or in patients with atypical pseudocholinesterase, the mechanism shifts. The post-junctional membrane becomes desensitized and repolarizes, but remains unresponsive to acetylcholine. This resulting **Phase II block** clinically mimics the characteristics of a non-depolarizing block (e.g., presence of "fade" on Train-of-Four stimulation and post-tetanic facilitation). **Analysis of Incorrect Options:** * **Options A, B, and C:** Vecuronium, Pancuronium, Atracurium, and Rocuronium are all **Non-Depolarizing Neuromuscular Blockers (NDNMBs)**. These drugs act as competitive antagonists at the nicotinic receptors. They produce a consistent Phase II-like block from the onset and do not transition through two distinct phases; therefore, they do not cause a "dual block." **Clinical Pearls for NEET-PG:** * **Mechanism:** Phase I block (Depolarizing) → Phase II block (Desensitizing/Dual). * **Reversal:** Neostigmine **antagonizes** a Phase II block but **augments** (worsens) a Phase I block. * **TOF Ratio:** In Phase I, the ratio is >0.7 (no fade); in Phase II, the ratio is <0.3 (significant fade). * **Drug of Choice for RSI:** Succinylcholine remains the gold standard for Rapid Sequence Induction due to its rapid onset and short duration.

Question 237: Thiopentone is contraindicated in which of the following conditions?

A. Acute intermittent porphyria (Correct Answer)
B. Bronchial Asthma
C. Both
D. None

Explanation: **Explanation:** **1. Why Acute Intermittent Porphyria (AIP) is the Correct Answer:** Thiopentone (a barbiturate) is an absolute contraindication in patients with Porphyria. Barbiturates are potent inducers of the hepatic enzyme **ALA synthetase** (Aminolevulinic acid synthetase). This enzyme is the rate-limiting step in heme synthesis. Induction of ALA synthetase leads to the overproduction and accumulation of porphyrins and their precursors (like porphobilinogen), which can precipitate a life-threatening **acute neurovisceral crisis** characterized by abdominal pain, psychiatric symptoms, and paralysis. **2. Analysis of Incorrect Options:** * **Bronchial Asthma:** While Thiopentone causes histamine release and can theoretically cause bronchospasm, it is a **relative contraindication**, not an absolute one. In modern practice, Propofol or Ketamine are preferred for asthmatics, but Thiopentone is not strictly prohibited if the airway is managed carefully. * **Both/None:** Since AIP is a definitive absolute contraindication and Asthma is only relative, "Both" is incorrect in the context of standard NEET-PG questioning where the most "absolute" contraindication is sought. **3. High-Yield Clinical Pearls for NEET-PG:** * **Absolute Contraindications of Thiopentone:** Porphyria, Status Asthmaticus (severe acute asthma), and known hypersensitivity. * **Cardiovascular Effects:** Thiopentone causes peripheral vasodilation and myocardial depression; it should be used with extreme caution in **hypovolemic shock**. * **pH Fact:** Thiopentone is highly alkaline (pH 10.5). Accidental **intra-arterial injection** causes severe pain and gangrene due to crystal formation (Treatment: Papaverine/Lidocaine and Heparin). * **Recovery:** Recovery from a single dose occurs due to **redistribution** from the brain to skeletal muscle, not metabolism.

Question 238: What is the preferred anesthetic agent in a patient with renal failure?

A. Doxacurium
B. Atracurium (Correct Answer)
C. Pancuronium
D. Gallamine

Explanation: **Explanation:** The preferred anesthetic agent in patients with renal failure is **Atracurium** (or its isomer, Cisatracurium). [1] **1. Why Atracurium is Correct:** In renal failure, the primary concern is the accumulation of drugs that depend on renal excretion, leading to prolonged neuromuscular blockade. [2] Atracurium is unique because it undergoes **Hofmann Elimination**—a spontaneous, non-enzymatic degradation at physiological pH and temperature—and ester hydrolysis. [1], [2] Since its metabolism is independent of renal or hepatic function, its duration of action remains predictable even in end-stage renal disease (ESRD). [1] **2. Why the Other Options are Incorrect:** * **Pancuronium:** This is a long-acting muscle relaxant primarily excreted by the kidneys (approx. 80%). In renal failure, its half-life is significantly prolonged, risking residual paralysis. [3] * **Gallamine:** This drug is almost entirely (95-100%) excreted unchanged in the urine. It is strictly contraindicated in renal failure as it can cause recurarization. * **Doxacurium:** Similar to other long-acting benzylisoquinolines, it relies significantly on renal elimination, making it less ideal than Atracurium for patients with impaired kidney function. **3. Clinical Pearls for NEET-PG:** * **Cisatracurium** is often preferred over Atracurium because it produces less **Laudanosine** (a metabolite that can cause seizures) and does not cause histamine release. [1] * **Drug of choice for Induction:** Propofol or Etomidate are generally safe. [4] * **Avoid Succinylcholine** if the patient’s potassium level is >5.5 mEq/L, as it can cause a life-threatening hyperkalemic response. [4] * **Sugammadex** is generally avoided in severe renal impairment (CrCl <30 ml/min) due to slow clearance of the sugammadex-rocuronium complex.

Question 239: Who was the first dentist to use ether as a general anesthetic?

A. Martin
B. Morton (Correct Answer)
C. Morrison
D. Murray

Explanation: **Explanation:** **Correct Answer: B. Morton** **William T.G. Morton**, an American dentist, is credited with the first successful public demonstration of ether as a general anesthetic. On **October 16, 1846** (now celebrated as World Anesthesia Day), he administered diethyl ether to a patient named Gilbert Abbott for the removal of a neck tumor at Massachusetts General Hospital. This event took place in the famous "Ether Dome." While Horace Wells had previously attempted to use Nitrous Oxide for dental extractions, Morton was the first to successfully demonstrate ether's efficacy for surgical anesthesia. **Incorrect Options:** * **A. Martin:** There is no significant historical figure named Martin associated with the discovery of general anesthesia in the mid-19th century. * **C. Morrison:** This is a distractor; James Morrison was a pioneer in dentistry (inventing the dental foot engine), but not anesthesia. * **D. Murray:** Joseph Murray was a famous surgeon who performed the first successful human kidney transplant (1954), but he was not involved in the discovery of ether. **High-Yield Clinical Pearls for NEET-PG:** * **Father of Anesthesia:** William T.G. Morton. * **First use of Ether (Private):** Crawford W. Long used ether in 1842 for a cyst removal but did not publish his results until later. * **First use of Nitrous Oxide:** Horace Wells (1844), though his public demonstration was considered a failure. * **First use of Chloroform:** James Young Simpson (1847) for obstetric anesthesia. * **Term "Anesthesia":** Coined by Oliver Wendell Holmes Sr. after Morton’s demonstration.

Question 240: Which of the following anesthetic agents causes hypertension on injection?

A. Ketamine (Correct Answer)
B. Propofol
C. Halothane
D. Thiopentone

Explanation: **Explanation:** **Ketamine** is the correct answer because it is a unique induction agent that acts as a **sympathomimetic**. Unlike most other anesthetics, it stimulates the sympathetic nervous system, leading to an increase in heart rate, cardiac output, and arterial blood pressure (hypertension). This occurs due to the inhibition of neuronal catecholamine reuptake and direct central stimulation. **Why the other options are incorrect:** * **Propofol:** Known for causing significant **hypotension** due to profound peripheral vasodilation and mild myocardial depression. * **Thiopentone:** A barbiturate that causes **hypotension** primarily through peripheral venodilation (pooling of blood) and direct myocardial depression. * **Halothane:** An inhalational agent that causes **hypotension** by decreasing cardiac output and sensitizing the myocardium to catecholamines (which can lead to arrhythmias, but not hypertension). **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Ketamine is the induction agent of choice in **hypovolemic shock** and **bronchial asthma** (due to its bronchodilatory properties). * **Contraindications:** Avoid Ketamine in patients with hypertension, ischemic heart disease (increases myocardial oxygen demand), and raised intracranial or intraocular pressure. * **Dissociative Anesthesia:** Ketamine produces a state where the patient appears awake (eyes open) but is unconscious and feels no pain, characterized by electroencephalographic dissociation between the thalamocortical and limbic systems. * **Emergence Delirium:** A common side effect of Ketamine, which can be mitigated by co-administering benzodiazepines like Midazolam.

Practice by Chapter

History of Anesthesia

Practice Questions

Preoperative Evaluation

Practice Questions

Pharmacology of Inhalational Anesthetics

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Pharmacology of Intravenous Anesthetics

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Neuromuscular Blocking Agents

Practice Questions

Airway Management

Practice Questions

Endotracheal Intubation

Practice Questions

Difficult Airway Algorithms

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Intraoperative Monitoring

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Depth of Anesthesia Monitoring

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Emergence from Anesthesia

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Postoperative Care

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