General Anesthesia — MCQs

General Anesthesia Indian Medical PG Practice Questions and MCQs

Question 21: Which of the following general anaesthetics causes characteristic 'dissociative anaesthesia'?

A. Thiopentone
B. Althesin
C. Ketamine (Correct Answer)
D. Barbiturate

Explanation: **Explanation:** **Ketamine** is the correct answer because it is the classic agent that produces **dissociative anesthesia**. This unique state is characterized by a functional and electrophysiological dissociation between the thalamoneocortical and limbic systems. Clinically, the patient appears to be in a trance-like state—eyes may remain open with a slow nystagmic gaze, but they are unconscious and insensitive to pain (profound analgesia) while maintaining stable spontaneous respiration and airway reflexes. **Analysis of Options:** * **Thiopentone (A) & Barbiturates (D):** These are GABA-A receptor agonists that cause generalized CNS depression. They produce a smooth induction but lack analgesic properties (in fact, they can be anti-analgesic at low doses) and do not cause dissociation. * **Althesin (B):** This was a steroid anesthetic (mixture of alphaxalone and alphadolone) withdrawn from clinical use due to high rates of anaphylaxis. It acted similarly to other IV hypnotics and did not produce a dissociative state. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Ketamine is a non-competitive antagonist at the **NMDA receptor**. * **Hemodynamics:** Unlike most induction agents, Ketamine is **sympathomimetic**; it increases heart rate, blood pressure, and cardiac output (ideal for hypovolemic shock). * **Airway:** It is a potent **bronchodilator** (drug of choice for asthmatics) but causes significant **hypersalivation** (often pre-treated with glycopyrrolate). * **Side Effects:** Associated with **emergence delirium** and hallucinations (minimized by benzodiazepines) and increases intracranial/intraocular pressure.

Question 22: Which of the following statements regarding ether as an anesthetic agent is false?

A. It is highly inflammable.
B. It can cause hyperglycemia.
C. It provides good muscle relaxation.
D. It allows for rapid recovery. (Correct Answer)

Explanation: **Explanation:** Diethyl ether is a historical anesthetic agent, and understanding its pharmacological profile is high-yield for NEET-PG. **Why Option D is the Correct (False) Statement:** Ether has a **high Blood-Gas Partition Coefficient (approx. 12.1)**. In anesthesia, the solubility of a gas in blood determines its speed of onset and recovery. Because ether is highly soluble in blood, it acts as a large reservoir, taking a long time to saturate the blood (slow induction) and an equally long time to be eliminated (prolonged/slow recovery). Modern agents like Sevoflurane have low solubility, allowing for the "rapid recovery" that ether lacks. **Analysis of Other Options:** * **Option A (Inflammable):** Ether is highly flammable and explosive, especially when mixed with oxygen or nitrous oxide. This is the primary reason it is no longer used in modern operating theaters where cautery is common. * **Option B (Hyperglycemia):** Ether stimulates the sympathetic nervous system, leading to catecholamine release. This triggers glycogenolysis in the liver, resulting in an increase in blood glucose levels. * **Option C (Muscle Relaxation):** Ether has a direct curare-like effect on the neuromuscular junction, providing excellent skeletal muscle relaxation, which historically made it favorable for abdominal surgeries. **High-Yield Clinical Pearls for NEET-PG:** * **Vomiting:** Ether is highly emetogenic; postoperative nausea and vomiting (PONV) are very common. * **Respiration:** It is a potent bronchodilator and irritates the airways, leading to increased secretions (often requiring atropine premedication). * **Safety:** It is considered 100% safe for the heart as it does not sensitize the myocardium to catecholamines (unlike halothane). * **Induction:** It is the classic agent used in the **Guedel’s stages of anesthesia**.

Question 23: Which induction agent possesses anti-emetic properties?

A. Thiopentone
B. Methohexitone
C. Propanidid
D. Propofol (Correct Answer)

Explanation: **Explanation:** **Propofol** is the induction agent of choice for patients at high risk of Postoperative Nausea and Vomiting (PONV). Its **anti-emetic properties** are attributed to its ability to decrease dopamine levels in the area postrema and its antagonistic effect on 5-HT3 receptors. Even at sub-hypnotic doses (10–20 mg), it effectively suppresses nausea, making it a cornerstone of Total Intravenous Anesthesia (TIVA). **Analysis of Incorrect Options:** * **Thiopentone (A):** A barbiturate that is considered "emetic-neutral." It neither significantly causes nor prevents nausea and vomiting. * **Methohexitone (B):** Another barbiturate, often used in Electroconvulsive Therapy (ECT). Like thiopentone, it lacks specific anti-emetic properties and can occasionally trigger excitatory phenomena. * **Propanidid (C):** An older eugenol derivative (now largely obsolete). It was notorious for a high incidence of excitatory movements and did not possess anti-emetic activity. **High-Yield Clinical Pearls for NEET-PG:** * **Propofol** is also the drug of choice for **day-care surgery** due to its rapid recovery profile ("clear-headed" recovery). * **Pain on injection** is a common side effect of Propofol; this is minimized by using larger veins or pre-treatment with Lidocaine. * **Etomidate** is the induction agent of choice for patients with **cardiovascular instability**, but it is associated with a *high* incidence of PONV and adrenocortical suppression. * **Ketamine** is known to *increase* the risk of PONV and causes emergence delirium.

Question 24: Which of the following acts as a non-depolarizing neuromuscular blocker?

A. Succinylcholine
B. Rocuronium (Correct Answer)
C. Atracurium
D. Pancuronium

Explanation: **Explanation:** Neuromuscular blocking agents (NMBAs) are classified into two main categories based on their mechanism of action at the nicotinic acetylcholine receptor (nAChR) of the motor endplate: **Depolarizing** and **Non-depolarizing**. **Why Rocuronium is Correct:** **Rocuronium** is a non-depolarizing NMBA belonging to the aminosteroid group. It acts as a competitive antagonist; it binds to the nAChR without activating it, thereby preventing acetylcholine from binding and causing muscle contraction. It is highly favored in clinical practice (and frequently tested) because it has the fastest onset of action among non-depolarizing agents, making it a suitable alternative to Succinylcholine for Rapid Sequence Induction (RSI). **Analysis of Other Options:** * **A. Succinylcholine:** This is the only **depolarizing** NMBA used clinically. It acts as an agonist, causing persistent depolarization (often seen as fasciculations) followed by flaccid paralysis. * **C & D. Atracurium and Pancuronium:** These are also non-depolarizing NMBAs. However, in the context of single-choice questions where multiple options seem correct, the question often aims for the "most representative" or "clinically preferred" agent. *Note: If this were a multiple-choice question (MSQ), B, C, and D would all be correct. In a single-choice format, Rocuronium is often the intended answer due to its unique pharmacological profile (fast onset).* **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice for RSI:** Succinylcholine (fastest). If contraindicated (e.g., hyperkalemia, burns), **Rocuronium** is the alternative. * **Reversal Agent:** Sugammadex is a specific reversal agent for Rocuronium and Vecuronium. * **Hoffman Elimination:** Atracurium and Cisatracurium undergo spontaneous degradation (Hoffman elimination), making them the drugs of choice in **renal or hepatic failure**. * **Side Effects:** Succinylcholine is associated with malignant hyperthermia and post-operative myalgia.

Question 25: Which of the following anesthetic agents possesses anti-pruritic properties?

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

Explanation: **Explanation:** **Propofol (Option B)** is the correct answer because it possesses unique **anti-pruritic** properties. While the exact mechanism is not fully elucidated, it is believed that sub-hypnotic doses of propofol (approx. 10 mg) can effectively relieve itching, particularly **opioid-induced pruritus** and pruritus associated with cholestatic liver disease. This effect is likely mediated through the suppression of the spinal cord's dorsal horn activity and interaction with the GABA-A receptors. **Analysis of Incorrect Options:** * **Thiopentone (Option A):** A barbiturate primarily known for its rapid onset and potent anticonvulsant properties. It does not possess anti-pruritic effects; in fact, like other barbiturates, it can occasionally trigger histamine release, which might worsen itching. * **Etomidate (Option C):** An imidazole derivative used for induction in hemodynamically unstable patients. Its side effect profile is dominated by myoclonus and adrenocortical suppression, with no known effect on pruritus. * **Ketamine (Option D):** A dissociative anesthetic that acts as an NMDA receptor antagonist. While it provides excellent analgesia and bronchodilation, it is not used for treating pruritus. **High-Yield Clinical Pearls for NEET-PG:** * **Propofol** is also a potent **anti-emetic** (due to its action on the chemoreceptor trigger zone and vagal nuclei). * **Drug of Choice:** Propofol is the agent of choice for Day Care Surgery due to its rapid recovery ("clear-headed" emergence). * **Contraindication:** Avoid propofol in patients with egg or soy allergies (due to the lipid emulsion vehicle). * **Ketamine** is the only induction agent that is a potent bronchodilator and increases sympathetic outflow (BP and HR).

Question 26: What is the final common metabolism of atracurium, mivacurium, and succinylcholine?

A. Conjugation
B. Reduction
C. Hydrolysis (Correct Answer)
D. Acetylation

Explanation: **Explanation:** The correct answer is **Hydrolysis**. This is because all three drugs—atracurium, mivacurium, and succinylcholine—contain **ester bonds** in their chemical structure, which are cleaved by various esterases through the addition of water (hydrolysis). * **Succinylcholine:** A depolarizing muscle relaxant rapidly hydrolyzed by **pseudocholinesterase** (butyrylcholinesterase) in the plasma. * **Mivacurium:** A short-acting non-depolarizing relaxant also primarily metabolized by **pseudocholinesterase** via hydrolysis. * **Atracurium:** Undergoes two methods of elimination: **Hofmann elimination** (spontaneous non-enzymatic degradation) and **ester hydrolysis** (catalyzed by non-specific plasma esterases). **Why other options are incorrect:** * **Conjugation & Acetylation:** These are Phase II metabolic reactions (e.g., glucuronidation or N-acetyltransferase) typically occurring in the liver for drugs like morphine or isoniazid. They do not play a primary role in the breakdown of these neuromuscular blockers. * **Reduction:** This is a Phase I reaction involving the gain of electrons, which is not the mechanism for ester-linked anesthetic agents. **High-Yield Clinical Pearls for NEET-PG:** 1. **Pseudocholinesterase Deficiency:** Patients with atypical pseudocholinesterase (prolonged dibucaine number) will experience prolonged paralysis after receiving succinylcholine or mivacurium. 2. **Organ Independent Elimination:** Atracurium and Cisatracurium are the drugs of choice in **liver or renal failure** because their metabolism (Hofmann elimination/ester hydrolysis) does not depend on these organs. 3. **Laudanosine:** A metabolite of atracurium hydrolysis which, in high concentrations, can cross the blood-brain barrier and potentially cause seizures.

Question 27: Which skeletal muscle relaxant is the drug of choice in patients with liver failure?

A. Gallamine
B. Thiopentone
C. Atracurium (Correct Answer)
D. Lignocaine

Explanation: **Explanation:** The correct answer is **Atracurium**. **Why Atracurium is the Drug of Choice:** In patients with liver or renal failure, the metabolism of most neuromuscular blocking agents (NMBAs) is impaired, leading to prolonged paralysis. Atracurium (and its isomer Cisatracurium) is unique because it undergoes **Hofmann Elimination**. This is a spontaneous, non-enzymatic degradation that occurs at physiological pH and temperature. Additionally, it is metabolized by **nonspecific ester hydrolysis**. Since neither process depends on hepatic or renal function, the duration of action remains predictable even in end-stage liver disease. **Analysis of Incorrect Options:** * **Gallamine (A):** This is a long-acting relaxant that is excreted almost entirely unchanged by the kidneys. It is contraindicated in renal failure and rarely used today due to significant tachycardia. * **Thiopentone (B):** This is an intravenous induction agent (barbiturate), not a skeletal muscle relaxant. It is metabolized by the liver, so its half-life may actually be prolonged in liver failure. * **Lignocaine (D):** This is a local anesthetic and anti-arrhythmic agent. It is not a skeletal muscle relaxant. **High-Yield Clinical Pearls for NEET-PG:** 1. **Cisatracurium:** Often preferred over Atracurium in clinical practice because it is more potent, does not cause histamine release, and also undergoes Hofmann elimination. 2. **Laudanosine:** A metabolite of Atracurium/Cisatracurium that can cross the blood-brain barrier; in very high concentrations, it may act as a CNS stimulant (pro-convulsant). 3. **Vecuronium/Rocuronium:** These are primarily metabolized and excreted by the liver/bile; their effects are significantly prolonged in liver failure. 4. **Succinylcholine:** Its metabolism may be prolonged in liver disease due to decreased production of **pseudocholinesterase** (plasma cholinesterase) by the liver.

Question 28: Which drug is known to cause dissociative anesthesia?

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

Explanation: **Explanation** **Ketamine** is the classic agent used to induce **dissociative anesthesia**. This unique state is characterized by profound analgesia, amnesia, and a "trance-like" appearance where the patient’s eyes remain open with a slow nystagmic gaze, but they are disconnected from their surroundings. **Mechanism:** Ketamine acts as a non-competitive antagonist at the **NMDA (N-methyl-D-aspartate) receptors**. It causes functional dissociation between the thalamocortical and limbic systems—essentially "quieting" the cortex while the limbic system remains active. **Analysis of Incorrect Options:** * **Fentanyl:** A potent opioid analgesic. While it provides intense pain relief and can be used in "neuroleptanalgesia" (when combined with droperidol), it does not produce the specific dissociative state. * **Propofol:** A GABA-A agonist used for induction and maintenance. It causes generalized CNS depression (hypnosis) rather than dissociation. * **Nitrous Oxide:** An inhalational anesthetic gas. While it has analgesic properties, it is primarily used as an adjuvant and does not produce a dissociative state. **High-Yield Clinical Pearls for NEET-PG:** * **Hemodynamics:** Unlike most induction agents, Ketamine is **sympathomimetic** (increases HR, BP, and CO), making it the drug of choice for **hypovolemic shock**. * **Airway:** It preserves laryngeal reflexes and is a potent **bronchodilator** (ideal for asthmatics). * **Side Effects:** It increases Intraocular Pressure (IOP) and Intracranial Pressure (ICP). It is notorious for causing **emergence delirium/hallucinations**, which can be pre-treated with benzodiazepines. * **Secretions:** It causes hypersalivation (often requiring an anticholinergic like Glycopyrrolate).

Question 29: All are true about classical Rapid Sequence Induction EXCEPT?

A. Preoxygenation is mandatory.
B. Cricoid pressure is applied.
C. Positive pressure ventilation by bag and mask with small tidal volume. (Correct Answer)
D. The neuromuscular blocker used is succinylcholine.

Explanation: **Explanation:** Rapid Sequence Induction (RSI) is a specialized technique designed to minimize the time between loss of consciousness and tracheal intubation, primarily to prevent **aspiration of gastric contents** in "full stomach" patients. **Why Option C is the correct answer (The Exception):** In **classical** RSI, positive pressure ventilation (PPV) via bag and mask is strictly avoided after the patient loses consciousness. The rationale is that PPV can cause gastric insufflation, increasing intragastric pressure and significantly raising the risk of regurgitation and subsequent pulmonary aspiration. The patient is allowed to remain apneic until the endotracheal tube is secured. **Analysis of Incorrect Options:** * **A. Preoxygenation:** Mandatory to create an "oxygen reservoir" in the functional residual capacity (FRC). This allows for a period of safe apnea during intubation without desaturation, as PPV is avoided. * **B. Cricoid Pressure (Sellick’s Maneuver):** A hallmark of classical RSI. Downward pressure on the cricoid cartilage occludes the esophagus against the cervical vertebrae, preventing passive regurgitation. * **D. Succinylcholine:** The traditional drug of choice due to its rapid onset (30–60 seconds) and short duration, allowing for the fastest possible securing of the airway. **Clinical Pearls for NEET-PG:** * **Modified RSI:** Unlike classical RSI, modified RSI allows for gentle mask ventilation (pressures <15-20 cm H₂O) if the patient is at high risk of rapid desaturation (e.g., pediatrics, pregnancy, or obesity). * **Rocunorium:** At a dose of 1.2 mg/kg, it is the preferred non-depolarizing alternative to Succinylcholine for RSI when the latter is contraindicated (e.g., hyperkalemia, burns). * **Order of Drugs:** In RSI, the induction agent is followed immediately by the neuromuscular blocker without waiting to check if the patient can be ventilated.

Question 30: Which of the following is true about propofol?

A. Indicated in egg allergy
B. Can be used in porphyria (Correct Answer)
C. It is of barbiturate group
D. All of the above

Explanation: **Explanation:** **Propofol (2,6-diisopropylphenol)** is the most commonly used intravenous induction agent in modern anesthesia. 1. **Why Option B is Correct:** Propofol is considered **safe in patients with Porphyria**. Porphyrias are metabolic disorders of heme biosynthesis where certain drugs (like barbiturates and etomidate) can induce the enzyme ALA synthetase, triggering an acute attack. Propofol does not induce this enzyme and is therefore a preferred induction agent for these patients. 2. **Why Other Options are Incorrect:** * **Option A (Egg Allergy):** Propofol is formulated as an emulsion containing **soybean oil, glycerol, and egg lecithin** (derived from egg yolk). While most egg allergies are to egg white proteins (albumin), the official recommendation remains to exercise extreme caution or avoid propofol in patients with a documented severe egg allergy. * **Option C (Barbiturate Group):** Propofol is an **alkylphenol** derivative, not a barbiturate. Thiopental sodium is the classic example of the barbiturate group. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Potentiates **GABA-A** receptors (increases chloride conductance). * **Drug of Choice:** For Day-care (Ambulatory) surgery due to rapid recovery and "clear-headedness." * **Antiemetic Property:** It possesses intrinsic antiemetic properties (unlike most other anesthetics). * **Pain on Injection:** A common side effect, often mitigated by using larger veins or pre-treatment with lidocaine. * **Propofol Infusion Syndrome (PRIS):** A rare but fatal complication of prolonged high-dose infusion characterized by metabolic acidosis, rhabdomyolysis, and cardiac failure. * **Contraindication:** It should be avoided in patients with **Pancreatitis** due to its lipid-based formulation which can cause hypertriglyceridemia.

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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