General Anesthesia — MCQs

General Anesthesia Indian Medical PG Practice Questions and MCQs

Question 451: All are true about cisatracurium except?

A. It is the pure cis isomer of atracurium
B. It is more potent than atracurium
C. It also causes histamine release like atracurium (Correct Answer)
D. Its metabolism is similar to atracurium

Explanation: **Explanation:** Cisatracurium is a benzylisoquinolinium neuromuscular blocking agent (NMBA) and is one of the ten isomers of atracurium. **Why Option C is the correct answer (The False Statement):** Unlike its parent compound atracurium, **cisatracurium does not cause histamine release**, even at doses up to 8 times its $ED_{95}$. Atracurium is notorious for triggering mast cell degranulation, leading to skin flushing, hypotension, and bronchospasm. The absence of histamine release makes cisatracurium hemodynamically stable and a preferred choice in patients with reactive airway disease or cardiovascular instability. **Analysis of Incorrect Options:** * **Option A:** Cisatracurium is indeed the isolated **1R-cis 1’R-cis isomer** of atracurium. By isolating this specific isomer, the side effects associated with the other isomers are eliminated. * **Option B:** It is approximately **3 to 4 times more potent** than atracurium. The $ED_{95}$ of cisatracurium is ~0.05 mg/kg, compared to ~0.2 mg/kg for atracurium. * **Option D:** Like atracurium, it undergoes **Hofmann elimination** (spontaneous degradation at physiological pH and temperature). This makes its clearance independent of renal or hepatic function. **High-Yield Clinical Pearls for NEET-PG:** 1. **Organ-Independent Elimination:** Cisatracurium is the "drug of choice" for muscle relaxation in patients with **renal or hepatic failure**. 2. **Laudanosine Toxicity:** Hofmann elimination produces a metabolite called laudanosine (a CNS stimulant). However, because cisatracurium is more potent, less drug is used, resulting in significantly **lower levels of laudanosine** compared to atracurium, reducing the risk of seizures. 3. **Temperature/pH Sensitivity:** Since it relies on Hofmann elimination, its duration of action is prolonged in patients with **hypothermia or acidosis**.

Question 452: All of the following are inhalational anesthetic agents except?

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

Explanation: **Explanation:** The correct answer is **Ketamine** because it is an **intravenous (IV) anesthetic agent**, not an inhalational one. Inhalational anesthetics are gases or volatile liquids administered via a vaporizer and breathing circuit to induce or maintain anesthesia. **Why Ketamine is the correct choice:** Ketamine is a phencyclidine derivative that acts primarily as an **NMDA receptor antagonist**. It is administered intravenously or intramuscularly to produce **"dissociative anesthesia,"** characterized by profound analgesia, amnesia, and a cataleptic state where the patient appears awake but is unresponsive to pain. **Why the other options are incorrect:** * **Halothane:** A volatile liquid and a halogenated hydrocarbon. It was historically the gold standard for pediatric mask induction due to its non-pungent odor, though its use has declined due to the risk of "Halothane Hepatitis." * **Enflurane:** A halogenated ether used as an inhalational agent. It is known for its potential to lower the seizure threshold (pro-convulsant), especially in the presence of hypocapnia. * **Isoflurane:** A structural isomer of enflurane and one of the most commonly used volatile anesthetics worldwide. It is favored for its stability and minimal organ toxicity. **High-Yield Clinical Pearls for NEET-PG:** * **Ketamine** is the induction agent of choice in **hypovolemic shock** (due to sympathetic stimulation) and **bronchial asthma** (due to bronchodilation). * **Contraindication:** Ketamine should be avoided in patients with increased intracranial pressure (ICP) or intraocular pressure. * **Side Effect:** It is notorious for causing **emergence delirium/hallucinations**, which can be pre-treated with benzodiazepines (e.g., Midazolam). * **Inhalational Agent of Choice:** **Sevoflurane** is currently the agent of choice for smooth inhalational induction in children.

Question 453: Which of the following is NOT an intravenous anesthetic agent?

A. Ketamine
B. Thiopental
C. Etomidate
D. Cyclopropane (Correct Answer)

Explanation: **Explanation:** The correct answer is **Cyclopropane** because it is an **inhalational (volatile) anesthetic gas**, not an intravenous agent. Historically used for its rapid induction, it is now largely obsolete in modern practice due to its high flammability and risk of explosions in the operating room. **Analysis of Options:** * **Ketamine (Option A):** A phencyclidine derivative used intravenously. It is unique for producing "dissociative anesthesia" and providing potent analgesia. * **Thiopental (Option B):** An ultra-short-acting barbiturate. It was the gold standard for IV induction for decades before being largely replaced by Propofol. It acts via GABA-A receptors. * **Etomidate (Option C):** An intravenous carboxylated imidazole derivative. It is the agent of choice for hemodynamically unstable patients (e.g., trauma or heart failure) due to its minimal effect on heart rate and blood pressure. **NEET-PG High-Yield Pearls:** 1. **Cyclopropane** is known for the "Cyclopropane Shock," a sudden drop in blood pressure after discontinuation of the gas. It also sensitizes the myocardium to catecholamines, leading to arrhythmias. 2. **Propofol** (not listed) is currently the most common IV induction agent; it is known for its anti-emetic properties. 3. **Etomidate** side effect: It can cause transient **adrenocortical suppression** by inhibiting the enzyme 11-beta-hydroxylase. 4. **Ketamine** is the only induction agent that stimulates the sympathetic nervous system, making it ideal for asthmatics (bronchodilation) but contraindicated in head injuries (increases ICP).

Question 454: Which of the following statements regarding propofol is NOT TRUE?

A. It is used in day care anesthesia.
B. It is contraindicated in porphyria. (Correct Answer)
C. Commercial preparations contain egg extract.
D. It does not cause airway irritation.

Explanation: **Explanation:** Propofol is the most commonly used intravenous induction agent in modern anesthesia. The statement that it is contraindicated in porphyria is **NOT TRUE**, making it the correct answer. **1. Why Option B is the correct answer (The Concept):** Propofol is considered **safe** in patients with Porphyria. Unlike barbiturates (like Thiopentone) and Etomidate, which are potent enzyme inducers and can trigger an acute porphyric crisis by increasing heme synthesis, Propofol does not induce the enzyme ALA synthetase. Therefore, it is often the induction agent of choice for porphyric patients. **2. Analysis of Incorrect Options:** * **Option A (Day care anesthesia):** This is **True**. Propofol has a rapid onset and a very short context-sensitive half-life, leading to "clear-headed" recovery with minimal psychomotor impairment, making it the gold standard for ambulatory (day care) surgery. * **Option C (Egg extract):** This is **True**. The commercial formulation is an emulsion containing 10% soybean oil, 2.25% glycerol, and **1.2% purified egg phosphatide** (lecithin). Caution is advised in patients with severe egg allergies. * **Option D (Airway irritation):** This is **True**. Unlike agents like Desflurane or Thiopentone (which can cause laryngospasm), Propofol is a potent **airway reflex suppressant**. This property makes it ideal for the insertion of a Laryngeal Mask Airway (LMA). **Clinical Pearls for NEET-PG:** * **Drug of Choice:** For Day care surgery, TIVA (Total Intravenous Anesthesia), and induction in asthmatics. * **Anti-emetic:** Propofol has unique anti-emetic properties at sub-hypnotic doses (10-20 mg). * **Pain on Injection:** A common side effect; can be mitigated by using larger veins or pre-treatment with Lidocaine. * **PRIS (Propofol Related Infusion Syndrome):** A rare but fatal complication of long-term high-dose infusion characterized by metabolic acidosis, rhabdomyolysis, and cardiac failure.

Question 455: Which of the following statements regarding depolarizing muscle relaxants is FALSE?

A. Cause muscle fasciculation
B. No fade
C. Reversed by neostigmine (Correct Answer)
D. No post tetanic facilitation

Explanation: ### Explanation Depolarizing muscle relaxants (DMRs), primarily **Succinylcholine (Suxamethonium)**, act as nicotinic acetylcholine receptor (nAChR) agonists. They mimic acetylcholine, causing prolonged depolarization of the motor endplate, which leads to a **Phase I block**. **Why Option C is the Correct (False) Statement:** Neostigmine is an acetylcholinesterase inhibitor. By preventing the breakdown of acetylcholine (ACh), it increases the concentration of ACh at the neuromuscular junction. In a Phase I block, more ACh further depolarizes the membrane, which **potentiates (worsens)** the neuromuscular blockade rather than reversing it. Therefore, neostigmine does not reverse a depolarizing block; it antagonizes only non-depolarizing blocks. **Analysis of Other Options:** * **A. Cause muscle fasciculation:** Succinylcholine causes initial disorganized muscle contractions (fasciculations) before paralysis occurs because it initially stimulates the receptors. * **B. No fade:** In a Phase I block, the response to Train-of-Four (TOF) stimulation is characterized by a constant but diminished height in all four twitches. There is no progressive decline (fade) in strength. * **D. No post-tetanic facilitation:** Unlike non-depolarizing blocks, DMRs do not show an exaggerated response to a single twitch after a tetanic stimulus. **High-Yield Clinical Pearls for NEET-PG:** * **Phase II Block:** Occurs with high doses or prolonged infusion of Succinylcholine. It mimics a non-depolarizing block (shows fade and post-tetanic facilitation) and *can* be reversed by neostigmine. * **Metabolism:** Succinylcholine is metabolized by **Pseudocholinesterase** (Plasma cholinesterase). * **Key Side Effects:** Hyperkalemia (avoid in burns/trauma), Malignant Hyperthermia trigger, and post-operative myalgia. * **Dibucaine Number:** Used to test for atypical pseudocholinesterase; a low number (e.g., 20) indicates a high risk of prolonged apnea.

Question 456: Who coined the term 'balanced anesthesia'?

A. Simpson
B. Fischer
C. Lundy (Correct Answer)
D. Moan

Explanation: **Explanation:** The correct answer is **Lundy (C)**. In 1926, **John Silas Lundy** introduced the concept of **'Balanced Anesthesia.'** The underlying medical principle is that no single anesthetic agent can safely provide all the necessary components of anesthesia (unconsciousness, analgesia, and muscle relaxation) without causing significant side effects. By combining different drugs (such as thiopentone for induction, nitrous oxide for maintenance, and curare for relaxation), clinicians can achieve a state of surgical anesthesia using smaller, safer doses of each individual agent, thereby minimizing toxicity and improving patient recovery. **Analysis of Incorrect Options:** * **A. Simpson:** Sir James Young Simpson is famous for discovering the anesthetic properties of **Chloroform** (1847) and introducing its use in obstetrics. * **B. Fischer:** Emil Fischer synthesized **Barbital** (the first barbiturate) in 1902, but he did not coin the term balanced anesthesia. * **D. Moan:** This is a distractor and is not associated with any major milestone in anesthetic history. **High-Yield Clinical Pearls for NEET-PG:** * **William T.G. Morton:** Performed the first successful public demonstration of **Ether** anesthesia (1846) at "Ether Dome." * **Oliver Wendell Holmes:** Coined the actual term **"Anesthesia."** * **August Bier:** Performed the first **Spinal Anesthesia** (1898) and described the "Bier Block" (Intravenous Regional Anesthesia). * **Modern Balanced Anesthesia:** Now typically includes a combination of an inhaled agent, an intravenous induction agent, an opioid for analgesia, and a neuromuscular blocker.

Question 457: Ketamine is a:

A. Short general anesthetic agent (Correct Answer)
B. Local anesthetic agent
C. Antidepressive agent
D. Hypnotic agent

Explanation: **Explanation:** **Ketamine** is a phencyclidine derivative primarily classified as a **short-acting general anesthetic agent**. It is unique because it produces **"Dissociative Anesthesia,"** a state characterized by profound analgesia, amnesia, and catalepsy, where the patient appears awake (eyes open) but is detached from the environment. 1. **Why Option A is Correct:** Ketamine acts as a non-competitive antagonist at the **NMDA (N-methyl-D-aspartate) receptors**. When administered intravenously, it has a rapid onset (30–60 seconds) and a short duration of action (10–15 minutes), making it an ideal induction agent for short surgical procedures. 2. **Why Options B, C, and D are Incorrect:** * **Local Anesthetic:** These agents (e.g., Lidocaine) block sodium channels in peripheral nerves; Ketamine acts centrally. * **Antidepressive Agent:** While low-dose Ketamine is recently FDA-approved for treatment-resistant depression (Esketamine), its primary pharmacological classification in anesthesia remains a general anesthetic. * **Hypnotic Agent:** Pure hypnotics (like Propofol or Etomidate) cause sleep but lack significant analgesic properties. Ketamine provides potent analgesia along with unconsciousness. **High-Yield Clinical Pearls for NEET-PG:** * **Hemodynamics:** It is the induction agent of choice for **hypovolemic shock** because it stimulates the sympathetic nervous system (increases HR, BP, and CO). * **Respiratory:** It is a potent **bronchodilator**, making it the drug of choice for patients with **Asthma/COPD**. It also preserves airway reflexes and respiratory drive. * **Side Effects:** Associated with **Emergence Delirium** (vivid dreams/hallucinations), which can be prevented by co-administering Benzodiazepines (Midazolam). * **Contraindications:** Traditionally avoided in patients with increased Intracranial Pressure (ICP) and Intraocular Pressure (IOP).

Question 458: Which of the following is a depolarizing muscle relaxant?

A. Scoline (Correct Answer)
B. Ketamine
C. Halothane
D. Atracurium

Explanation: ### Explanation **Correct Answer: A. Scoline** **Mechanism of Action:** Scoline (Succinylcholine or Suxamethonium) is the only **depolarizing neuromuscular blocking agent** used clinically. It works by mimicking the action of acetylcholine (ACh) at the nicotinic receptors of the motor endplate. Unlike ACh, it is not metabolized by acetylcholinesterase, leading to persistent depolarization. This results in initial muscle twitching (**fasciculations**) followed by flaccid paralysis because the post-junctional membrane becomes unresponsive to further stimuli (Phase I block). **Analysis of Incorrect Options:** * **B. Ketamine:** This is an **intravenous induction agent** known as a dissociative anesthetic. It acts primarily as an NMDA receptor antagonist and has no muscle relaxant properties. * **C. Halothane:** This is a **volatile inhalation anesthetic**. While it may provide some degree of uterine relaxation and potentiate neuromuscular blockers, it is not a muscle relaxant itself. * **D. Atracurium:** This is a **non-depolarizing muscle relaxant** (NDMR). It acts as a competitive antagonist at the nicotinic receptors, preventing ACh from binding. It is notable for being metabolized via **Hofmann elimination**. **High-Yield Clinical Pearls for NEET-PG:** * **Onset/Duration:** Scoline has the fastest onset (30–60 seconds) and shortest duration (5–10 minutes), making it the drug of choice for **Rapid Sequence Induction (RSI)**. * **Metabolism:** It is metabolized by **Pseudocholinesterase** (Plasma cholinesterase). Deficiency in this enzyme leads to prolonged apnea. * **Side Effects:** Important complications include hyperkalemia (avoid in burn/trauma patients), muscle soreness, increased intraocular pressure, and it is a potent trigger for **Malignant Hyperthermia**.

Question 459: What is the index of potency of general anesthesia?

A. Minimum alveolar concentration (Correct Answer)
B. Diffusion coefficient
C. Dead space concentration
D. Alveolar blood concentration

Explanation: **Explanation:** The potency of an inhalational anesthetic agent is measured by its **Minimum Alveolar Concentration (MAC)**. **1. Why MAC is the Correct Answer:** MAC is defined as the concentration of a vapor in the alveoli (at 1 atmosphere) that prevents a motor response (movement) in 50% of subjects in response to a standard surgical stimulus (e.g., skin incision). It is inversely proportional to the potency of the drug: the lower the MAC, the more potent the anesthetic. This relationship is explained by the **Meyer-Overton Hypothesis**, which states that anesthetic potency correlates with lipid solubility. **2. Why Other Options are Incorrect:** * **Diffusion Coefficient:** This refers to the rate at which a gas moves across the alveolar-capillary membrane. While it affects the speed of induction, it does not define the potency (strength) of the drug. * **Dead Space Concentration:** Dead space refers to the volume of ventilated air that does not participate in gas exchange. It is a physiological parameter of the respiratory system, not a measure of anesthetic potency. * **Alveolar Blood Concentration:** This relates to the **Blood-Gas Partition Coefficient**, which determines the *solubility* and the *speed* of induction and recovery, rather than the potency. **High-Yield Clinical Pearls for NEET-PG:** * **Most Potent Agent:** Methoxyflurane (Lowest MAC ~0.16%). * **Least Potent Agent:** Nitrous Oxide (Highest MAC ~104%). * **MAC-Awake:** The concentration at which 50% of patients respond to verbal commands (usually ~0.33 MAC). * **MAC-BAR:** The concentration required to block autonomic responses to stimulus (~1.7 to 2.0 MAC). * **Factors increasing MAC (Decreasing potency):** Hyperthermia, chronic alcohol abuse, hypernatremia, and young age (highest at 6 months). * **Factors decreasing MAC (Increasing potency):** Hypothermia, pregnancy, acute alcohol intoxication, old age, and anemia.

Question 460: A patient with alcoholic liver failure requires general anesthesia. Which anesthetic agent is most appropriate?

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

Explanation: **Explanation:** The primary goal in managing anesthesia for a patient with liver failure is to maintain hepatic blood flow and minimize drug-induced hepatotoxicity. **Isoflurane** is the drug of choice because it undergoes minimal hepatic metabolism (only **0.2%**). Crucially, it preserves hepatic oxygen delivery better than other agents by maintaining the hepatic artery buffer response, ensuring stable blood flow to the liver. **Analysis of Options:** * **Halothane (Incorrect):** It is the most hepatotoxic volatile anesthetic. It undergoes significant metabolism (up to 20%) and can cause "Halothane Hepatitis" via immune-mediated mechanisms or reductive metabolites. It also significantly reduces hepatic blood flow. * **Methoxyflurane (Incorrect):** It is highly metabolized (up to 50-70%) and is primarily known for its **nephrotoxicity** due to the release of inorganic fluoride ions. It is contraindicated in patients with renal or hepatic impairment. * **Ether (Incorrect):** It causes significant sympathetic stimulation, leading to vasoconstriction and reduced splanchnic/hepatic blood flow, which can worsen liver ischemia in a failing organ. **High-Yield Clinical Pearls for NEET-PG:** * **Metabolism Rule:** Remember the mnemonic **MHISE** (highest to lowest metabolism): **M**ethoxyflurane (50-70%) > **H**alothane (20%) > **I**soflurane (0.2%) > **S**evoflurane (2-3%) > **D**esflurane (0.02%). * **Desflurane** is also safe for the liver (metabolism 0.02%), but Isoflurane remains the classic textbook answer for liver failure due to its superior preservation of hepatic blood flow. * **Muscle Relaxant of Choice:** In liver failure, **Atracurium** or **Cisatracurium** are preferred as they undergo Hoffman elimination and do not depend on the liver for clearance.

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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