General Anesthesia — MCQs

General Anesthesia Indian Medical PG Practice Questions and MCQs

Question 481: Postoperative muscle ache is commonly caused by which of the following agents?

A. d-Tubocurarine
B. Suxamethonium (Correct Answer)
C. Gallamine
D. Pancuronium

Explanation: **Explanation:** **Suxamethonium (Succinylcholine)** is the correct answer. It is a depolarizing neuromuscular blocker that works by mimicking acetylcholine at the nicotinic receptors of the motor endplate. This causes a sustained depolarization, clinically manifesting as visible muscle twitches known as **fasciculations**. These disorganized contractions lead to micro-trauma of the muscle fibers and the release of lactic acid and potassium, resulting in **postoperative myalgia (muscle ache)**. This pain is most common in the neck, shoulders, and abdominal muscles, typically occurring 24–48 hours post-surgery, and is more frequent in young adults undergoing ambulatory (day-care) surgery. **Why other options are incorrect:** * **d-Tubocurarine, Gallamine, and Pancuronium** are all **Non-depolarizing Neuromuscular Blockers (NDNMBs)**. They act as competitive antagonists at the nicotinic receptors and do not cause initial depolarization or fasciculations. Consequently, they are not associated with postoperative muscle aches. In fact, a small "pre-curarizing" dose of an NDNMB is often used clinically to prevent the fasciculations caused by Suxamethonium. **High-Yield Clinical Pearls for NEET-PG:** * **Prevention:** Post-suxamethonium myalgia can be reduced by pre-treatment with a small dose of a non-depolarizing agent (e.g., Vecuronium) or NSAIDs. * **Contraindications:** Suxamethonium should be avoided in patients with burns, massive trauma, or denervation injuries due to the risk of **hyperkalemia**. * **Genetic Link:** Prolonged apnea after Suxamethonium administration suggests a deficiency or abnormality in **Pseudocholinesterase (Butyrylcholinesterase)**. * **Malignant Hyperthermia:** Suxamethonium is a known trigger for Malignant Hyperthermia in genetically susceptible individuals.

Question 482: Which of the following statements about Total Intra-Venous Anaesthesia (TIVA) is true?

A. Causes more renal toxicity
B. Reduces cerebral metabolic rate (Correct Answer)
C. Risk of malignant hyperthermia is high
D. Inhibits hypoxic pulmonary vasoconstriction

Explanation: **Explanation:** **Total Intra-Venous Anaesthesia (TIVA)** refers to the induction and maintenance of anesthesia using only intravenous agents, most commonly a combination of **Propofol** and an opioid like Remifentanil. **Why Option B is Correct:** Intravenous anesthetics (specifically Propofol and Barbiturates) cause **dose-dependent suppression of neuronal activity**, which leads to a significant **reduction in the Cerebral Metabolic Rate of Oxygen (CMRO2)**. This reduction in metabolic demand results in a secondary decrease in Cerebral Blood Flow (CBF) and **Intracranial Pressure (ICP)**. This makes TIVA the preferred technique for neurosurgical procedures where brain relaxation is critical. **Why Other Options are Incorrect:** * **A. Renal Toxicity:** Unlike certain volatile anesthetics (e.g., Sevoflurane, which can produce Compound A), TIVA agents like Propofol do not produce nephrotoxic metabolites and are generally safe for the kidneys. * **C. Malignant Hyperthermia (MH):** TIVA is the **technique of choice** for patients susceptible to MH. MH is triggered exclusively by volatile inhalational agents and Succinylcholine; IV agents like Propofol are "safe" triggers. * **D. Hypoxic Pulmonary Vasoconstriction (HPV):** Inhalational agents inhibit HPV, potentially worsening shunting. In contrast, **TIVA agents do not inhibit HPV**, maintaining better oxygenation during one-lung ventilation. **High-Yield Clinical Pearls for NEET-PG:** * **Propofol** is the "Gold Standard" for TIVA due to its rapid onset and short context-sensitive half-life. * **Target Controlled Infusion (TCI)** is the specialized delivery system used to maintain steady-state plasma concentrations in TIVA. * **Advantages of TIVA:** Lower incidence of Post-Operative Nausea and Vomiting (PONV) and faster cognitive recovery compared to inhalational anesthesia.

Question 483: What is the role of egg lecithin in propofol formulation?

A. Acts as an emulsifying agent (Correct Answer)
B. Acts as a preservative
C. Acts as a carrier vehicle
D. Acts as an antibacterial agent

Explanation: **Explanation:** Propofol is a highly lipid-soluble drug that is insoluble in water. To make it suitable for intravenous administration, it is formulated as an **oil-in-water emulsion**. **1. Why Option A is Correct:** **Egg lecithin** (purified from egg yolk) is a phospholipid that acts as the **emulsifying agent**. It coats the lipid droplets (containing propofol and soybean oil), preventing them from coalescing and ensuring they remain uniformly dispersed in the aqueous phase. This stability is crucial for consistent drug delivery and preventing fat embolism. **2. Why Other Options are Incorrect:** * **Option B (Preservative):** Egg lecithin has no preservative properties. In fact, it supports bacterial growth. EDTA (in Diprivan) or sodium metabisulfite are added as preservatives to inhibit microbial growth. * **Option C (Carrier Vehicle):** **Soybean oil** (10%) acts as the primary lipid vehicle/carrier in which propofol is dissolved. * **Option D (Antibacterial agent):** As mentioned, the lipid emulsion is a potent culture medium for bacteria. It lacks antibacterial properties, which is why strict aseptic techniques must be followed, and the syringe must be discarded within 6–12 hours of opening. **High-Yield Clinical Pearls for NEET-PG:** * **Composition:** 1% Propofol, 10% Soybean oil, 1.2% Egg lecithin, and 2.25% Glycerol (to adjust tonicity). * **Allergy Warning:** While most egg allergies are to egg *white* (albumin), propofol uses egg *yolk* lecithin. However, it is traditionally avoided or used with caution in patients with severe egg anaphylaxis. * **Pain on Injection:** Propofol causes pain due to the activation of the kinin system; this is often mitigated by pre-treatment with Lidocaine. * **PRIS:** Propofol Related Infusion Syndrome is a rare but fatal complication of long-term high-dose infusion, characterized by metabolic acidosis, rhabdomyolysis, and cardiac failure.

Question 484: Which of the following inhalation agents has a blood-gas partition coefficient similar to nitrous oxide?

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

Explanation: ***Correct: Desflurane*** - Desflurane has a **blood-gas partition coefficient** of 0.42, which is the closest value to that of **nitrous oxide (N2O)** (0.47) among the volatile agents listed. - This very low solubility in blood facilitates rapid **wash-in** and **wash-out**, translating to the fastest induction and emergence profiles among potent volatile anesthetics. *Incorrect: Isoflurane* - Isoflurane has a moderate-to-high blood-gas partition coefficient (around **1.4**), indicating high solubility compared to N2O. - Due to its high solubility, it has relatively slow **wash-in** and **wash-out** kinetics, leading to slower induction and emergence. *Incorrect: Sevoflurane* - Sevoflurane has a low blood-gas partition coefficient (around **0.65**), making its onset and offset faster than Isoflurane or Halothane. - Although it is considered a fast agent, its solubility is still higher than both **Desflurane** and **N2O**. *Incorrect: Halothane* - Halothane has the highest blood-gas partition coefficient of the agents listed (approximately **2.5**). - Its high solubility results in the slowest **induction** and **emergence** profiles because the blood must be saturated significantly before the partial pressure in the brain rises enough to cause anesthesia.

Question 485: A 35 y/o asthmatic patient is scheduled for a minor surgical procedure. Which induction agent and muscle relaxant combination is safest for this patient?

A. Ketamine and Vecuronium (Correct Answer)
B. Propofol and Succinylcholine
C. Ketamine and d-tubocurarine
D. Thiopental and Rocuronium

Explanation: ***Ketamine and Vecuronium***- **Ketamine** is strongly recommended for asthmatics as it possesses potent **bronchodilating properties** via its sympathomimetic effects, helping prevent **bronchospasm**.- **Vecuronium** is an intermediate-acting non-depolarizing muscle relaxant that causes **minimal to no histamine release**, ensuring cardiovascular stability and avoiding airway irritation.*Propofol and Succinylcholine*- While **Propofol** is often used and generally considered safe (neutral to mild bronchodilation), **Succinylcholine**, a depolarizing agent, carries a potential risk of **histamine release**, although low.- The combination is generally acceptable but less preferred than Ketamine based on the strength of Ketamine's **bronchodilating effect**.*Ketamine and d-tubocurarine*- **Ketamine** is beneficial due to its **bronchodilating effect**, but **d-tubocurarine (DTC)** is highly associated with massive **histamine release**.- DTC often causes severe **hypotension** and significant **bronchospasm**, making it extremely unsafe for an asthmatic patient.*Thiopental and Rocuronium*- **Thiopental**, a barbiturate, is associated with a risk of **histamine release** and potential exacerbation of asthma symptoms or cough upon induction.- Although **Rocuronium** is a safe, low-histamine muscle relaxant, the use of **Thiopental** makes this combination less safe than using Ketamine.

Question 486: During regional anesthesia, which of the following local anesthetic agents has the longest duration of action when used for peripheral nerve block?

A. Procaine
B. Ropivacaine
C. Bupivacaine (Correct Answer)
D. Lignocaine (Lidocaine)

Explanation: ***Bupivacaine*** - **Bupivacaine** (and its stereoisomer, **levobupivacaine**) and **ropivacaine** are long-acting local anesthetics, but bupivacaine typically provides the longest duration of action for peripheral nerve blocks (4-12 hours). - The long duration is due to its high **lipid solubility** and high degree of **protein binding**, resulting in slow systemic absorption from the injection site. *Lidocaine* - Lidocaine is a **medium-potency, intermediate-duration** local anesthetic, typically lasting only 1-2 hours for peripheral nerve block unless combined with vasoconstrictors like epinephrine. - Its shorter duration compared to bupivacaine is due to its lower lipid solubility and lower protein binding. *Mepivacaine* - Mepivacaine is categorized as an intermediate-duration agent, similar to lidocaine, offering a slightly longer duration of action (approximately 1.5-3 hours) than lidocaine but significantly shorter than bupivacaine. - It has a faster onset than bupivacaine but a shorter duration, making it suitable when intermediate duration is preferred. *Procaine* - Procaine is an **ester-type** local anesthetic known for its rapid metabolism by plasma pseudocholinesterase, leading to a very short duration of action (less than 1 hour). - It is currently used less frequently for peripheral nerve blocks due to its short half-life and higher potential for allergic reactions.

Question 487: A 50-year-old male patient underwent lower abdominal surgery under general anaesthesia. Vecuronium was administered as a muscle relaxant during the procedure. At the end of the surgery, which of the following is the most appropriate agent to reverse the effects of vecuronium?

A. Baclofen
B. Neostigmine (Correct Answer)
C. Atropine
D. Drotaverine

Explanation: ***Neostigmine*** - Neostigmine is an **acetylcholinesterase inhibitor** that increases the amount of acetylcholine at the neuromuscular junction, effectively reversing the competitive block caused by **non-depolarizing muscle relaxants** like vecuronium. - It is the standard pharmacological agent used for reversal of intermediate-acting neuromuscular blockades at the end of general anesthesia. *Baclofen* - Baclofen is a **centrally acting skeletal muscle relaxant** that works as a GABAB receptor agonist, typically used for managing **spasticity**. - It has no meaningful effect on the **nicotinic acetylcholine receptors** at the neuromuscular junction and cannot reverse the paralytic effects of vecuronium. *Atropine* - Atropine is an **anticholinergic agent** used to block the muscarinic side effects (e.g., bradycardia, hypersalivation) that occur when **neostigmine** is administered. - While often given concurrently with neostigmine, atropine itself **does not reverse** the skeletal muscle paralysis induced by vecuronium. *Drotaverine* - Drotaverine is a **smooth muscle antispasmodic** (PDE IV inhibitor) primarily used for conditions such as biliary or renal colic. - It targets smooth muscle and is entirely ineffective in reversing the **neuromuscular blockade** affecting skeletal muscles caused by vecuronium.

Question 488: A 70-year-old patient with bilateral avascular necrosis of hip joint is undergoing total hip replacement in general anesthesia. The device shown below is used for?

A. Improving oxygen levels before induction of GA
B. Prevent hypothermia (Correct Answer)
C. Allay anxiety of patient
D. Reduce carbon dioxide levels before induction of GA

Explanation: ***Prevent hypothermia*** - The device shown is a **forced-air warming blanket** (e.g., Bair Hugger), which blows warm air over the patient to maintain normothermia. - Preventing **intraoperative hypothermia** is crucial, especially in elderly patients undergoing general anesthesia, to reduce complications like cardiac events, bleeding, and prolonged recovery. *Improving oxygen levels before induction of GA* - Improving oxygen levels usually involves **pre-oxygenation** using a face mask with 100% oxygen, not a warming device. - This device is not designed to deliver oxygen to the patient's respiratory system. *Allay anxiety of patient* - Patient anxiety is typically addressed with **premedication** (e.g., benzodiazepines) or psycho-supportive measures. - While comfort from warmth might indirectly reduce anxiety, it is not the primary purpose of this medical device. *Reduce carbon dioxide levels before induction of GA* - Reducing carbon dioxide levels (e.g., in hypercapnia) is typically achieved through **ventilation** adjustments or increasing respiratory rate/depth. - This warming device has no mechanism to alter a patient's CO2 levels.

Question 489: Which is correct about the anesthetic drugs X and Y respectively?

A. Drug X has more potency than drug Y
B. Drug Y has more potency than drug X (Correct Answer)
C. Drug X and Y have equal potency
D. Drug X and Y have equal potency but different speed of recovery

Explanation: ***Drug Y has more potency than drug X*** - The graph shows that as the **oil:gas partition coefficient** increases, the **Minimum Alveolar Concentration (MAC)** decreases. A lower MAC indicates **higher potency** for an inhaled anesthetic. - Drug Y has a higher oil:gas partition coefficient than drug X (meaning it's more lipid-soluble and thus more potent) and a lower MAC value, making it **more potent** than Drug X. *Drug X has more potency than drug Y* - Drug X has a higher MAC value and a lower oil:gas partition coefficient compared to Drug Y. - A higher MAC value signifies **lower potency**, as a greater concentration is needed to achieve the same anesthetic effect. *Drug X and Y have equal potency* - The graph clearly demonstrates that Drug X and Drug Y have different MAC values and different oil:gas partition coefficients. - Since MAC is inversely related to potency, different MAC values directly imply **different potencies**. *Drug X and Y have equal potency but different speed of recovery* - As established, Drug X and Drug Y do not have equal potency due to their different MAC values. - While lipid solubility (represented by the oil:gas partition coefficient) does affect the **speed of recovery** (higher coefficients generally lead to slower recovery), the premise of equal potency is incorrect.

Question 490: The commonly used muscle relaxant with quickest onset of action and spontaneous recovery is :

A. Vecuronium
B. Rocuronium
C. Suxamethonium (Correct Answer)
D. Atracurium

Explanation: ***Suxamethonium*** - Suxamethonium (succinylcholine) is a **depolarizing neuromuscular blocker** with the most rapid onset of action (30-60 seconds) due to its unique mechanism. - Its short duration of action and **spontaneous recovery** are due to its rapid hydrolysis by **plasma pseudocholinesterase**, making it ideal for rapid sequence intubation. *Vecuronium* - Vecuronium is an **intermediate-duration non-depolarizing neuromuscular blocker** with an onset of action typically around 3-5 minutes, which is slower than suxamethonium. - It does not undergo spontaneous recovery as rapidly as suxamethonium and often requires administration of a **reversal agent**. *Rocuronium* - Rocuronium is a **non-depolarizing neuromuscular blocker** known for its relatively rapid onset of action (60-90 seconds) among non-depolarizing agents, but it is still slower than suxamethonium. - While it can be reversed quickly with sugammadex, its **spontaneous recovery** is much slower than suxamethonium. *Atracurium* - Atracurium is an **intermediate-duration non-depolarizing neuromuscular blocker** with an onset of action (3-5 minutes) that is slower than suxamethonium. - Its metabolism involves **Hofmann elimination** and ester hydrolysis, providing a degree of organ-independent elimination, but its recovery is not as rapid or spontaneous as suxamethonium.

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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