General Anesthesia — MCQs

General Anesthesia Indian Medical PG Practice Questions and MCQs

Question 251: Surgical anaesthesia is defined as which stage?

A. Stage I
B. Stage II
C. Stage III (Correct Answer)
D. Stage IV

Explanation: **Explanation:** The stages of anesthesia were originally described by **Arthur Guedel** in 1920, primarily based on the effects of inhaled diethyl ether. **Correct Option: C (Stage III)** Stage III is known as the **Stage of Surgical Anesthesia**. It begins with the onset of regular rhythmic breathing and ends with the cessation of spontaneous respiration. This stage is characterized by the loss of the lash reflex and the depression of various protective reflexes. It is further divided into four planes (Plane 1 to 4) based on ocular movements, pupil size, and respiratory effort. Most surgical procedures are performed during this stage because it provides sufficient analgesia, amnesia, and muscle relaxation. **Incorrect Options:** * **Stage I (Analgesia):** Extends from the induction of anesthesia to the loss of consciousness. The patient remains conscious but feels less pain. * **Stage II (Delirium/Excitement):** Extends from the loss of consciousness to the onset of regular breathing. It is characterized by agitation, irregular respiration, and risk of laryngospasm. It is a "danger zone" that clinicians aim to bypass quickly. * **Stage IV (Medullary Paralysis):** This is an overdose stage. It begins with the cessation of respiration and ends with circulatory collapse/death due to extreme CNS depression. **High-Yield Clinical Pearls for NEET-PG:** * **Guedel’s Classification** is most accurate for slow-acting agents like Ether; it is less distinct with modern rapid-acting IV agents (e.g., Propofol). * **Loss of Eyelash Reflex** is the classic clinical marker for the transition from Stage II to Stage III. * **Plane 2 of Stage III** is generally considered the ideal depth for most abdominal surgeries. * **Stage II** is the period where the risk of vomiting and aspiration is highest.

Question 252: What is the effect of ketamine on intraocular pressure (IOP)?

A. Increases it (Correct Answer)
B. Decreases it
C. Does not affect
D. First increases then decreases

Explanation: **Explanation:** **1. Why Option A is Correct:** Ketamine is a unique intravenous anesthetic agent that acts as an NMDA receptor antagonist. Unlike most other induction agents, ketamine **increases intraocular pressure (IOP)**. This effect is primarily attributed to two mechanisms: * **Increased Muscle Tone:** Ketamine causes an increase in the tone of the extraocular muscles, which exerts external pressure on the globe. * **Sympathetic Stimulation:** It stimulates the sympathetic nervous system, leading to an increase in systemic blood pressure and heart rate, which can indirectly elevate IOP. * **Nystagmus:** Ketamine often induces nystagmus and blepharospasm, further contributing to the rise in pressure. **2. Why Other Options are Incorrect:** * **Option B:** Most general anesthetics (Propofol, Etomidate, Thiopental) and volatile agents (Isoflurane, Sevoflurane) **decrease** IOP by reducing aqueous humor production or improving its drainage. Ketamine is the notable exception. * **Option C & D:** Ketamine has a definitive and measurable stimulatory effect on IOP; it does not remain neutral, nor does it follow a biphasic pattern of increasing then decreasing. **3. High-Yield Clinical Pearls for NEET-PG:** * **Contraindication:** Due to the rise in IOP, Ketamine is traditionally **avoided in patients with open globe injuries** or penetrating eye trauma, as it may cause extrusion of intraocular contents. * **The "Rule of K":** Ketamine increases almost everything—**IOP, ICP (Intracranial Pressure), BP, HR, and Secretions.** * **Exception:** While Ketamine increases IOP, it is still frequently used in pediatric ophthalmological examinations (like EUA - Examination Under Anesthesia) because it maintains spontaneous respiration, though results must be interpreted knowing the baseline may be elevated.

Question 253: Which of the following is NOT true about propofol?

A. Provides pleasant sedation and rapid recovery.
B. Is safe to use in patients with porphyria.
C. Has an antiemetic effect.
D. Acts as a cardiac stimulant. (Correct Answer)

Explanation: **Explanation:** Propofol (2,6-diisopropylphenol) is the most commonly used intravenous induction agent. The correct answer is **D** because propofol is a **potent cardiovascular depressant**, not a stimulant. **1. Why Option D is the Correct Answer (The Concept):** Propofol causes a significant decrease in systemic vascular resistance (vasodilation) and myocardial contractility. It also blunts the baroreceptor reflex, meaning the heart rate often stays the same or decreases despite a drop in blood pressure. This makes it potentially dangerous in hemodynamically unstable or hypovolemic patients. **2. Why the other options are incorrect (True statements about Propofol):** * **Option A:** Propofol is known for "clear-headed" recovery with minimal hangover effect due to its rapid metabolism and redistribution. This makes it the gold standard for day-care surgeries. * **Option B:** Unlike barbiturates (e.g., Thiopentone), propofol does not induce the enzyme ALA synthetase, making it safe for patients with **Porphyria**. * **Option C:** Propofol possesses unique **antiemetic properties** (at sub-hypnotic doses of 10–20 mg), making it ideal for patients prone to Postoperative Nausea and Vomiting (PONV). **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Facilitates inhibitory neurotransmission via **GABA-A receptors**. * **Pain on Injection:** Common; can be mitigated by using larger veins or pre-treatment with Lidocaine. * **Propofol Infusion Syndrome (PRIS):** A rare, fatal complication of long-term high-dose infusion characterized by metabolic acidosis, rhabdomyolysis, and cardiac failure. * **Preservative:** Formulated in a lipid emulsion (soybean oil, egg lecithin); must be used within 6–12 hours of opening due to risk of bacterial growth. * **Drug of Choice:** For **TIVA** (Total Intravenous Anesthesia) and **Malignant Hyperthermia** susceptible patients.

Question 254: Which of the following is a recognized side effect of halothane?

A. Hypertension
B. Malignant hyperthermia (Correct Answer)
C. Tachycardia
D. Uterine contraction

Explanation: **Explanation:** **Malignant Hyperthermia (MH)** is a life-threatening pharmacogenetic hypermetabolic state triggered by volatile anesthetic agents (like halothane) and the depolarizing muscle relaxant succinylcholine. In susceptible individuals (often with mutations in the **RYR1 receptor**), halothane causes an uncontrolled release of calcium from the sarcoplasmic reticulum. This leads to sustained muscle contraction, massive heat production, and metabolic acidosis. Management requires immediate cessation of the trigger and administration of **Dantrolene**. **Analysis of Incorrect Options:** * **A & C (Hypertension and Tachycardia):** Halothane actually causes **hypotension** (via direct myocardial depression) and **bradycardia** (due to its vagomimetic effect). It is notorious for sensitizing the myocardium to catecholamines, which can lead to arrhythmias, but its primary hemodynamic profile is depressant. * **D (Uterine contraction):** Halothane is a potent **uterine relaxant**. While this is useful for intrauterine fetal manipulation, it is contraindicated during the third stage of labor as it can lead to significant postpartum hemorrhage. **High-Yield Clinical Pearls for NEET-PG:** * **Halothane Hepatitis:** A rare but severe immune-mediated hepatotoxicity ("Halothane shakes" or fever often precede it). * **Sweet Smell:** It is non-pungent, making it the agent of choice for **smooth inhalation induction** in pediatric patients. * **Blood-Gas Partition Coefficient:** 2.4 (slower induction/recovery compared to Sevoflurane). * **Preservation:** It is stored in amber-colored bottles with **thymol** to prevent spontaneous decomposition.

Question 255: Which of the following statements about Total Intravenous Anesthesia (TIVA) is false?

A. It is contraindicated in neurosurgery. (Correct Answer)
B. It can be safely used in individuals with a history of malignant hyperthermia.
C. Pulmonary vasoconstriction is maintained by it.
D. Propofol is the commonest used agent for it.

Explanation: **Explanation:** **1. Why Option A is the Correct Answer (The False Statement):** Contrary to the statement, TIVA (specifically using Propofol) is often the **technique of choice in neurosurgery**. Propofol reduces the Cerebral Metabolic Rate of Oxygen ($CMRO_2$) and Cerebral Blood Flow (CBF), which leads to a decrease in **Intracranial Pressure (ICP)**. Unlike volatile inhalational agents, which can cause cerebral vasodilation and increase ICP at higher concentrations, TIVA maintains favorable cerebral hemodynamics and allows for better intraoperative neuromonitoring (SSEP/MEP). **2. Analysis of Incorrect Options (True Statements):** * **Option B:** TIVA is the gold standard for patients with a history of **Malignant Hyperthermia (MH)**. MH is triggered by volatile halogenated anesthetics and succinylcholine; since TIVA avoids these triggers, it is perfectly safe. * **Option C:** Inhalational agents inhibit **Hypoxic Pulmonary Vasoconstriction (HPV)**, potentially worsening shunting. TIVA agents (like Propofol) do not interfere with this protective reflex, thus maintaining better oxygenation in certain clinical scenarios. * **Option D:** **Propofol** is indeed the most common agent used for TIVA due to its rapid onset, short duration of action (favorable pharmacokinetics), and smooth recovery profile with minimal postoperative nausea and vomiting (PONV). **Clinical Pearls for NEET-PG:** * **Context-Sensitive Half-Time:** Propofol has a relatively short context-sensitive half-time even after prolonged infusion, making it ideal for TIVA. * **Target Controlled Infusion (TCI):** Often used in TIVA to achieve steady-state plasma concentrations using the **Marsh or Schnider models**. * **Triad of TIVA:** Usually consists of Propofol (hypnotic), an Opioid (usually Remifentanil/Fentanyl for analgesia), and a muscle relaxant if required.

Question 256: What are the factors responsible for the cardiovascular effects of non-depolarizing neuromuscular blockers?

A. Histamine release
B. Effects mediated by autonomic nicotinic cholinergic receptors
C. Pancuronium produced a profound vagolytic response
D. All of the above (Correct Answer)

Explanation: The cardiovascular effects of non-depolarizing neuromuscular blockers (NDNMBs) are primarily mediated through three distinct pharmacological mechanisms: 1. **Histamine Release:** Certain NDNMBs (classically the benzylisoquinoliniums like **atracurium** and **mivacurium**) trigger mast cell degranulation [1]. This leads to systemic vasodilation and a compensatory increase in heart rate (tachycardia), often accompanied by hypotension and flushing. 2. **Autonomic Nicotinic Receptor Effects:** NDNMBs act on nicotinic receptors at the neuromuscular junction, but they can also interact with nicotinic receptors in the **autonomic ganglia** [2]. While newer agents are more selective, older agents can cause ganglionic blockade or stimulation, leading to fluctuations in blood pressure and heart rate. 3. **Vagolytic Response:** **Pancuronium** is the classic example of an NDNMB that exhibits significant antimuscarinic activity [1]. It blocks M2 muscarinic receptors in the SA node, leading to a profound **vagolytic effect** (tachycardia). It also inhibits norepinephrine reuptake, further contributing to its sympathomimetic profile. **Why Option D is Correct:** Since histamine release, autonomic ganglionic interactions, and specific vagolytic actions (like those of pancuronium) all contribute to the hemodynamic profile of this drug class, "All of the above" is the most accurate choice. **High-Yield Clinical Pearls for NEET-PG:** * **Vecuronium & Rocuronium:** These are considered "cardiovascularly stable" because they lack significant histamine release or vagolytic effects [1]. * **Pancuronium:** Avoid in patients where tachycardia is detrimental (e.g., CAD or Mitral Stenosis) [1]. * **Atracurium:** Known for the "Hoffman elimination" but carries a risk of histamine-induced hypotension if injected rapidly [1]. * **Cisatracurium:** Unlike atracurium, it does not cause significant histamine release, making it more hemodynamically stable [1].

Question 257: Which muscle relaxant should not be used in a patient with liver failure?

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

Explanation: **Explanation:** The liver plays a critical role in the metabolism and excretion of several neuromuscular blocking agents (NMBAs). **Pancuronium** is a long-acting aminosteroid muscle relaxant that is primarily dependent on the liver for its metabolism (deacetylation) and the kidneys for excretion. In patients with liver failure, the clearance of Pancuronium is significantly reduced, and its volume of distribution is increased. This leads to a prolonged half-life and an unpredictable, extended duration of neuromuscular blockade, making it unsuitable for patients with hepatic impairment. **Analysis of Incorrect Options:** * **d-Tubocurarine:** While it undergoes some biliary excretion, it is primarily excreted unchanged in the urine. It is rarely used today due to significant histamine release, but it is not as strictly contraindicated in liver failure as Pancuronium. * **Suxamethonium (Succinylcholine):** This is a depolarizing NMBA metabolized by **pseudocholinesterase** (produced by the liver). While liver failure can decrease enzyme levels and slightly prolong its action, it is not "avoided" as a rule, though caution is required. * **Decamethonium:** A historical depolarizing agent primarily excreted unchanged by the kidneys. **NEET-PG High-Yield Pearls:** * **Drug of Choice in Liver/Renal Failure:** **Atracurium** or **Cisatracurium**. They undergo **Hofmann elimination** (spontaneous non-enzymatic degradation), making their clearance independent of organ function. * **Vecuronium & Rocuronium:** These are also aminosteroids (like Pancuronium) but have shorter durations; however, their action is still significantly prolonged in hepatic cirrhosis. * **Mnemonic:** Remember **"P"** for **P**ancuronium is **P**rolonged in **P**ortal hypertension/Liver failure.

Question 258: What is the minimum alveolar concentration (MAC) of sevoflurane in %?

A. 0.75
B. 0.42
C. 1.15
D. 2 (Correct Answer)

Explanation: **Explanation:** **Minimum Alveolar Concentration (MAC)** is defined as the concentration of an inhalational anesthetic at 1 atmosphere that prevents skeletal muscle movement in response to a noxious stimulus (surgical incision) in 50% of patients. It is an index of **anesthetic potency**; the lower the MAC, the more potent the agent. **Correct Option (D): 2%** Sevoflurane has a MAC of approximately **2.0%** in adults. It is a non-pungent, sweet-smelling agent with a low blood-gas partition coefficient (0.65), making it the drug of choice for **smooth inhalational induction**, especially in pediatric patients. **Incorrect Options:** * **A. 0.75%:** This is the MAC of **Halothane**. It is the most potent volatile anesthetic but is less commonly used now due to risks of halothane hepatitis and cardiac arrhythmias. * **B. 0.42%:** This is the MAC of **Methoxyflurane**. While highly potent, it is no longer used for general anesthesia due to nephrotoxicity caused by inorganic fluoride metabolites. * **C. 1.15%:** This is the MAC of **Isoflurane**. It is a gold-standard maintenance agent known for its stability and neuroprotective properties. **High-Yield Clinical Pearls for NEET-PG:** * **MAC Values to Remember:** Nitrous Oxide (104%), Desflurane (6%), Sevoflurane (2%), Isoflurane (1.15%), Halothane (0.75%). * **Factors increasing MAC:** Hyperthermia, hypernatremia, chronic alcohol abuse, and increased central neurotransmitters (e.g., MAO inhibitors, cocaine). * **Factors decreasing MAC:** Hypothermia, hyponatremia, pregnancy, acute alcohol intoxication, elderly age, and pregnancy. * **Sevoflurane Specifics:** It can react with soda lime to produce **Compound A** (potentially nephrotoxic in rats, though clinical significance in humans is debated).

Question 259: Who demonstrated the anesthetic effect of ether?

A. Morgan
B. Priestly
C. Morton (Correct Answer)
D. None of the above

Explanation: **Explanation:** The correct answer is **William T.G. Morton**. On **October 16, 1846**, Morton, a dentist, famously demonstrated the anesthetic properties of diethyl ether at Massachusetts General Hospital (now known as the "Ether Dome"). He successfully administered ether to a patient named Gilbert Abbott for the removal of a neck tumor by surgeon John Collins Warren. This event is considered the birth of modern anesthesia. **Analysis of Options:** * **Morton (Correct):** Credited with the first successful public demonstration of ether. Note: While **Crawford Long** used ether earlier (1842), he did not publish his results until after Morton, making Morton the historically recognized pioneer. * **Priestly (Incorrect):** Joseph Priestley was a chemist who discovered **Nitrous Oxide** in 1772 and Oxygen in 1774, but he did not use them for anesthesia. * **Morgan (Incorrect):** Likely a distractor. While John Morgan founded the first medical school in America, he is not associated with the discovery of ether. **High-Yield Clinical Pearls for NEET-PG:** * **First Public Demonstration:** October 16 is celebrated globally as **World Anaesthesia Day**. * **Nitrous Oxide:** First used clinically by **Horace Wells** (1844), though his public demonstration was considered a failure. * **Chloroform:** First used in obstetrics by **James Young Simpson** (1847). * **Cocaine:** The first local anesthetic, discovered by **Carl Koller** (1884) for ophthalmic use. * **Term "Anaesthesia":** Coined by **Oliver Wendell Holmes Sr.** following Morton's demonstration.

Question 260: Which muscles are the first to be affected by muscle relaxants?

A. Laryngeal muscles (Correct Answer)
B. Diaphragm
C. Thenar muscles
D. Intercostals

Explanation: The sensitivity of muscles to neuromuscular blocking agents (NMBAs) depends primarily on their **blood flow** and **metabolic rate**. ### 1. Why Laryngeal Muscles are Correct The **laryngeal muscles** (along with the extraocular muscles) are among the first to be affected by muscle relaxants. This is due to their high density of acetylcholine receptors and, most importantly, their **high regional blood flow**. Because they receive a greater volume of blood per gram of tissue compared to peripheral muscles, the muscle relaxant reaches the neuromuscular junctions of the larynx more rapidly. This allows for early paralysis, facilitating endotracheal intubation. ### 2. Analysis of Incorrect Options * **B. Diaphragm:** The diaphragm is the **most resistant** muscle to NMBAs. It requires a much higher dose (nearly 2x) to achieve the same level of block as peripheral muscles. It is also the first to recover. * **D. Intercostals:** Like the diaphragm, these are respiratory muscles. They are relatively resistant and are among the last to be paralyzed and the first to recover. * **C. Thenar muscles:** These are peripheral muscles (adductor pollicis). They are paralyzed **after** the laryngeal muscles but **before** the diaphragm. Monitoring the adductor pollicis via a nerve stimulator is the standard for assessing recovery, as it reflects the return of airway protection. ### Clinical Pearls for NEET-PG * **Sequence of Paralysis:** Small, fast-moving muscles (Eyes/Larynx) → Extremities → Trunk (Intercostals) → Diaphragm. * **Sequence of Recovery:** Exactly the reverse (Diaphragm recovers first; Eyes/Larynx recover last). * **Monitoring Tip:** To predict **intubation** conditions, monitor the **orbicularis oculi** (reflects laryngeal block). To predict **recovery**, monitor the **adductor pollicis** (reflects return of respiratory function).

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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