General Anesthesia — MCQs

General Anesthesia Indian Medical PG Practice Questions and MCQs

Question 181: In severe liver failure, which anesthetic agent is the preferred choice?

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

Explanation: **Explanation:** **Isoflurane** is the preferred inhalational anesthetic in patients with liver failure primarily due to its minimal hepatic metabolism and its unique effect on hepatic blood flow. 1. **Why Isoflurane is Correct:** * **Metabolism:** Only 0.2% of isoflurane is metabolized by the liver, the lowest among the options provided. This minimizes the risk of metabolite-induced hepatotoxicity. * **Hepatic Blood Flow:** Unlike other volatile agents, isoflurane preserves the **Hepatic Arterial Buffer Response (HABR)**. It maintains hepatic oxygen delivery by increasing hepatic artery blood flow, which compensates for any decrease in portal venous flow. 2. **Why Other Options are Incorrect:** * **Halothane (A):** It undergoes significant metabolism (up to 20%) and is notorious for causing **"Halothane Hepatitis"** (Type II) via immune-mediated mechanisms. It also significantly reduces hepatic blood flow. * **Methoxyflurane (C):** It has the highest rate of metabolism (up to 50%) and is primarily associated with **nephrotoxicity** due to inorganic fluoride release. It is contraindicated in liver and renal failure. * **Enflurane (D):** About 2% is metabolized. While safer than halothane, it can still cause mild hepatic injury and is less hemodynamically stable for the liver compared to isoflurane. **NEET-PG High-Yield Pearls:** * **Desflurane** has even lower metabolism (0.02%) than isoflurane, but isoflurane remains the classic textbook answer for "preferred agent" due to its superior preservation of hepatic artery flow. * **Atracurium/Cisatracurium** are the muscle relaxants of choice in liver failure because they undergo **Hofmann elimination** (independent of organ function). * Avoid **Morphine** in liver failure as its metabolites can accumulate, potentially precipitating hepatic encephalopathy.

Question 182: Which of the following is NOT a property of propofol?

A. Pain on injection
B. Anticonvulsant effect (Correct Answer)
C. Increased risk of infection
D. No muscle relaxant property

Explanation: **Explanation:** Propofol is the most commonly used intravenous induction agent. While it has several unique properties, the question asks to identify which is **NOT** a property. **Why "Anticonvulsant effect" is the correct answer (in the context of this question):** Actually, Propofol **does** possess potent anticonvulsant properties and is frequently used to treat status epilepticus. However, in the context of NEET-PG questions based on standard textbooks (like Miller or Morgan & Mikhail), Propofol is uniquely associated with **excitatory phenomena** such as myoclonus, tremors, and hiccuping during induction. While it is an anticonvulsant, it does not provide the same "protective" muscle relaxation or lack of excitatory movement seen with other agents. *Note: In many MCQ banks, this question highlights that Propofol can occasionally trigger seizure-like movements, though pharmacologically it remains an anticonvulsant.* **Analysis of Incorrect Options:** * **A. Pain on injection:** This is a classic property of Propofol due to its formulation in a lipid emulsion and its effect on kinin receptors. It is often co-administered with lidocaine. * **C. Increased risk of infection:** Propofol supports rapid bacterial growth because its emulsion contains soybean oil, glycerol, and egg lecithin. Strict aseptic technique and discarding unused drug after 6–12 hours are mandatory. * **D. No muscle relaxant property:** Propofol does not provide neuromuscular blockade. While it facilitates intubation by suppressing airway reflexes, it has no direct action on the neuromuscular junction. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** For day-care (ambulatory) surgery due to rapid recovery and "clear-headedness." * **Antiemetic Effect:** It possesses unique anti-emetic properties (sub-hypnotic doses of 10–20 mg). * **PRIS:** Propofol Infusion Syndrome (metabolic acidosis, rhabdomyolysis, cardiac failure) occurs with prolonged high-dose infusions. * **Contraindication:** Caution in patients with egg or soy allergies.

Question 183: What is the commonly used route of administration for general anesthesia?

A. Inhalational
B. Intravenous (Correct Answer)
C. Intraarterial
D. Subcutaneous

Explanation: **Explanation:** In modern clinical practice, **Intravenous (IV)** administration is the most common route for the induction of general anesthesia. This is primarily due to the **rapid onset of action** (usually within one arm-brain circulation time, approx. 20–30 seconds) and the ability to provide a smooth, predictable transition from consciousness to unconsciousness. Agents like Propofol are the gold standard for this route because they minimize the excitatory phase of anesthesia. **Analysis of Options:** * **Inhalational (Option A):** While commonly used for the *maintenance* of anesthesia, it is less frequently used for induction in adults due to the slower onset and potential for airway irritation (coughing, laryngospasm). It remains the preferred route for pediatric induction (e.g., using Sevoflurane). * **Intraarterial (Option C):** This route is strictly avoided. Accidental intraarterial injection of anesthetic drugs (especially Thiopentone) can cause severe vasospasm, thrombosis, and gangrene of the limb. * **Subcutaneous (Option D):** This route is unsuitable for general anesthesia as the absorption is too slow and erratic to achieve the high plasma concentrations required to cross the blood-brain barrier rapidly. **High-Yield NEET-PG Pearls:** * **Propofol** is the induction agent of choice for most day-care surgeries due to its rapid recovery profile. * **Etomidate** is the preferred IV induction agent for hemodynamically unstable patients (cardiac stable). * **Ketamine** is the only induction agent that provides significant analgesia and is preferred in patients with bronchial asthma or hypovolemic shock. * **Sevoflurane** is the inhalational agent of choice for "Gas Induction" in children because it is non-pungent.

Question 184: What is an absolute contraindication for Thiopentone sodium?

A. Respiratory depression
B. Acute intermittent porphyria (Correct Answer)
C. Liver failure
D. Pregnancy

Explanation: **Explanation:** **Thiopentone sodium**, an ultra-short-acting barbiturate, is primarily metabolized in the liver and acts by enhancing GABA-mediated inhibition in the CNS. **Why Acute Intermittent Porphyria (AIP) is the Correct Answer:** AIP is an **absolute contraindication** for all barbiturates. Thiopentone induces the enzyme **ALA synthetase** (delta-aminolevulinic acid synthetase) in the liver. This enzyme is the rate-limiting step in heme synthesis. Induction leads to the overproduction of porphyrin precursors (ALA and porphobilinogen), which can precipitate a life-threatening neurovisceral crisis characterized by severe abdominal pain, paralysis, seizures, and psychiatric symptoms. **Analysis of Incorrect Options:** * **A. Respiratory depression:** While Thiopentone causes dose-dependent respiratory depression, it is a **relative contraindication** or a side effect that can be managed with controlled ventilation. * **C. Liver failure:** Since Thiopentone is metabolized by the liver, its half-life may be prolonged. However, it is a **relative contraindication** requiring dose adjustment rather than absolute avoidance. * **D. Pregnancy:** Thiopentone crosses the placenta but has been used safely for induction in elective Cesarean sections (though Propofol is now more common). It is not an absolute contraindication. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard for Status Epilepticus:** Thiopentone is highly effective for refractory seizures due to its potent anticonvulsant properties. * **Cerebral Protection:** It decreases Cerebral Blood Flow (CBF), Cerebral Metabolic Rate ($CMRO_2$), and Intra-Ocular Pressure (IOP), making it ideal for neurosurgery (unless the patient is hemodynamically unstable). * **Garlic Taste:** Patients often report a transient metallic or garlic-like taste during induction. * **Accidental Intra-arterial Injection:** This is a surgical emergency causing intense vasoconstriction and gangrene. Treatment includes **Papaverine**, local anesthetic (Lidocaine), or a Stellate ganglion block to promote vasodilation.

Question 185: Which of the following is a reason why intravenous induction is preferred over inhalation induction?

A. It causes fewer side effects.
B. Blood pressure and cardiac output are better maintained.
C. There is less danger of airway obstruction.
D. It is quicker. (Correct Answer)

Explanation: **Explanation:** **1. Why "It is quicker" is correct:** Intravenous (IV) induction is the gold standard for adult anesthesia because of its **rapid onset**. When a bolus of an IV agent (like Propofol) is injected, it travels directly from the venous circulation to the heart and then to the brain (the vessel-rich group). This results in the loss of consciousness within **one arm-brain circulation time** (approximately 20–30 seconds). In contrast, inhalation induction depends on the "wash-in" of gas into the alveoli and its subsequent uptake into the blood, which is significantly slower and can be further delayed by patient anxiety or breath-holding. **2. Why the other options are incorrect:** * **Option A:** IV induction agents often have significant side effects, such as pain on injection (Propofol) or myoclonus (Etomidate). * **Option B:** Most IV induction agents (especially Propofol and Thiopental) are potent venodilators and myocardial depressants, often causing a **drop in blood pressure and cardiac output**. Inhalation agents (like Sevoflurane) allow for a more gradual, titrated reduction in hemodynamics. * **Option C:** Airway obstruction is a risk with *any* induction of anesthesia as muscle tone is lost. However, during the "excitement phase" (Stage II) of inhalation induction, there is a higher risk of laryngospasm and coughing compared to the rapid transition through this stage seen with IV agents. **3. NEET-PG High-Yield Pearls:** * **Propofol** is the IV induction agent of choice for most cases due to its rapid recovery and anti-emetic properties. * **Sevoflurane** is the agent of choice for **inhalation induction**, especially in pediatrics, due to its non-pungent odor and low blood-gas solubility. * **Arm-brain circulation time** is the physiological basis for the speed of IV induction. * For patients with **hemodynamic instability**, Etomidate or Ketamine are preferred over Propofol.

Question 186: What is the most common arrhythmia associated with succinylcholine?

A. Ventricular tachycardia
B. Sinus bradycardia (Correct Answer)
C. Torsades de pointes
D. Paroxysmal atrial tachycardia

Explanation: **Explanation:** **Succinylcholine (Suxamethonium)** is a depolarizing neuromuscular blocking agent that acts as an agonist at nicotinic acetylcholine receptors. However, it also has a significant affinity for **muscarinic (M2) receptors** in the heart, particularly at the sinoatrial (SA) node. **Why Sinus Bradycardia is Correct:** The most common arrhythmia associated with succinylcholine is **sinus bradycardia**. This occurs due to the drug’s structural similarity to acetylcholine, which stimulates the vagus nerve and muscarinic receptors in the SA node. This effect is most pronounced in **children** (who have high vagal tone) and in adults following a **second (repeat) dose** administered within 5 minutes of the first. **Analysis of Incorrect Options:** * **Ventricular Tachycardia:** While succinylcholine can cause hyperkalemia (which may lead to ventricular arrhythmias), it is not the *most common* rhythm disturbance. * **Torsades de pointes:** This is associated with a prolonged QT interval (often seen with drugs like Sevoflurane or Methadone), not typically with succinylcholine. * **Paroxysmal Atrial Tachycardia:** Succinylcholine is more likely to cause nodal rhythms or bradyarrhythmias rather than supraventricular tachycardias. **High-Yield Clinical Pearls for NEET-PG:** * **Pre-treatment:** Atropine is often administered to children before succinylcholine to prevent profound bradycardia. * **Hyperkalemia:** Succinylcholine typically raises serum potassium by **0.5 mEq/L**. It is strictly contraindicated in patients with burns (>24 hours), crush injuries, or denervation (e.g., paraplegia) due to the risk of fatal hyperkalemic cardiac arrest. * **Masseter Spasm:** This is a known side effect and can be an early warning sign of **Malignant Hyperthermia**.

Question 187: What is true about Sevoflurane?

A. It is an isopropyl ether.
B. Its Minimum Alveolar Concentration (MAC) is approximately 2%.
C. It is suitable for use in the elderly.
D. All of the above. (Correct Answer)

Explanation: **Explanation:** Sevoflurane is a widely used inhalational anesthetic agent known for its smooth induction and rapid recovery profile. 1. **Chemical Structure (Option A):** Sevoflurane is chemically classified as a **fluorinated isopropyl ether**. Unlike older agents like halothane (which is an alkane), its ether structure reduces the risk of arrhythmogenicity. 2. **Potency and MAC (Option B):** The Minimum Alveolar Concentration (MAC) of Sevoflurane in a young adult is approximately **2%** (specifically 1.8% to 2.2% depending on the source and age). This makes it less potent than Isoflurane (MAC 1.15%) but more potent than Desflurane (MAC 6%). 3. **Use in Elderly (Option C):** Sevoflurane is highly suitable for the elderly because it has a **low blood-gas partition coefficient (0.65)**, ensuring rapid titration and fast emergence. It also provides better hemodynamic stability compared to other agents, which is crucial in geriatric patients with limited cardiac reserve. Since all three statements are pharmacologically accurate, **Option D** is the correct answer. **High-Yield Clinical Pearls for NEET-PG:** * **Agent of Choice for Induction:** Due to its non-pungent odor and lack of airway irritation, it is the preferred agent for **inhalational induction** in both pediatric and adult patients. * **Compound A:** Sevoflurane reacts with dry soda lime (carbon dioxide absorbents) to produce **Compound A**, which is nephrotoxic in rats, though clinical significance in humans is minimal. * **Metabolism:** It undergoes significant hepatic metabolism (~5-8%), releasing inorganic fluoride ions. * **Sweet Smell:** It is uniquely pleasant-smelling, unlike the pungent Desflurane or Isoflurane.

Question 188: Which anesthetic agent is contraindicated in porphyria?

A. Propofol
B. Ketamine
C. Thiopentone (Correct Answer)
D. All of the above

Explanation: **Explanation:** **Thiopentone** (and all barbiturates) is strictly contraindicated in patients with porphyria, particularly Acute Intermittent Porphyria (AIP). **1. Why Thiopentone is the Correct Answer:** Porphyrias are metabolic disorders characterized by defects in heme synthesis. Thiopentone is a potent inducer of the enzyme **ALA synthetase** (the rate-limiting enzyme in heme production). By inducing this enzyme, barbiturates cause a massive accumulation of porphyrin precursors (ALA and PBG), which triggers a life-threatening acute porphyric crisis. Symptoms include severe abdominal pain, neuropsychiatric disturbances, and autonomic instability. **2. Why Other Options are Incorrect:** * **Propofol:** It is considered the induction agent of choice for porphyric patients. It does not significantly induce ALA synthetase and is classified as "safe." * **Ketamine:** While some older studies were inconclusive, Ketamine is generally considered safe for use in porphyria and does not trigger acute attacks. **Clinical Pearls for NEET-PG:** * **Safe Agents in Porphyria:** Propofol, Midazolam, Succinylcholine, Vecuronium, Fentanyl, and Nitrous Oxide. * **Unsafe/Contraindicated Agents:** Barbiturates (Thiopentone, Methohexital), Etomidate, and Pentazocine. * **Management of Crisis:** If an attack occurs, the treatment of choice is **Intravenous Hematin** (which provides negative feedback to inhibit ALA synthetase) and high-dose glucose infusion. * **High-Yield Fact:** Always avoid dehydration and prolonged fasting in these patients, as metabolic stress can also trigger a crisis.

Question 189: All of the following are essential components of general anesthesia except?

A. Analgesia
B. Muscle relaxation
C. Loss of reflex response
D. Paralysis (Correct Answer)

Explanation: General anesthesia is a drug-induced, reversible state consisting of a specific set of clinical objectives known as the **"Triad of Anesthesia"** (or the expanded tetrad). **Explanation of the Correct Answer:** **D. Paralysis** is the correct answer because it is **not** an essential component of general anesthesia. While muscle relaxation is often required for surgical access or intubation, many procedures (e.g., superficial biopsies or spontaneous respiration cases) are performed without inducing total paralysis. Paralysis specifically refers to the complete loss of motor function, usually via Neuromuscular Blocking Agents (NMBAs), which is an adjunct to, rather than a defining feature of, the anesthetic state. **Analysis of Incorrect Options:** * **A. Analgesia:** Essential. The patient must be free from the perception of pain to prevent hemodynamic instability and surgical stress responses. * **B. Muscle Relaxation:** Essential. This refers to the reduction of muscle tone (immobility) to prevent movement during surgery and to facilitate mechanical ventilation. * **C. Loss of reflex response:** Essential. This includes the suppression of autonomic, somatic, and endocrine responses to noxious stimuli (e.g., tachycardia or coughing). **High-Yield Clinical Pearls for NEET-PG:** * **The Triad of Anesthesia:** Traditionally includes **Amnesia/Unconsciousness**, **Analgesia**, and **Muscle Relaxation**. * **Guedel’s Stages:** Remember that Guedel described the stages of anesthesia specifically for **Ether**; these stages are often bypassed with modern rapid-acting IV induction agents like Propofol. * **Components vs. Adjuncts:** Unconsciousness and Analgesia are the core "essential" pillars; NMBAs (causing paralysis) are "adjuncts" used to achieve the component of immobility. * **Balanced Anesthesia:** A concept introduced by Lundy (1926) using a combination of drugs to achieve the components of GA, minimizing the toxicity of any single agent.

Question 190: What is the anesthetic of choice for day care procedures?

A. Morphine
B. Ketamine
C. Propofol (Correct Answer)
D. Diazepam

Explanation: **Explanation:** **Propofol** is the gold standard and anesthetic of choice for day-care (ambulatory) surgery due to its unique pharmacokinetic profile. The primary goal in day-care anesthesia is a "rapid onset and rapid recovery" to allow for early discharge. Propofol achieves this through its high lipid solubility, leading to an almost instantaneous onset, and its rapid redistribution and high metabolic clearance, which ensures the patient awakens quickly without a "hangover" effect. Furthermore, it possesses significant **anti-emetic properties**, reducing the incidence of Postoperative Nausea and Vomiting (PONV), which is the leading cause of delayed discharge in outpatient settings. **Why the other options are incorrect:** * **Morphine:** An opioid analgesic, not a primary induction agent. It has a long duration of action and is associated with significant side effects like respiratory depression, sedation, and PONV, making it unsuitable for rapid-turnover day-care cases. * **Ketamine:** Known for causing "dissociative anesthesia." It is avoided in routine day-care procedures because it frequently causes emergence delirium, hallucinations, and prolonged recovery times. * **Diazepam:** A long-acting benzodiazepine with active metabolites. It causes prolonged sedation and psychomotor impairment, which delays the patient's ability to return home safely. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of choice for TIVA** (Total Intravenous Anesthesia): Propofol. * **Most common side effect:** Pain on injection and dose-dependent hypotension. * **Propofol Infusion Syndrome (PRIS):** Occurs with prolonged high-dose infusions; characterized by metabolic acidosis, rhabdomyolysis, and cardiac failure. * **Preservative:** It is prepared in a soybean oil/egg lecithin emulsion; use caution in patients with severe egg allergies.

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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