General Anesthesia — MCQs

General Anesthesia Indian Medical PG Practice Questions and MCQs

Question 141: All of the following are intravenous anesthetic induction agents except?

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

Explanation: **Explanation:** The correct answer is **D. Bupivacaine**. The fundamental distinction here lies between **General Anesthetics** and **Local Anesthetics**. * **Why Bupivacaine is the correct answer:** Bupivacaine is a potent, long-acting **Local Anesthetic (LA)** of the amide group. It works by blocking voltage-gated sodium channels in peripheral nerves or the spinal cord to prevent signal conduction. It is used for regional anesthesia (spinal, epidural) and nerve blocks, but it is **never** used as an intravenous induction agent for general anesthesia. In fact, accidental intravenous injection of Bupivacaine is highly toxic, leading to severe cardiotoxicity. **Analysis of Incorrect Options (Intravenous Induction Agents):** * **A. Thiopentone Sodium:** An ultra-short-acting barbiturate. It was the gold standard for induction for decades. It acts via GABA-A receptors. * **B. Ketamine:** A dissociative anesthetic that acts as an NMDA receptor antagonist. It is unique because it provides significant analgesia and maintains sympathetic tone. * **C. Etomidate:** An imidazole derivative used for induction, favored in hemodynamically unstable patients (e.g., trauma or heart failure) due to its minimal effect on blood pressure and heart rate. **High-Yield Clinical Pearls for NEET-PG:** * **Propofol:** Currently the most common induction agent; known for its anti-emetic properties and "milk of amnesia" appearance. * **Etomidate Side Effect:** Can cause transient **adrenocortical suppression** by inhibiting the enzyme 11-beta-hydroxylase. * **Ketamine:** The drug of choice for induction in **bronchial asthma** (bronchodilator) and **hypovolemic shock**. * **Bupivacaine Toxicity:** If systemic toxicity (LAST) occurs, the specific antidote is **Intralipid (20% Lipid Emulsion)**.

Question 142: All of the following are considered stages of anesthesia except:

A. Analgesia
B. Allodynia (Correct Answer)
C. Delirium
D. Surgical anesthesia

Explanation: This question tests your knowledge of **Guedel’s Classification**, which describes the four clinical stages of anesthesia traditionally observed with inhalational agents (specifically diethyl ether). ### **Why Allodynia is the Correct Answer** **Allodynia** is a clinical symptom where a person feels pain from a stimulus that does not normally provoke pain (e.g., a light touch). It is a feature of neuropathic pain or central sensitization, not a stage of general anesthesia. ### **Explanation of the Stages of Anesthesia** Guedel’s classification divides the induction of anesthesia into four distinct stages: * **Stage I (Analgesia):** Starts from the induction of anesthesia and lasts until the loss of consciousness. The patient experiences a reduction in pain but remains conscious and can follow commands. * **Stage II (Delirium/Excitement):** Begins with the loss of consciousness and is characterized by uninhibited movement, irregular breathing (breath-holding), and potential vomiting. This is a dangerous stage where the risk of laryngospasm is high. * **Stage III (Surgical Anesthesia):** This is the stage where most surgical procedures are performed. It is characterized by the stabilization of breathing and the loss of the lash reflex. It is further divided into four planes based on eyeball movement and pupillary size. * **Stage IV (Medullary Paralysis/Overdose):** This is an undesirable stage where severe depression of the respiratory and vasomotor centers occurs, leading to potential death without immediate support. ### **High-Yield Clinical Pearls for NEET-PG** * **Guedel’s Stages** were originally described for **Ether**. Modern intravenous agents (like Propofol) pass through Stages I and II so rapidly that these stages are often not clinically visible. * **Loss of Eyelash Reflex** is the classic clinical sign marking the transition from Stage II to Stage III. * **Stage II Management:** Always avoid stimulating the patient during Stage II to prevent laryngospasm or vomiting. * **Stage III, Plane 2** is generally considered the ideal depth for most surgical procedures.

Question 143: Which of the following is contraindicated in chronic renal failure (CRF)?

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

Explanation: **Explanation:** The primary concern when using volatile anesthetics in patients with Chronic Renal Failure (CRF) is the production of **inorganic fluoride ions** during hepatic metabolism. High levels of fluoride are nephrotoxic, causing a vasopressin-resistant polyuric state (nephrogenic diabetes insipidus). **Why Enflurane is the Correct Answer:** Enflurane undergoes significant metabolism (approx. 2.4%), releasing high concentrations of inorganic fluoride. In patients with pre-existing renal impairment, the kidney's inability to excrete these ions increases the risk of further parenchymal damage. Therefore, it is traditionally contraindicated in CRF. **Analysis of Other Options:** * **Halothane:** It is primarily associated with hepatotoxicity ("Halothane Hepatitis") rather than nephrotoxicity. It undergoes minimal metabolism to fluoride. * **Isoflurane:** It is highly stable with very low metabolism (0.2%). It produces negligible fluoride levels, making it one of the safest choices for patients with renal failure. * **Desflurane:** It has the lowest metabolism rate (0.02%) among all potent volatile agents. It is considered safe in CRF due to minimal fluoride production. **High-Yield Clinical Pearls for NEET-PG:** 1. **Sevoflurane & Compound A:** While Sevoflurane produces fluoride, the main concern in renal patients is **Compound A**, a nephrotoxic byproduct formed when Sevoflurane reacts with dry soda lime. 2. **Drug of Choice:** **Isoflurane** is often considered the volatile agent of choice in renal failure due to its cardiovascular stability and minimal metabolism. 3. **Muscle Relaxant of Choice:** **Atracurium or Cisatracurium** are preferred in CRF because they undergo **Hofmann elimination**, which is independent of renal function.

Question 144: Which of the following statements about cisatracurium, the pure cis isomer of atracurium, is FALSE?

A. It is metabolized primarily by Hoffman degradation.
B. It is cardiovascularly stable.
C. It produces more laudanosine than an equipotent dose of atracurium. (Correct Answer)
D. It has an onset and duration similar to atracurium.

Explanation: **Explanation:** Cisatracurium is the **1R-cis 1’R-cis isomer** of atracurium. It is approximately **3 to 4 times more potent** than atracurium. Because of this higher potency, a much smaller dose is required to achieve the same level of neuromuscular blockade. Consequently, the metabolic byproduct **laudanosine** is produced in significantly lower quantities (about 1/3rd to 1/5th) compared to an equipotent dose of atracurium. This makes Option C the false statement and the correct answer. **Analysis of other options:** * **Option A:** Like atracurium, cisatracurium undergoes **Hoffman degradation** (a spontaneous, non-enzymatic chemical breakdown at physiological pH and temperature). It does not rely on pseudocholinesterase or organ-based elimination, making it ideal for patients with renal or hepatic failure. * **Option B:** Unlike atracurium, cisatracurium **does not trigger histamine release**, even at high doses (up to 8x ED95). This ensures remarkable cardiovascular stability. * **Option D:** Both drugs are classified as **intermediate-acting** muscle relaxants. They share a similar onset (3–5 minutes) and clinical duration (30–45 minutes). **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Cisatracurium is the preferred NMBA for patients with **multi-organ failure** (Renal/Hepatic) due to organ-independent elimination. * **Laudanosine Toxicity:** High levels of laudanosine (seen more with atracurium) can cross the blood-brain barrier and act as a **CNS stimulant**, potentially causing seizures. * **Storage:** Cisatracurium must be **refrigerated** (2°–8°C) to maintain its potency, as it degrades at room temperature.

Question 145: What is the approximate incidence of hepatitis following halothane use?

A. 20%
B. 40%
C. 1 in 30,000 (Correct Answer)
D. 1 in 3,000

Explanation: **Explanation:** Halothane-induced hepatotoxicity is a classic pharmacological concept categorized into two types. Type I (minor) is common, characterized by a transient rise in transaminases. Type II (major) is **Halothane Hepatitis**, a rare but severe immune-mediated fulminant hepatic failure. **1. Why Option C is Correct:** Large-scale epidemiological studies (such as the National Halothane Study) established that the incidence of severe halothane hepatitis is approximately **1 in 30,000** exposures. The mechanism involves the metabolism of halothane by Cytochrome P450 to **trifluoroacetyl chloride**, which binds to hepatic proteins. In susceptible individuals, these "neo-antigens" trigger an IgG-mediated immune response, leading to massive hepatic necrosis. **2. Why Other Options are Incorrect:** * **Options A (20%) and B (40%):** These percentages are far too high for a rare idiosyncratic drug reaction. However, roughly 20% of patients may show a subclinical, transient rise in liver enzymes (Type I), which should not be confused with true hepatitis. * **Option D (1 in 3,000):** While some older studies suggested higher rates in specific high-risk populations (e.g., obese females undergoing multiple exposures), the globally accepted standard for the general population remains 1 in 30,000. **High-Yield Clinical Pearls for NEET-PG:** * **Risk Factors:** "Middle-aged, obese females" is the classic demographic. Multiple exposures within a short period (less than 28 days) significantly increase risk. * **Metabolism:** Halothane undergoes significant hepatic metabolism (~20%), much higher than Isoflurane (0.2%) or Desflurane (0.02%), explaining its higher hepatotoxic potential. * **Clinical Presentation:** Fever, jaundice, and eosinophilia typically appear 3–14 days post-exposure. * **Pediatrics:** Children are remarkably resistant to halothane hepatitis, making it historically popular in pediatric anesthesia.

Question 146: Remifentanil is:

A. A long-acting anesthetic
B. Useful for short, painful procedures (Correct Answer)
C. Administered by intravenous bolus dose
D. Metabolized by plasma esterases

Explanation: **Explanation:** Remifentanil is a unique, ultra-short-acting synthetic $\mu$-opioid receptor agonist. Its clinical profile is defined by its rapid onset and exceptionally fast offset of action. **Why Option B is Correct:** The primary clinical utility of Remifentanil lies in its **ultra-short duration of action**. It reaches a steady state quickly and, more importantly, its effects dissipate within 5–10 minutes after stopping the infusion, regardless of the duration of administration. This makes it ideal for **short, painful procedures** (e.g., retrobulbar blocks, brief endoscopic procedures) or surgeries requiring intense but transient analgesia where rapid recovery is desired. **Analysis of Incorrect Options:** * **Option A:** Remifentanil is the shortest-acting opioid available, not long-acting. * **Option C:** It is primarily administered via **continuous intravenous infusion** rather than bolus doses. Bolus administration is generally avoided because it can cause significant muscle rigidity (especially chest wall rigidity) and profound bradycardia/hypotension. * **Option D:** While it is metabolized by esterases, it is specifically metabolized by **non-specific tissue and plasma esterases**, not pseudocholinesterase (butyrylcholinesterase). This distinction is high-yield, as its metabolism remains unaffected by pseudocholinesterase deficiency. **High-Yield Clinical Pearls for NEET-PG:** * **Context-Sensitive Half-Time:** Remifentanil has a constant context-sensitive half-time of approximately **3–4 minutes**, which is independent of the infusion duration. * **Metabolism:** It contains an ester linkage that undergoes rapid hydrolysis. It is safe to use in patients with hepatic or renal failure. * **Side Effect:** Like other fentanyls, it can cause **chest wall rigidity** ("Wooden Chest Syndrome") if given too rapidly. * **Post-operative Pain:** Because it leaves the system so quickly, clinicians must plan for alternative analgesia before stopping the infusion to prevent "rebound pain."

Question 147: Arrange the following inhalational anesthetic agents according to increasing MAC values: Isoflurane, Desflurane, Sevoflurane, Halothane?

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

Explanation: **Explanation:** The core concept tested here is the relationship between **Minimum Alveolar Concentration (MAC)** and **Anesthetic Potency**. MAC is defined as the concentration of an inhalational anesthetic at 1 atmosphere that prevents skeletal muscle movement in response to a noxious stimulus in 50% of patients. Crucially, **MAC is inversely proportional to potency**: the lower the MAC value, the more potent the agent. Potency is also directly related to the **Oil:Gas partition coefficient** (Meyer-Overton Hypothesis). The standard MAC values for these agents (in 100% Oxygen) are: 1. **Halothane:** ~0.75% (Most potent) 2. **Isoflurane:** ~1.15% 3. **Sevoflurane:** ~2.0% 4. **Desflurane:** ~6.0% (Least potent) Therefore, the correct increasing order of MAC values is **Halothane < Isoflurane < Sevoflurane < Desflurane**. **Analysis of Options:** * **Option A is correct** as it follows the established potency hierarchy. * **Option B** incorrectly places Sevoflurane before Isoflurane; Isoflurane is more potent and has a lower MAC than Sevoflurane. * **Option C** starts with Desflurane, which actually has the highest MAC (lowest potency) among the four. * **Option D** is incorrect as it places Halothane as the least potent agent, whereas it is the most potent. **High-Yield Clinical Pearls for NEET-PG:** * **Nitrous Oxide (N₂O):** Has the highest MAC (~104%), making it the least potent. * **Factors increasing MAC:** Infancy (highest at 6 months), hyperthermia, hypernatremia, and chronic alcohol abuse. * **Factors decreasing MAC:** Elderly age, pregnancy, acute alcohol intoxication, hypoxia, and anemia. * **Mnemonic for Potency (Highest to Lowest):** **H**is **I**nner **S**pirit **D**ied (**H**alothane > **I**soflurane > **S**evoflurane > **D**esflurane).

Question 148: Which intravenous anesthetic agent is preferred in patients with renal failure?

A. Atracurium
B. Vivacurium
C. Pancuronium
D. Cisatracurium (Correct Answer)

Explanation: **Explanation:** The choice of anesthetic agents in renal failure depends on the drug's metabolism and excretion. In patients with end-stage renal disease (ESRD), drugs dependent on renal clearance can have a prolonged duration of action, leading to delayed recovery or toxicity. **Why Cisatracurium is the Correct Answer:** Cisatracurium (an isomer of atracurium) is the preferred neuromuscular blocking agent in renal failure because it undergoes **Hofmann elimination**. This is a spontaneous, non-enzymatic degradation that occurs at physiological pH and temperature. Because its clearance is entirely independent of renal or hepatic function, its duration of action remains predictable even in complete organ failure. **Analysis of Incorrect Options:** * **Atracurium:** While it also undergoes Hofmann elimination, it produces a metabolite called **laudanosine**. Laudanosine is excreted by the kidneys; in renal failure, it can accumulate, potentially causing CNS excitation and seizures. Cisatracurium produces significantly less laudanosine. * **Mivacurium (misspelled as Vivacurium):** It is metabolized by plasma cholinesterase. However, its clearance is decreased in renal failure, and it can cause significant histamine release. * **Pancuronium:** This is a long-acting muscle relaxant primarily excreted by the kidneys (approx. 80%). It is strictly contraindicated in renal failure as it leads to profound, prolonged neuromuscular blockade. **High-Yield Clinical Pearls for NEET-PG:** * **Hofmann Elimination:** Dependent on **Temperature and pH**. (Increased temp/pH = faster degradation; Decreased temp/pH = slower degradation). * **Drug of Choice (DOC):** Cisatracurium is the DOC for both renal and hepatic failure. * **Laudanosine Toxicity:** Always associate atracurium with laudanosine-induced seizures. * **Vecuronium/Rocuronium:** These are primarily biliary-excreted but still show slightly prolonged effects in renal failure compared to cisatracurium.

Question 149: Which is the most potent bronchodilator among the inhalational anesthetic agents?

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

Explanation: **Explanation:** The correct answer is **Halothane**. **1. Why Halothane is the correct answer:** Halothane is historically recognized as the most potent bronchodilator among volatile anesthetic agents. It acts by directly relaxing airway smooth muscle and inhibiting reflex bronchoconstriction mediated by the vagus nerve. It also decreases the release of histamine and other inflammatory mediators. Due to its superior bronchodilatory properties and non-pungent odor, it was traditionally the "gold standard" for inhalational induction in patients with reactive airway diseases like asthma or COPD. **2. Analysis of Incorrect Options:** * **Sevoflurane:** While Sevoflurane is an excellent bronchodilator and is the current drug of choice for inhalational induction (due to its low pungency and rapid onset), it is pharmacologically slightly less potent than Halothane in terms of direct smooth muscle relaxation. * **Isoflurane:** This agent possesses bronchodilatory properties but is highly pungent. This pungency can cause airway irritation, coughing, and laryngospasm during induction, making it unsuitable for patients with active bronchospasm. * **Desflurane:** This is the most pungent volatile agent. At higher concentrations, it can actually cause **bronchoconstriction** and increased airway resistance due to sympathetic stimulation and airway irritation. It is generally avoided in patients with asthma. **3. High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice for Induction in Asthma:** Sevoflurane (due to the best balance of bronchodilation and lack of irritation). * **Most Pungent/Irritant:** Desflurane > Isoflurane. * **Least Pungent:** Sevoflurane > Halothane. * **Arrhythmogenic Potential:** Halothane sensitizes the myocardium to catecholamines; therefore, it is contraindicated if exogenous adrenaline is being used.

Question 150: Which of the following colloid solutions has a proven thromboprophylactic effect?

A. Gelatin
B. Dextran 40 (Correct Answer)
C. Dextran 100
D. Hetastarch

Explanation: **Explanation:** **Dextran 40** (Low Molecular Weight Dextran) is the correct answer because it possesses unique antithrombotic properties beyond simple volume expansion. Its **thromboprophylactic effect** is mediated through several mechanisms: 1. **Decreased Platelet Adhesiveness:** It coats the surface of platelets and vascular endothelium, reducing their interaction. 2. **Alteration of Fibrin Structure:** It makes fibrin clots more susceptible to fibrinolysis (easier to break down). 3. **Reduced Blood Viscosity:** By decreasing erythrocyte aggregation (sludging), it improves microcirculatory flow, which is particularly beneficial in vascular surgeries. **Analysis of Incorrect Options:** * **Gelatin:** These are urea-linked or succinylated bovine collagens. While they have minimal effects on coagulation compared to other colloids, they do not possess active thromboprophylactic properties and are associated with a higher risk of anaphylaxis. * **Dextran 100:** Higher molecular weight dextrans are less effective for thromboprophylaxis and are more likely to cause "rouleaux formation" (interfering with blood cross-matching) compared to Dextran 40. * **Hetastarch (HES):** Hydroxyethyl starches are notorious for *causing* coagulopathy by reducing Factor VIII and von Willebrand factor levels. They are generally avoided in critically ill patients due to risks of acute kidney injury (AKI) and bleeding. **High-Yield Pearls for NEET-PG:** * **Dextran 40** is primarily used to improve microcirculation in vascular grafts and replantation surgeries. * **Side Effect:** Dextrans can cause **osmotic nephrosis** and acute renal failure if the patient is dehydrated. * **Interference:** Dextran can interfere with blood grouping and cross-matching (though less so with Dextran 40 than Dextran 70/100). * **Maximum Dose:** Limit Dextran 40 to **1.5 g/kg/day** to avoid bleeding complications.

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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