General Anesthesia — MCQs

General Anesthesia Indian Medical PG Practice Questions and MCQs

Question 31: Which muscle relaxant is excreted exclusively by the kidney?

A. Gallamine (Correct Answer)
B. Atracurium
C. Cisatracurium
D. Succinylcholine

Explanation: **Explanation:** The correct answer is **Gallamine**. This is a classic high-yield fact in anesthesiology regarding the elimination kinetics of neuromuscular blocking agents (NMBAs). **1. Why Gallamine is Correct:** Gallamine is a long-acting, non-depolarizing muscle relaxant that is unique because it is **excreted 100% unchanged by the kidneys**. Because it lacks any hepatic metabolism or biliary excretion, it is strictly contraindicated in patients with renal failure, as it would lead to profound, prolonged paralysis (recurarization). **2. Why the Other Options are Incorrect:** * **Atracurium:** It undergoes **Hofmann elimination** (spontaneous non-enzymatic degradation at physiological pH and temperature) and ester hydrolysis. It is the drug of choice in renal or hepatic failure. * **Cisatracurium:** An isomer of atracurium, it also undergoes **Hofmann elimination**. It is more potent and produces less histamine than atracurium. * **Succinylcholine:** A depolarizing muscle relaxant that is rapidly hydrolyzed by **pseudocholinesterase** (plasma cholinesterase) in the blood, not the kidneys. **3. Clinical Pearls for NEET-PG:** * **Pancuronium:** Primarily renal (80%), but has some biliary excretion. * **Vecuronium/Rocuronium:** Primarily eliminated via **biliary/hepatic** routes. * **Mnemonic for Renal Failure:** Avoid "Gallamine and Pancuronium" (Long-acting/Renal dependent). Use "Atracurium or Cisatracurium." * **Side Effect Note:** Gallamine is also known for causing significant **tachycardia** due to its strong vagolytic effect on the M2 receptors of the heart.

Question 32: Which of the following statements regarding halothane is true except?

A. It is contraindicated in patients with intracranial lesions.
B. It can cause hypotension.
C. It allows smooth and rapid loss of unconsciousness.
D. It is contraindicated in patients with bronchial asthma. (Correct Answer)

Explanation: **Explanation:** The correct answer is **D**, as Halothane is actually **indicated** (not contraindicated) in patients with bronchial asthma. **1. Why Option D is the Correct Answer (The Exception):** Halothane is a potent **bronchodilator**. It reduces airway resistance by relaxing bronchial smooth muscle and inhibiting airway reflexes. Historically, it was the agent of choice for inducing anesthesia in patients with reactive airway diseases like asthma. Therefore, stating it is contraindicated in asthma is medically incorrect. **2. Analysis of Other Options:** * **Option A (True):** Halothane is a potent cerebral vasodilator. This increases cerebral blood flow (CBF) and, consequently, **intracranial pressure (ICP)**. Therefore, it is generally avoided or used with extreme caution in patients with space-occupying intracranial lesions. * **Option B (True):** Halothane causes dose-dependent **hypotension**. This occurs primarily through direct myocardial depression (decreased cardiac output) rather than peripheral vasodilation. * **Option C (True):** Halothane has a pleasant, non-pungent odor and does not irritate the airways. This allows for a **smooth and rapid inhalation induction**, making it a classic choice for pediatric anesthesia (though largely replaced by Sevoflurane in modern practice). **NEET-PG High-Yield Pearls:** * **Halothane Hepatitis:** A rare but serious immune-mediated hepatotoxicity (more common in obese females after multiple exposures). * **Catecholamine Sensitivity:** Halothane sensitizes the myocardium to endogenous and exogenous catecholamines, increasing the risk of **ventricular arrhythmias** (especially if adrenaline is used). * **Malignant Hyperthermia:** Like all volatile anesthetics, Halothane is a known trigger. * **Blood-Gas Partition Coefficient:** 2.3 (higher than Sevoflurane/Desflurane, leading to slower recovery).

Question 33: Which of the following statements regarding the effect of inhalational agents on the neuromuscular system is true?

A. Inhalational agents relax skeletal muscle and decrease the effect of neuromuscular blocking drugs (NMBDs).
B. Inhalational agents contract skeletal muscle and potentiate the effect of NMBDs.
C. Inhalational agents directly relax skeletal muscle and potentiate the action of NMBDs. (Correct Answer)
D. Inhalational agents have no effect on the neuromuscular system.

Explanation: **Explanation:** The correct answer is **C**. Inhalational anesthetics exert a significant effect on the neuromuscular system through two primary mechanisms: they produce dose-dependent **direct skeletal muscle relaxation** and **potentiate (enhance)** the effects of neuromuscular blocking drugs (NMBDs). **1. Why Option C is correct:** Inhalational agents (like Isoflurane, Sevoflurane, and Desflurane) cause muscle relaxation by acting at multiple levels: * **Central Nervous System:** Depression of alpha and gamma motor neurons in the spinal cord. * **Neuromuscular Junction (NMJ):** They decrease the sensitivity of the post-junctional membrane to acetylcholine and increase the fluidity of the lipid matrix of the nicotinic receptor. * **Potentiation:** Because they already "prime" the NMJ and relax the muscle, they significantly reduce the required dose of both depolarizing and non-depolarizing NMBDs. **2. Why other options are incorrect:** * **Option A:** While they relax muscle, they **increase** (not decrease) the effect of NMBDs. * **Option B:** Inhalational agents do not cause contraction; they are depressants. * **Option D:** This is factually incorrect as these agents have well-documented effects on muscle tone and NMJ transmission. **High-Yield Clinical Pearls for NEET-PG:** * **Order of Potentiation:** The degree of NMBD potentiation follows the order: **Desflurane > Sevoflurane > Isoflurane > Halothane > Nitrous Oxide** (N2O has the least effect). * **Clinical Benefit:** This potentiation allows for a lower dose of NMBDs, reducing the risk of residual neuromuscular blockade postoperatively. * **Exception:** While they relax most muscles, inhalational agents (except N2O) are triggers for **Malignant Hyperthermia**, where they cause pathological muscle contraction in susceptible individuals.

Question 34: Ketamine is the preferred anesthetic agent in which of the following conditions, except?

A. Cyanotic congenital heart disease
B. Hypertension (Correct Answer)
C. Shock
D. Asthmatic patients

Explanation: **Explanation:** The correct answer is **Hypertension**. Ketamine is a unique anesthetic agent that acts as a **sympathomimetic**. It inhibits the reuptake of catecholamines (norepinephrine), leading to an increase in heart rate, cardiac output, and arterial blood pressure. Therefore, it is strictly **contraindicated** in patients with pre-existing hypertension, ischemic heart disease, or increased intracranial pressure, as it can exacerbate these conditions. **Analysis of Options:** * **Cyanotic Congenital Heart Disease (Option A):** Ketamine is preferred here because it maintains or increases Systemic Vascular Resistance (SVR). In conditions like Tetralogy of Fallot, maintaining high SVR prevents the worsening of right-to-left shunts, thereby maintaining oxygenation. * **Shock (Option C):** Due to its ability to stimulate the sympathetic nervous system, Ketamine is the induction agent of choice in hypovolemic and septic shock. It helps maintain hemodynamic stability where other agents (like Propofol) would cause dangerous hypotension. * **Asthmatic Patients (Option D):** Ketamine has potent **bronchodilatory** properties. It is the induction agent of choice for patients with active bronchospasm or reactive airway disease. **NEET-PG High-Yield Pearls:** * **Mechanism:** NMDA receptor antagonist. * **State:** Produces "Dissociative Anesthesia" (eyes remain open with a slow nystagmic gaze). * **Analgesia:** Provides excellent profound analgesia and amnesia. * **Reflexes:** Pharyngeal and laryngeal reflexes are usually maintained. * **Side Effect:** Emergence delirium (minimized by co-administration of Benzodiazepines). * **Secretions:** Increases salivation (often pre-treated with Glycopyrrolate).

Question 35: Which of the following is the best induction agent?

A. Ketamine
B. Diazepam
C. Nitrous oxide
D. Thiopentone (Correct Answer)

Explanation: **Explanation:** **Thiopentone** is historically considered the "gold standard" induction agent for general anesthesia. The primary reason it is the correct answer in this context is its **ultra-short duration of action** and **rapid onset**. Upon intravenous injection, it crosses the blood-brain barrier almost instantly (within one arm-brain circulation time, approx. 10–20 seconds). Its effect is terminated not by metabolism, but by **redistribution** from the brain to less vascular tissues like muscle and fat. **Analysis of Options:** * **Ketamine (A):** While a potent induction agent, it causes "dissociative anesthesia" and sympathetic stimulation (tachycardia/hypertension). It is the drug of choice for shocked patients but is not the general "best" or standard agent due to emergence delirium. * **Diazepam (B):** This is a benzodiazepine used primarily for premedication or sedation. It has a slow onset and prolonged recovery period, making it unsuitable for rapid induction of anesthesia. * **Nitrous Oxide (C):** This is an inhalational gas with a high MAC (104%), meaning it is a weak anesthetic. It cannot be used alone for induction as it lacks the potency to reach surgical planes of anesthesia safely. **Clinical Pearls for NEET-PG:** * **Propofol** has largely replaced Thiopentone in modern practice due to better recovery profiles (anti-emetic properties), but in classic MCQ patterns, Thiopentone remains the benchmark for "rapid induction." * **Thiopentone** is the drug of choice for **Status Epilepticus** (refractory) and provides cerebral protection by decreasing ICP and CMRO2. * **Contraindication:** It is strictly contraindicated in **Porphyria** (induces ALA synthetase). * **Complication:** Accidental intra-arterial injection causes severe vasospasm and gangrene; treatment involves Heparin, Papaverine, or Lidocaine.

Question 36: A 20-year-old patient presents for medical termination of pregnancy in a day care facility. What is the anesthetic induction agent of choice?

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

Explanation: ### Explanation The correct answer is **Propofol (Option C)**. #### Why Propofol is the Choice Propofol is the induction agent of choice for **day-care (ambulatory) surgeries** like Medical Termination of Pregnancy (MTP). Its selection is based on its unique pharmacokinetic profile: 1. **Rapid Onset and Recovery:** It has a very short distribution half-life, leading to quick awakening. 2. **Clear Head Recovery:** Unlike other agents, it is associated with minimal "hangover" effects, allowing patients to be discharged sooner. 3. **Antiemetic Properties:** It possesses intrinsic antiemetic effects, significantly reducing Postoperative Nausea and Vomiting (PONV), which is crucial for early oral intake and discharge in day-care settings. #### Why Other Options are Incorrect * **Thiopentone (A):** While it has a rapid onset, it undergoes slow metabolism and significant redistribution into fat stores, leading to a "hangover" effect and delayed psychomotor recovery. * **Ketamine (B):** It is associated with **emergence delirium**, hallucinations, and prolonged recovery. It also increases uterine tone, which is generally undesirable during an MTP. * **Diazepam (D):** This is a benzodiazepine used primarily for sedation or premedication. It has a long half-life and active metabolites, making it unsuitable as a primary induction agent for rapid-turnover day-care procedures. #### High-Yield NEET-PG Pearls * **Propofol** is also the agent of choice for **Total Intravenous Anesthesia (TIVA)** and **ECT** (due to its short duration, though it may shorten seizure duration). * **Pain on injection** is the most common side effect of Propofol (minimized by using larger veins or lidocaine). * **Egg/Soy Allergy:** Traditionally, Propofol was avoided in these patients due to its lipid emulsion, though recent guidelines suggest it is safe for most. * **MTP specific:** For MTP, Propofol provides excellent relaxation of the cervix, facilitating the procedure.

Question 37: Which is the most pungent inhalational anesthetic agent?

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

Explanation: ### Explanation The correct answer is **Desflurane**. **Why Desflurane is the correct answer:** Pungency refers to the irritating nature of an anesthetic gas on the airway mucosa. **Desflurane** is the most pungent inhalational agent currently in clinical use. When administered to an awake or lightly anesthetized patient, its high pungency triggers airway reflexes, leading to **coughing, breath-holding, and laryngospasm**. Consequently, Desflurane is strictly contraindicated for **inhalation induction**, especially in pediatric patients. **Analysis of Incorrect Options:** * **Halothane:** Known for its pleasant, sweet smell and non-irritant nature. It was historically the gold standard for smooth inhalation induction but is now rarely used due to hepatotoxicity ("Halothane Hepatitis"). * **Isoflurane:** It is pungent and can cause airway irritation, but significantly less so than Desflurane. It is generally avoided for induction but is widely used for maintenance. * **Enflurane:** While it has a mild ether-like odor and some irritant properties, its pungency does not reach the clinical significance of Desflurane. (Note: It is also associated with seizure-like EEG activity). **High-Yield Clinical Pearls for NEET-PG:** * **Agent of Choice for Induction:** **Sevoflurane** is the least pungent and most preferred agent for smooth inhalation induction. * **Boiling Point:** Desflurane has a very low boiling point (23.5°C), requiring a specialized heated vaporizer (**Tec 6**). * **Blood-Gas Partition Coefficient:** Desflurane has the lowest coefficient (0.42), leading to the fastest induction and emergence among potent volatile agents. * **Sympathetic Stimulation:** Rapid increases in Desflurane concentration can cause transient tachycardia and hypertension.

Question 38: Which intravenous anesthetic agent is associated with uncommon postoperative vomiting and allows patients to ambulate sooner compared to other anesthetic agents?

A. Ketamine
B. Enflurane
C. Propofol (Correct Answer)
D. Remifentanil

Explanation: **Explanation:** **Propofol** is the intravenous anesthetic of choice for day-care surgery due to its unique pharmacokinetic profile. It is characterized by a rapid onset and a very short duration of action because of its high lipid solubility and rapid redistribution. 1. **Anti-emetic Properties:** Unlike most other anesthetics, Propofol possesses inherent anti-emetic properties (likely due to its action on the chemoreceptor trigger zone and subcortical pathways). This significantly reduces the incidence of Postoperative Nausea and Vomiting (PONV). 2. **Early Ambulation:** Because it is rapidly metabolized by the liver and cleared from the system, patients experience a "clear-headed" recovery with minimal residual sedation, allowing them to ambulate and be discharged sooner than with other agents. **Analysis of Incorrect Options:** * **Ketamine:** Known for causing a "dissociative" state. It is associated with a high incidence of emergence delirium, hallucinations, and significant postoperative nausea, which delays discharge. * **Enflurane:** This is an inhalational (volatile) anesthetic, not an intravenous agent. Volatile agents are generally associated with a higher incidence of PONV compared to Propofol. * **Remifentanil:** While it is an ultra-short-acting opioid, it is primarily used for analgesia, not as a primary anesthetic induction agent. Furthermore, opioids are notorious for inducing nausea and vomiting. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Propofol is the drug of choice for **TIVA** (Total Intravenous Anesthesia) and **Day-care surgery**. * **Pain on Injection:** A common side effect of Propofol; can be mitigated by using larger veins or pre-treatment with Lidocaine. * **Egg/Soy Allergy:** Use caution as Propofol is formulated in a lipid emulsion containing egg lecithin and soybean oil. * **Propofol Infusion Syndrome (PRIS):** A rare but fatal complication involving metabolic acidosis, rhabdomyolysis, and cardiac failure during prolonged high-dose infusions.

Question 39: Hypertension with tachycardia is a side effect of which anesthetic agent?

A. Morphine
B. Thiopentone
C. Ketamine (Correct Answer)
D. Halothane

Explanation: **Explanation** **Ketamine** is a unique induction agent known for its **sympathomimetic** properties. Unlike most other anesthetics that cause cardiovascular depression, Ketamine stimulates the sympathetic nervous system, leading to an increase in heart rate (tachycardia), blood pressure (hypertension), and cardiac output. This occurs due to the inhibition of neuronal catecholamine reuptake and direct central sympathetic stimulation. **Why the other options are incorrect:** * **Morphine:** An opioid that typically causes **bradycardia** (via vagal stimulation) and **hypotension** (due to histamine release and peripheral vasodilation). * **Thiopentone:** A barbiturate that acts as a potent venodilator and myocardial depressant, leading to a **decrease in blood pressure**. While it may cause a compensatory (reflex) tachycardia, it does not cause hypertension. * **Halothane:** A volatile anesthetic that causes **hypotension** through direct myocardial depression. It also sensitizes the myocardium to catecholamines but is generally associated with a decrease in systemic vascular resistance. **High-Yield Clinical Pearls for NEET-PG:** * **Dissociative Anesthesia:** Ketamine produces a state where the patient appears awake (eyes open) but is unconscious and does not feel pain. * **Drug of Choice:** Ketamine is the preferred induction agent for patients in **hypovolemic shock** or those with **bronchial asthma** (due to its bronchodilatory effects). * **Contraindications:** Avoid in patients with **Ischemic Heart Disease (IHD)**, severe hypertension, or increased **Intracranial Pressure (ICP)**, as it increases cerebral blood flow and myocardial oxygen demand. * **Emergence Delirium:** A common side effect characterized by hallucinations, which can be prevented by pre-treating with **Benzodiazepines** (e.g., Midazolam).

Question 40: What is the anesthetic of choice in status asthmaticus?

A. Thiopentone
B. Ketamine (Correct Answer)
C. Ether
D. Nitrous oxide

Explanation: **Explanation:** **Ketamine** is the induction agent of choice in status asthmaticus and patients with reactive airway disease due to its potent **bronchodilatory properties**. It works through two primary mechanisms: 1. **Sympathomimetic action:** It stimulates the release of endogenous catecholamines, which act on $\beta_2$ receptors to cause bronchodilation. 2. **Direct effect:** It exerts a direct relaxant effect on the bronchial smooth muscle. **Analysis of Incorrect Options:** * **Thiopentone (Option A):** It is generally avoided in asthmatics because it can cause **histamine release**, which may trigger or worsen bronchospasm. Furthermore, it does not suppress airway reflexes as effectively as other agents. * **Ether (Option C):** While Ether is a potent bronchodilator, it is an **irritant to the respiratory mucosa**, leading to increased secretions and a high risk of laryngospasm during induction. It is also obsolete in modern practice due to its flammability. * **Nitrous Oxide (Option D):** $N_2O$ is an inert gas with no significant effect on bronchial smooth muscle tone. It is not used as a primary treatment or induction agent for status asthmaticus. **High-Yield Clinical Pearls for NEET-PG:** * **Halothane** is the most potent bronchodilator among volatile anesthetics but sensitizes the myocardium to catecholamines. **Sevoflurane** is currently the preferred volatile agent for mask induction in asthmatics due to its non-pungency and bronchodilatory effects. * **Propofol** is also safe in asthmatics as it effectively suppresses airway reflexes, though it lacks the profound sympathomimetic bronchodilation of Ketamine. * **Avoid Morphine** in asthmatics due to histamine release; **Fentanyl** is a safer opioid alternative.

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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