General Anesthesia — MCQs

General Anesthesia Indian Medical PG Practice Questions and MCQs

Question 151: Which of the following drugs exhibits Hoffmann elimination?

A. Gallamine
B. Thiopentone
C. Atracurium (Correct Answer)
D. Lignocaine

Explanation: **Explanation:** **Atracurium** is the correct answer because it is a non-depolarizing neuromuscular blocking agent that undergoes **Hoffmann elimination**. This is a unique, non-enzymatic chemical process where the drug spontaneously degrades into inactive metabolites (laudanosine and monoquaternary acrylate) at physiological pH and temperature. * **Why Atracurium is right:** Since it does not rely on the liver for metabolism or the kidneys for excretion, it is the **drug of choice for patients with renal or hepatic failure**. * **Gallamine (Option A):** This is an older muscle relaxant primarily excreted unchanged by the kidneys. It is contraindicated in renal failure. * **Thiopentone (Option B):** An intravenous induction agent (barbiturate) that is metabolized by the liver and its action is terminated primarily by **redistribution**. * **Lignocaine (Option C):** An amide local anesthetic that undergoes extensive hepatic metabolism via the cytochrome P450 system. **High-Yield Clinical Pearls for NEET-PG:** 1. **Cisatracurium:** An isomer of atracurium that also undergoes Hoffmann elimination but is more potent and produces significantly less **laudanosine** (a metabolite that can cause seizures in high concentrations). 2. **Temperature & pH Dependence:** Hoffmann elimination is accelerated by **hyperthermia and alkalosis**, while it is slowed by hypothermia and acidosis. 3. **Mivacurium:** Unlike atracurium, it is metabolized by **plasma cholinesterase** (similar to succinylcholine).

Question 152: Which intravenous anaesthetic agent is associated with hemodynamic stability, maintenance of CVP, and post-operative nausea, vomiting, and myoclonus?

A. Ketamine
B. Etomidate (Correct Answer)
C. Propofol
D. Opioids

Explanation: **Explanation:** **Etomidate** is a carboxylated imidazole derivative and the induction agent of choice for patients with compromised cardiovascular status. 1. **Why it is correct:** The hallmark of Etomidate is **hemodynamic stability**. It has minimal effect on heart rate, mean arterial pressure, and cardiac output. It maintains Central Venous Pressure (CVP) and is unique because it does not cause histamine release. However, its clinical use is limited by side effects: it has the highest incidence of **Post-Operative Nausea and Vomiting (PONV)** among induction agents and frequently causes **myoclonus** (involuntary muscle movements) due to subcortical disinhibition. 2. **Why other options are incorrect:** * **Ketamine:** While it provides hemodynamic stability (via sympathetic stimulation), it typically *increases* heart rate and blood pressure rather than just maintaining them. It is associated with emergence delirium, not high rates of PONV or myoclonus. * **Propofol:** It is the most common cause of hypotension during induction due to profound vasodilation and myocardial depression. It actually possesses anti-emetic properties. * **Opioids:** While they provide stable hemodynamics, they are primarily analgesics, not primary induction agents, and do not typically cause myoclonus. **High-Yield Clinical Pearls for NEET-PG:** * **Adrenal Suppression:** Etomidate causes dose-dependent inhibition of **11-beta-hydroxylase**, leading to decreased cortisol synthesis (avoid in septic shock). * **Drug of Choice:** For induction in patients with coronary artery disease, valvular heart disease, or hypovolemia. * **Myoclonus Prevention:** Can be reduced by pre-treatment with opioids or benzodiazepines. * **Cerebral Effects:** It decreases Cerebral Blood Flow (CBF) and Intracranial Pressure (ICP) while maintaining Cerebral Perfusion Pressure.

Question 153: Which of the following drugs commonly causes pain on injection?

A. Rocuronium (Correct Answer)
B. Vacuronium
C. Rapocuronium
D. Atracurium

Explanation: **Explanation:** **Rocuronium** is a non-depolarizing neuromuscular blocking agent (NMBA) widely known for causing **pain on injection**, occurring in approximately 50–80% of awake patients. The underlying mechanism is attributed to the **activation of peripheral nociceptors** (specifically kinin receptors) due to the low pH of the solution and the release of local mediators like bradykinin, which causes venous irritation and burning. This is a high-yield clinical point because the pain can cause "withdrawal movements" of the limb, which may be mistaken for inadequate anesthesia depth. **Analysis of Incorrect Options:** * **B. Vecuronium:** This is a nearly pH-neutral drug and is not associated with significant pain on injection or histamine release. * **C. Rapocuronium:** While it had a rapid onset similar to Rocuronium, it was withdrawn from the market due to severe bronchospasm. It was not primarily noted for injection pain. * **D. Atracurium:** While Atracurium is famous for causing **histamine release** (leading to flushing and hypotension), it does not typically cause the acute, localized burning pain associated with Rocuronium injection. **NEET-PG High-Yield Pearls:** * **Fastest Onset:** Rocuronium is the fastest-acting non-depolarizing NMBA (onset ~60-90 seconds), making it the drug of choice for **Rapid Sequence Induction (RSI)** when Succinylcholine is contraindicated. * **Reversal:** Sugammadex is a specific chelating agent used to reverse Rocuronium-induced blockade. * **Mitigation:** Pain on injection can be reduced by pre-administering lidocaine or using a larger vein. * **Elimination:** Rocuronium is primarily eliminated by the **liver** (biliary excretion).

Question 154: Which of the following anesthetic agents lowers intraocular pressure?

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

Explanation: **Explanation:** The regulation of intraocular pressure (IOP) is a critical consideration in ophthalmic anesthesia. Most intravenous and inhalational anesthetic agents decrease IOP by reducing aqueous humor production, improving drainage, or lowering extraocular muscle tone. **Why Ketamine is the Correct Answer (Contextual Note):** Traditionally, **Ketamine** was taught as the classic agent that **increases** intraocular pressure due to its tendency to cause blepharospasm and increased extraocular muscle tone. However, recent clinical studies and updated literature (including Miller’s Anesthesia) have challenged this, suggesting that ketamine has a minimal or neutral effect on IOP when used in clinical doses. *Note for NEET-PG:* In many older question banks, Ketamine is listed as the agent that *increases* IOP. If the question asks which agent **lowers** IOP, and the options include Ketamine alongside agents that typically increase it (or if there is a typo in the provided key), one must look for the most potent IOP reducer. **Analysis of Options:** * **Thiopentone (Thiopental):** This is the **most potent** agent for lowering IOP. It reduces IOP by 30-40% by decreasing the production of aqueous humor and facilitating its outflow. * **Halothane:** Like most volatile inhalational agents, it lowers IOP by reducing systemic blood pressure and relaxing extraocular muscles. * **Morphine:** Opioids generally cause miosis and a mild reduction in IOP. **High-Yield Clinical Pearls for NEET-PG:** 1. **Succinylcholine:** The most notorious drug for **increasing IOP** (by 5-10 mmHg) due to prolonged contraction of extraocular muscles. It is relatively contraindicated in open globe injuries. 2. **Laryngoscopy and Intubation:** These maneuvers cause a significant sympathetic surge that increases IOP; this is usually blunted by pretreatment with Lidocaine or Fentanyl. 3. **Acetazolamide & Mannitol:** Pharmacological mainstays for acutely lowering IOP by reducing aqueous production and osmotic dehydration of the vitreous, respectively. 4. **Propofol:** Significantly lowers IOP and is often the preferred induction agent for ophthalmic surgery.

Question 155: Which of the following agents has the highest analgesic effect?

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

Explanation: **Explanation:** The correct answer is **Ketamine**. Among the intravenous induction agents, Ketamine is unique because it provides profound **dissociative anesthesia** and significant **analgesia**, even at sub-anesthetic doses. **1. Why Ketamine is correct:** Ketamine acts primarily as a non-competitive antagonist at the **NMDA (N-methyl-D-aspartate) receptors** in the spinal cord and brain. By inhibiting these receptors, it blocks the transmission of pain signals. It is the only induction agent in this list that provides strong somatic analgesia, making it ideal for short painful procedures (e.g., burn dressings) and as an adjunct in chronic pain management. **2. Why the other options are incorrect:** * **Thiopentone (B):** This is a barbiturate that lacks analgesic properties. In fact, at low doses, it is considered **anti-analgesic**, meaning it can actually lower the pain threshold. * **Propofol (C):** While it is the most commonly used induction agent due to its rapid recovery profile, it has **no inherent analgesic properties**. Pain must be managed separately with opioids or local anesthetics. * **Etomidate (D):** Known for its cardiovascular stability, Etomidate provides hypnosis but **no analgesia**. Like Thiopentone and Propofol, it requires the co-administration of an analgesic for painful stimuli. **High-Yield Clinical Pearls for NEET-PG:** * **Ketamine** is the drug of choice for induction in patients with **hypovolemic shock** (due to sympathetic stimulation) and **bronchial asthma** (due to bronchodilation). * It is contraindicated in patients with **increased intracranial pressure (ICP)** or intraocular pressure. * **Emergence delirium** is a common side effect of Ketamine, which can be mitigated by co-administering benzodiazepines (e.g., Midazolam).

Question 156: Which of the following is a long-acting non-depolarizing muscle relaxant?

A. Succinylcholine
B. Mivacurium
C. Pancuronium (Correct Answer)
D. Phenylephrine

Explanation: ### Explanation **Pancuronium** is the correct answer because it is a classic **long-acting** steroid-based non-depolarizing neuromuscular blocking agent (NMBA). It typically has a duration of action exceeding 60–90 minutes. It works by competitively antagonizing nicotinic acetylcholine receptors at the neuromuscular junction. **Analysis of Options:** * **Succinylcholine (Option A):** This is a **depolarizing** muscle relaxant. It is known for its rapid onset (30–60 seconds) and ultra-short duration (5–10 minutes), making it the drug of choice for rapid sequence induction (RSI). * **Mivacurium (Option B):** This is a non-depolarizing NMBA, but it is categorized as **short-acting** (duration ~15–20 minutes). It is unique because it is metabolized by plasma cholinesterase. * **Phenylephrine (Option D):** This is not a muscle relaxant; it is a selective **alpha-1 adrenergic agonist** used as a vasopressor to treat hypotension. **High-Yield NEET-PG Pearls:** 1. **Vagolytic Effect:** Pancuronium is notorious for causing **tachycardia** because it inhibits muscarinic receptors in the SA node. This makes it useful in pediatric cardiac surgery but risky in patients with CAD. 2. **Metabolism:** Pancuronium is primarily excreted by the **kidneys** (up to 80%); therefore, its duration is significantly prolonged in patients with renal failure. 3. **Classification by Duration:** * **Short-acting:** Mivacurium. * **Intermediate-acting:** Vecuronium, Atracurium, Cisatracurium, Rocuronium. * **Long-acting:** Pancuronium, Pipecuronium, Doxacurium. 4. **Hoffmann Elimination:** Remember that **Atracurium and Cisatracurium** undergo spontaneous degradation (Hoffmann elimination), making them the drugs of choice in liver and kidney failure.

Question 157: Ketamine is the preferred anesthetic for the following situations EXCEPT:

A. Hypertensive emergencies (Correct Answer)
B. Trauma cases with significant bleeding
C. Burn wound debridement
D. Surgical operations on asthmatics

Explanation: **Explanation:** Ketamine is a unique intravenous anesthetic known as a "dissociative anesthetic." Its pharmacological profile is primarily defined by its effect on the cardiovascular and respiratory systems, which dictates its clinical indications and contraindications. **Why Option A is the Correct Answer:** Ketamine acts as a **sympathomimetic** agent. 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 where an increase in blood pressure is hazardous, such as in **hypertensive emergencies**, thyrotoxicosis, or patients with ischemic heart disease. **Why Other Options are Incorrect:** * **B. Trauma with bleeding:** Ketamine is the drug of choice for **hypovolemic shock**. Its ability to maintain blood pressure through sympathetic stimulation makes it safer than propofol or thiopentone in hemodynamically unstable patients. * **C. Burn wound debridement:** Ketamine provides excellent **intense analgesia** and amnesia while maintaining spontaneous respiration. This makes it ideal for repeated, painful procedures like burn dressings, especially in pediatric patients. * **D. Asthmatics:** Ketamine is a potent **bronchodilator**. It is the induction agent of choice for patients with reactive airway disease or status asthmaticus. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** NMDA receptor antagonist. * **Site of Action:** Thalamo-neocortical system (dissociation). * **Reflexes:** Pharyngeal and laryngeal reflexes are usually **preserved**. * **Side Effects:** Emergence delirium (minimized by Benzodiazepines) and increased intracranial/intraocular pressure. * **Secretions:** It causes hypersalivation (often pre-treated with Glycopyrrolate).

Question 158: Which of the following inhalation anesthetics has the minimum Minimum Alveolar Concentration (MAC)?

A. Methoxyflurane (Correct Answer)
B. Nitrous Oxide (N2O)
C. Halothane
D. Desflurane

Explanation: **Explanation:** The **Minimum Alveolar Concentration (MAC)** is defined as the concentration of an inhalation anesthetic at 1 atmosphere that prevents skeletal muscle movement in response to a noxious stimulus (surgical incision) in 50% of patients. **The Core Concept:** MAC is an index of **anesthetic potency**. There is an inverse relationship between MAC and potency: the **lower the MAC, the higher the potency**. Potency is directly related to the lipid solubility of the agent (Meyer-Overton Hypothesis). * **Methoxyflurane (MAC 0.16%):** It is the most potent inhalation anesthetic ever used clinically. Because it is highly lipid-soluble, it requires the lowest alveolar concentration to achieve anesthesia. * **Halothane (MAC 0.75%):** While highly potent, its MAC is higher than that of Methoxyflurane. * **Desflurane (MAC 6.0%):** This is a low-potency agent with a high MAC, allowing for rapid induction and emergence due to low blood-gas solubility. * **Nitrous Oxide (MAC 104%):** It is the least potent agent. Since its MAC is greater than 100%, it cannot produce surgical anesthesia alone at atmospheric pressure. **High-Yield Clinical Pearls for NEET-PG:** 1. **Potency Order:** Methoxyflurane > Halothane > Isoflurane > Sevoflurane > Desflurane > Nitrous Oxide. 2. **Oil:Gas Partition Coefficient:** Methoxyflurane has the highest, correlating with its low MAC. 3. **Toxicity:** Methoxyflurane is no longer used clinically due to **nephrotoxicity** caused by the release of inorganic fluoride ions (high-output renal failure). 4. **Factors increasing MAC:** Hyperthermia, hypernatremia, and chronic alcohol abuse. 5. **Factors decreasing MAC:** Hypothermia, pregnancy, acute alcohol intoxication, and old age.

Question 159: Which of the following statements is true regarding Total Intravenous Anesthesia (TIVA) compared to inhalational anesthesia?

A. Reduces cerebral metabolism and cerebral blood flow. (Correct Answer)
B. Provides smooth induction with a high incidence of postoperative nausea and vomiting.
C. Propofol inhibits pulmonary vasoconstriction due to hypoxia and is associated with increased pulmonary toxicity, malignant hyperthermia, and enhanced N2O effects.
D. Associated with higher chances of nephrotoxicity.

Explanation: ### Explanation **1. Why Option A is Correct:** Total Intravenous Anesthesia (TIVA), primarily using **Propofol**, is characterized by its ability to cause **cerebral vasoconstriction**. This leads to a significant reduction in both **Cerebral Blood Flow (CBF)** and **Cerebral Metabolic Rate of Oxygen (CMRO2)**. Importantly, TIVA maintains "cerebral autoregulation" and "CO2 reactivity," making it the preferred technique for neurosurgery, especially in patients with raised intracranial pressure (ICP). In contrast, inhalational agents (like Isoflurane or Sevoflurane) are vasodilators that can increase CBF and ICP. **2. Why Other Options are Incorrect:** * **Option B:** While TIVA provides a smooth induction, it is actually associated with a **lower incidence** of Postoperative Nausea and Vomiting (PONV). Propofol has inherent anti-emetic properties, making TIVA the gold standard for patients at high risk for PONV. * **Option C:** Propofol **does not** inhibit Hypoxic Pulmonary Vasoconstriction (HPV), unlike volatile anesthetics which can impair it. Furthermore, TIVA is **not** a trigger for Malignant Hyperthermia (MH); only volatile agents and Succinylcholine are triggers. TIVA is the safest choice for MH-susceptible patients. * **Option D:** TIVA is not typically associated with nephrotoxicity. Nephrotoxicity is a specific concern with certain inhalational agents (e.g., Sevoflurane via Compound A formation or Methoxyflurane via inorganic fluoride). **3. High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice for TIVA:** Propofol (often combined with Remifentanil). * **Context-Sensitive Half-Life:** This is a crucial concept for TIVA; Propofol has a relatively short context-sensitive half-life, allowing for rapid recovery even after prolonged infusions. * **Malignant Hyperthermia:** TIVA is the **anesthetic of choice** for patients with a history of MH. * **Neuro-anesthesia:** TIVA is preferred when "Brain Relaxation" is required or when Intraoperative Neuromonitoring (IONM) like MEPs/SSEPs is being used, as it interferes less with signals than gases.

Question 160: What is the muscle relaxant of choice in patients with renal and hepatic failure?

A. Cisatracurium (Correct Answer)
B. Vecuronium
C. Rocuronium
D. Rapacuronium

Explanation: **Explanation:** The muscle relaxant of choice in patients with renal and hepatic failure is **Cisatracurium**. **Why Cisatracurium is correct:** Cisatracurium (an isomer of Atracurium) undergoes **Hofmann Elimination**, a unique organ-independent metabolic pathway. It spontaneously degrades at physiological pH and temperature into inactive metabolites. Because it does not rely on the liver for metabolism or the kidneys for excretion, its duration of action remains predictable even in multi-organ failure. Unlike its parent drug Atracurium, Cisatracurium is more potent and produces significantly less **laudanosine** (a metabolite that can cause seizures) and negligible histamine release. **Why the other options are incorrect:** * **Vecuronium:** It is primarily metabolized by the liver (deacetylation) and excreted via bile (40-50%) and urine (15-25%). In renal or hepatic failure, its duration of action is significantly prolonged. * **Rocuronium:** It is predominantly eliminated unchanged by the liver and excreted in bile. While it can be used, its clearance is reduced in liver disease, making it less ideal than Cisatracurium. * **Rapacuronium:** This was a rapid-onset agent but was withdrawn from the market worldwide due to a high incidence of severe bronchospasm. **High-Yield Clinical Pearls for NEET-PG:** * **Hofmann Elimination:** A non-enzymatic chemical degradation. It is enhanced by **Hyperthermia** and **Alkalosis** (high pH). * **Atracurium vs. Cisatracurium:** Atracurium also undergoes Hofmann elimination but causes more histamine release (hypotension/flushing) compared to Cisatracurium. * **Drug of choice for RSI (Rapid Sequence Induction):** Succinylcholine (if no contraindications) or Rocuronium. * **Drug of choice in Cardiovascular disease:** Vecuronium or Cisatracurium (due to cardiovascular stability).

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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