General Anesthesia Practice Questions

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

Halothane, Isoflurane, Sevoflurane, Desflurane. **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).

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

Dextran 40. **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.

Q: Which of the following drugs exhibits Hoffmann elimination?

Atracurium. **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).

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

Etomidate. **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.

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

Rocuronium. **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).

Q: Which of the following agents has the highest analgesic effect?

Ketamine. **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).

Q: Ketamine is the preferred anesthetic for the following situations EXCEPT:

Hypertensive emergencies. **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).

Q: Which of the following is the most likely reason why fentanyl does not disturb cardiovascular stability as much as morphine?

It does not stimulate histamine release. **Explanation:** The primary reason **Fentanyl** maintains superior cardiovascular stability compared to **Morphine** is that it **does not stimulate histamine release**. **1. Why the Correct Answer is Right:** Morphine is known to cause non-immunologic (direct) mast cell degranulation, leading to the release of histamine. Histamine causes systemic vasodilation (decreasing systemic vascular resistance) and increases capillary permeability, which can result in significant **hypotension** and compensatory tachycardia. Fentanyl, a synthetic phenylpiperidine derivative, lacks this property. Consequently, it does not cause the vasodilation associated with histamine, making it the preferred opioid for hemodynamically unstable patients or those undergoing cardiac surgery. **2. Why Incorrect Options are Wrong:** * **A & B (Solubility):** Fentanyl is highly **lipid-soluble** (not water-soluble), which allows it to cross the blood-brain barrier rapidly. While lipid solubility dictates its rapid onset and redistribution, it is not the direct mechanism for cardiovascular stability. * **D (Duration of Action):** Fentanyl is a **short-acting** drug due to rapid redistribution, whereas Morphine has a longer duration of action. Duration does not correlate with the immediate hemodynamic profile during induction. **Clinical Pearls for NEET-PG:** * **Hemodynamic Profile:** Fentanyl is considered "cardio-stable" because it does not depress myocardial contractility or cause histamine-induced hypotension. * **Side Effect:** The most common cardiovascular side effect of high-dose Fentanyl is **bradycardia** (via central vagal stimulation), not hypotension. * **Chest Wall Rigidity:** Rapid IV bolus of Fentanyl can cause "Wooden Chest Syndrome," which may interfere with ventilation. * **Potency:** Fentanyl is approximately **100 times** more potent than Morphine.

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

Methoxyflurane. **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 1

What anesthetic maintenance strategy is ideal for a 70-year-old male undergoing a 4-6 hour surgery?

Accepted Answer

Oxygen + Air + Desflurane + Atracurium + Remifentanyl

Answer

Oxygen + Air + Isoflurane + Pancuronium + Morphine

Answer

Oxygen + Air + Sevoflurane + Pancuronium + Remifentanyl

Answer

Oxygen + Air + Halothane + Vecuronium + Morphine

Question 2

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

Accepted Answer

Halothane, Isoflurane, Sevoflurane, Desflurane

Answer

Halothane, Sevoflurane, Isoflurane, Desflurane

Answer

Desflurane, Halothane, Sevoflurane, Isoflurane

Answer

Isoflurane, Desflurane, Sevoflurane, Halothane

Question 3

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

Accepted Answer

Dextran 40

Answer

Gelatin

Answer

Dextran 100

Answer

Hetastarch

Question 4

Which of the following drugs exhibits Hoffmann elimination?

Accepted Answer

Atracurium

Answer

Gallamine

Answer

Thiopentone

Answer

Lignocaine

Question 5

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

Accepted Answer

Etomidate

Answer

Ketamine

Answer

Propofol

Answer

Opioids

Question 6

Which of the following drugs commonly causes pain on injection?

Accepted Answer

Rocuronium

Answer

Vacuronium

Answer

Rapocuronium

Answer

Atracurium

Question 7

Which of the following agents has the highest analgesic effect?

Accepted Answer

Ketamine

Answer

Thiopentone

Answer

Propofol

Answer

Etomidate

Question 8

Ketamine is the preferred anesthetic for the following situations EXCEPT:

Accepted Answer

Hypertensive emergencies

Answer

Trauma cases with significant bleeding

Answer

Burn wound debridement

Answer

Surgical operations on asthmatics

Question 9

Which of the following is the most likely reason why fentanyl does not disturb cardiovascular stability as much as morphine?

Accepted Answer

It does not stimulate histamine release

Answer

It is water soluble

Answer

It is lipid soluble

Answer

It is long acting

Question 10

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

Accepted Answer

Methoxyflurane

Answer

Nitrous Oxide (N2O)

Answer

Halothane

Answer

Desflurane

General Anesthesia — MCQs

General Anesthesia — MCQs

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