General Anesthesia Practice Questions

Q: A 40-year-old dental assistant presents with increased weakness and fatigue. Lab tests reveal megaloblastic anemia. Which of the following is most likely responsible for the presence of this anemia?

Nitrous oxide. **Explanation:** The correct answer is **Nitrous oxide (N₂O)**. The clinical presentation of megaloblastic anemia in a dental assistant—who has chronic occupational exposure to anesthetic gases—is a classic scenario for Nitrous oxide toxicity. **Mechanism of Action:** Nitrous oxide irreversibly oxidizes the cobalt atom of **Vitamin B12 (cobalamin)** from the monovalent (Co+) to the bivalent (Co++) state. This inactivation inhibits the enzyme **Methionine Synthase**, which is essential for converting homocysteine to methionine. This process is critical for DNA synthesis; its inhibition leads to impaired erythropoiesis, resulting in **megaloblastic anemia** and, in severe cases, subacute combined degeneration of the spinal cord. **Why other options are incorrect:** * **Propofol:** An intravenous sedative-hypnotic that acts via GABA-A receptors. It is associated with "Propofol Infusion Syndrome" (acidosis, rhabdomyolysis) but does not affect Vitamin B12 or DNA synthesis. * **Lignocaine:** An amide-type local anesthetic that blocks sodium channels. Toxicity typically involves CNS (seizures) and CVS (arrhythmias) effects, not hematological changes. * **Halothane:** An inhaled volatile anesthetic primarily associated with hepatotoxicity ("Halothane Hepatitis") due to the formation of trifluoroacetylated liver proteins. **High-Yield Clinical Pearls for NEET-PG:** * **Enzyme Inhibited:** Methionine Synthase. * **Occupational Hazard:** Most common in dental surgeons and operating room personnel without adequate scavenging systems. * **Bone Marrow Changes:** Acute exposure (e.g., prolonged sedation in ICU) can cause megaloblastic changes within 12–24 hours. * **Contraindication:** Avoid N₂O in patients with pre-existing Vitamin B12 deficiency or pernicious anemia.

Q: All of the following are pharmacological effects of ketamine, EXCEPT?

Severe fall in blood pressure. **Explanation:** Ketamine is a unique intravenous anesthetic agent that acts primarily as an **NMDA receptor antagonist**. It produces a state known as **"Dissociative Anesthesia,"** characterized by a functional dissociation between the thalamocortical and limbic systems. **Why Option B is the Correct Answer:** Unlike most induction agents (like propofol or thiopentone) which cause myocardial depression and vasodilation, Ketamine is a **sympathomimetic**. It inhibits the reuptake of catecholamines (norepinephrine), leading to an **increase in blood pressure (hypertension)**, heart rate, and cardiac output. Therefore, a "severe fall in blood pressure" is pharmacologically incorrect. **Analysis of Other Options:** * **A. Profound Analgesia:** Ketamine provides excellent somatic analgesia even at sub-anesthetic doses, making it ideal for short painful procedures and burn dressings. * **C. Amnesia:** While patients may appear awake (eyes open, slow nystagmic gaze), they experience significant anterograde amnesia and lack of awareness of the procedure. * **D. Increased Cerebral Blood Flow (CBF):** Ketamine is a potent cerebral vasodilator. It increases CBF, cerebral metabolic rate ($CMRO_2$), and consequently, **Intracranial Pressure (ICP)**. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** For induction in patients with **hypovolemic shock** or **bronchial asthma** (due to its bronchodilatory effects). * **Contraindications:** Head injuries (due to $\uparrow$ ICP), Hypertensive emergencies, and Ischemic heart disease. * **Side Effects:** **Emergence delirium** and hallucinations (minimized by co-administering benzodiazepines like Midazolam). * **Reflexes:** Pharyngeal and laryngeal reflexes are usually **preserved**, though the airway is not always fully protected.

Q: Which drug is not suitable for intravenous induction in patients with acute porphyria?

Thiopentone sodium. **Explanation:** The correct answer is **Thiopentone sodium**. **1. Why Thiopentone is Contraindicated:** Acute Porphyrias (such as Acute Intermittent Porphyria) are metabolic disorders characterized by a deficiency in enzymes of the heme synthesis pathway. **Thiopentone sodium** (a barbiturate) is a potent inducer of the enzyme **ALA synthetase**. By inducing this enzyme, it increases the production of porphyrin precursors (ALA and PBG), which can precipitate a life-threatening acute porphyric crisis. This crisis manifests as severe abdominal pain, neuropsychiatric symptoms, and autonomic instability. **2. Analysis of Other Options:** * **Propofol (B):** Currently considered the induction agent of choice in porphyria. While historically debated, extensive clinical use has proven it to be safe. * **Midazolam (C):** Benzodiazepines are generally considered safe for use in patients with porphyria. * **Etomidate (D):** While some sources list etomidate as potentially porphyrinogenic in animal models, it is clinically considered a safer alternative than barbiturates when hemodynamic stability is required. **3. High-Yield Clinical Pearls for NEET-PG:** * **Safe Induction Agents:** Propofol, Ketamine (usually considered safe). * **Safe Muscle Relaxants:** Succinylcholine, Vecuronium, Atracurium. * **Safe Analgesics:** Morphine, Fentanyl. * **Absolute Contraindications:** Barbiturates (Thiopentone, Methohexital), Etomidate (relative/avoid if possible), and Pentazocine. * **Management of Crisis:** The mainstay of treatment for an acute attack is **Intravenous Hematin** (which inhibits ALA synthetase via negative feedback) and high-dose glucose infusion.

Q: Which of the following opioids causes the least amount of nausea?

Alfentanil. **Explanation:** The incidence of opioid-induced nausea and vomiting (OINV) is primarily mediated by the stimulation of the **Chemoreceptor Trigger Zone (CTZ)** in the area postrema of the medulla. While all mu-opioid agonists can cause nausea, **Alfentanil** is clinically associated with the lowest incidence of emetic symptoms among the potent phenylpiperidine derivatives. **Why Alfentanil is the correct answer:** Alfentanil has a very rapid onset and a short duration of action due to its low pKa (6.5), meaning most of the drug exists in the non-ionized, lipid-soluble form at physiological pH. Studies comparing equianalgesic doses of rapid-acting opioids have consistently shown that Alfentanil triggers the CTZ less aggressively than its counterparts, making it the preferred choice when minimizing postoperative nausea is a priority. **Analysis of Incorrect Options:** * **Fentanyl:** A standard synthetic opioid used widely; however, it has a moderate to high incidence of nausea, especially when used for postoperative analgesia or as a bolus. * **Sufentanil:** 5–10 times more potent than fentanyl. Its high potency and high affinity for mu-receptors often lead to a higher incidence of nausea compared to Alfentanil. * **Remifentanil:** Despite its ultra-short duration (metabolized by plasma esterases), it is notorious for causing significant nausea and vomiting, particularly during high-dose infusions or upon emergence from anesthesia. **High-Yield Clinical Pearls for NEET-PG:** * **Potency Ratio:** Sufentanil > Fentanyl > Remifentanil > Alfentanil > Morphine. * **Context-Sensitive Half-Time:** Remifentanil is the only opioid whose context-sensitive half-time remains constant (approx. 4 mins) regardless of infusion duration. * **Drug of Choice:** Alfentanil is often preferred for short, painful procedures like **Electroconvulsive Therapy (ECT)** or retrobulbar blocks due to its rapid peak effect (1–2 mins).

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

Isoflurane. **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.

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

It is quicker.. **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.

Q: What is the most common arrhythmia associated with succinylcholine?

Sinus bradycardia. **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**.

Q: What is true about Sevoflurane?

All of the above.. **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 1

A 40-year-old dental assistant presents with increased weakness and fatigue. Lab tests reveal megaloblastic anemia. Which of the following is most likely responsible for the presence of this anemia?

Accepted Answer

Nitrous oxide

Answer

Propofol

Answer

Lignocaine

Answer

Halothane

Question 2

All of the following are pharmacological effects of ketamine, EXCEPT?

Accepted Answer

Severe fall in blood pressure

Answer

Profound analgesia

Answer

Amnesia

Answer

Increased cerebral blood flow

Question 3

Which drug is not suitable for intravenous induction in patients with acute porphyria?

Accepted Answer

Thiopentone sodium

Answer

Propofol

Answer

Midazolam

Answer

Etomidate

Question 4

Which of the following opioids causes the least amount of nausea?

Accepted Answer

Alfentanil

Answer

Fentanyl

Answer

Sufentanil

Answer

Remifentanil

Question 5

A child presents with bladder exstrophy and chronic renal failure. What is the muscle relaxant of choice to be used during surgery for exstrophy in this child?

Accepted Answer

Atracurium

Answer

Mivacurium

Answer

Pancuronium

Answer

Rocuronium

Question 6

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

Accepted Answer

Isoflurane

Answer

Halothane

Answer

Methoxyflurane

Answer

Enflurane

Question 7

Which of the following is NOT a property of propofol?

Accepted Answer

Anticonvulsant effect

Answer

Pain on injection

Answer

Increased risk of infection

Answer

No muscle relaxant property

Question 8

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

Accepted Answer

It is quicker.

Answer

It causes fewer side effects.

Answer

Blood pressure and cardiac output are better maintained.

Answer

There is less danger of airway obstruction.

Question 9

What is the most common arrhythmia associated with succinylcholine?

Accepted Answer

Sinus bradycardia

Answer

Ventricular tachycardia

Answer

Torsades de pointes

Answer

Paroxysmal atrial tachycardia

Question 10

What is true about Sevoflurane?

Accepted Answer

All of the above.

Answer

It is an isopropyl ether.

Answer

Its Minimum Alveolar Concentration (MAC) is approximately 2%.

Answer

It is suitable for use in the elderly.

General Anesthesia — MCQs

General Anesthesia — MCQs

On this page

Practice by Chapter

Want unlimited practice?