General Anesthesia Practice Questions

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.

Q: The clinical use of which of the following drugs has been discontinued due to its association with severe bronchospasm?

Rapacuronium. **Explanation:** **Rapacuronium (Option A)** is the correct answer. It was introduced as a non-depolarizing neuromuscular blocking agent (NMBA) with a rapid onset and short duration, intended to be an alternative to Succinylcholine. However, it was voluntarily withdrawn from the market worldwide in 2001 shortly after its release. The primary reason was its association with an unacceptably high incidence of **severe, life-threatening bronchospasm**, particularly in pediatric patients. The underlying mechanism is attributed to its potent **antimuscarinic effects at M2 receptors** (which normally inhibit acetylcholine release), leading to an unchecked release of acetylcholine and subsequent stimulation of M3 receptors on bronchial smooth muscle. **Why other options are incorrect:** * **Rocuronium (Option B):** Currently the most widely used rapid-onset NMBA. It does not cause significant histamine release or bronchospasm and is considered safe for asthmatic patients. * **Atracurium (Option C):** Known for causing **histamine release**, which can lead to mild bronchoconstriction, flushing, and hypotension, but it is not discontinued and remains in clinical use (metabolized by Hofmann elimination). * **Mivacurium (Option D):** A short-acting benzylisoquinolinium that also triggers histamine release. While it should be used cautiously in patients with reactive airways, it has not been discontinued. **High-Yield Clinical Pearls for NEET-PG:** * **Rapacuronium:** Remember the "Rapid" onset but "Fatal" bronchospasm. * **M2 vs. M3:** Bronchospasm in Rapacuronium is due to **M2 blockade** (presynaptic) leading to increased ACh. * **Drug of Choice for RSI:** Rocuronium is the preferred non-depolarizing agent for Rapid Sequence Induction (RSI) when Succinylcholine is contraindicated. * **Histamine Releasers:** Atracurium, Mivacurium, and Tubocurarine (the "curium/curarine" group) are the classic histamine releasers in anesthesia.

Q: What is considered the ideal colloidal solution?

Albumin. **Explanation:** The "ideal" colloid is defined as a solution that provides effective volume expansion, remains in the intravascular space for a predictable duration, and has a superior safety profile with minimal side effects. **Why Albumin is the Correct Answer:** Albumin (specifically the 5% or 25% concentration) is considered the **gold standard or "ideal" colloid** because it is a naturally occurring plasma protein. It accounts for 70–80% of the normal plasma oncotic pressure. It is non-antigenic (when human-derived), does not interfere with blood grouping or coagulation, and carries no risk of nephrotoxicity. Furthermore, it possesses antioxidant and anti-inflammatory properties, making it physiologically superior to synthetic alternatives. **Analysis of Incorrect Options:** * **Dextran:** Associated with a high risk of anaphylaxis, interference with blood cross-matching, and impairment of platelet aggregation (increased bleeding). * **Plasma (FFP):** While natural, it is not used as a primary volume expander due to the risk of transfusion-transmitted infections (TTIs), TRALI (Transfusion-Related Acute Lung Injury), and the need for ABO compatibility. * **Hydroxyethyl Starch (HES):** Synthetic colloids like HES are associated with dose-dependent coagulopathy and significant risk of acute kidney injury (AKI), leading to "black box" warnings in critically ill patients. **NEET-PG High-Yield Pearls:** * **Intravascular Half-life:** Albumin remains in the circulation for approximately 16 hours in healthy individuals. * **Colloid vs. Crystalloid:** Colloids have a smaller volume of distribution (intravascular only) compared to crystalloids, requiring less volume (1:1 ratio) for resuscitation. * **SAFE Study:** This landmark trial proved that albumin is as safe as saline for fluid resuscitation, except in patients with Traumatic Brain Injury (TBI), where it may increase mortality.

Question 1

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

Accepted Answer

Thiopentone sodium

Answer

Propofol

Answer

Midazolam

Answer

Etomidate

Question 2

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

Accepted Answer

Alfentanil

Answer

Fentanyl

Answer

Sufentanil

Answer

Remifentanil

Question 3

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 4

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

Accepted Answer

Isoflurane

Answer

Halothane

Answer

Methoxyflurane

Answer

Enflurane

Question 5

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 6

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 7

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 8

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.

Question 9

The clinical use of which of the following drugs has been discontinued due to its association with severe bronchospasm?

Accepted Answer

Rapacuronium

Answer

Rocuronium

Answer

Atracurium

Answer

Mivacurium

Question 10

What is considered the ideal colloidal solution?

Accepted Answer

Albumin

Answer

Dextran

Answer

Plasma

Answer

Hydroxyethyl starch

General Anesthesia — MCQs

General Anesthesia — MCQs

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