General Anesthesia Practice Questions

Q: Which of the following anesthetic agents is nephrotoxic?

Methoxyflurane. **Explanation:** **Methoxyflurane** is the correct answer because it is the most potent and lipid-soluble volatile anesthetic, but it undergoes extensive hepatic metabolism (approx. 50–70%). This metabolism releases high levels of **inorganic fluoride ions (F⁻)**. These ions interfere with the action of Antidiuretic Hormone (ADH) in the distal convoluted tubules and collecting ducts, leading to **Vasopressin-resistant high-output renal failure**. Due to this dose-related nephrotoxicity, its use as a general anesthetic has been largely abandoned. **Analysis of Incorrect Options:** * **Halothane:** Primarily known for **hepatotoxicity** ("Halothane Hepatitis") rather than nephrotoxicity. It is metabolized to trifluoroacetic acid, which can trigger an immune-mediated liver injury. * **Ether:** Historically significant but not nephrotoxic. Its main drawbacks include high flammability, slow induction, and significant post-operative nausea and vomiting (PONV). * **Cyclopropane:** An explosive gas that is not nephrotoxic. Its primary clinical concern was "Cyclopropane shock" (hypotension upon discontinuation) and sensitization of the myocardium to catecholamines, leading to arrhythmias. **High-Yield Clinical Pearls for NEET-PG:** * **Fluoride-induced Nephrotoxicity:** Methoxyflurane (highest risk) > Enflurane > Sevoflurane. * **Sevoflurane & Compound A:** Sevoflurane can react with soda lime (CO₂ absorbers) to produce **Compound A**, which is nephrotoxic in rats, though clinical significance in humans is minimal if fresh gas flows are >1-2 L/min. * **Desflurane:** Has the lowest metabolism (0.02%) and is the least likely to cause organ toxicity. * **Penthrox:** Methoxyflurane is still used in very low doses via a "Green Whistle" inhaler for emergency analgesia, where it does not reach nephrotoxic thresholds.

Q: Which of the following is NOT an intermediate-acting muscle relaxant?

Mivacurium. **Explanation:** Neuromuscular blocking agents (NMBAs) are primarily classified based on their **duration of action**. This classification is a high-yield topic for NEET-PG, as it dictates the clinical utility of the drug during surgery. **Why Mivacurium is the correct answer:** Mivacurium is a **short-acting** non-depolarizing muscle relaxant. It has a duration of action of approximately **15–20 minutes**. It is unique among non-depolarizing agents because it is metabolized by **plasma cholinesterase** (pseudocholinesterase), similar to Succinylcholine. Therefore, its action is prolonged in patients with atypical plasma cholinesterase deficiency. **Analysis of incorrect options (Intermediate-acting agents):** Intermediate-acting relaxants typically have a duration of action between **20–50 minutes**. * **Cisatracurium:** An isomer of Atracurium. It undergoes **Hofmann elimination** (organ-independent clearance), making it the drug of choice in renal or hepatic failure. * **Rocuronium:** An aminosteroid with the fastest onset of action among non-depolarizing agents, often used for Rapid Sequence Induction (RSI) when Succinylcholine is contraindicated. * **Vecuronium:** An aminosteroid with minimal cardiovascular side effects, primarily metabolized by the liver. **High-Yield Clinical Pearls for NEET-PG:** * **Ultra-short acting:** Succinylcholine (Depolarizing; 5–10 mins). * **Short-acting:** Mivacurium. * **Intermediate-acting:** Vecuronium, Rocuronium, Atracurium, Cisatracurium. * **Long-acting:** Pancuronium (Duration >50 mins). * **Hofmann Elimination:** A spontaneous non-enzymatic degradation at physiological pH and temperature (seen with Atracurium and Cisatracurium). * **Sugammadex:** Specifically reverses aminosteroids (Rocuronium > Vecuronium).

Q: A 32-year-old chronic alcoholic patient with a known case of chronic liver disease is scheduled for an emergency laparoscopic appendectomy. Which of the following inhalational anesthetic agents should be used for induction?

Desflurane. **Explanation:** The primary concern in a patient with chronic liver disease (CLD) undergoing anesthesia is the potential for drug-induced hepatotoxicity and the preservation of hepatic blood flow. **Why Desflurane is the Correct Answer:** Desflurane is the preferred inhalational agent in this scenario because it undergoes the **least amount of hepatic metabolism** (only **0.02%**). Since it is minimally metabolized by the liver, it produces the lowest concentration of trifluoroacetylated protein adducts, making the risk of "halothane-like" hepatitis virtually non-existent. Furthermore, Desflurane preserves hepatic arterial blood flow better than older agents, which is crucial in a patient with already compromised liver function. **Analysis of Incorrect Options:** * **A. Methoxyflurane:** It has the highest rate of metabolism (approx. 50%) and is notoriously nephrotoxic due to the release of inorganic fluoride ions. It is contraindicated in almost all modern surgical settings. * **B. Sevoflurane:** While commonly used, it undergoes significantly more metabolism (approx. 2–5%) than Desflurane. It also carries a theoretical risk of nephrotoxicity due to Compound A formation. * **D. Isoflurane:** Isoflurane is also relatively safe for liver patients (metabolism ~0.2%), but Desflurane remains the superior choice due to its even lower metabolic rate and faster recovery profile. **High-Yield Clinical Pearls for NEET-PG:** * **Metabolism Gradient:** Methoxyflurane (50%) > Halothane (20%) > Sevoflurane (2%) > Isoflurane (0.2%) > Desflurane (0.02%). * **Halothane Hepatitis:** Caused by the metabolite **trifluoroacetic acid**. Desflurane produces the least, while Halothane produces the most. * **Agent of Choice for CLD:** Desflurane or Isoflurane (Desflurane is preferred for its minimal metabolism). * **Emergency Laparoscopy:** Rapid emergence provided by Desflurane is beneficial for airway protection in emergency cases.

Q: Which of the following statements are true about non-depolarizing muscle relaxants?

Metabolized by pseudocholinesterase. **Explanation:** Non-depolarizing muscle relaxants (NDMRs) act as competitive antagonists at the nicotinic acetylcholine receptors (nAChR) of the neuromuscular junction. **Why Option B is Correct:** While most NDMRs are metabolized by the liver or excreted by the kidneys, specific agents like **Mivacurium** are unique because they are metabolized by **plasma pseudocholinesterase** (butyrylcholinesterase). This is a high-yield fact for NEET-PG, as patients with pseudocholinesterase deficiency will experience a prolonged block when given Mivacurium, similar to the effect seen with Succinylcholine. **Analysis of Other Options:** * **Option A:** NDMRs are **competitive antagonists**, not inhibitors. They bind to the receptor and prevent acetylcholine from binding, but they do not inhibit the neurotransmitter itself. * **Option C:** **Magnesium (Mg²⁺)** potentiates (enhances) the neuromuscular block. It inhibits the pre-junctional release of acetylcholine and decreases the sensitivity of the post-junctional membrane. Therefore, it "predisposes" or strengthens the block. * **Option D:** **Calcium (Ca²⁺)** is essential for the release of acetylcholine from the presynaptic terminal. Increasing calcium levels can help overcome the competitive blockade, thus **antagonizing** the effect of NDMRs. **High-Yield Clinical Pearls for NEET-PG:** 1. **Hofmann Elimination:** Atracurium and Cisatracurium undergo spontaneous degradation (Hofmann elimination) independent of organ function, making them the drugs of choice in liver or renal failure. 2. **Reversal:** The block is reversed using Acetylcholinesterase inhibitors (e.g., Neostigmine) or Sugammadex (specifically for Rocuronium/Vecuronium). 3. **Train-of-Four (TOF):** NDMRs typically show "fade" on TOF monitoring and post-tetanic facilitation.

Q: Which muscle is most resistant to a non-depolarizing neuromuscular block?

Diaphragm. **Explanation:** The sensitivity of muscles to non-depolarizing neuromuscular blocking agents (NMBA) varies significantly based on muscle fiber composition, blood flow, and acetylcholine receptor density. **Why the Diaphragm is the Correct Answer:** The **diaphragm** is the most resistant muscle to NMBAs. This resistance is attributed to its high density of acetylcholine receptors and its high regional blood flow, which allows for rapid delivery and equally rapid washout of the drug. Clinically, this means the diaphragm is the **last muscle to be paralyzed** and the **first to recover**. Consequently, a patient may demonstrate spontaneous respiratory efforts (bucking) even when peripheral muscles are still fully blocked. **Analysis of Incorrect Options:** * **Intercostal and Abdominal Muscles:** These are considered "intermediate" in sensitivity. They are paralyzed after the small muscles (like the adductor pollicis) but before the diaphragm. * **Adductor Muscles (e.g., Adductor Pollicis):** These peripheral muscles are highly sensitive to NMBAs. They are among the first to be paralyzed and the last to recover. This is why the adductor pollicis is the standard site for monitoring recovery using Train-of-Four (TOF) stimulation. **NEET-PG High-Yield Pearls:** 1. **Sequence of Paralysis:** Small muscles (eyes, fingers) → Extremities → Trunk (Abdominal) → Intercostals → Diaphragm. 2. **Sequence of Recovery:** Reverse of paralysis (Diaphragm recovers first). 3. **Monitoring Tip:** To monitor the **onset** of blockade (intubation readiness), the **Orbicularis Oculi** is preferred as it reflects the diaphragm's status. To monitor **recovery**, the **Adductor Pollicis** is used as it is the last to recover. 4. **Rule of Thumb:** Central muscles (diaphragm, laryngeal muscles) are resistant; peripheral muscles are sensitive.

Q: Chest wall rigidity can be caused by rapid infusion of which of the following opioids?

All of the above. **Explanation:** **Opioid-Induced Chest Wall Rigidity** (also known as "Wooden Chest Syndrome") is a well-documented phenomenon associated with the rapid intravenous administration of potent, lipophilic **synthetic opioids** (phenylpiperidines). **Mechanism:** The rigidity is primarily mediated by **mu-opioid receptors** in the central nervous system (specifically the substantia nigra and corpus striatum), which modulate GABAergic and dopaminergic pathways. This leads to intense contraction of the truncal and abdominal muscles, making bag-mask ventilation nearly impossible due to decreased thoracic compliance. **Analysis of Options:** * **Fentanyl:** The most common culprit in clinical practice due to its frequent use during induction. * **Sufentanil:** A highly potent analogue of fentanyl; it carries a significant risk of rigidity, especially at higher doses. * **Remifentanil:** Despite its ultra-short half-life, its rapid onset and high potency make it a frequent cause of chest wall rigidity if pushed quickly. Since all three are potent synthetic opioids capable of inducing this effect, **Option D (All of the above)** is correct. **Clinical Pearls for NEET-PG:** 1. **Management:** The definitive treatment is the administration of a rapid-acting **neuromuscular blocking agent** (e.g., Succinylcholine) to relax the skeletal muscles. Opioid antagonists like Naloxone can reverse it but are rarely used in the OR as they also reverse analgesia. 2. **Prevention:** Rigidity can be minimized by administering opioids slowly, using lower doses, or pre-treating with a non-depolarizing muscle relaxant (priming). 3. **Differential Diagnosis:** Must be distinguished from laryngospasm; however, in "wooden chest," the primary issue is the inability to expand the chest wall rather than a glottic obstruction.

Question 1

Minimum alveolar concentration is an indicator of?

Accepted Answer

Potency of an anesthetic

Answer

Efficacy of an anesthetic

Answer

Rate of onset of action

Answer

None of the above

Question 2

Which of the following anesthetic agents is nephrotoxic?

Accepted Answer

Methoxyflurane

Answer

Halothane

Answer

Ether

Answer

Cyclopropane

Question 3

An 18-year-old male was undergoing anesthesia for appendectomy. On administration of a muscle relaxant, a gradual fall in the blood pressure together with increased airway resistance was noticed. The airway resistance improved with the administration of diphenhydramine. Which is the most likely muscle relaxant that was administered?

Accepted Answer

d-tubocurarine

Answer

Atracurium

Answer

Pancuronium

Answer

Vecuronium

Question 4

Which of the following is NOT an intermediate-acting muscle relaxant?

Accepted Answer

Mivacurium

Answer

Cisatracurium

Answer

Rocuronium

Answer

Vecuronium

Question 5

A 32-year-old chronic alcoholic patient with a known case of chronic liver disease is scheduled for an emergency laparoscopic appendectomy. Which of the following inhalational anesthetic agents should be used for induction?

Accepted Answer

Desflurane

Answer

Methoxyflurane

Answer

Sevoflurane

Answer

Isoflurane

Question 6

Which of the following statements are true about non-depolarizing muscle relaxants?

Accepted Answer

Metabolized by pseudocholinesterase

Answer

Competitive inhibitor of acetylcholine

Answer

Mg2+ predisposes the block

Answer

Ca2+ antagonizes the block

Question 7

Which muscle is most resistant to a non-depolarizing neuromuscular block?

Accepted Answer

Diaphragm

Answer

Intercostal muscles

Answer

Abdominal muscles

Answer

Adductor muscles

Question 8

As a general anaesthetic, halothane has the following advantages EXCEPT:

Accepted Answer

Very good analgesic action

Answer

Non-inflammable and non-explosive

Answer

Reasonably rapid induction of anaesthesia

Answer

Pleasant and non-irritating

Question 9

Chest wall rigidity can be caused by rapid infusion of which of the following opioids?

Accepted Answer

All of the above

Answer

Fentanyl

Answer

Sufentanil

Answer

Remifentanil

Question 10

Which of the following statements is FALSE regarding light anesthesia?

Accepted Answer

The patient may have explicit memory of the period.

Answer

Pain may be felt during light anesthesia.

Answer

It is desirable in certain high-risk conditions.

Answer

It can lead to post-traumatic stress disorders.

General Anesthesia — MCQs

General Anesthesia — MCQs

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