General Anesthesia Practice Questions

Q: Dexmedetomidine is:

An agent of choice for conscious sedation. **Explanation:** **Dexmedetomidine** is a highly selective **alpha-2 ($\alpha_2$) adrenergic agonist**. It is considered an agent of choice for **conscious sedation** (procedural sedation) because it provides "cooperative sedation"—patients appear to be in a sleep-like state but are easily rousable and can follow commands without significant respiratory depression. * **Why Option B is correct:** Its unique ability to produce sedation via the *locus coeruleus* and analgesia via the spinal cord, while sparing the respiratory drive, makes it ideal for fiberoptic intubation and ICU sedation. * **Why Option A is incorrect:** Dexmedetomidine is an **agonist**, not an antagonist. It stimulates $\alpha_2$ receptors to inhibit the release of norepinephrine. * **Why Option C is incorrect:** Dexmedetomidine is **8 times more selective** for $\alpha_2$ receptors than clonidine ($\alpha_2:\alpha_1$ ratio of 1600:1 for dexmedetomidine vs. 200:1 for clonidine). * **Why Option D is incorrect:** While it has opioid-sparing effects and provides mild visceral analgesia, it is **not** classified as a "good" or potent analgesic on its own compared to opioids or NSAIDs. Its primary clinical utility is sedation. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Selective $\alpha_2$ agonist acting on the **Locus Coeruleus** (sedation) and **Dorsal Horn** of the spinal cord (analgesia). * **Side Effects:** Most common are **Bradycardia** and **Hypotension** (due to decreased sympathetic outflow). * **Key Advantage:** Does not cause respiratory depression (unlike propofol or midazolam). * **Uses:** Awake fiberoptic intubation, ICU weaning, and pediatric procedural sedation.

Q: Which of the following drugs is contraindicated in a patient with myasthenia gravis?

Tubocurare. **Explanation:** The primary pathology in **Myasthenia Gravis (MG)** is the autoimmune destruction of postsynaptic nicotinic acetylcholine receptors (nAChR) at the neuromuscular junction. This leads to a significant reduction in available receptors. **Why Tubocurare is the Correct Answer:** Patients with MG are **exquisitely sensitive** to **Non-Depolarizing Neuromuscular Blocking Agents (NDNMBAs)** like Tubocurare, Vecuronium, or Atracurium. Because they have fewer functional receptors, even a small dose of a competitive antagonist can cause profound, prolonged, and potentially irreversible respiratory paralysis. Therefore, these drugs are generally contraindicated or must be used in drastically reduced doses (1/10th of the normal dose) with extreme caution. **Analysis of Incorrect Options:** * **A. Succinylcholine:** While patients with MG are often **resistant** to Succinylcholine (requiring higher doses to achieve blockade), it is not strictly contraindicated. However, its use is generally avoided if possible due to unpredictable responses. * **C. Pyridostigmine:** This is an acetylcholinesterase inhibitor and is the **first-line treatment** for MG. It increases the availability of acetylcholine at the synapse to improve muscle strength. * **D. Halothane:** While volatile anesthetics can have some muscle relaxant properties, they are not contraindicated and are often used as part of a "gas induction" technique to avoid the need for NMBAs entirely. **High-Yield Clinical Pearls for NEET-PG:** * **Sensitivity Rule:** MG patients are **Sensitive** to Non-depolarizers (NDNMBAs) but **Resistant** to Depolarizers (Succinylcholine). * **Eaton-Lambert Syndrome:** Unlike MG, these patients are **sensitive to both** depolarizers and non-depolarizers. * **Postoperative Care:** The most critical concern in MG patients post-surgery is **respiratory failure**; many require postoperative mechanical ventilation (Osserman criteria).

Q: What is true about Ringer's Lactate?

Isotonic. **Explanation:** Ringer’s Lactate (RL) is a balanced salt solution and the most commonly used **isotonic crystalloid** in perioperative care. It is considered isotonic because its osmolarity (approx. 273 mOsm/L) is close to that of human plasma (285–295 mOsm/L), ensuring minimal fluid shifts between intracellular and extracellular compartments. **Analysis of Options:** * **A (Correct):** RL is an **isotonic crystalloid**. While slightly hypotonic compared to plasma, it is clinically classified as isotonic and is the fluid of choice for major surgery and trauma. * **B (Incorrect):** RL is a **crystalloid**, containing low-molecular-weight salts that freely cross the capillary membrane. Colloids (e.g., Albumin, Hetastarch) contain large molecules that remain in the intravascular space. * **C (Incorrect):** The potassium concentration in RL is **4 mEq/L**, whereas the normal range for serum potassium is **3.5–5.5 mEq/L**. While similar, it is not "the same," and RL should be used cautiously in patients with renal failure or hyperkalemia. * **D (Incorrect):** RL helps in acidosis not by direct neutralization, but through **metabolic conversion**. The sodium lactate in RL is metabolized by the **liver** into bicarbonate, which then buffers the acidosis. **High-Yield NEET-PG Pearls:** * **Composition:** Na⁺ (130), Cl⁻ (109), K⁺ (4), Ca²⁺ (3), and Lactate (28) mEq/L. * **Hartmann’s Solution:** Another name for Ringer’s Lactate. * **Contraindication:** Do not co-administer with **blood transfusions** in the same IV line; the calcium in RL can bind with the citrate anticoagulant in blood bags, leading to clot formation. * **Fluid of Choice:** For replacement of extracellular fluid losses, burns, and intraoperative maintenance.

Q: Which of the following statements regarding inhalation anesthetic agents is incorrect?

Sevoflurane is more potent than isoflurane.. To answer this question correctly, one must understand the relationship between **MAC (Minimum Alveolar Concentration)** and **Potency**. ### 1. Why Option A is the Correct (Incorrect Statement) Potency is inversely proportional to MAC ($Potency \propto 1/MAC$). A drug with a lower MAC value is more potent because it requires a lower concentration to achieve the same clinical effect (immobility in 50% of patients). * **MAC of Isoflurane:** ~1.15% * **MAC of Sevoflurane:** ~2.0% Since Isoflurane has a lower MAC, it is **more potent** than Sevoflurane. Therefore, the statement "Sevoflurane is more potent than isoflurane" is false. ### 2. Analysis of Other Options * **Option B:** Sevoflurane is indeed less cardiodepressant and less likely to cause tachycardia compared to Isoflurane, making it safer for patients with coronary artery disease. * **Option C:** Desflurane has a blood-gas partition coefficient of **0.42**, while Sevoflurane is **0.65**. A lower coefficient means Desflurane is less soluble in blood, leading to faster induction and emergence. * **Option D:** As noted above, Sevoflurane (MAC 2.0%) has a higher MAC than Isoflurane (MAC 1.15%). ### 3. High-Yield Clinical Pearls for NEET-PG * **Oil-Gas Partition Coefficient:** Directly proportional to potency (Meyer-Overton Hypothesis). * **Blood-Gas Partition Coefficient:** Inversely proportional to the speed of induction/recovery. * **Order of Potency:** Halothane > Isoflurane > Sevoflurane > Desflurane > $N_2O$. * **Order of Speed of Induction:** Desflurane > Sevoflurane > Isoflurane > Halothane. * **Agent of Choice for Induction:** Sevoflurane (non-pungent, pleasant odor). * **Pungent Agents:** Desflurane and Isoflurane (can cause breath-holding/laryngospasm).

Q: An alcoholic patient with a history of diabetic nephropathy and liver failure is scheduled for open abdominal surgery. Which muscle relaxant is most appropriate for this patient?

Cisatracurium. ### Explanation The correct answer is **Cisatracurium**. **Why Cisatracurium is the drug of choice:** The patient presents with a combination of **liver failure** and **diabetic nephropathy** (renal failure). Most neuromuscular blocking agents (NMBAs) rely on hepatic metabolism or renal excretion for clearance. However, Cisatracurium (an isomer of Atracurium) undergoes **Hofmann Elimination**. This is a unique organ-independent chemical degradation process that occurs at physiological pH and temperature. Because it does not rely on the liver or kidneys, its duration of action remains predictable even in multi-organ failure, making it the safest choice for this patient. **Analysis of Incorrect Options:** * **Rocuronium (B) and Vecuronium (C):** These are aminosteroid compounds. They are primarily metabolized by the **liver** and excreted via **bile and urine**. In patients with liver or renal failure, their half-life is significantly prolonged, leading to unpredictable recovery and prolonged neuromuscular blockade. * **Rapacuronium (D):** This was a rapid-onset steroid NMBA that was withdrawn from the market worldwide due to a high incidence of severe **bronchospasm**. **NEET-PG High-Yield Pearls:** * **Hofmann Elimination:** A non-enzymatic degradation. It is temperature and pH-dependent (rate increases with hyperthermia and alkalosis; decreases with hypothermia and acidosis). * **Laudanosine:** A metabolite of both Atracurium and Cisatracurium. It is a CNS stimulant that can lower the seizure threshold. However, Cisatracurium produces significantly less laudanosine than Atracurium. * **Histamine Release:** Unlike Atracurium, Cisatracurium does **not** cause significant histamine release, making it more hemodynamically stable. * **Drug of Choice in ICU:** Due to its organ-independent clearance, Cisatracurium is the preferred NMBA for long-term infusion in critically ill patients with organ dysfunction.

Q: Which of the following muscle relaxants causes maximal pain on injection?

Rocuronium. **Explanation:** **Rocuronium** is the correct answer as it is well-documented to cause the highest incidence of injection pain (up to 50–80% in awake patients) among all neuromuscular blocking agents. The underlying mechanism is attributed to its **low pH (approximately 4.0)** and the release of local mediators like **kinins**, which irritate the venous nociceptors. This often manifests as "withdrawal movement" of the limb during induction. **Analysis of Incorrect Options:** * **Succinylcholine (Option A):** While it causes post-operative muscle soreness (myalgia) due to fasciculations, it does not typically cause acute pain at the site of injection. * **Vecuronium (Option B):** It is a nearly pH-neutral, lyophilized powder. It is considered "cardiovascularly stable" and is generally painless upon administration [1]. * **Cisatracurium (Option C):** As an isomer of atracurium, it is designed to be potent and stable without significant histamine release or local irritation, making it painless on injection [1]. **Clinical Pearls for NEET-PG:** * **Mitigation:** Pain from Rocuronium can be reduced by pre-administering **Lidocaine**, using a larger vein, or priming with a small dose of an induction agent (Propofol). * **Rapidity:** Rocuronium is the non-depolarizing muscle relaxant (NDMR) with the **fastest onset of action** (60–90 seconds), making it the drug of choice for Rapid Sequence Induction (RSI) when Succinylcholine is contraindicated [1]. * **Reversal:** Its effects are specifically and rapidly reversed by **Sugammadex**.

Q: Which of the following gases exhibits the second gas effect?

Nitrous oxide. **Explanation:** The **Second Gas Effect** is a phenomenon where the rapid uptake of a high-volume primary gas (usually Nitrous Oxide) accelerates the rate of increase in the alveolar concentration of a concurrently administered "second gas" (a potent volatile anesthetic). **Why Nitrous Oxide is Correct:** Nitrous oxide ($N_2O$) is highly insoluble in blood but is administered in high concentrations (up to 70%). When $N_2O$ is inhaled, it is rapidly absorbed from the alveoli into the pulmonary capillaries. This rapid removal of $N_2O$ causes the remaining gases in the alveoli to be "concentrated" into a smaller volume. This increases the fractional concentration ($F_A$) of the second gas (e.g., Halothane or Sevoflurane), leading to a faster induction of anesthesia. **Why Other Options are Incorrect:** * **Ether:** It is highly soluble in blood, leading to a slow induction. It does not achieve the rapid alveolar uptake required to produce a concentration effect for other gases. * **Desflurane & Sevoflurane:** These are potent volatile anesthetics typically used as the "second gas." They are administered in low concentrations (usually <8%) and therefore do not occupy enough volume in the alveoli to trigger the second gas effect for other agents. **High-Yield NEET-PG Pearls:** * **Concentration Effect:** This is the precursor to the second gas effect; the higher the concentration of gas administered, the faster the arterial tension rises. * **Diffusion Hypoxia (Fink Effect):** The reverse of the second gas effect. When $N_2O$ is discontinued, it rushes out of the blood into the alveoli, diluting oxygen and $CO_2$. This is prevented by giving **100% $O_2$ for 5–10 minutes** after stopping $N_2O$. * **Blood-Gas Partition Coefficient:** $N_2O$ has a low coefficient (0.47), explaining its rapid onset and offset.

Question 1

Dexmedetomidine is:

Accepted Answer

An agent of choice for conscious sedation

Answer

A selective alpha-2 antagonist

Answer

Less sensitive to alpha-2 receptors than clonidine

Answer

A good analgesic

Question 2

Which of the following inhalational anesthetic agents demonstrates the most potent bronchodilating effect?

Accepted Answer

Halothane

Answer

Isoflurane

Answer

Sevoflurane

Answer

Desflurane

Question 3

Which of the following drugs is contraindicated in a patient with myasthenia gravis?

Accepted Answer

Tubocurare

Answer

Succinylcholine

Answer

Pyridostigmine

Answer

Halothane

Question 4

What is true about Ringer's Lactate?

Accepted Answer

Isotonic

Answer

Colloidal solution

Answer

Potassium level is the same as that of serum potassium

Answer

Helps in acidosis by acid neutralization

Question 5

What is the drug of choice for reversal of neuromuscular blockade by vecuronium?

Accepted Answer

Sugamadex

Answer

Edrophonium

Answer

Neostigmine

Answer

Pyridostigmine

Question 6

Which of the following statements regarding inhalation anesthetic agents is incorrect?

Accepted Answer

Sevoflurane is more potent than isoflurane.

Answer

Sevoflurane is less cardiodepressant than isoflurane.

Answer

Desflurane has a lower blood-gas partition coefficient than sevoflurane.

Answer

Sevoflurane has a higher MAC than isoflurane.

Question 7

Ether is still used as a general anesthetic in India, especially in peripheral hospitals because:

Accepted Answer

It is cheap and can be administered without an anesthetic machine

Answer

It is non-explosive

Answer

It is pleasant smelling and non-irritating

Answer

It induces anesthesia rapidly

Question 8

An alcoholic patient with a history of diabetic nephropathy and liver failure is scheduled for open abdominal surgery. Which muscle relaxant is most appropriate for this patient?

Accepted Answer

Cisatracurium

Answer

Rocuronium

Answer

Vecuronium

Answer

Rapacuronium

Question 9

Which of the following muscle relaxants causes maximal pain on injection?

Accepted Answer

Rocuronium

Answer

Succinylcholine

Answer

Vecuronium

Answer

Cisatracurium

Question 10

Which of the following gases exhibits the second gas effect?

Accepted Answer

Nitrous oxide

Answer

Ether

Answer

Desflurane

Answer

Sevoflurane

General Anesthesia — MCQs

General Anesthesia — MCQs

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