General Anesthesia Practice Questions

Q: Non-depolarizing muscle relaxants are potentiated by all except?

Phenytoin. **Explanation:** The potentiation or antagonism of non-depolarizing muscle relaxants (NDMRs) depends on their interaction with the neuromuscular junction (NMJ) and hepatic enzyme induction. **Why Phenytoin is the correct answer:** Phenytoin is a potent **hepatic enzyme inducer**. Chronic administration of phenytoin (and carbamazepine) leads to an increased rate of metabolism of NDMRs (especially vecuronium and rocuronium). Furthermore, it causes an up-regulation of acetylcholine receptors at the NMJ. Both mechanisms lead to **resistance** to NDMRs, meaning higher doses are required and the duration of action is shortened. Therefore, it does not potentiate but rather **antagonizes** the effect. **Why the other options are incorrect:** * **Aminoglycosides (e.g., Neomycin, Gentamicin):** These potentiate NDMRs by inhibiting the pre-junctional release of Acetylcholine (ACh) and reducing post-junctional sensitivity to ACh. * **Polymyxins:** These exert a potent neuromuscular blocking effect by acting like "membrane stabilizers," significantly prolonging the block. * **Quinidine:** This Class IA antiarrhythmic potentiates NDMRs by depressing muscle fiber excitability and decreasing ACh release. **High-Yield Clinical Pearls for NEET-PG:** * **Antibiotics that potentiate NDMRs:** Aminoglycosides, Tetracyclines, Polymyxin, and Lincomycin. (Note: Penicillins and Cephalosporins do **not** have this effect). * **Electrolytes that potentiate NDMRs:** Hypokalemia, Hypermagnesemia, and Hypocalcemia. * **Other potentiators:** Inhalational anesthetics (Desflurane > Sevoflurane > Isoflurane), Local anesthetics, and Hypothermia. * **Acute vs. Chronic Phenytoin:** While chronic use causes resistance, an *acute* IV dose of phenytoin can occasionally potentiate the block. However, for exam purposes, Phenytoin is the classic example of resistance/antagonism.

Q: What is the primary site of action of ketamine?

Thalamoneocortical projection. **Explanation:** Ketamine is a unique anesthetic agent known for producing **"dissociative anesthesia."** This state is characterized by a functional and electrophysiological dissociation between the thalamocortical and limbic systems. **Why Thalamoneocortical Projection is Correct:** The primary mechanism of ketamine involves the non-competitive antagonism of **NMDA (N-methyl-D-aspartate) receptors**. By blocking these receptors, ketamine inhibits the **thalamoneocortical projection system**. This interrupts the transmission of sensory impulses from the reticular activating system to the cerebral cortex. While the patient may appear awake (eyes open, intact swallow reflex), the cortex cannot process sensory input, leading to profound analgesia and amnesia. **Analysis of Incorrect Options:** * **A. Spinal cord:** While ketamine does have some minor inhibitory effects on the dorsal horn of the spinal cord (contributing to analgesia), this is not its *primary* site for inducing anesthesia. * **B. Local nerve fibers:** Ketamine does not act like local anesthetics (which block sodium channels in peripheral nerves). * **D. Posterior column:** The posterior columns are responsible for fine touch and proprioception; they are not the target for ketamine’s dissociative effects. **High-Yield Clinical Pearls for NEET-PG:** * **Dissociative Anesthesia:** Characterized by catalepsy, amnesia, and analgesia. * **Hemodynamics:** Unlike most anesthetics, ketamine is a **sympathomimetic** (increases HR, BP, and CO), making it the drug of choice for **hypovolemic shock. * **Airway:** It is a potent **bronchodilator** (useful in status asthmaticus) and preserves laryngeal reflexes. * **Side Effects:** Causes **emergence delirium/hallucinations** (minimized by benzodiazepines) and increases **Intracranial Pressure (ICP)** and Intraocular Pressure (IOP).

Q: Minimum alveolar concentration (MAC) of an anesthetic agent means it produces lack of reflex response to skin incision in what percentage of subjects?

50%. **Explanation:** The **Minimum Alveolar Concentration (MAC)** is a fundamental concept in inhalational anesthesia, representing the potency of an anesthetic agent. It is defined as the steady-state alveolar concentration of an anesthetic gas (at 1 atmosphere) that prevents gross purposeful movement in response to a standard surgical stimulus (skin incision) in **50% of subjects**. **Why 50% is Correct:** MAC is essentially the **ED50** (Median Effective Dose) for inhalational agents. It provides a standardized measure to compare the potency of different gases; the lower the MAC value, the more potent the anesthetic (e.g., Halothane has a MAC of 0.75%, while Nitrous Oxide is >100%). **Why Other Options are Incorrect:** * **25% (Option A):** This value does not correspond to any standard clinical definition of anesthetic potency. * **75% (Option C):** While higher concentrations increase the depth of anesthesia, 75% is not the statistical benchmark used for MAC. * **100% (Option D):** To ensure 95-99% of patients do not move, clinicians use **MAC-BAR** (Blunt Autonomic Response) or roughly **1.3 MAC**, which is the surgical dose required for most clinical procedures. **High-Yield Clinical Pearls for NEET-PG:** * **MAC-Awake:** The concentration at which 50% of patients respond to verbal commands (usually ~0.3–0.4 MAC). * **Factors that INCREASE MAC (Require more gas):** Hyperthermia, hypernatremia, chronic alcohol abuse, and increased central neurotransmitters (e.g., cocaine, ephedrine). * **Factors that DECREASE MAC (Require less gas):** Hypothermia, pregnancy, acute alcohol intoxication, old age, and concurrent use of opioids or benzodiazepines. * **Meyer-Overton Hypothesis:** States that MAC is inversely proportional to lipid solubility (Oil:Gas partition coefficient).

Q: Ketamine is contraindicated in which of the following conditions?

Glaucoma. ### Explanation **Correct Option: C. Glaucoma** Ketamine is a dissociative anesthetic that causes sympathetic stimulation. It is contraindicated in **Glaucoma** because it increases **Intraocular Pressure (IOP)**. This occurs due to an increase in choroidal blood flow and potential tonic-clonic movements of the extraocular muscles. For the same reason, it is avoided in penetrating eye injuries where an increase in IOP could lead to the expulsion of intraocular contents. **Analysis of Incorrect Options:** * **A. Status Asthmaticus:** Ketamine is actually a **drug of choice** for induction in asthmatic patients. It has potent **bronchodilatory** properties mediated by catecholamine release and direct relaxant effects on bronchial smooth muscle. * **B. Obstetric Hemorrhage:** Ketamine is frequently used in obstetric emergencies (like placental abruption or hemorrhage) because it maintains blood pressure and uterine blood flow. However, it should be used in low doses (<1 mg/kg) to avoid uterine hypertonicity. * **D. Shock:** Ketamine is the **induction agent of choice in hypovolemic/hemorrhagic shock**. Its sympathomimetic effects (increased heart rate, CO, and BP) help maintain hemodynamic stability compared to agents like propofol or thiopentone. **High-Yield Clinical Pearls for NEET-PG:** 1. **Triple Increase:** Ketamine increases **IOP** (Intraocular), **ICP** (Intracranial), and **ICT** (Intrathoracic/BP). 2. **The "Exception" in Shock:** While usually preferred in shock, Ketamine can cause **myocardial depression** in "critically ill" patients who are catecholamine-depleted. 3. **Emergence Delirium:** This common side effect (hallucinations/vivid dreams) can be prevented by pre-medicating with **Benzodiazepines** (e.g., Midazolam). 4. **Secretions:** It is a potent **sialagogue** (increases salivation); hence, it is often co-administered with Glycopyrrolate.

Q: Which of the following is NOT true regarding neurolept analgesia?

None of the above. **Explanation:** **Neuroleptanalgesia (NLA)** is a state of profound sedation and analgesia produced by the combination of an opioid analgesic and a neuroleptic (antipsychotic) drug. The classic combination used is **Fentanyl** (opioid) and **Droperidol** (butyrophenone neuroleptic). 1. **Why Option D is correct:** All the statements (A, B, and C) are medically accurate descriptions of neuroleptanalgesia. Since the question asks for the statement that is **NOT** true, "None of the above" is the correct choice. 2. **Analysis of Options:** * **Option A:** NLA can indeed be used with **O₂ and N₂O**. When these inhalation gases are added to the fentanyl-droperidol combination, the state is upgraded to **Neurolept anesthesia**, which provides complete unconsciousness suitable for surgery. * **Option B:** Droperidol is a dopamine (D2) receptor antagonist. Like other antipsychotics, it can cause **extrapyramidal side effects**, most notably **focal dystonia** (e.g., oculogyric crisis or torticollis). * **Option C:** The combination of **Fentanyl and Droperidol** (commercially known as Innovar in a 1:50 ratio) is the prototype example of neuroleptanalgesia. **High-Yield Clinical Pearls for NEET-PG:** * **Innovar Ratio:** Contains 0.05 mg Fentanyl and 2.5 mg Droperidol per mL. * **Patient State:** The patient remains conscious, detached from surroundings, and cooperative but feels no pain (quiescence). * **Contraindication:** Avoid in patients with **Parkinson’s disease** due to the dopamine-blocking effects of droperidol. * **Side Effects:** Droperidol can cause **QT interval prolongation**; therefore, ECG monitoring is recommended.

Q: Which of the following statements regarding propofol is FALSE?

It has a longer half-life.. **Explanation:** Propofol is the "gold standard" for intravenous induction and maintenance in ambulatory (daycare) anesthesia due to its unique pharmacokinetic profile. **1. Why Option C is the Correct (False) Statement:** Propofol is characterized by a **short elimination half-life** (approx. 30–90 minutes) and, more importantly, a very short **context-sensitive half-time**. Its action is terminated rapidly by **redistribution** from the brain to peripheral tissues, followed by rapid hepatic and extra-hepatic clearance. This ensures quick emergence and minimal "hangover" effect, making the statement that it has a "longer half-life" incorrect. **2. Analysis of Incorrect Options:** * **Option A:** It is the **agent of choice** for daycare surgery because it allows for rapid recovery, early ambulation, and has significant **anti-emetic** properties, reducing Postoperative Nausea and Vomiting (PONV). * **Option B:** It undergoes **rapid metabolism** primarily in the liver (glucuronidation) and also has extra-hepatic metabolism (lungs and kidneys), contributing to its fast clearance. * **Option D:** The standard commercial preparation (Diprivan) is an emulsion containing **1% propofol, 10% soybean oil, 2.25% glycerol, and 1.2% purified egg lecithin**. **Clinical Pearls for NEET-PG:** * **Pain on injection:** Most common side effect; can be mitigated by using larger veins or pre-treatment with Lidocaine. * **PRIS (Propofol Related Infusion Syndrome):** Occurs with prolonged high-dose infusions (>48 hrs); characterized by metabolic acidosis, rhabdomyolysis, and cardiac failure. * **Egg Allergy:** Use with caution in patients with severe anaphylactic egg allergies (though most are allergic to egg white/albumin, and propofol uses egg yolk lecithin). * **Color Coded:** Propofol ampoules/vials are coded **Yellow**.

Q: Which of the following drugs potentiates neuromuscular blockade?

Amlodipine. **Explanation:** The correct answer is **Amlodipine**. **Mechanism of Potentiation:** Calcium channel blockers (CCBs) like Amlodipine, Verapamil, and Nifedipine potentiate both depolarizing and non-depolarizing neuromuscular blocking agents (NMBAs). The underlying mechanism is twofold: 1. **Pre-junctional:** CCBs inhibit the entry of calcium into the motor nerve terminal, which is essential for the release of Acetylcholine (ACh) into the synaptic cleft. 2. **Post-junctional:** They interfere with the excitation-contraction coupling in the muscle fiber and may stabilize the post-junctional membrane. **Analysis of Incorrect Options:** * **Propranolol:** While some older studies suggest high-dose beta-blockers might slightly prolong blockade, they are not classically recognized as potentiation agents in standard clinical practice compared to CCBs. * **Metformin:** This biguanide used for diabetes has no known interaction with the nicotinic receptors at the neuromuscular junction. * **Penicillin:** Most penicillins do not affect NMBAs. However, other antibiotic classes—specifically **Aminoglycosides** (e.g., Neomycin, Gentamicin), **Polymyxins**, and **Tetracyclines**—are high-yield causes of potentiation. **High-Yield Clinical Pearls for NEET-PG:** * **Antibiotics that potentiate NMBAs:** Aminoglycosides (most potent), Clindamycin, and Lincomycin. * **Electrolyte abnormalities:** Hypokalemia, Hypermagnesemia, and Hypocalcemia all potentiate neuromuscular blockade. * **Other Drugs:** Lithium, Quinidine, Local Anesthetics, and Volatile Anesthetics (Isoflurane > Sevoflurane) also prolong the block. * **Note:** CCBs can also increase the risk of hypotension when combined with volatile anesthetics.

Q: Indications for hypotensive anesthesia include:

All of the above. **Explanation:** **Hypotensive anesthesia** (controlled hypotension) is a technique used to deliberately reduce the mean arterial pressure (MAP) to 50–65 mmHg or by 30% of the patient’s baseline. The primary goal is to **minimize blood loss** and **improve the surgical field visibility** by reducing capillary oozing. **Why "All of the Above" is Correct:** * **Mastoid Surgery (A):** In microsurgeries of the ear, even a tiny amount of blood can obscure the microscopic view, potentially leading to complications like facial nerve injury. Controlled hypotension ensures a "dry" surgical field. * **Spinal Surgery (B):** Extensive procedures like scoliosis correction or multi-level laminectomies involve significant blood loss from bone and epidural veins. Reducing MAP decreases the need for blood transfusions. * **Arteriovenous Malformations (C):** AVMs are high-flow vascular lesions. Lowering the pressure reduces the risk of intraoperative rupture and facilitates easier dissection and clipping of the vessels. **Clinical Pearls for NEET-PG:** * **Commonly used agents:** Sodium Nitroprusside (fastest), Nitroglycerin, Magnesium sulfate, and potent inhalational agents (Isoflurane/Sevoflurane). * **Contraindications:** These are high-yield! Avoid in patients with **uncontrolled hypertension**, **cerebrovascular disease** (risk of stroke), **severe renal/hepatic dysfunction**, and **closed-angle glaucoma**. * **Monitoring:** Invasive arterial blood pressure monitoring is mandatory to ensure real-time accuracy. * **Safe Limit:** In healthy individuals, the lower limit of MAP is generally kept at **50-60 mmHg** to maintain cerebral autoregulation.

Question 1

Which of the following fluorinated anesthetic agents does not produce toxic fluoride ions?

Accepted Answer

Desflurane

Answer

Sevoflurane

Answer

Methoxyflurane

Answer

Enflurane

Question 2

Non-depolarizing muscle relaxants are potentiated by all except?

Accepted Answer

Phenytoin

Answer

Aminoglycoside antibiotics

Answer

Polymyxin

Answer

Quinidine

Question 3

What is the primary site of action of ketamine?

Accepted Answer

Thalamoneocortical projection

Answer

Spinal cord

Answer

Local nerve fibers

Answer

Posterior column

Question 4

Minimum alveolar concentration (MAC) of an anesthetic agent means it produces lack of reflex response to skin incision in what percentage of subjects?

Accepted Answer

50%

Answer

25%

Answer

75%

Answer

100%

Question 5

Ketamine is contraindicated in which of the following conditions?

Accepted Answer

Glaucoma

Answer

Status asthmaticus

Answer

Obstetric hemorrhage

Answer

Shock

Question 6

Which of the following is NOT true regarding neurolept analgesia?

Accepted Answer

None of the above

Answer

Can be used along with O2 and N2O

Answer

Causes focal dystonia

Answer

Is exemplified by Fentanyl-droperidol

Question 7

Which of the following statements regarding propofol is FALSE?

Accepted Answer

It has a longer half-life.

Answer

It is an intravenous agent of choice for daycare surgery.

Answer

It undergoes rapid metabolism.

Answer

It contains egg lecithin and glycerol.

Question 8

Which of the following drugs potentiates neuromuscular blockade?

Accepted Answer

Amlodipine

Answer

Propranolol

Answer

Metformin

Answer

Penicillin

Question 9

Potency of an inhalational anesthetic agent is measured by:

Accepted Answer

Minimum alveolar concentration

Answer

Diffusion coefficient

Answer

Dead space concentration

Answer

Alveolar blood concentration

Question 10

Indications for hypotensive anesthesia include:

Accepted Answer

All of the above

Answer

Mastoid surgery

Answer

Spinal surgery

Answer

Arteriovenous malformations

General Anesthesia — MCQs

General Anesthesia — MCQs

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