General Anesthesia Practice Questions

Q: What is the duration of action of flumazenil?

40 minutes. **Explanation:** **Flumazenil** is a specific competitive antagonist at the benzodiazepine receptor. It is used to reverse the sedative and respiratory-depressant effects of benzodiazepines (like Midazolam or Diazepam). **Why Option D is Correct:** The duration of action of flumazenil is approximately **30 to 60 minutes** (with a mean clinical effect of roughly **40 minutes**). This is significantly shorter than the half-life of most benzodiazepines it is intended to reverse. Because it is rapidly cleared by the liver, its antagonistic effect wears off quickly. **Why Other Options are Incorrect:** * **Options A & B (10-20 mins):** While the onset of action is rapid (1–2 minutes), the clinical duration is longer than 20 minutes. * **Option C (30 mins):** While 30 minutes is the lower end of the range, 40 minutes is the standard textbook value cited in major anesthesia references (like Miller’s) and frequently tested in NEET-PG as the definitive duration. **Clinical Pearls & High-Yield Facts:** 1. **Resedation (Recurarization):** Because flumazenil’s duration (40 mins) is shorter than that of benzodiazepines (e.g., Diazepam lasts hours), patients may experience "resedation" once the flumazenil wears off. Monitoring for at least 2 hours is essential. 2. **Seizure Risk:** Flumazenil can precipitate acute withdrawal or seizures in patients on long-term benzodiazepine therapy or in cases of mixed tricyclic antidepressant overdose. 3. **Metabolism:** It is metabolized exclusively by the liver (high hepatic extraction ratio). 4. **Dose:** Typically administered in increments of 0.2 mg IV, up to a total of 1 mg.

Q: Which of the following agents can be used for anaesthesia in dogs?

All of the above. **Explanation:** In veterinary anesthesia, particularly for dogs, a multimodal approach is used to ensure sedation, analgesia, and muscle relaxation. All three agents listed are standard components of canine anesthetic protocols. 1. **Ketamine (Option A):** A dissociative anesthetic and NMDA receptor antagonist. It provides excellent somatic analgesia and is frequently used in dogs for induction or as part of a "triple drip" (Ketamine-Guaifenesin-Xylazine) to maintain anesthesia. 2. **Medetomidine hydrochloride (Option B):** A potent alpha-2 adrenergic agonist. It is widely used in veterinary medicine for sedation, premedication, and analgesia. It provides reliable chemical restraint in dogs and is often preferred over xylazine due to higher specificity. 3. **Midazolam (Option C):** A short-acting benzodiazepine used for its anxiolytic, anticonvulsant, and muscle-relaxant properties. In dogs, it is commonly used as a pre-anesthetic medication to facilitate smooth induction and reduce the dose of induction agents like Propofol. **Why "All of the above" is correct:** These drugs are often used in combination (e.g., the "Ket-Mid" protocol) to achieve balanced anesthesia, minimizing the side effects of any single agent while ensuring the animal remains unconscious and pain-free. **High-Yield Clinical Pearls for NEET-PG:** * **Ketamine** is unique because it stimulates the sympathetic nervous system (increasing HR and BP), making it useful in hemodynamically unstable patients, though it increases intracranial pressure. * **Atipamezole** is the specific reversal agent for Medetomidine. * **Flumazenil** is the reversal agent for Midazolam. * In veterinary anesthesia, **Xylazine** is another common alpha-2 agonist, but it is highly emetic in cats.

Q: Which of the following anesthetic agents are known to cause pain on injection?

Etomidate, Methohexitone, and Propofol. **Explanation:** The sensation of pain during the intravenous injection of anesthetic agents is a common clinical challenge, primarily caused by the **osmolality** of the formulation or the presence of **propylene glycol** as a solvent, which irritates the venous intima. **1. Why Option C is Correct:** * **Propofol:** The most notorious for causing pain (reported in up to 70% of patients). The pain is attributed to the activation of the **kallikrein-kinin system** and the release of bradykinin. * **Etomidate:** Formulated in 35% propylene glycol, which is highly hyperosmolar and irritating to the veins. * **Methohexitone:** An oxybarbiturate that frequently causes pain on injection and is also associated with excitatory phenomena like myoclonus. **2. Why Other Options are Incorrect:** * **Thiopentone (Options B & D):** While highly alkaline (pH ~10.5) and capable of causing tissue necrosis if injected intra-arterially, it typically does **not** cause significant pain when injected into a large, patent vein. * **Ketamine (Option B):** Generally considered painless upon intravenous injection. **Clinical Pearls for NEET-PG:** * **Prevention:** Pain from Propofol can be reduced by using larger veins (antecubital fossa), prior administration of **IV Lidocaine**, or mixing lidocaine with the drug. * **Excitatory Phenomena:** Both Etomidate and Methohexitone are associated with high incidences of **myoclonus** and hiccups. * **Drug of Choice:** Despite the pain, Etomidate remains the drug of choice for induction in **hemodynamically unstable** patients due to its minimal cardiovascular effects. * **Contraindication:** Avoid Methohexitone and Etomidate in patients with a history of **seizures** (though Methohexitone is used to prolong seizures in ECT).

Q: Which of the following increases intraocular pressure?

Ketamine. **Explanation:** **Ketamine** is the correct answer because it is one of the few anesthetic agents that **increases intraocular pressure (IOP)**. The mechanism is attributed to an increase in extraocular muscle tone and a rise in choroidal blood flow due to sympathetic stimulation. Consequently, Ketamine is generally avoided in patients with penetrating eye injuries or glaucoma where a rise in IOP could lead to the expulsion of intraocular contents or optic nerve damage. **Analysis of Incorrect Options:** * **Thiopentone & Barbiturates (Options A & D):** Most intravenous induction agents, particularly barbiturates, significantly **decrease IOP**. They achieve this by depressing the central nervous system, reducing aqueous humor production, and improving its outflow. * **Althesin (Option B):** This is a steroid-based anesthetic (now largely obsolete due to anaphylaxis) that also causes a **decrease in IOP**, similar to the profile of most non-ketamine induction agents. **High-Yield Clinical Pearls for NEET-PG:** * **IOP & Intubation:** While most induction agents (Propofol, Etomidate, Thiopentone) decrease IOP, the act of **Laryngoscopy and Intubation** causes a sharp rise in IOP. * **Muscle Relaxants:** **Succinylcholine** (Suxamethonium) is notorious for increasing IOP (by ~5-10 mmHg) due to prolonged contraction of extraocular muscles. It is contraindicated in open globe injuries. * **Inhalational Agents:** Most volatile anesthetics (e.g., Sevoflurane, Isoflurane) decrease IOP. * **Exceptions:** Only **Ketamine** and **Succinylcholine** are classic "red flags" for increasing intraocular pressure in anesthesia.

Q: Which of the following drugs can cause bradycardia during anaesthesia?

Propofol. **Explanation:** **Propofol (Correct Answer):** Propofol is a potent intravenous anesthetic agent that frequently causes **bradycardia** and hypotension. The underlying mechanism involves a significant reduction in sympathetic tone and an inhibition of the baroreceptor reflex. Unlike other induction agents, propofol resets the baroreflex, meaning the heart rate does not increase reflexively in response to the drop in blood pressure. In some cases, it can lead to profound vagotonic effects, occasionally resulting in asystole. **Analysis of Incorrect Options:** * **Pancuronium:** This is a long-acting non-depolarizing neuromuscular blocker (NMBA) known for causing **tachycardia**. It has vagolytic properties and stimulates the release of norepinephrine from cardiac sympathetic nerve endings. * **Vecuronium:** This is considered a **cardiovascularly stable** NMBA. It lacks significant vagolytic or histamine-releasing effects, typically resulting in no change in heart rate. * **Atracurium:** While it can cause hypotension due to **histamine release**, the physiological response to this hypotension is usually a compensatory **reflex tachycardia**, not bradycardia. **High-Yield Clinical Pearls for NEET-PG:** * **Propofol Infusion Syndrome (PRIS):** A rare but fatal complication of long-term high-dose infusion characterized by metabolic acidosis, rhabdomyolysis, hyperkalemia, and cardiac failure. * **Drug of Choice:** Propofol is the drug of choice for Day Care Surgery due to its rapid recovery and anti-emetic properties. * **Ketamine vs. Propofol:** While Propofol causes bradycardia and hypotension, Ketamine is the "opposite," causing tachycardia and hypertension (sympathomimetic).

Q: What is true about midazolam as an inducing agent?

Does not produce pain on intravenous injection.. **Explanation:** Midazolam is a water-soluble benzodiazepine frequently used for preoperative sedation and induction of anesthesia. **Why Option B is Correct:** Unlike its predecessor Diazepam, which is insoluble in water and requires a propylene glycol solvent (causing significant venous irritation and thrombophlebitis), **Midazolam contains an imidazole ring**. At a pH of less than 4.0, this ring remains open, making the drug **water-soluble**. This eliminates the need for irritating solvents, ensuring that it **does not produce pain on intravenous injection**. Once injected, the physiological pH of the blood (7.4) causes the ring to close, making the drug lipid-soluble so it can cross the blood-brain barrier. **Analysis of Incorrect Options:** * **Option A & D:** Midazolam typically causes a **decrease in systemic vascular resistance (SVR)** and a modest **decrease in blood pressure**. It does not increase peripheral vascular resistance; rather, it has a mild vasodilatory effect. * **Option C:** Benzodiazepines, including midazolam, **decrease cerebral metabolic rate of oxygen consumption (CMRO2)** and cerebral blood flow (CBF) while maintaining the CO2 reactivity of the cerebral vasculature. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Potentiates GABA-A receptors by increasing the **frequency** of chloride channel opening. * **Metabolism:** Metabolized by hepatic CYP3A4 enzymes; its active metabolite is 1-hydroxymidazolam. * **Specific Antagonist:** **Flumazenil** (competitive antagonist) is used to reverse its effects. * **Anterograde Amnesia:** Midazolam is highly effective at producing anterograde amnesia, making it ideal for premedication.

Q: All of the following are false statements regarding Nitrous Oxide (N2O) EXCEPT:

It is the least potent inhalational anesthetic agent.. **Explanation:** Nitrous Oxide ($N_2O$) is a unique inorganic inhalational anesthetic. To identify the correct statement, we must evaluate its physical and pharmacological properties. **1. Why Option A is Correct:** Potency of an inhalational agent is inversely proportional to its **Minimum Alveolar Concentration (MAC)**. $N_2O$ has a MAC of approximately **104%**, which is the highest among all anesthetic gases. Since it cannot achieve surgical anesthesia at 1 atmosphere without causing hypoxia, it is clinically the **least potent** agent. **2. Why Other Options are Incorrect:** * **Option B:** $N_2O$ provides excellent analgesia but has **no significant muscle relaxant properties**. It is often used alongside neuromuscular blockers for this reason. * **Option C:** $N_2O$ is **heavier than air** (Specific gravity of 1.5). This is clinically relevant as it can accumulate in low-lying areas. * **Option D:** $N_2O$ is highly insoluble in blood. When discontinued, it rushes out of the blood into the alveoli, diluting oxygen concentration. This phenomenon is known as **Diffusion Hypoxia (Fink Effect)**. It is prevented by administering 100% $O_2$ for 5–10 minutes after stopping $N_2O$. **High-Yield Clinical Pearls for NEET-PG:** * **Second Gas Effect:** $N_2O$ accelerates the uptake of a companion volatile anesthetic (like Halothane or Isoflurane). * **Closed Spaces:** $N_2O$ is 34 times more soluble than Nitrogen. It diffuses into air-filled cavities faster than Nitrogen can leave, causing **expansion of closed spaces**. It is strictly **contraindicated** in pneumothorax, air embolism, intestinal obstruction, and middle ear surgeries (tympanoplasty). * **Toxicity:** Chronic exposure inhibits **Vitamin B12** (Methionine Synthase), leading to megaloblastic anemia and peripheral neuropathy. * **Storage:** Stored in **Blue Cylinders** as a liquid under pressure.

Q: What is the recommended oxygen content in an anesthetic mixture?

33%. **Explanation:** In modern anesthetic practice, the primary goal of oxygen delivery is to prevent hypoxia while maintaining an adequate depth of anesthesia. **Why 33% is the Correct Answer:** The standard recommendation for a safe anesthetic mixture is a **1:2 ratio of Oxygen (O₂) to Nitrous Oxide (N₂O)**. This translates to approximately **33% Oxygen** and 67% Nitrous Oxide. This specific concentration is favored because: 1. **Safety Margin:** It provides a higher fraction of inspired oxygen ($FiO_2$) than room air (21%), offering a safety buffer against hypoventilation or technical glitches. 2. **Diffusion Hypoxia Prevention:** Maintaining at least 30-33% oxygen helps mitigate the risk of diffusion hypoxia (the Fink effect) during the emergence phase when N₂O rapidly exits the blood into the alveoli. 3. **Potency:** It allows for a high enough concentration of N₂O to utilize its analgesic properties and the "Second Gas Effect" for volatile anesthetics. **Analysis of Incorrect Options:** * **A (25%):** While higher than room air, it is not the standard clinical ratio used in the 1:2 O₂:N₂O mixture. * **B (30%):** Though 30% is often cited as a minimum safe limit in many textbooks, **33%** is the more precise value derived from the classic 1:2 delivery ratio frequently tested in exams. * **D (38%):** This concentration is unnecessarily high for routine maintenance and would limit the concentration of N₂O, potentially reducing anesthetic efficacy. **High-Yield Clinical Pearls for NEET-PG:** * **Hypoxic Guard System:** Modern anesthesia machines (like the Ohmeda Link-25) have a mandatory minimum oxygen concentration of **25%** to prevent the delivery of a hypoxic mixture. * **Critical Ratio:** Always remember the **1:2 ratio** (O₂:N₂O) for maintenance and the **1:1 ratio** (Entonox) for analgesia. * **Color Coding:** Oxygen cylinders are **Black with a White shoulder**, while Nitrous Oxide cylinders are **French Blue**.

Question 1

Which of the following statements regarding halothane is incorrect?

Accepted Answer

It is generally considered unsuitable for the pediatric population.

Answer

It potentiates the effects of competitive neuromuscular blockers.

Answer

Hepatitis is a known potential adverse effect.

Answer

It is contraindicated in patients with certain cardiac arrhythmias.

Question 2

What is the duration of action of flumazenil?

Accepted Answer

40 minutes

Answer

10 minutes

Answer

20 minutes

Answer

30 minutes

Question 3

Which of the following agents can be used for anaesthesia in dogs?

Accepted Answer

All of the above

Answer

Ketamine

Answer

Medetomidine hydrochloride

Answer

Midazolam

Question 4

Which of the following anesthetic agents are known to cause pain on injection?

Accepted Answer

Etomidate, Methohexitone, and Propofol

Answer

Etomidate and Propofol

Answer

Etomidate, Ketamine, and Thiopentone

Answer

Etomidate, Methohexitone, Propofol, and Thiopentone

Question 5

Which of the following increases intraocular pressure?

Accepted Answer

Ketamine

Answer

Thiopentone

Answer

Althesin

Answer

Barbiturate

Question 6

Which of the following drugs can cause bradycardia during anaesthesia?

Accepted Answer

Propofol

Answer

Pancuronium

Answer

Vecuronium

Answer

Atracurium

Question 7

What is true about midazolam as an inducing agent?

Accepted Answer

Does not produce pain on intravenous injection.

Answer

Causes an increase in blood pressure.

Answer

Increases cerebral oxygen consumption.

Answer

Increases peripheral vascular resistance.

Question 8

All are false about propofol except?

Accepted Answer

Propofol infusion at a rate >4 mg/hr can cause propofol infusion syndrome.

Answer

Propofol is the best bronchodilator.

Answer

Propofol is a cardiovascular stable drug.

Answer

Propofol causes malignant hyperthermia.

Question 9

All of the following are false statements regarding Nitrous Oxide (N2O) EXCEPT:

Accepted Answer

It is the least potent inhalational anesthetic agent.

Answer

It possesses significant muscle relaxant properties.

Answer

It is lighter than air.

Answer

It does not cause diffusion hypoxia.

Question 10

What is the recommended oxygen content in an anesthetic mixture?

Accepted Answer

33%

Answer

25%

Answer

30%

Answer

38%

General Anesthesia — MCQs

General Anesthesia — MCQs

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