General Anesthesia Practice Questions

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**.

Q: Which of the following solutions is hypertonic?

3% normal saline. **Explanation:** The tonicity of an intravenous fluid is determined by its **osmolarity** relative to human plasma (normal range: **275–295 mOsm/L**). **1. Why 3% Normal Saline is Correct:** 3% Normal Saline (NaCl) is a **hypertonic** crystalloid. It contains 513 mEq/L of Sodium and 513 mEq/L of Chloride, resulting in a total osmolarity of **1026 mOsm/L**. Since this is significantly higher than plasma osmolarity, it causes water to shift from the intracellular space to the extracellular space. Clinically, it is used in the emergency management of symptomatic hyponatremia and to reduce intracranial pressure in neurosurgery. **2. Analysis of Incorrect Options:** * **5% Dextrose (D5W):** It is considered **isostatic/isotonic** in the bag (osmolarity ~252 mOsm/L). However, once infused, dextrose is rapidly metabolized, leaving behind free water, making it **physiologically hypotonic**. * **0.45% Normal Saline (Half-strength saline):** This is a **hypotonic** solution (osmolarity ~154 mOsm/L). It is used to treat cellular dehydration. * **0.9% Normal Saline:** This is the standard **isotonic** crystalloid (osmolarity ~308 mOsm/L). While slightly hyperosmolar compared to plasma, it does not cause significant fluid shifts across the cell membrane. **High-Yield Clinical Pearls for NEET-PG:** * **Ringer’s Lactate (RL):** The most physiological "balanced" salt solution (osmolarity ~273 mOsm/L). It is slightly **hypotonic**. * **Ideal Fluid for Brain Injury:** Avoid hypotonic fluids (like D5W or 0.45% NS) as they increase cerebral edema. Isotonic or hypertonic fluids are preferred. * **Rapid Correction Warning:** Rapid administration of hypertonic saline can lead to **Central Pontine Myelinolysis (Osmotic Demyelination Syndrome).**

Q: Which of the following is true about halothane?

Causes bronchodilation. **Explanation:** Halothane is a potent volatile anesthetic agent that belongs to the halogenated hydrocarbon group. **1. Why Option A is Correct:** Halothane is a potent **bronchodilator**. It achieves this by directly relaxing bronchial smooth muscle and inhibiting the release of bronchoconstricting mediators like histamine. Because it is non-irritating to the airways and has a pleasant odor, it was historically the agent of choice for **inhalation induction**, especially in pediatric patients and those with reactive airway diseases like asthma or COPD. **2. Why the Other Options are Incorrect:** * **Option B:** Halothane is actually **arrhythmogenic**. It sensitizes the myocardium to the effects of endogenous and exogenous catecholamines (epinephrine), which can lead to ventricular arrhythmias. * **Option C:** Halothane is associated with **"Halothane Hepatitis."** About 20% of the drug undergoes hepatic metabolism, producing trifluoroacetylated proteins that can trigger an immune-mediated hepatotoxicity. It is contraindicated in patients with pre-existing liver disease or a history of unexplained jaundice after previous exposure. * **Option D:** Halothane causes **uterine relaxation**, not contraction. This can lead to increased postpartum hemorrhage (PPH) if used in high concentrations during obstetric procedures. **High-Yield Clinical Pearls for NEET-PG:** * **Blood-Gas Partition Coefficient:** 2.4 (Slower induction/recovery compared to Sevoflurane). * **Halothane Shake:** Post-operative shivering is a common side effect. * **Malignant Hyperthermia:** Like all volatile anesthetics, Halothane is a known trigger. * **Preservation:** It is stored in amber-colored bottles with **Thymol (0.01%)** as a preservative to prevent spontaneous decomposition.

Q: Which stage of anesthesia is known as the stage of analgesia?

Stage 1. **Explanation:** The stages of anesthesia were originally described by **Arthur Guedel** in 1920, based on the effects of inhaled diethyl ether. Understanding these stages is crucial for identifying the depth of anesthesia. **Correct Option: A. Stage 1 (Stage of Analgesia)** This stage begins with the induction of anesthesia and lasts until the loss of consciousness. It is characterized by the patient feeling drowsy and experiencing a significant reduction in pain perception (analgesia) while remaining conscious and able to follow commands. **Incorrect Options:** * **B. Stage 2 (Stage of Excitement/Delirium):** This stage starts from the loss of consciousness to the onset of automatic breathing. It is characterized by agitation, struggling, irregular respiration, and risk of laryngospasm or vomiting. * **C. Stage 3 (Stage of Surgical Anesthesia):** This is the goal for most surgeries. It is divided into four planes based on eye movements, pupil size, and respiratory patterns. It extends from the onset of regular breathing to respiratory paralysis. * **D. Stage 4 (Stage of Medullary Paralysis/Overdose):** This is a critical stage where severe depression of the vasomotor and respiratory centers in the medulla occurs. Without immediate support, it leads to circulatory collapse and death. **High-Yield Clinical Pearls for NEET-PG:** * **Guedel’s Classification** is most clearly seen with slow-acting agents like Ether; modern IV agents (Propofol) bypass Stages 1 and 2 almost instantaneously. * **Stage 2 Danger:** Always avoid stimulating a patient in Stage 2 due to the high risk of **laryngospasm**. * **Surgical Plane:** Plane 2 of Stage 3 is generally considered the ideal depth for most surgical procedures.

Q: Who described the stages of anesthesia?

Guedel. **Explanation:** The correct answer is **D. Guedel**. **Arthur Ernest Guedel** described the four stages of anesthesia in 1920, primarily based on the clinical signs observed during the administration of **Diethyl Ether** (a slow-acting inhalational agent) in spontaneously breathing patients. These stages were crucial for monitoring depth before the advent of modern monitoring and neuromuscular blockers. * **Stage I (Analgesia):** From induction to loss of consciousness. * **Stage II (Excitement/Delirium):** Characterized by irregular breathing, struggling, and risk of laryngospasm. * **Stage III (Surgical Anesthesia):** Divided into 4 planes; characterized by regular breathing and loss of reflexes. * **Stage IV (Medullary Paralysis/Overdose):** Respiratory and vasomotor collapse (to be avoided). **Why other options are incorrect:** * **WTG Morton (Option A):** Often confused with "Moon," William T.G. Morton gave the first successful public demonstration of ether anesthesia in 1846 at the "Ether Dome." * **Oliver Wendell Holmes (Option B):** A physician and poet who coined the term **"Anesthesia"** (meaning "without sensation"). * **John Snow (Option C):** Considered the first specialist anesthetist; he famously administered chloroform to Queen Victoria and is also the father of modern epidemiology. **High-Yield Clinical Pearls for NEET-PG:** * **Guedel’s signs** are best seen with **Ether**. They are obscured by modern rapid-acting IV agents (like Propofol) and muscle relaxants. * **Stage II** is the most dangerous stage (risk of vomiting and laryngospasm). * **Guedel’s Airway:** An oropharyngeal airway named after him, used to maintain patency in unconscious patients.

Q: Which of the following intravenous induction agents suppresses steroidogenesis?

Etomidate. **Explanation:** **Correct Answer: D. Etomidate** Etomidate is a carboxylated imidazole derivative used for intravenous induction. Its most significant side effect is the **dose-dependent inhibition of the enzyme 11-beta-hydroxylase**. This enzyme is essential for converting 11-deoxycortisol to cortisol and 11-deoxycorticosterone to aldosterone in the adrenal cortex. Even a single induction dose can suppress adrenal steroidogenesis for 6 to 24 hours, which may be detrimental in patients with sepsis or adrenal insufficiency. **Analysis of Incorrect Options:** * **A. Thiopentone:** A short-acting barbiturate that acts via GABA-A receptors. Its primary side effects are cardiovascular and respiratory depression; it does not interfere with the adrenal axis. * **B. Ketamine:** A NMDA receptor antagonist. It is unique because it causes sympathetic stimulation (increasing BP and HR) and has no inhibitory effect on steroid synthesis. * **C. Propofol:** An isopropylphenol that enhances GABAergic neurotransmission. While it causes significant vasodilation and hypotension, it does not affect the endocrine function of the adrenal gland. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Etomidate is the induction agent of choice for patients with **hemodynamic instability** (e.g., shock, severe cardiac disease) because it has minimal effects on heart rate and blood pressure. * **Myoclonus:** Etomidate is frequently associated with excitatory movements (myoclonus) during induction, which can be prevented by premedication with opioids or benzodiazepines. * **Porphyria:** Like barbiturates, Etomidate should be avoided in patients with acute intermittent porphyria as it can induce ALA synthetase. * **Nausea/Vomiting:** It has a higher incidence of Postoperative Nausea and Vomiting (PONV) compared to propofol.

Q: Ketamine should be avoided in which of the following conditions?

Increased arterial pressure. **Explanation:** Ketamine is a unique dissociative anesthetic agent that acts primarily as an **NMDA receptor antagonist**. Unlike most other induction agents, it stimulates the sympathetic nervous system, leading to a "sympathomimetic effect." **1. Why Option A is Correct:** Ketamine causes an indirect stimulation of the cardiovascular system by inhibiting the reuptake of catecholamines (norepinephrine). This results in an **increase in heart rate, cardiac output, and arterial blood pressure**. Therefore, it is strictly contraindicated in patients with pre-existing hypertension, ischemic heart disease, or increased intracranial pressure, as it can exacerbate these conditions. **2. Why Incorrect Options are Wrong:** * **B. Pregnancy:** Ketamine is not contraindicated in pregnancy. In fact, it is often used in obstetric emergencies (like placental abruption) due to its ability to maintain blood pressure. It does not affect uterine blood flow significantly at standard doses. * **C. Hypovolemic Shock:** Ketamine is the **induction agent of choice** for patients in hemorrhagic or hypovolemic shock. Its sympathomimetic properties help maintain hemodynamic stability when other agents (like propofol) would cause dangerous hypotension. * **D. Asthma:** Ketamine is the **induction agent of choice** for patients with reactive airway disease/asthma. It has potent **bronchodilatory** effects due to catecholamine release. **High-Yield Clinical Pearls for NEET-PG:** * **Dissociative Anesthesia:** Characterized by eyes remaining open with a slow nystagmic gaze (catalepsy). * **Emergence Delirium:** A common side effect (hallucinations/vivid dreams), which can be pre-treated with **Benzodiazepines** (Midazolam). * **Secretions:** Ketamine increases salivation; **Glycopyrrolate** is often co-administered to prevent this. * **Reflexes:** Pharyngeal and laryngeal reflexes are usually maintained, but the risk of aspiration still exists.

Question 1

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 2

What is the recommended oxygen content in an anesthetic mixture?

Accepted Answer

33%

Answer

25%

Answer

30%

Answer

38%

Question 3

A 46-year-old obese female patient is scheduled for incisional hernia repair. She has a history of deranged liver functions within two weeks postoperatively after an abdominal mass surgery 12 years ago. Which of the following anesthetic agents is most commonly used for induction in patients with a history of liver dysfunction?

Accepted Answer

Desflurane

Answer

Halothane

Answer

Isoflurane

Answer

Sevoflurane

Question 4

Which of the following solutions is hypertonic?

Accepted Answer

3% normal saline

Answer

5% dextrose

Answer

0.45% normal saline

Answer

0.9% normal saline

Question 5

Which of the following is true about halothane?

Accepted Answer

Causes bronchodilation

Answer

Has anti-arrhythmic properties

Answer

Can be used in patients with hepatitis

Answer

Causes uterine contraction

Question 6

Which stage of anesthesia is known as the stage of analgesia?

Accepted Answer

Stage 1

Answer

Stage 2

Answer

Stage 3

Answer

Stage 4

Question 7

Which of the following statements regarding muscle relaxants is true?

Accepted Answer

Vecuronium-induced muscle relaxation can be reversed by neostigmine.

Answer

Atracurium is contraindicated in renal failure.

Answer

Pancuronium causes bradycardia.

Answer

Cisatracurium is a depolarizing muscle relaxant.

Question 8

Who described the stages of anesthesia?

Accepted Answer

Guedel

Answer

WTG Moon

Answer

Oliver Wendell Holmes

Answer

John Snow

Question 9

Which of the following intravenous induction agents suppresses steroidogenesis?

Accepted Answer

Etomidate

Answer

Thiopentone

Answer

Ketamine

Answer

Propofol

Question 10

Ketamine should be avoided in which of the following conditions?

Accepted Answer

Increased arterial pressure

Answer

Pregnancy

Answer

Hypovolemic shock

Answer

Asthma

General Anesthesia — MCQs

General Anesthesia — MCQs

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