General Anesthesia Practice Questions

Q: All of the following are intravenous anesthetic induction agents except?

Bupivacaine. **Explanation:** The correct answer is **D. Bupivacaine**. The fundamental distinction here lies between **General Anesthetics** and **Local Anesthetics**. * **Why Bupivacaine is the correct answer:** Bupivacaine is a potent, long-acting **Local Anesthetic (LA)** of the amide group. It works by blocking voltage-gated sodium channels in peripheral nerves or the spinal cord to prevent signal conduction. It is used for regional anesthesia (spinal, epidural) and nerve blocks, but it is **never** used as an intravenous induction agent for general anesthesia. In fact, accidental intravenous injection of Bupivacaine is highly toxic, leading to severe cardiotoxicity. **Analysis of Incorrect Options (Intravenous Induction Agents):** * **A. Thiopentone Sodium:** An ultra-short-acting barbiturate. It was the gold standard for induction for decades. It acts via GABA-A receptors. * **B. Ketamine:** A dissociative anesthetic that acts as an NMDA receptor antagonist. It is unique because it provides significant analgesia and maintains sympathetic tone. * **C. Etomidate:** An imidazole derivative used for induction, favored in hemodynamically unstable patients (e.g., trauma or heart failure) due to its minimal effect on blood pressure and heart rate. **High-Yield Clinical Pearls for NEET-PG:** * **Propofol:** Currently the most common induction agent; known for its anti-emetic properties and "milk of amnesia" appearance. * **Etomidate Side Effect:** Can cause transient **adrenocortical suppression** by inhibiting the enzyme 11-beta-hydroxylase. * **Ketamine:** The drug of choice for induction in **bronchial asthma** (bronchodilator) and **hypovolemic shock**. * **Bupivacaine Toxicity:** If systemic toxicity (LAST) occurs, the specific antidote is **Intralipid (20% Lipid Emulsion)**.

Q: Which of the following is contraindicated in chronic renal failure (CRF)?

Enflurane. **Explanation:** The primary concern when using volatile anesthetics in patients with Chronic Renal Failure (CRF) is the production of **inorganic fluoride ions** during hepatic metabolism. High levels of fluoride are nephrotoxic, causing a vasopressin-resistant polyuric state (nephrogenic diabetes insipidus). **Why Enflurane is the Correct Answer:** Enflurane undergoes significant metabolism (approx. 2.4%), releasing high concentrations of inorganic fluoride. In patients with pre-existing renal impairment, the kidney's inability to excrete these ions increases the risk of further parenchymal damage. Therefore, it is traditionally contraindicated in CRF. **Analysis of Other Options:** * **Halothane:** It is primarily associated with hepatotoxicity ("Halothane Hepatitis") rather than nephrotoxicity. It undergoes minimal metabolism to fluoride. * **Isoflurane:** It is highly stable with very low metabolism (0.2%). It produces negligible fluoride levels, making it one of the safest choices for patients with renal failure. * **Desflurane:** It has the lowest metabolism rate (0.02%) among all potent volatile agents. It is considered safe in CRF due to minimal fluoride production. **High-Yield Clinical Pearls for NEET-PG:** 1. **Sevoflurane & Compound A:** While Sevoflurane produces fluoride, the main concern in renal patients is **Compound A**, a nephrotoxic byproduct formed when Sevoflurane reacts with dry soda lime. 2. **Drug of Choice:** **Isoflurane** is often considered the volatile agent of choice in renal failure due to its cardiovascular stability and minimal metabolism. 3. **Muscle Relaxant of Choice:** **Atracurium or Cisatracurium** are preferred in CRF because they undergo **Hofmann elimination**, which is independent of renal function.

Q: What is the approximate incidence of hepatitis following halothane use?

1 in 30,000. **Explanation:** Halothane-induced hepatotoxicity is a classic pharmacological concept categorized into two types. Type I (minor) is common, characterized by a transient rise in transaminases. Type II (major) is **Halothane Hepatitis**, a rare but severe immune-mediated fulminant hepatic failure. **1. Why Option C is Correct:** Large-scale epidemiological studies (such as the National Halothane Study) established that the incidence of severe halothane hepatitis is approximately **1 in 30,000** exposures. The mechanism involves the metabolism of halothane by Cytochrome P450 to **trifluoroacetyl chloride**, which binds to hepatic proteins. In susceptible individuals, these "neo-antigens" trigger an IgG-mediated immune response, leading to massive hepatic necrosis. **2. Why Other Options are Incorrect:** * **Options A (20%) and B (40%):** These percentages are far too high for a rare idiosyncratic drug reaction. However, roughly 20% of patients may show a subclinical, transient rise in liver enzymes (Type I), which should not be confused with true hepatitis. * **Option D (1 in 3,000):** While some older studies suggested higher rates in specific high-risk populations (e.g., obese females undergoing multiple exposures), the globally accepted standard for the general population remains 1 in 30,000. **High-Yield Clinical Pearls for NEET-PG:** * **Risk Factors:** "Middle-aged, obese females" is the classic demographic. Multiple exposures within a short period (less than 28 days) significantly increase risk. * **Metabolism:** Halothane undergoes significant hepatic metabolism (~20%), much higher than Isoflurane (0.2%) or Desflurane (0.02%), explaining its higher hepatotoxic potential. * **Clinical Presentation:** Fever, jaundice, and eosinophilia typically appear 3–14 days post-exposure. * **Pediatrics:** Children are remarkably resistant to halothane hepatitis, making it historically popular in pediatric anesthesia.

Q: Arrange the following inhalational anesthetic agents according to increasing MAC values: Isoflurane, Desflurane, Sevoflurane, Halothane?

Halothane, Isoflurane, Sevoflurane, Desflurane. **Explanation:** The core concept tested here is the relationship between **Minimum Alveolar Concentration (MAC)** and **Anesthetic Potency**. MAC is defined as the concentration of an inhalational anesthetic at 1 atmosphere that prevents skeletal muscle movement in response to a noxious stimulus in 50% of patients. Crucially, **MAC is inversely proportional to potency**: the lower the MAC value, the more potent the agent. Potency is also directly related to the **Oil:Gas partition coefficient** (Meyer-Overton Hypothesis). The standard MAC values for these agents (in 100% Oxygen) are: 1. **Halothane:** ~0.75% (Most potent) 2. **Isoflurane:** ~1.15% 3. **Sevoflurane:** ~2.0% 4. **Desflurane:** ~6.0% (Least potent) Therefore, the correct increasing order of MAC values is **Halothane < Isoflurane < Sevoflurane < Desflurane**. **Analysis of Options:** * **Option A is correct** as it follows the established potency hierarchy. * **Option B** incorrectly places Sevoflurane before Isoflurane; Isoflurane is more potent and has a lower MAC than Sevoflurane. * **Option C** starts with Desflurane, which actually has the highest MAC (lowest potency) among the four. * **Option D** is incorrect as it places Halothane as the least potent agent, whereas it is the most potent. **High-Yield Clinical Pearls for NEET-PG:** * **Nitrous Oxide (N₂O):** Has the highest MAC (~104%), making it the least potent. * **Factors increasing MAC:** Infancy (highest at 6 months), hyperthermia, hypernatremia, and chronic alcohol abuse. * **Factors decreasing MAC:** Elderly age, pregnancy, acute alcohol intoxication, hypoxia, and anemia. * **Mnemonic for Potency (Highest to Lowest):** **H**is **I**nner **S**pirit **D**ied (**H**alothane > **I**soflurane > **S**evoflurane > **D**esflurane).

Q: Which is the most potent bronchodilator among the inhalational anesthetic agents?

Halothane. **Explanation:** The correct answer is **Halothane**. **1. Why Halothane is the correct answer:** Halothane is historically recognized as the most potent bronchodilator among volatile anesthetic agents. It acts by directly relaxing airway smooth muscle and inhibiting reflex bronchoconstriction mediated by the vagus nerve. It also decreases the release of histamine and other inflammatory mediators. Due to its superior bronchodilatory properties and non-pungent odor, it was traditionally the "gold standard" for inhalational induction in patients with reactive airway diseases like asthma or COPD. **2. Analysis of Incorrect Options:** * **Sevoflurane:** While Sevoflurane is an excellent bronchodilator and is the current drug of choice for inhalational induction (due to its low pungency and rapid onset), it is pharmacologically slightly less potent than Halothane in terms of direct smooth muscle relaxation. * **Isoflurane:** This agent possesses bronchodilatory properties but is highly pungent. This pungency can cause airway irritation, coughing, and laryngospasm during induction, making it unsuitable for patients with active bronchospasm. * **Desflurane:** This is the most pungent volatile agent. At higher concentrations, it can actually cause **bronchoconstriction** and increased airway resistance due to sympathetic stimulation and airway irritation. It is generally avoided in patients with asthma. **3. High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice for Induction in Asthma:** Sevoflurane (due to the best balance of bronchodilation and lack of irritation). * **Most Pungent/Irritant:** Desflurane > Isoflurane. * **Least Pungent:** Sevoflurane > Halothane. * **Arrhythmogenic Potential:** Halothane sensitizes the myocardium to catecholamines; therefore, it is contraindicated if exogenous adrenaline is being used.

Q: Which of the following colloid solutions has a proven thromboprophylactic effect?

Dextran 40. **Explanation:** **Dextran 40** (Low Molecular Weight Dextran) is the correct answer because it possesses unique antithrombotic properties beyond simple volume expansion. Its **thromboprophylactic effect** is mediated through several mechanisms: 1. **Decreased Platelet Adhesiveness:** It coats the surface of platelets and vascular endothelium, reducing their interaction. 2. **Alteration of Fibrin Structure:** It makes fibrin clots more susceptible to fibrinolysis (easier to break down). 3. **Reduced Blood Viscosity:** By decreasing erythrocyte aggregation (sludging), it improves microcirculatory flow, which is particularly beneficial in vascular surgeries. **Analysis of Incorrect Options:** * **Gelatin:** These are urea-linked or succinylated bovine collagens. While they have minimal effects on coagulation compared to other colloids, they do not possess active thromboprophylactic properties and are associated with a higher risk of anaphylaxis. * **Dextran 100:** Higher molecular weight dextrans are less effective for thromboprophylaxis and are more likely to cause "rouleaux formation" (interfering with blood cross-matching) compared to Dextran 40. * **Hetastarch (HES):** Hydroxyethyl starches are notorious for *causing* coagulopathy by reducing Factor VIII and von Willebrand factor levels. They are generally avoided in critically ill patients due to risks of acute kidney injury (AKI) and bleeding. **High-Yield Pearls for NEET-PG:** * **Dextran 40** is primarily used to improve microcirculation in vascular grafts and replantation surgeries. * **Side Effect:** Dextrans can cause **osmotic nephrosis** and acute renal failure if the patient is dehydrated. * **Interference:** Dextran can interfere with blood grouping and cross-matching (though less so with Dextran 40 than Dextran 70/100). * **Maximum Dose:** Limit Dextran 40 to **1.5 g/kg/day** to avoid bleeding complications.

Question 1

All of the following are intravenous anesthetic induction agents except?

Accepted Answer

Bupivacaine

Answer

Thiopentone sodium

Answer

Ketamine

Answer

Etomidate

Question 2

All of the following are considered stages of anesthesia except:

Accepted Answer

Allodynia

Answer

Analgesia

Answer

Delirium

Answer

Surgical anesthesia

Question 3

Which of the following is contraindicated in chronic renal failure (CRF)?

Accepted Answer

Enflurane

Answer

Halothane

Answer

Desflurane

Answer

Isoflurane

Question 4

Which of the following statements about cisatracurium, the pure cis isomer of atracurium, is FALSE?

Accepted Answer

It produces more laudanosine than an equipotent dose of atracurium.

Answer

It is metabolized primarily by Hoffman degradation.

Answer

It is cardiovascularly stable.

Answer

It has an onset and duration similar to atracurium.

Question 5

What is the approximate incidence of hepatitis following halothane use?

Accepted Answer

1 in 30,000

Answer

20%

Answer

40%

Answer

1 in 3,000

Question 6

Remifentanil is:

Accepted Answer

Useful for short, painful procedures

Answer

A long-acting anesthetic

Answer

Administered by intravenous bolus dose

Answer

Metabolized by plasma esterases

Question 7

Arrange the following inhalational anesthetic agents according to increasing MAC values: Isoflurane, Desflurane, Sevoflurane, Halothane?

Accepted Answer

Halothane, Isoflurane, Sevoflurane, Desflurane

Answer

Halothane, Sevoflurane, Isoflurane, Desflurane

Answer

Desflurane, Halothane, Sevoflurane, Isoflurane

Answer

Isoflurane, Desflurane, Sevoflurane, Halothane

Question 8

Which intravenous anesthetic agent is preferred in patients with renal failure?

Accepted Answer

Cisatracurium

Answer

Atracurium

Answer

Vivacurium

Answer

Pancuronium

Question 9

Which is the most potent bronchodilator among the inhalational anesthetic agents?

Accepted Answer

Halothane

Answer

Isoflurane

Answer

Sevoflurane

Answer

Desflurane

Question 10

Which of the following colloid solutions has a proven thromboprophylactic effect?

Accepted Answer

Dextran 40

Answer

Gelatin

Answer

Dextran 100

Answer

Hetastarch

General Anesthesia — MCQs

General Anesthesia — MCQs

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