General Anesthesia Practice Questions

Q: Which of the following statements regarding halothane is true except?

It is contraindicated in patients with bronchial asthma.. **Explanation:** The correct answer is **D**, as Halothane is actually **indicated** (not contraindicated) in patients with bronchial asthma. **1. Why Option D is the Correct Answer (The Exception):** Halothane is a potent **bronchodilator**. It reduces airway resistance by relaxing bronchial smooth muscle and inhibiting airway reflexes. Historically, it was the agent of choice for inducing anesthesia in patients with reactive airway diseases like asthma. Therefore, stating it is contraindicated in asthma is medically incorrect. **2. Analysis of Other Options:** * **Option A (True):** Halothane is a potent cerebral vasodilator. This increases cerebral blood flow (CBF) and, consequently, **intracranial pressure (ICP)**. Therefore, it is generally avoided or used with extreme caution in patients with space-occupying intracranial lesions. * **Option B (True):** Halothane causes dose-dependent **hypotension**. This occurs primarily through direct myocardial depression (decreased cardiac output) rather than peripheral vasodilation. * **Option C (True):** Halothane has a pleasant, non-pungent odor and does not irritate the airways. This allows for a **smooth and rapid inhalation induction**, making it a classic choice for pediatric anesthesia (though largely replaced by Sevoflurane in modern practice). **NEET-PG High-Yield Pearls:** * **Halothane Hepatitis:** A rare but serious immune-mediated hepatotoxicity (more common in obese females after multiple exposures). * **Catecholamine Sensitivity:** Halothane sensitizes the myocardium to endogenous and exogenous catecholamines, increasing the risk of **ventricular arrhythmias** (especially if adrenaline is used). * **Malignant Hyperthermia:** Like all volatile anesthetics, Halothane is a known trigger. * **Blood-Gas Partition Coefficient:** 2.3 (higher than Sevoflurane/Desflurane, leading to slower recovery).

Q: All of the following factors decrease the Minimum Alveolar Concentration (MAC) of an inhalation anesthetic agent except?

Hypocalcemia. **Explanation:** Minimum Alveolar Concentration (MAC) is the concentration of an inhalation anesthetic at 1 atmosphere that prevents skeletal muscle movement in response to a noxious stimulus in 50% of patients. It is an index of anesthetic potency: the lower the MAC, the more potent the agent. **Why Hypocalcemia is the Correct Answer:** Serum electrolyte levels generally have a predictable effect on MAC, but **Hypocalcemia** (and Hypercalcemia) has **no significant effect** on MAC. While calcium is vital for neurotransmitter release, clinical variations in calcium levels do not alter the requirement for volatile anesthetics. **Analysis of Incorrect Options (Factors that DO decrease MAC):** * **Hypothermia:** MAC decreases by approximately 2–5% for every 1°C drop in body temperature. Lower temperatures reduce cerebral metabolic rate and increase the solubility of the gas in the blood. * **Hyponatremia:** Low sodium levels in the extracellular fluid lead to decreased neuronal excitability and increased sedation, thereby reducing the anesthetic requirement. (Conversely, Hypernatremia increases MAC). * **Anemia:** Severe anemia (Hemoglobin < 5 g/dL) decreases MAC because it reduces the oxygen-carrying capacity, leading to a degree of cerebral hypoxia which potentiates anesthesia. **High-Yield Clinical Pearls for NEET-PG:** * **Factors Increasing MAC:** Hyperthermia, Hypernatremia, Chronic alcoholism, and drugs that increase central neurotransmitters (MAO inhibitors, Cocaine, Ephedrine, Levodopa). * **Factors Decreasing MAC:** Pregnancy (due to progesterone), Acute alcohol intoxication, Old age, Hypoxia ($PaO_2 < 38$ mmHg), and Hypotension (MAP $< 40$ mmHg). * **Factors with NO effect on MAC:** Gender, Duration of anesthesia, Thyroid status (unless severe/myxedema), and Hyper/Hypokalemia.

Q: Which anesthetic agent is explosive in the presence of cautery?

Ether. **Explanation:** The correct answer is **Ether (Diethyl Ether)**. **1. Why Ether is the Correct Answer:** Ether is a highly volatile liquid that produces vapors heavier than air. It is extremely flammable and forms explosive mixtures when combined with air, oxygen, or nitrous oxide. In the presence of an ignition source—such as **electrocautery (diathermy)** or static sparks—ether can lead to devastating operating room fires or explosions. Due to this significant safety hazard, its use has been largely phased out in modern anesthetic practice in favor of non-flammable halogenated agents. **2. Analysis of Incorrect Options:** * **Nitrous Oxide (A):** While nitrous oxide is **not flammable** itself, it is an **oxidizer** that supports combustion. It can make an existing fire more intense, but it is not "explosive" on its own. * **Trilene (C):** Trichloroethylene is non-flammable and non-explosive at clinical concentrations. However, it is contraindicated with soda lime because it reacts to form toxic products like phosgene and dichloroacetylene. * **Halothane (D):** Halothane is a halogenated hydrocarbon designed specifically to be **non-flammable** and non-explosive, making it safe for use with cautery. **3. High-Yield Clinical Pearls for NEET-PG:** * **Non-flammable agents:** Halothane, Isoflurane, Sevoflurane, and Desflurane (all modern volatile agents). * **Flammable/Explosive agents:** Ether and Cyclopropane (both are now obsolete). * **The "Fire Triangle":** Requires a fuel (anesthetic), an oxidizer ($O_2$ or $N_2O$), and an ignition source (cautery/laser). * **Static Electricity:** To prevent sparks near flammable agents, operating rooms historically used antistatic flooring and black antistatic rubber tubing.

Q: Which is the most pungent inhalational anesthetic agent?

Desflurane. ### Explanation The correct answer is **Desflurane**. **Why Desflurane is the correct answer:** Pungency refers to the irritating nature of an anesthetic gas on the airway mucosa. **Desflurane** is the most pungent inhalational agent currently in clinical use. When administered to an awake or lightly anesthetized patient, its high pungency triggers airway reflexes, leading to **coughing, breath-holding, and laryngospasm**. Consequently, Desflurane is strictly contraindicated for **inhalation induction**, especially in pediatric patients. **Analysis of Incorrect Options:** * **Halothane:** Known for its pleasant, sweet smell and non-irritant nature. It was historically the gold standard for smooth inhalation induction but is now rarely used due to hepatotoxicity ("Halothane Hepatitis"). * **Isoflurane:** It is pungent and can cause airway irritation, but significantly less so than Desflurane. It is generally avoided for induction but is widely used for maintenance. * **Enflurane:** While it has a mild ether-like odor and some irritant properties, its pungency does not reach the clinical significance of Desflurane. (Note: It is also associated with seizure-like EEG activity). **High-Yield Clinical Pearls for NEET-PG:** * **Agent of Choice for Induction:** **Sevoflurane** is the least pungent and most preferred agent for smooth inhalation induction. * **Boiling Point:** Desflurane has a very low boiling point (23.5°C), requiring a specialized heated vaporizer (**Tec 6**). * **Blood-Gas Partition Coefficient:** Desflurane has the lowest coefficient (0.42), leading to the fastest induction and emergence among potent volatile agents. * **Sympathetic Stimulation:** Rapid increases in Desflurane concentration can cause transient tachycardia and hypertension.

Q: Which of the following has analgesic property?

Thiopental. **Explanation:** The question asks which of the following has analgesic properties. However, there appears to be a discrepancy in the provided key: **Thiopental is actually an anti-analgesic**, while **Nitrous Oxide and Ketamine are potent analgesics.** In the context of standard medical teaching for NEET-PG, the explanation is as follows: **1. Why the Correct Answer (as per your key) is unique:** **Thiopental (Option C)** is a barbiturate used for induction. It is notorious for being **hyperalgesic** (it lowers the pain threshold). It provides no pain relief; in fact, patients may react more intensely to painful stimuli under light thiopental anesthesia. If the question intended to ask which drug *lacks* analgesic property or is *anti-analgesic*, Thiopental would be the answer. **2. Analysis of Other Options:** * **Nitrous Oxide (Option A):** A potent **analgesic** gas. Its analgesic effect is mediated via the release of endogenous opioid peptides in the periaqueductal gray matter. * **Ketamine (Option B):** A phencyclidine derivative that produces "dissociative anesthesia." It is a **profound analgesic** even at sub-anesthetic doses, acting primarily as an NMDA receptor antagonist. * **Etomidate (Option D):** An imidazole derivative used for hemodynamically unstable patients. Like Thiopental, it **lacks analgesic properties**, but unlike Thiopental, it is not typically labeled as "anti-analgesic." **3. Clinical Pearls for NEET-PG:** * **Ketamine** is the only intravenous anesthetic that possesses significant analgesic properties and stimulates the cardiovascular system. * **Propofol, Thiopental, and Etomidate** provide hypnosis but **zero analgesia**; they must be supplemented with opioids or nitrous oxide. * **Thiopental High-Yields:** Causes garlic/onion taste before unconsciousness, is the drug of choice for ECT (though Methohexital is preferred globally), and is contraindicated in Porphyria.

Q: The complete fluorination in Desflurane produces all the following effects except:

High potency. **Explanation:** Desflurane is a fluorinated methyl ethyl ether. The "complete fluorination" refers to the substitution of all chlorine atoms with fluorine atoms (specifically, replacing the chlorine atom found in Isoflurane). **Why "High Potency" is the Correct Answer (The Exception):** Potency of an anesthetic agent is inversely proportional to its **Minimum Alveolar Concentration (MAC)** and directly related to its lipid solubility (Meyer-Overton hypothesis). Fluorination significantly **decreases lipid solubility**, which in turn **decreases potency**. Desflurane has a MAC of approximately 6%, making it the least potent among commonly used volatile anesthetics (compared to Isoflurane at 1.15% or Sevoflurane at 2%). **Analysis of Incorrect Options:** * **A. Decreases blood and tissue solubility:** Fluorination reduces the blood-gas partition coefficient (0.42 for Desflurane). This ensures rapid induction and, more importantly, the fastest emergence/recovery among volatile agents. * **B. High vapor pressure:** The fluorine atoms increase the vapor pressure significantly (669 mmHg at 20°C). This is near atmospheric pressure, meaning it would boil at room temperature in high altitudes. * **C. Requirement of special vaporizer:** Due to its high vapor pressure and low boiling point (22.8°C), Desflurane requires a specialized, heated, and pressurized vaporizer (e.g., **Tec 6** or Apex) to deliver a constant concentration. **Clinical Pearls for NEET-PG:** * **Pungency:** Desflurane is highly pungent and an irritant to the airway; it can cause coughing, breath-holding, and laryngospasm. Therefore, it is **not** used for inhalation induction (Sevoflurane is preferred). * **Sympathetic Stimulation:** Rapid increases in Desflurane concentration can lead to transient tachycardia and hypertension. * **Carbon Monoxide:** Desflurane produces the highest amount of Carbon Monoxide (CO) when passed through dry soda lime.

Q: Crystalloid required for replacement of 300ml of blood loss is:

900ml. **Explanation:** The correct answer is **900ml** based on the established physiological ratio for fluid resuscitation in the setting of acute blood loss. **1. The Underlying Concept (The 3:1 Rule):** When replacing blood loss with isotonic crystalloids (such as Normal Saline or Ringer’s Lactate), a **3:1 ratio** is required. This is because crystalloids do not remain entirely within the intravascular space; they rapidly redistribute into the interstitial compartment. Only about 1/3rd to 1/4th of the infused crystalloid volume remains intravascular after 20–30 minutes. Therefore, to replace a 300ml deficit in intravascular volume, you must administer three times that amount: **300ml × 3 = 900ml**. **2. Analysis of Incorrect Options:** * **Option A (300ml):** This represents a 1:1 ratio. This is only appropriate when replacing blood with **colloids** (like albumin or starches) or **blood products**, as these substances stay primarily within the intravascular space due to their high oncotic pressure. * **Option B (600ml):** This represents a 2:1 ratio, which is insufficient to compensate for the redistribution of crystalloids into the interstitium. * **Option D (1200ml):** This represents a 4:1 ratio. While some older texts mentioned a 3:1 to 4:1 range, the standard teaching for exam purposes and modern restrictive fluid strategies is the 3:1 ratio to avoid fluid overload and interstitial edema. **High-Yield Clinical Pearls for NEET-PG:** * **Crystalloid to Blood Ratio:** 3:1 * **Colloid to Blood Ratio:** 1:1 * **Maximum Allowable Blood Loss (MABL):** Calculated as $[EBV \times (Hct_{initial} - Hct_{target})] / Hct_{initial}$. * **Fluid of Choice:** Ringer’s Lactate is generally preferred over Normal Saline for large volume resuscitation to avoid hyperchloremic metabolic acidosis.

Q: Which non-depolarizing muscle relaxant is contraindicated in the patient shown?

Gallamine. ***Gallamine*** - **100% renal excretion** unchanged makes it absolutely contraindicated in **end-stage renal disease** patients with AV fistulas for hemodialysis. - Prolonged **neuromuscular blockade** can occur due to impaired kidney function and inability to clear the drug. *Pancuronium* - Only **80% renal excretion** with **20% hepatic metabolism**, making it relatively safer in renal impairment. - **Dose reduction** may be needed, but not absolutely contraindicated like gallamine. *Vecuronium* - Primarily **hepatic metabolism** with only **30% renal excretion**, making it safer in kidney disease. - **Shorter duration** and predictable recovery even in renal failure patients. *Rocuronium* - Predominantly **hepatic elimination** with minimal renal excretion (**10-20%**), making it suitable for renal patients. - **Rapid onset** and **intermediate duration** with reliable recovery regardless of kidney function.

Q: Which anaesthetic agent should NOT be used in a patient with a previous history of halothane-induced hepatitis?

Methoxyflurane. **Explanation:** The correct answer is **Methoxyflurane**. **1. Why Methoxyflurane is the correct choice:** Halothane-induced hepatitis is believed to be an immune-mediated reaction triggered by the metabolism of halothane into **trifluoroacetylated (TFA) proteins**. These proteins act as haptens, leading to the formation of autoantibodies. There is a high degree of **cross-sensitivity** between volatile anesthetics that undergo significant metabolism into TFA intermediates. Methoxyflurane, along with Halothane and Enflurane, undergoes significant hepatic metabolism (up to 50-70% for Methoxyflurane) and shares similar metabolic pathways. Therefore, it is strictly contraindicated in patients with a history of halothane-induced hepatitis to avoid a potentially fatal recurrent hepatic injury. **2. Analysis of Incorrect Options:** * **Sevoflurane:** It is not metabolized into TFA intermediates. It is primarily metabolized into inorganic fluoride and hexafluoroisopropanol, making it the safest volatile agent regarding halothane-related cross-reactivity. * **Isoflurane:** While it does produce a very small amount of TFA proteins, the metabolism is extremely low (0.2%). While caution is advised, it is not as strictly contraindicated as Methoxyflurane or Enflurane. * **Ketamine:** This is an intravenous induction agent, not a halogenated ether. It does not share the metabolic pathway or the chemical structure responsible for halothane-induced hepatitis. **3. Clinical Pearls for NEET-PG:** * **Metabolism Rule:** The risk of hepatitis correlates with the degree of hepatic metabolism: Halothane (20%) > Enflurane (2%) > Isoflurane (0.2%) > Desflurane (0.02%). * **Methoxyflurane** is also notorious for **nephrotoxicity** due to the release of inorganic fluoride ions (High-output renal failure). * **Risk Factors for Halothane Hepatitis:** Female gender, obesity, middle age, and multiple exposures to halothane.

Question 1

Which of the following statements regarding halothane is true except?

Accepted Answer

It is contraindicated in patients with bronchial asthma.

Answer

It is contraindicated in patients with intracranial lesions.

Answer

It can cause hypotension.

Answer

It allows smooth and rapid loss of unconsciousness.

Question 2

All of the following factors decrease the Minimum Alveolar Concentration (MAC) of an inhalation anesthetic agent except?

Accepted Answer

Hypocalcemia

Answer

Hypothermia

Answer

Hyponatremia

Answer

Anemia

Question 3

Which anesthetic agent is explosive in the presence of cautery?

Accepted Answer

Ether

Answer

Nitrous oxide

Answer

Trilene

Answer

Halothane

Question 4

Which is the most pungent inhalational anesthetic agent?

Accepted Answer

Desflurane

Answer

Halothane

Answer

Isoflurane

Answer

Enflurane

Question 5

'Diffusion hypoxia' is likely to occur only after use of nitrous oxide because it?

Accepted Answer

Has low blood solubility and is used in high concentration

Answer

Is a respiratory depressant

Answer

Is a very potent anaesthetic

Answer

Interferes with diffusion of oxygen into the tissues

Question 6

Which of the following has analgesic property?

Accepted Answer

Thiopental

Answer

Nitrous oxide

Answer

Ketamine

Answer

Etomidate

Question 7

The complete fluorination in Desflurane produces all the following effects except:

Accepted Answer

High potency

Answer

Decreases blood and tissue solubility

Answer

High vapor pressure

Answer

Requirement of special vaporizer

Question 8

Crystalloid required for replacement of 300ml of blood loss is:

Accepted Answer

900ml

Answer

300ml

Answer

600ml

Answer

1200ml

Question 9

Which non-depolarizing muscle relaxant is contraindicated in the patient shown?

Accepted Answer

Gallamine

Answer

Pancuronium

Answer

Vecuronium

Answer

Rocuronium

Question 10

Which anaesthetic agent should NOT be used in a patient with a previous history of halothane-induced hepatitis?

Accepted Answer

Methoxyflurane

Answer

Sevoflurane

Answer

Isoflurane

Answer

Ketamine

General Anesthesia — MCQs

General Anesthesia — MCQs

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