General Anesthesia Practice Questions

Q: A patient with chronic kidney disease on dialysis is posted for emergency laparotomy. Which of the following anesthetic agents is contraindicated in this patient?

Gallamine. **Explanation:** The correct answer is **Gallamine**. **1. Why Gallamine is the Correct Answer:** Gallamine is a long-acting non-depolarizing neuromuscular blocking agent that is **exclusively (100%) excreted by the kidneys** in an unchanged form. In patients with chronic kidney disease (CKD) or renal failure, the elimination of Gallamine is virtually non-existent, leading to prolonged neuromuscular blockade and "recurarization." Due to this absolute dependence on renal excretion, it is strictly contraindicated in patients with renal impairment. **2. Analysis of Incorrect Options:** * **d-Tubocurarine:** While it is primarily excreted by the kidneys (approx. 60-70%), it undergoes significant **biliary excretion** as an alternative pathway in renal failure. Thus, it is not strictly contraindicated, though it should be used with caution. * **Scoline (Succinylcholine):** It is metabolized by plasma pseudocholinesterase. While it can cause a transient rise in serum potassium (approx. 0.5 mEq/L), it is not contraindicated in CKD unless the patient is already **hyperkalemic** (K+ > 5.5 mEq/L). * **Halothane:** This is an inhalational anesthetic metabolized primarily by the liver (20%) and exhaled by the lungs. It does not depend on renal clearance and is not contraindicated in renal failure. **3. High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice (DOC):** **Atracurium** or **Cisatracurium** are the muscle relaxants of choice in renal failure because they undergo **Hofmann elimination** (organ-independent metabolism). * **Pancuronium & Decamethonium:** Like Gallamine, these are also primarily excreted by the kidneys and should be avoided. * **Vecuronium/Rocuronium:** These are mainly eliminated via the biliary system and are relatively safe in renal failure.

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. Its chemical structure makes it extremely **flammable and explosive** when mixed with air, oxygen, or nitrous oxide. In the presence of an ignition source, such as **electrocautery** or static electricity in the operating theater, it can lead to devastating fires or explosions. Due to this significant safety hazard, its use has been entirely phased out in modern anesthetic practice in favor of non-flammable fluorinated hydrocarbons. **2. Analysis of Incorrect Options:** * **Nitrous Oxide (A):** While it is a **supporter of combustion** (it can make an existing fire burn more intensely), it is not flammable or explosive by itself. * **Trilene (C):** Trichloroethylene is non-flammable at clinical concentrations. However, it is contraindicated in closed circuits because it reacts with soda lime to form toxic products like phosgene and cranial nerve toxins (e.g., heat-induced decomposition). * **Halothane (D):** Halothane is a halogenated hydrocarbon designed specifically to be **non-flammable and non-explosive**, which was its primary advantage over ether when it was introduced. **3. High-Yield Clinical Pearls for NEET-PG:** * **Modern Volatile Agents:** All current agents (Isoflurane, Sevoflurane, Desflurane) are non-flammable. * **Cyclopropane:** Another historical agent (not listed here) that is even more explosive than ether. * **Fire Triad:** Surgical fires require an oxidizer (O2/N2O), an ignition source (Cautery/Laser), and fuel (Drapes/Alcohol-based preps). * **Ether Day:** October 16, 1846 (First public demonstration by W.T.G. Morton).

Q: Which is the most physiological intravenous fluid?

Ringer's Lactate. **Explanation:** The term "physiological" refers to how closely an intravenous fluid mimics the electrolyte composition and pH of human plasma. **Ringer’s Lactate (RL)** is considered the most physiological crystalloid among the options provided. **Why Ringer’s Lactate is the Correct Answer:** RL is a balanced salt solution. Its electrolyte concentrations (Sodium 130 mEq/L, Potassium 4 mEq/L, Calcium 3 mEq/L) are very close to plasma levels. Crucially, it contains **Sodium Lactate**, which is metabolized by the liver into bicarbonate, acting as a buffer to maintain acid-base balance. Its osmolarity (273 mOsm/L) is also near-isotonic to plasma. **Why Other Options are Incorrect:** * **Normal Saline (0.9% NaCl):** Despite its name, it is "unphysiological." It has a much higher Chloride content (154 mEq/L) than plasma (98–106 mEq/L). Large volumes lead to **Hyperchloremic Metabolic Acidosis** and can cause renal vasoconstriction. * **5% Dextrose:** Once the glucose is metabolized by the body, it becomes free water. It is essentially a hypotonic solution that distributes throughout the total body water, making it ineffective for intravascular volume resuscitation and potentially causing cellular edema (e.g., cerebral edema). **High-Yield Clinical Pearls for NEET-PG:** * **Fluid of Choice:** RL is the preferred fluid for trauma, burns (Parkland Formula), and most intraoperative replacements. * **Contraindications for RL:** Avoid in patients receiving blood transfusions (Calcium in RL can cause clotting in the tubing) and in patients with head injuries (due to its slight hypotonicity). * **Plasma-Lyte:** Often cited as even more physiological than RL because it uses acetate/gluconate buffers and has an osmolarity even closer to plasma (295 mOsm/L). If Plasma-Lyte were an option, it would be the superior "physiological" choice.

Q: Which of the following intravenous anesthetic agents is considered the most immunogenically safe?

Etomidate. **Explanation:** The correct answer is **Etomidate**. Immunogenic safety in intravenous anesthetics refers to the drug’s potential to trigger histamine release or anaphylactoid reactions. **Why Etomidate is the Correct Answer:** Etomidate is a carboxylated imidazole derivative. It is uniquely characterized by its **lack of histamine release**, making it the most immunogenically safe agent among the options. Clinically, this makes it a preferred choice for patients with reactive airway disease (asthma) or those with a high risk of allergic sensitivity. Additionally, its hemodynamic stability (minimal effect on heart rate and blood pressure) makes it the gold standard for induction in patients with cardiovascular compromise. **Analysis of Incorrect Options:** * **Thiopentone:** This is the most common IV anesthetic associated with true anaphylaxis and significant dose-dependent histamine release. It is strictly contraindicated in patients with porphyria and should be used with caution in asthmatics. * **Propofol:** While generally safe, propofol is formulated in an emulsion containing soybean oil and egg lecithin. It can trigger allergic reactions in susceptible individuals and has been known to cause rare but documented anaphylaxis. * **Ketamine:** Although ketamine is a bronchodilator, it can occasionally cause mild histamine release and increased secretions, making it less "immunogenically inert" than etomidate. **NEET-PG High-Yield Pearls:** * **Etomidate Side Effect:** Its most significant drawback is **adrenocortical suppression** (inhibits 11-beta-hydroxylase), which can last for 24 hours after a single dose. * **Drug of Choice:** Etomidate is the drug of choice for **cardiac induction** and **ECT** (due to its minimal effect on seizure threshold). * **Thiopentone:** Known for its "garlic/onion" taste during induction and its role as a potent cerebral protectant.

Q: Which anesthetic agent is contraindicated in epilepsy?

Enflurane. **Explanation:** The correct answer is **Enflurane**. **Why Enflurane is the correct answer:** Enflurane is unique among volatile anesthetics because it can induce **seizure-like activity** on an Electroencephalogram (EEG), characterized by high-voltage, high-frequency spikes and spike-and-wave complexes. This pro-convulsant effect is significantly potentiated by **hypocapnia** (low $PaCO_2$ due to hyperventilation) and high concentrations of the drug. In some cases, these EEG changes are accompanied by visible tonic-clonic muscle twitching. Therefore, it is strictly contraindicated in patients with a history of epilepsy or seizure disorders. **Analysis of Incorrect Options:** * **Isoflurane:** An isomer of enflurane, but it does not provoke seizure activity. In fact, it has anticonvulsant properties at higher concentrations and is often used to suppress status epilepticus. * **Halothane:** It does not induce seizures and is generally considered safe for the brain's electrical activity, though it is rarely used today due to hepatotoxicity. * **Ether:** While historically significant, ether does not have a specific association with inducing epilepsy; its primary drawbacks are flammability and slow induction/recovery. **NEET-PG High-Yield Pearls:** * **Drug of Choice for Epilepsy:** **Thiopentone** (Barbiturate) is the gold standard for brain protection and seizure suppression. Among inhalational agents, **Isoflurane** is preferred. * **Ketamine & Methohexital:** These are other intravenous agents known to lower the seizure threshold (Methohexital is often used to *induce* seizures during Electroconvulsive Therapy). * **Sevoflurane:** While generally safe, at very high concentrations in pediatric patients, it has occasionally been associated with epileptiform EEG patterns, though Enflurane remains the classic "textbook" contraindication.

Q: Histamine release is one of the common features with administration of which of the following drugs?

Atracurium. **Explanation:** **Atracurium** is a benzylisoquinolinium neuromuscular blocking agent known for its potential to cause **non-immunologic histamine release** from mast cells. This occurs via direct displacement of histamine and is typically dose- and rate-dependent. Clinically, this may manifest as cutaneous flushing, tachycardia, and hypotension. To mitigate this, it is often administered slowly. Another high-yield fact about Atracurium is its metabolism via **Hofmann elimination** (spontaneous non-enzymatic degradation), making it safe in renal and hepatic failure. **Why the other options are incorrect:** * **Adrenaline:** This is a catecholamine that acts as a physiological antagonist to histamine. It is the drug of choice for anaphylaxis because it stabilizes mast cells and reverses the effects of histamine (bronchodilation and vasoconstriction). * **Thiopentone:** While Thiopentone can occasionally cause histamine release, it is significantly less common than with Atracurium. In modern exams, Atracurium remains the classic "textbook" example for histamine release among muscle relaxants. * **Ketamine:** Ketamine is a dissociative anesthetic that actually causes a sympathetic surge (bronchodilation and increased heart rate), making it a preferred agent in asthmatic patients rather than a trigger for histamine-mediated bronchospasm. **High-Yield Clinical Pearls for NEET-PG:** * **Muscle Relaxants & Histamine:** Benzylisoquinoliniums (Atracurium, Mivacurium, Tubocurarine) release histamine. Aminosteroids (Vecuronium, Rocuronium) generally do not. * **Cisatracurium:** An isomer of atracurium that is more potent and, crucially, **does not** cause histamine release. * **Laudanosine:** A metabolite of atracurium that can cross the blood-brain barrier and potentially cause seizures (pro-convulsant).

Q: The dose of which of the following muscle relaxants needs to be calculated on the basis of total body weight of an obese person rather than their ideal weight?

Atracurium. **Explanation:** In obese patients, drug dosing is a critical clinical decision. Most muscle relaxants are polar (water-soluble) and do not distribute extensively into adipose tissue. Therefore, dosing them based on **Total Body Weight (TBW)** can lead to overdose and prolonged paralysis. **1. Why Atracurium is the Correct Answer:** Atracurium (and its isomer Cisatracurium) are unique because they undergo **Hofmann elimination** (spontaneous non-enzymatic degradation at physiological pH and temperature). Because of this rapid, organ-independent clearance, the risk of accumulation is lower. Clinical studies have shown that dosing Atracurium based on **Total Body Weight (TBW)** provides more predictable intubating conditions and a more consistent duration of action in obese patients compared to Ideal Body Weight (IBW). **2. Why the Other Options are Incorrect:** * **Vecuronium, Rocuronium, and Pancuronium:** These are steroidal neuromuscular blockers. They are highly water-soluble and have a limited volume of distribution. If dosed on TBW, the plasma concentration becomes excessively high, leading to a significantly prolonged duration of neuromuscular blockade. Therefore, these drugs must be calculated based on **Ideal Body Weight (IBW)** or **Lean Body Weight (LBW)** to avoid delayed recovery. **High-Yield Clinical Pearls for NEET-PG:** * **Succinylcholine:** Unlike non-depolarizers, the dose of Succinylcholine should be calculated based on **Total Body Weight (TBW)** in obese patients because pseudocholinesterase activity increases with body weight. * **Propofol:** Induction dose is based on **LBW**, but the maintenance dose (infusion) is based on **TBW**. * **Opioids (Fentanyl/Sufentanil):** Generally dosed based on **LBW** to prevent respiratory depression. * **Rule of Thumb:** When in doubt for obese patients, most anesthetic drugs are dosed on **LBW/IBW**, except for **Succinylcholine** and **Atracurium**.

Question 1

A patient with chronic kidney disease on dialysis is posted for emergency laparotomy. Which of the following anesthetic agents is contraindicated in this patient?

Accepted Answer

Gallamine

Answer

d-Tubocurarine

Answer

Scoline

Answer

Halothane

Question 2

Which anesthetic agent is explosive in the presence of cautery?

Accepted Answer

Ether

Answer

Nitrous Oxide

Answer

Trilene

Answer

Halothane

Question 3

Which is the most physiological intravenous fluid?

Accepted Answer

Ringer's Lactate

Answer

Normal Saline

Answer

5% Dextrose

Answer

All of the above

Question 4

Which of the following intravenous anesthetic agents is considered the most immunogenically safe?

Accepted Answer

Etomidate

Answer

Thiopentone

Answer

Propofol

Answer

Ketamine

Question 5

Which anesthetic agent is contraindicated in epilepsy?

Accepted Answer

Enflurane

Answer

Isoflurane

Answer

Halothane

Answer

Ether

Question 6

Histamine release is one of the common features with administration of which of the following drugs?

Accepted Answer

Atracurium

Answer

Adrenaline

Answer

Thiopentone

Answer

Ketamine

Question 7

A patient, without prior medication, breathes a gas mixture consisting of 50 percent nitrous oxide and 50 percent oxygen by volume. Which of the following effects would be expected?

Accepted Answer

Analgesia

Answer

Excitation

Answer

Surgical anesthesia

Answer

Respiratory arrest

Question 8

Thiopentone is a fast-acting induction agent because of which of the following?

Accepted Answer

High lipid solubility

Answer

Rapid redistribution

Answer

Increased clearance

Answer

Metabolized in plasma

Question 9

Which of the following statements regarding the effect of neuromuscular blockers in patients with myasthenia gravis is FALSE?

Accepted Answer

Neuromuscular blockers should be avoided in these patients; if used, three times the dose of the reversal agent should be given for reversal.

Answer

Patients with myasthenia gravis are resistant to succinylcholine.

Answer

They are more sensitive to non-depolarizing neuromuscular blockers.

Answer

If a neuromuscular blocker is used in a myasthenic patient, they should be mechanically ventilated until recovery.

Question 10

The dose of which of the following muscle relaxants needs to be calculated on the basis of total body weight of an obese person rather than their ideal weight?

Accepted Answer

Atracurium

Answer

Vecuronium

Answer

Pancuronium

Answer

Rocuronium

General Anesthesia — MCQs

General Anesthesia — MCQs

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