General Anesthesia Practice Questions

Q: Hyperkalemia due to succinylcholine is seen in all EXCEPT?

Abdominal sepsis. **Explanation:** The primary mechanism behind succinylcholine-induced hyperkalemia is the **upregulation of extrajunctional nicotinic acetylcholine receptors (nAChRs)**. Normally, receptors are localized at the neuromuscular junction. However, in specific pathological states, these receptors proliferate across the entire muscle membrane. When succinylcholine (a depolarizing muscle relaxant) binds to these widespread receptors, it causes massive, prolonged efflux of potassium from the muscle cells into the extracellular fluid. * **Why Abdominal Sepsis is the Correct Answer:** While severe systemic inflammation can cause metabolic derangements, **abdominal sepsis** is not typically associated with the massive proliferation of extrajunctional receptors required to cause a life-threatening potassium spike. Therefore, it is considered the "exception" among the provided options. * **Why the other options are incorrect:** * **Crush Injury & Burns:** These are classic triggers for receptor upregulation. Following massive tissue trauma or thermal injury, extrajunctional receptors appear within 24–48 hours. Succinylcholine administration in these patients can raise serum potassium by >5.0 mEq/L, leading to cardiac arrest. * **Muscular Dystrophy (e.g., Duchenne’s):** In these patients, the muscle membrane is unstable. Succinylcholine can cause profound rhabdomyolysis and hyperkalemic cardiac arrest. It is generally contraindicated in children with undiagnosed myopathy. **Clinical Pearls for NEET-PG:** 1. **Safe Window:** Succinylcholine is generally safe within the first **24 hours** of a burn or trauma; the risk of hyperkalemia peaks after 48 hours and can last for years. 2. **Normal Rise:** In a healthy individual, succinylcholine increases serum $K^+$ by only **0.5 mEq/L**. 3. **Other High-Yield Contraindications:** Upper/lower motor neuron lesions (paraplegia, stroke), prolonged immobilization, and denervation injuries.

Q: Which muscles are the first to be affected by muscle relaxants?

Laryngeal muscles. The sensitivity of muscles to neuromuscular blocking agents (NMBAs) depends primarily on their **blood flow** and **metabolic rate**. ### 1. Why Laryngeal Muscles are Correct The **laryngeal muscles** (along with the extraocular muscles) are among the first to be affected by muscle relaxants. This is due to their high density of acetylcholine receptors and, most importantly, their **high regional blood flow**. Because they receive a greater volume of blood per gram of tissue compared to peripheral muscles, the muscle relaxant reaches the neuromuscular junctions of the larynx more rapidly. This allows for early paralysis, facilitating endotracheal intubation. ### 2. Analysis of Incorrect Options * **B. Diaphragm:** The diaphragm is the **most resistant** muscle to NMBAs. It requires a much higher dose (nearly 2x) to achieve the same level of block as peripheral muscles. It is also the first to recover. * **D. Intercostals:** Like the diaphragm, these are respiratory muscles. They are relatively resistant and are among the last to be paralyzed and the first to recover. * **C. Thenar muscles:** These are peripheral muscles (adductor pollicis). They are paralyzed **after** the laryngeal muscles but **before** the diaphragm. Monitoring the adductor pollicis via a nerve stimulator is the standard for assessing recovery, as it reflects the return of airway protection. ### Clinical Pearls for NEET-PG * **Sequence of Paralysis:** Small, fast-moving muscles (Eyes/Larynx) → Extremities → Trunk (Intercostals) → Diaphragm. * **Sequence of Recovery:** Exactly the reverse (Diaphragm recovers first; Eyes/Larynx recover last). * **Monitoring Tip:** To predict **intubation** conditions, monitor the **orbicularis oculi** (reflects laryngeal block). To predict **recovery**, monitor the **adductor pollicis** (reflects return of respiratory function).

Q: The volatility of an anesthetic agent is directly proportional to lowering the flow in the portal vein. Portal flow is maximally reduced by which agent?

Halothane. **Explanation:** Total hepatic blood flow is the sum of flow from the hepatic artery and the portal vein. Inhalational anesthetics generally decrease total hepatic blood flow by causing systemic vasodilation and reducing cardiac output. **Why Halothane is the correct answer:** Halothane causes the most significant reduction in hepatic blood flow among all volatile agents. It reduces portal vein flow by approximately **30–50%** due to a marked decrease in cardiac output and an increase in splanchnic vascular resistance. Crucially, Halothane also inhibits the **"Hepatic Artery Buffer Response" (HABR)**—the compensatory mechanism where hepatic arterial flow increases when portal flow decreases. This dual effect makes Halothane the most potent depressant of hepatic perfusion. **Analysis of Incorrect Options:** * **Ether:** While it maintains blood pressure via sympathetic stimulation, it causes significant splanchnic vasoconstriction; however, it is no longer used in modern practice and Halothane remains the classic "high-yield" answer for maximal reduction. * **Isoflurane:** It is considered the agent of choice for maintaining hepatic oxygenation. While it reduces portal flow, it better preserves the HABR, allowing the hepatic artery to compensate. * **Enflurane:** It reduces hepatic blood flow more than Isoflurane but significantly less than Halothane. **High-Yield Pearls for NEET-PG:** * **Order of reduction in Hepatic Blood Flow:** Halothane > Enflurane > Isoflurane/Sevoflurane. * **Halothane Hepatitis:** Associated with the formation of trifluoroacetylated liver proteins (Type II hypersensitivity). * **Best Agent for Liver Disease:** Isoflurane (preserves hepatic arterial flow best). * **Metabolism:** Halothane is the most metabolized volatile agent (~20%), contributing to its potential for hepatotoxicity.

Q: Use of nitrous oxide is contraindicated in all of the following surgeries except?

Exentration operation. **Explanation:** The core concept behind this question is the **Blood-Gas Partition Coefficient** of Nitrous Oxide ($N_2O$). $N_2O$ is 34 times more soluble in blood than Nitrogen ($N_2$). Consequently, $N_2O$ leaves the blood and enters air-filled closed spaces faster than $N_2$ can leave them, leading to an increase in **volume** (in compliant spaces) or **pressure** (in non-compliant spaces). **Why Exenteration is the Correct Answer:** Exenteration (orbital or pelvic) involves the radical removal of contents from an open body cavity. Since there is no enclosed, air-filled space, $N_2O$ cannot cause pressure buildup or expansion. Therefore, it is safe to use. **Why the Other Options are Contraindicated:** * **Cochlear Implant/Tympanoplasty:** The middle ear is a non-compliant space. $N_2O$ increases middle ear pressure, which can displace a tympanic membrane graft or interfere with delicate implant placement. * **Microlaryngeal Surgery:** These procedures often involve the use of lasers. $N_2O$ supports combustion and increases the risk of an **airway fire**, making it hazardous. * **Vitreoretinal Surgery:** If an intraocular gas bubble (e.g., $SF_6$ or $C_3F_8$) is used to flatten the retina, $N_2O$ will rapidly diffuse into the bubble, increasing intraocular pressure (IOP) and potentially causing retinal artery occlusion and blindness. **High-Yield Clinical Pearls for NEET-PG:** * **Diffusion Hypoxia:** Occurs at the end of surgery when $N_2O$ floods the alveoli; prevent by giving 100% $O_2$ for 5–10 minutes. * **Second Gas Effect:** $N_2O$ speeds up the uptake of a companion volatile anesthetic. * **Absolute Contraindications:** Pneumothorax (doubles in size in 10 mins), air embolism, bowel obstruction, and recent vitreoretinal surgery (avoid $N_2O$ for 7–10 days after $SF_6$ use).

Q: Which of the following statements about colloids is false?

None of the above. **Explanation:** The correct answer is **None of the above** because all the statements provided (A, B, and C) are clinically accurate descriptions of colloids. **1. Understanding Colloids:** Colloids are high-molecular-weight substances (like Albumin, Dextran, or Hydroxyethyl starch) that do not easily cross the semi-permeable capillary membrane. Because they remain in the intravascular compartment, they exert **oncotic pressure**, effectively drawing and holding fluid within the vessels. **2. Analysis of Options:** * **Option A (Expands plasma volume for 2-4 hours):** Unlike crystalloids, which redistribute into the interstitial space within 20–30 minutes, colloids have a longer intravascular half-life. They typically maintain plasma volume expansion for several hours (usually 2–6 hours depending on the specific colloid). * **Option B (Are isotonic solutions):** Most commercially available colloid preparations are formulated in an isotonic vehicle (like 0.9% Normal Saline) to prevent osmotic shifts of water into or out of the red blood cells. * **Option C (Replaced in a 1:1 ratio for blood loss):** Because colloids remain primarily in the intravascular space, 1 mL of colloid replaces approximately 1 mL of blood loss. In contrast, crystalloids require a 3:1 or 4:1 ratio because only about 25% of the infused volume remains intravascular. **Clinical Pearls for NEET-PG:** * **Crystalloid vs. Colloid:** Crystalloids are the first-line for fluid resuscitation; Colloids are used for rapid volume expansion. * **Complications:** Synthetic colloids (like Starches) are associated with **coagulopathy** (interference with Factor VIII/vWF) and **acute kidney injury (AKI)**. * **Dextran:** Can interfere with blood cross-matching and cause anaphylaxis. * **Albumin:** The only natural colloid; used in patients with cirrhosis or post-paracentesis.

Q: Which of the following anesthetic drugs is contraindicated in hepatic failure?

Halothane. **Explanation:** **Halothane** is the correct answer because of its significant potential for hepatotoxicity, historically categorized into two types: a mild, transient elevation of transaminases and a rare, life-threatening condition known as **Halothane Hepatitis**. The underlying mechanism involves the metabolism of halothane by the cytochrome P450 system into **trifluoroacetylated (TFA) proteins**. In susceptible individuals, these act as haptens, triggering an immune-mediated response that leads to massive hepatic necrosis. Because halothane undergoes significant hepatic metabolism (up to 20%), it is strictly contraindicated in patients with pre-existing hepatic failure or a history of unexplained jaundice after previous exposure. **Analysis of Incorrect Options:** * **Desflurane & Isoflurane:** These are modern volatile anesthetics with much lower metabolism rates (0.02% and 0.2%, respectively). They produce minimal TFA proteins and are considered safe alternatives in patients with liver disease. * **Remifentanil:** This is an ultra-short-acting opioid metabolized by **non-specific plasma and tissue esterases**, not the liver. Its clearance is entirely independent of hepatic function, making it an ideal choice for patients with liver failure. **High-Yield Clinical Pearls for NEET-PG:** * **Metabolism Rule:** Halothane (20%) > Sevoflurane (2%) > Isoflurane (0.2%) > Desflurane (0.02%). * **Drug of Choice:** **Isoflurane** is often preferred in liver surgery because it best preserves hepatic blood flow (the "Hepatic Artery Buffer Response"). * **Atracurium/Cisatracurium:** These are the muscle relaxants of choice in hepatic failure due to **Hofmann elimination**.

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

Reduces arterial pressure. **Explanation:** Halothane is a potent volatile anesthetic agent that primarily causes a dose-dependent reduction in arterial blood pressure. **1. Why Option A is Correct:** Halothane reduces arterial pressure through two main mechanisms: **direct myocardial depression** (negative inotropy) and a reduction in cardiac output. Unlike other volatile agents (like isoflurane), it causes minimal peripheral vasodilation, meaning the drop in blood pressure is almost entirely due to its effect on the heart muscle itself. **2. Why the other options are incorrect:** * **Option B (Increases heart rate):** Halothane actually tends to cause **bradycardia** or maintain a normal heart rate. It blunts the baroreceptor reflex, meaning the body does not mount a compensatory tachycardia in response to the falling blood pressure. * **Option C (Decreases cardiac output):** While halothane *does* decrease cardiac output, the question asks for the most definitive clinical effect. In many standardized exams, "reduction in arterial pressure" is considered the hallmark hemodynamic effect of halothane. (Note: In some contexts, C is also physiologically true, but A is the primary clinical manifestation). * **Option D (Increases sympathoadrenal activity):** Halothane **depresses** the sympathetic nervous system. It does not cause the "sympathetic surge" seen with agents like desflurane. **High-Yield NEET-PG Pearls for Halothane:** * **Catecholamine Sensitization:** Halothane sensitizes the myocardium to epinephrine, increasing the risk of **ventricular arrhythmias** if exogenous adrenaline is used. * **Hepatotoxicity:** Associated with "Halothane Hepatitis" (Type II is immune-mediated and severe). * **Uterine Relaxation:** It is a potent uterine relaxant, making it useful for version but risky for postpartum hemorrhage. * **Sweet Odor:** It is non-pungent, making it the classic agent for **smooth inhalation induction** in pediatric patients.

Question 1

Hyperkalemia due to succinylcholine is seen in all EXCEPT?

Accepted Answer

Abdominal sepsis

Answer

Crush injury

Answer

Burn

Answer

Muscular dystrophy

Question 2

Which muscles are the first to be affected by muscle relaxants?

Accepted Answer

Laryngeal muscles

Answer

Diaphragm

Answer

Thenar muscles

Answer

Intercostals

Question 3

The volatility of an anesthetic agent is directly proportional to lowering the flow in the portal vein. Portal flow is maximally reduced by which agent?

Accepted Answer

Halothane

Answer

Ether

Answer

Isoflurane

Answer

Enflurane

Question 4

Use of nitrous oxide is contraindicated in all of the following surgeries except?

Accepted Answer

Exentration operation

Answer

Cochlear implant

Answer

Microlaryngeal surgery

Answer

Vitrioretinal surgery

Question 5

Which of the following statements about colloids is false?

Accepted Answer

None of the above

Answer

Expands plasma volume for 2-4 hours

Answer

Are isotonic solutions

Answer

Are replaced in a 1:1 ratio for blood loss

Question 6

The partition coefficient of an anesthetic agent in blood gas tells about what?

Accepted Answer

Time lag of induction of anesthesia

Answer

Solubility in blood

Answer

Potency of the agent

Answer

All of the above

Question 7

Which of the following anesthetic drugs is contraindicated in hepatic failure?

Accepted Answer

Halothane

Answer

Desflurane

Answer

Remifentanil

Answer

Isoflurane

Question 8

Pentothal sodium should preferably be injected into which of the following veins?

Accepted Answer

Veins on the outer aspect of the forearm

Answer

Femoral vein

Answer

Antecubital vein

Answer

Neck vein

Question 9

Which of the following statements regarding halothane is true?

Accepted Answer

Reduces arterial pressure

Answer

Increases heart rate

Answer

Decreases cardiac output

Answer

Increases sympathoadrenal activity

Question 10

A child presents with bladder exstrophy and chronic renal failure. What is the muscle relaxant of choice to be used during the surgery for exstrophy in this child?

Accepted Answer

Atracurium

Answer

Mivacurium

Answer

Pancuronium

Answer

Rocuronium

General Anesthesia — MCQs

General Anesthesia — MCQs

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