General Anesthesia — MCQs

General Anesthesia Indian Medical PG Practice Questions and MCQs

Question 321: Which opioid can cause tachycardia?

A. Fentanyl
B. Remifentanyl
C. Pethidine (Correct Answer)
D. Morphine

Explanation: **Explanation:** The correct answer is **Pethidine** (also known as Meperidine). **Why Pethidine causes Tachycardia:** Most opioids are associated with dose-dependent bradycardia due to central stimulation of the vagus nerve. Pethidine is the notable exception. Structurally, Pethidine is related to **Atropine**. It possesses intrinsic **antimuscarinic (atropine-like) activity**, which leads to an increase in heart rate (tachycardia) and occasionally mydriasis (pupillary dilation), rather than the classic opioid-induced miosis. **Analysis of Incorrect Options:** * **Fentanyl & Remifentanil:** These are potent synthetic phenylpiperidine derivatives. They typically cause significant **bradycardia** by increasing vagal tone and decreasing sympathetic outflow. * **Morphine:** Morphine generally causes **bradycardia**. Additionally, it triggers histamine release, which can lead to peripheral vasodilation and hypotension; while a reflex tachycardia *could* theoretically occur due to hypotension, the primary direct effect remains a reduction in heart rate. **High-Yield Clinical Pearls for NEET-PG:** 1. **Miosis Exception:** Pethidine is the only opioid that does not cause significant miosis (pinpoint pupils) due to its anticholinergic effect. 2. **Metabolite Toxicity:** Pethidine is metabolized to **norpethidine**, which is a CNS stimulant. Accumulation (especially in renal failure) can cause **seizures**. 3. **Shivering:** Pethidine is the drug of choice for treating **post-operative shivering** (via stimulation of κ-receptors). 4. **Interaction:** It is strictly contraindicated with **MAO Inhibitors**, as it can precipitate a life-threatening serotonin syndrome or hyperpyrexic coma.

Question 322: Which of the following is NOT an intravenous anesthetic?

A. Propofol
B. Opioids
C. Ketamine
D. Desflurane (Correct Answer)

Explanation: **Explanation:** The correct answer is **D. Desflurane**. **1. Why Desflurane is the correct answer:** Desflurane is a **volatile inhalation anesthetic**, not an intravenous (IV) agent. It is a halogenated methyl ethyl ether that exists as a liquid at room temperature but is delivered as a gas via a specialized heated vaporizer due to its high vapor pressure and low boiling point (23.5°C). It is primarily used for the maintenance of general anesthesia. **2. Why the other options are incorrect:** * **Propofol (A):** The most commonly used IV induction agent. It is a substituted isopropylphenol known for its rapid onset, short duration, and "milk of amnesia" appearance (lipid emulsion). * **Opioids (B):** Agents like Fentanyl, Sufentanil, and Remifentanil are classified as IV anesthetics/analgesics. They are frequently used as part of "Balanced Anesthesia" or "Total Intravenous Anesthesia" (TIVA) to provide intense analgesia and supplement induction. * **Ketamine (C):** A phencyclidine derivative used as an IV anesthetic. It produces "dissociative anesthesia" and is unique for providing both anesthesia and potent analgesia while maintaining airway reflexes. **3. Clinical Pearls for NEET-PG:** * **Desflurane:** Has the lowest blood-gas partition coefficient (0.42) among volatile agents, leading to the fastest recovery ("fastest out"). However, it is a known airway irritant and can cause coughing or laryngospasm during induction. * **Propofol:** Drug of choice for TIVA and day-care surgery; possesses anti-emetic properties. * **Ketamine:** Drug of choice for induction in patients with bronchial asthma (bronchodilator) and hypovolemic shock (sympathomimetic). * **Etomidate:** The most cardiostable IV induction agent, preferred in patients with coronary artery disease.

Question 323: Which of the following is not an amino steroid derivative?

A. Alcuronium (Correct Answer)
B. Vecuronium
C. Pancuronium
D. Pipecuronium

Explanation: ### Explanation Neuromuscular blocking agents (NMBAs) are broadly classified based on their chemical structure into two main categories: **Aminosteroids** and **Benzylisoquinolines**. **1. Why Alcuronium is the Correct Answer:** Alcuronium is a semi-synthetic derivative of toxiferine, an alkaloid derived from South American curare. Chemically, it belongs to the **Benzylisoquinoline** (or more specifically, the indole alkaloid) class, not the aminosteroid group. It is a long-acting non-depolarizing muscle relaxant that is rarely used in modern practice due to its tendency to cause hypotension via histamine release and ganglion blockade. **2. Why the Other Options are Incorrect:** * **Pancuronium:** The prototype **aminosteroid**. It is long-acting and known for its vagolytic effect (causing tachycardia). * **Vecuronium:** A monoquaternary **aminosteroid** derived from pancuronium. It is intermediate-acting and lacks significant cardiovascular side effects. * **Pipecuronium:** A potent, long-acting **aminosteroid** similar to pancuronium but without the vagolytic effects. **3. High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Aminosteroids:** They usually end in **"-curonium"** (Pancuronium, Vecuronium, Rocuronium, Pipecuronium). * **Mnemonic for Benzylisoquinolines:** They usually end in **"-curium"** (Atracurium, Cisatracurium, Mivacurium) — *Exception: Alcuronium.* * **Metabolism:** Aminosteroids are primarily metabolized by the **liver** and excreted by the **kidneys**. In contrast, Atracurium and Cisatracurium undergo **Hofmann elimination** (organ-independent breakdown), making them the drugs of choice in liver or renal failure. * **Rocuronium** is the aminosteroid with the fastest onset, making it an alternative to Succinylcholine for Rapid Sequence Induction (RSI).

Question 324: A 40-year-old female underwent surgery. Postoperatively, she stated she was aware of preoperative events. Intraoperative awareness is evaluated by?

A. Pulse oximetry
B. Colour doppler
C. Bispectral imaging (Correct Answer)
D. End tidal CO2

Explanation: **Explanation:** **1. Why Bispectral Index (BIS) is Correct:** Intraoperative awareness (accidental consciousness under general anesthesia) occurs when the depth of anesthesia is inadequate. The **Bispectral Index (BIS)** is a processed EEG parameter used to monitor the **depth of anesthesia** and the hypnotic effect of drugs on the brain. It provides a dimensionless score from 0 to 100: * **100:** Fully awake. * **40–60:** Recommended range for general anesthesia (low risk of awareness). * **0:** Isoelectric EEG (brain inactivity). By monitoring cortical activity, BIS helps clinicians titrate anesthetic doses to prevent awareness while avoiding over-sedation. **2. Why Other Options are Incorrect:** * **Pulse Oximetry (A):** Measures oxygen saturation ($SpO_2$) in arterial blood. It monitors respiratory function and oxygenation, not neurological depth. * **Color Doppler (B):** An ultrasound technique used to visualize blood flow through vessels and heart chambers. It has no role in monitoring consciousness. * **End-Tidal $CO_2$ (ETCO2) (D):** Measures the concentration of carbon dioxide at the end of expiration. It is the gold standard for confirming endotracheal tube placement and monitoring ventilation/perfusion, but it does not reflect the patient's level of awareness. **Clinical Pearls for NEET-PG:** * **Isolated Forearm Technique:** The "Gold Standard" for detecting intraoperative awareness (though rarely used clinically). * **Incidence:** Awareness is most common in **Trauma surgery, Emergency Cesarean sections, and Cardiac surgery** due to lighter anesthesia levels. * **Other Depth Monitors:** Entropy, Patient State Index (PSI), and Auditory Evoked Potentials (AEP). * **Risk Factors:** Chronic alcohol/opioid use, difficult airway, and use of neuromuscular blockers (which mask movement).

Question 325: Oxygen is administered during anesthesia to prevent which of the following?

A. Pain
B. Hypoxia (Correct Answer)
C. Hypercapnia
D. Hypotension

Explanation: **Explanation:** The primary objective of administering supplemental oxygen during anesthesia is to prevent **Hypoxia** (low oxygen levels in the tissues). During general anesthesia, several factors compromise oxygenation: 1. **Hypoventilation:** Anesthetic agents and neuromuscular blockers depress the respiratory drive and weaken respiratory muscles. 2. **Reduced Functional Residual Capacity (FRC):** Induction of anesthesia causes a decrease in FRC, leading to atelectasis and ventilation-perfusion (V/Q) mismatch. 3. **Apnea during Intubation:** Pre-oxygenation (denitrogenation) is performed specifically to create an oxygen reservoir in the lungs to prevent hypoxia during the period of apnea required for securing the airway. **Analysis of Incorrect Options:** * **A. Pain:** Pain is managed using analgesics (e.g., opioids, NSAIDs) or regional blocks, not oxygen. * **C. Hypercapnia:** This refers to elevated $CO_2$ levels. While oxygenation is vital, hypercapnia is prevented by maintaining adequate **minute ventilation** (tidal volume × respiratory rate) via manual or mechanical ventilation. * **D. Hypotension:** Low blood pressure is typically managed with intravenous fluids, vasopressors, or by adjusting the depth of anesthesia. **High-Yield Clinical Pearls for NEET-PG:** * **Pre-oxygenation:** Involves breathing 100% $O_2$ for 3 minutes (or 8 vital capacity breaths) to replace nitrogen in the FRC, increasing the "safety period" of apnea. * **Diffusion Hypoxia (Fink Effect):** Occurs at the end of nitrous oxide ($N_2O$) administration. Rapid diffusion of $N_2O$ from the blood into the alveoli dilutes the $O_2$ concentration. This is prevented by administering 100% $O_2$ for 5–10 minutes after stopping $N_2O$. * **Color Coding:** In India/International standards, Oxygen cylinders are **Black with a White shoulder**.

Question 326: Dissociative sedation and analgesia, as described by Robert and Rosebaum in 1971, is associated with what concentration range of N2O?

A. 5 to 20% N2O
B. 20 to 30% N2O
C. 30 to 50% N2O
D. 50 to 70% N2O (Correct Answer)

Explanation: **Explanation** The concept of **Dissociative Sedation and Analgesia** using Nitrous Oxide ($N_2O$) was popularized by **Robert and Rosenbaum in 1971**. They described a specific state where the patient remains conscious and cooperative but experiences significant analgesia, amnesia, and a feeling of detachment (dissociation) from the environment. **Why Option D is Correct:** At concentrations of **50% to 70% $N_2O$** (mixed with oxygen), the gas produces a reliable state of "relative analgesia" or dissociative sedation. In this range, $N_2O$ acts as a potent NMDA receptor antagonist (similar to Ketamine), leading to the characteristic "dream-like" state. This concentration is high enough to provide surgical-grade analgesia for minor procedures while maintaining protective airway reflexes. **Why Other Options are Incorrect:** * **Option A (5-20%):** This range is sub-therapeutic for most patients, providing only mild anxiolysis without significant analgesia or dissociation. * **Option B (20-30%):** This is the typical range for "Relative Analgesia" used in dentistry for mild sedation, but it does not consistently reach the "dissociative" threshold described by Robert and Rosenbaum. * **Option C (30-50%):** While this provides moderate sedation, the specific clinical description of dissociative sedation in the 1971 landmark study specifically targeted the higher 50-70% range for maximal efficacy. **High-Yield Clinical Pearls for NEET-PG:** * **Second Gas Effect:** $N_2O$ is used to speed up the induction of other volatile anesthetics. * **Diffusion Hypoxia (Fink Effect):** Occurs during recovery when $N_2O$ rushes out of the blood into the alveoli, diluting oxygen. Prevented by giving 100% $O_2$ for 5 minutes post-op. * **Contraindications:** Avoid in closed-space pathologies (Pneumothorax, Intestinal obstruction, Middle ear surgery, Air embolism) because $N_2O$ is 34 times more soluble than Nitrogen and expands these spaces. * **Vitamin B12:** Chronic exposure inhibits methionine synthase, leading to megaloblastic anemia and peripheral neuropathy.

Question 327: Which of the following is true regarding Remifentanil?

A. Useful for short painful procedures
B. Metabolized by plasma esterases
C. Equipotent as fentanyl
D. All of these (Correct Answer)

Explanation: **Explanation:** Remifentanil is a unique, ultra-short-acting synthetic $\mu$-opioid receptor agonist. Its pharmacological profile makes it a high-yield topic for NEET-PG. * **Metabolism (Option B):** Unlike other opioids metabolized by the liver, Remifentanil contains an **ester linkage**. This allows it to be rapidly broken down by **non-specific plasma and tissue esterases**. This metabolism is independent of renal or hepatic function, leading to a predictable, ultra-short duration of action. * **Clinical Use (Option A):** Because of its rapid onset and offset (context-sensitive half-life of ~3–4 minutes), it is ideal for **short, painful procedures** (e.g., retrobulbar blocks, brief endoscopies) and for providing intense intraoperative analgesia via continuous infusion without the risk of drug accumulation. * **Potency (Option C):** Remifentanil is roughly **equipotent to Fentanyl** (both are approximately 100 times more potent than morphine). **Why "All of these" is correct:** Remifentanil satisfies all three criteria: it is highly potent (equipotent to fentanyl), uniquely metabolized by esterases, and specifically indicated for short procedures where rapid recovery is desired. **High-Yield Clinical Pearls for NEET-PG:** 1. **Context-Sensitive Half-life:** It is the only opioid whose context-sensitive half-life remains constant (approx. 3-4 mins) regardless of the duration of infusion. 2. **Opioid-Induced Hyperalgesia:** Rapid offset can lead to "acute opioid tolerance" or hyperalgesia; therefore, longer-acting analgesics must be administered before stopping the infusion. 3. **Side Effects:** Can cause significant bradycardia and chest wall rigidity if administered too rapidly.

Question 328: Thiopentone is contraindicated in which of the following conditions?

A. Narcoanalysis
B. Neurosurgery
C. Acute intermittent porphyria (Correct Answer)
D. Induction of anaesthesia

Explanation: **Explanation:** **Thiopentone Sodium** is an ultra-short-acting barbiturate. The absolute contraindication in **Acute Intermittent Porphyria (AIP)** is a classic high-yield fact for NEET-PG. **1. Why Acute Intermittent Porphyria is the Correct Answer:** Barbiturates like Thiopentone induce the enzyme **ALA synthetase** in the liver. This enzyme is the rate-limiting step in heme synthesis. In patients with porphyria, this induction leads to the overproduction and accumulation of porphyrins and their precursors (like delta-aminolevulinic acid). This can trigger a life-threatening acute crisis characterized by severe abdominal pain, neurological deficits, psychiatric symptoms, and cardiovascular instability. **2. Why the Other Options are Incorrect:** * **Narcoanalysis:** Thiopentone is historically known as "Truth Serum." In sub-therapeutic doses, it causes disinhibition, making it a standard agent used for narcoanalysis. * **Neurosurgery:** Thiopentone is actually **indicated** in neurosurgery because it reduces the Cerebral Metabolic Rate of Oxygen (CMRO2), decreases Cerebral Blood Flow (CBF), and lowers Intracranial Pressure (ICP), providing cerebral protection. * **Induction of Anesthesia:** This is the primary clinical use of Thiopentone due to its rapid onset (one arm-brain circulation time) and smooth induction. **Clinical Pearls for NEET-PG:** * **Other Contraindications:** Status asthmaticus (due to histamine release causing bronchospasm) and severe shock/hypovolemia. * **Storage:** It is stored as a yellow hygroscopic powder in an atmosphere of **Nitrogen** with 6% **Sodium Carbonate** to prevent it from reacting with atmospheric CO2. * **pH:** It is highly alkaline (pH 10.5). Accidental **intra-arterial injection** causes severe vasospasm and gangrene; treatment includes Heparin, Papaverine, and Brachial Plexus block. * **Recovery:** Recovery from a single dose occurs due to **redistribution** from the brain to muscle and fat, not metabolism.

Question 329: Which of the following anesthetic agents is known to cause dissociative anesthesia?

A. Ketamine (Correct Answer)
B. Thiopentone
C. Suxamethonium
D. Diazepam

Explanation: **Explanation:** **Ketamine** is the correct answer because it is the classic agent used to induce **dissociative anesthesia**. This unique state is characterized by profound analgesia, amnesia, and a "trance-like" state where the patient appears awake (eyes may remain open with a slow nystagmic gaze) but is disconnected from the environment and sensory input. * **Mechanism:** Ketamine acts primarily as a non-competitive antagonist at the **NMDA (N-methyl-D-aspartate) receptors**. It causes functional dissociation between the thalamocortical and limbic systems. **Why other options are incorrect:** * **Thiopentone:** An ultra-short-acting barbiturate used for induction. It causes generalized CNS depression (GABA-A agonist) rather than dissociation. * **Suxamethonium (Succinylcholine):** A depolarizing neuromuscular blocker used for muscle relaxation/intubation. It has no anesthetic or analgesic properties. * **Diazepam:** A benzodiazepine used for sedation and anxiolysis. While it causes amnesia, it does not produce the specific state of dissociative anesthesia. **High-Yield Clinical Pearls for NEET-PG:** * **Hemodynamics:** Unlike most induction agents, Ketamine is **sympathomimetic** (increases HR, BP, and CO), making it the drug of choice for **hypovolemic shock**. * **Airway:** It preserves laryngeal reflexes and causes bronchodilation (drug of choice for **status asthmaticus**). * **Side Effects:** Known for causing **emergence delirium** (hallucinations), which can be pre-treated with benzodiazepines (e.g., Midazolam). * **Contraindications:** Avoid in patients with increased intracranial pressure (ICP) or intraocular pressure (IOP).

Question 330: Which modality is best utilized for neuromuscular monitoring during the maintenance of anesthesia?

A. Train of four (Correct Answer)
B. Single twitch
C. Tetanic stimulation
D. Post-tetanic stimulation

Explanation: **Explanation:** **Train of Four (TOF)** is the gold standard for monitoring neuromuscular blockade during the maintenance phase of anesthesia. It involves four supramaximal stimuli delivered at 2 Hz (every 0.5 seconds). It is preferred because it is **non-invasive, does not require a baseline (pre-relaxant) value, and is highly sensitive** in assessing the degree of competitive (non-depolarizing) block. By comparing the strength of the fourth twitch (T4) to the first (T1), clinicians can quantify the "TOF ratio," which guides the titration of muscle relaxants and ensures safe recovery. **Why other options are incorrect:** * **Single Twitch:** Requires a pre-drug baseline for comparison. It is a "yes/no" indicator of block but cannot quantify the depth of the block or the degree of recovery. * **Tetanic Stimulation:** Involves high-frequency (50-100 Hz) stimulation. It is painful and can lead to "post-tetanic facilitation," which temporarily alters the neuromuscular junction, making subsequent monitoring inaccurate. * **Post-Tetanic Count (PTC):** This is specifically used to monitor **deep neuromuscular blockade** when the TOF count is zero. It is not the primary modality for routine maintenance but rather a specialized tool for profound paralysis. **Clinical Pearls for NEET-PG:** * **TOF Ratio for Extubation:** A ratio of **>0.9** (at the adductor pollicis) is required to safely exclude residual paralysis and allow extubation. * **Site of Monitoring:** The **Adductor Pollicis** (Ulnar nerve) is the most common site for monitoring recovery, while the **Orbicularis Oculi** (Facial nerve) better reflects the blockade of the diaphragm. * **Fade:** The progressive diminution of twitch response (Fade) is a hallmark of **Non-depolarizing** (Phase I) and **Depolarizing** (Phase II) blocks.

Practice by Chapter

History of Anesthesia

Practice Questions

Preoperative Evaluation

Practice Questions

Pharmacology of Inhalational Anesthetics

Practice Questions

Pharmacology of Intravenous Anesthetics

Practice Questions

Neuromuscular Blocking Agents

Practice Questions

Airway Management

Practice Questions

Endotracheal Intubation

Practice Questions

Difficult Airway Algorithms

Practice Questions

Intraoperative Monitoring

Practice Questions

Depth of Anesthesia Monitoring

Practice Questions

Emergence from Anesthesia

Practice Questions

Postoperative Care

Practice Questions

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