General Anesthesia — MCQs

General Anesthesia Indian Medical PG Practice Questions and MCQs

Question 401: What is true about midazolam as an inducing agent?

A. Causes an increase in blood pressure.
B. Does not produce pain on intravenous injection. (Correct Answer)
C. Increases cerebral oxygen consumption.
D. Increases peripheral vascular resistance.

Explanation: **Explanation:** Midazolam is a water-soluble benzodiazepine frequently used for preoperative sedation and induction of anesthesia. **Why Option B is Correct:** Unlike its predecessor Diazepam, which is insoluble in water and requires a propylene glycol solvent (causing significant venous irritation and thrombophlebitis), **Midazolam contains an imidazole ring**. At a pH of less than 4.0, this ring remains open, making the drug **water-soluble**. This eliminates the need for irritating solvents, ensuring that it **does not produce pain on intravenous injection**. Once injected, the physiological pH of the blood (7.4) causes the ring to close, making the drug lipid-soluble so it can cross the blood-brain barrier. **Analysis of Incorrect Options:** * **Option A & D:** Midazolam typically causes a **decrease in systemic vascular resistance (SVR)** and a modest **decrease in blood pressure**. It does not increase peripheral vascular resistance; rather, it has a mild vasodilatory effect. * **Option C:** Benzodiazepines, including midazolam, **decrease cerebral metabolic rate of oxygen consumption (CMRO2)** and cerebral blood flow (CBF) while maintaining the CO2 reactivity of the cerebral vasculature. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Potentiates GABA-A receptors by increasing the **frequency** of chloride channel opening. * **Metabolism:** Metabolized by hepatic CYP3A4 enzymes; its active metabolite is 1-hydroxymidazolam. * **Specific Antagonist:** **Flumazenil** (competitive antagonist) is used to reverse its effects. * **Anterograde Amnesia:** Midazolam is highly effective at producing anterograde amnesia, making it ideal for premedication.

Question 402: All are false about propofol except?

A. Propofol is the best bronchodilator.
B. Propofol is a cardiovascular stable drug.
C. Propofol causes malignant hyperthermia.
D. Propofol infusion at a rate >4 mg/hr can cause propofol infusion syndrome. (Correct Answer)

Explanation: **Explanation:** Propofol (2,6-diisopropylphenol) is the most commonly used intravenous anesthetic agent. Understanding its clinical profile is crucial for NEET-PG. **1. Why Option D is Correct:** **Propofol Infusion Syndrome (PRIS)** is a rare but fatal complication associated with prolonged, high-dose infusions. It is defined by a dose **>4 mg/kg/hr** for more than 48 hours. The syndrome is characterized by metabolic acidosis, rhabdomyolysis, hyperkalemia, hepatomegaly, and refractory bradycardia leading to heart failure. It occurs due to the inhibition of mitochondrial fatty acid oxidation. **2. Why Other Options are Incorrect:** * **Option A:** While propofol has bronchodilatory properties, it is **not the "best"** bronchodilator. **Ketamine** is the induction agent of choice for patients with reactive airway disease (asthma/COPD) due to its potent sympathomimetic effects. Among inhalational agents, Sevoflurane is preferred. * **Option B:** Propofol is **not cardiovascularly stable**. It is a potent vasodilator and direct myocardial depressant, causing a significant drop in systemic vascular resistance (SVR) and blood pressure. **Etomidate** is the drug of choice for cardiovascular stability. * **Option C:** Propofol does **not** cause Malignant Hyperthermia (MH). In fact, it is considered a **safe agent** for patients susceptible to MH. The primary triggers for MH are volatile anesthetics (e.g., Halothane) and Succinylcholine. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** For Day-care surgery (due to rapid recovery) and TIVA (Total Intravenous Anesthesia). * **Antiemetic:** Propofol has unique sub-hypnotic antiemetic properties. * **Pain on Injection:** Common; mitigated by using larger veins or pre-treatment with Lidocaine. * **Egg/Soy Allergy:** Use with caution as the emulsion contains egg lecithin and soybean oil. * **Color:** Known as "Milk of Amnesia" due to its white, milky appearance.

Question 403: Which of the following is a non-depolarizing muscle relaxant?

A. Mivacurium (Correct Answer)
B. Halothane
C. Desflurane
D. Isoflurane

Explanation: **Explanation:** **Mivacurium** is the correct answer because it is a short-acting **benzylisoquinolinium** derivative belonging to the class of **non-depolarizing neuromuscular blocking agents (NDMRs)**. These drugs act as competitive antagonists at the nicotinic acetylcholine receptors (nAChR) at the neuromuscular junction, preventing muscle contraction without causing initial fasciculations. **Analysis of Incorrect Options:** * **Halothane, Desflurane, and Isoflurane (Options B, C, and D):** These are all **volatile inhalation anesthetics** used for the induction and maintenance of general anesthesia. While they can provide some degree of skeletal muscle relaxation by acting on the central nervous system and spinal cord, they are not classified as muscle relaxants or neuromuscular blockers. **High-Yield Clinical Pearls for NEET-PG:** * **Metabolism:** Mivacurium is unique among NDMRs because it is metabolized by **plasma cholinesterase (pseudocholinesterase)**, similar to Succinylcholine. This results in a very short duration of action (approx. 15–20 minutes). * **Prolonged Block:** Patients with **atypical plasma cholinesterase** deficiency will experience a significantly prolonged duration of action when given Mivacurium. * **Side Effects:** It is known for causing **histamine release**, which can lead to cutaneous flushing, hypotension, and bronchospasm if injected rapidly. * **Classification Tip:** Remember that most non-depolarizing relaxants end in **"-curium"** (atracurium, mivacurium) or **"-onium"** (vecuronium, rocuronium, pancuronium).

Question 404: All of the following are false statements regarding Nitrous Oxide (N2O) EXCEPT:

A. It is the least potent inhalational anesthetic agent. (Correct Answer)
B. It possesses significant muscle relaxant properties.
C. It is lighter than air.
D. It does not cause diffusion hypoxia.

Explanation: **Explanation:** Nitrous Oxide ($N_2O$) is a unique inorganic inhalational anesthetic. To identify the correct statement, we must evaluate its physical and pharmacological properties. **1. Why Option A is Correct:** Potency of an inhalational agent is inversely proportional to its **Minimum Alveolar Concentration (MAC)**. $N_2O$ has a MAC of approximately **104%**, which is the highest among all anesthetic gases. Since it cannot achieve surgical anesthesia at 1 atmosphere without causing hypoxia, it is clinically the **least potent** agent. **2. Why Other Options are Incorrect:** * **Option B:** $N_2O$ provides excellent analgesia but has **no significant muscle relaxant properties**. It is often used alongside neuromuscular blockers for this reason. * **Option C:** $N_2O$ is **heavier than air** (Specific gravity of 1.5). This is clinically relevant as it can accumulate in low-lying areas. * **Option D:** $N_2O$ is highly insoluble in blood. When discontinued, it rushes out of the blood into the alveoli, diluting oxygen concentration. This phenomenon is known as **Diffusion Hypoxia (Fink Effect)**. It is prevented by administering 100% $O_2$ for 5–10 minutes after stopping $N_2O$. **High-Yield Clinical Pearls for NEET-PG:** * **Second Gas Effect:** $N_2O$ accelerates the uptake of a companion volatile anesthetic (like Halothane or Isoflurane). * **Closed Spaces:** $N_2O$ is 34 times more soluble than Nitrogen. It diffuses into air-filled cavities faster than Nitrogen can leave, causing **expansion of closed spaces**. It is strictly **contraindicated** in pneumothorax, air embolism, intestinal obstruction, and middle ear surgeries (tympanoplasty). * **Toxicity:** Chronic exposure inhibits **Vitamin B12** (Methionine Synthase), leading to megaloblastic anemia and peripheral neuropathy. * **Storage:** Stored in **Blue Cylinders** as a liquid under pressure.

Question 405: Which of the following induction agents may cause adrenal cortex suppression?

A. Propofol
B. Ketamine
C. Etomidate (Correct Answer)
D. Thiopentone

Explanation: **Explanation:** **Etomidate** is the correct answer because it causes dose-dependent inhibition of the enzyme **11-beta-hydroxylase**. This enzyme is essential for converting 11-deoxycortisol to cortisol in the adrenal cortex. Even a single induction dose can suppress adrenal steroidogenesis for 6–24 hours, leading to decreased plasma cortisol levels. While this makes it less ideal for patients in septic shock, it remains a popular choice for hemodynamically unstable patients due to its minimal cardiovascular impact. **Analysis of Incorrect Options:** * **Propofol (A):** The most common induction agent; it acts via GABA-A receptors. Its primary side effects are hypotension and respiratory depression, not adrenal suppression. * **Ketamine (B):** A dissociative anesthetic that acts as an NMDA receptor antagonist. It actually stimulates the sympathetic nervous system, increasing heart rate and blood pressure, and does not affect the adrenal cortex. * **Thiopentone (D):** An ultra-short-acting barbiturate. While it can cause cardiovascular and respiratory depression, it has no specific inhibitory effect on adrenal enzymes. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Etomidate is the induction agent of choice for patients with **cardiovascular disease** or **hemodynamic instability** (e.g., trauma, hypovolemia) because it maintains heart rate and blood pressure. * **Myoclonus:** Etomidate is frequently associated with involuntary muscle movements (myoclonus) during induction, which can be prevented by premedication with opioids or benzodiazepines. * **Avoidance:** Due to adrenal suppression, etomidate is generally avoided as a continuous infusion in the ICU.

Question 406: Which of the following is true about halothane?

A. Causes bronchodilation (Correct Answer)
B. Has anti-arrhythmic properties
C. Can be used in patients with hepatitis
D. Causes uterine contraction

Explanation: **Explanation:** Halothane is a potent volatile anesthetic agent that belongs to the halogenated hydrocarbon group. **1. Why Option A is Correct:** Halothane is a potent **bronchodilator**. It achieves this by directly relaxing bronchial smooth muscle and inhibiting the release of bronchoconstricting mediators like histamine. Because it is non-irritating to the airways and has a pleasant odor, it was historically the agent of choice for **inhalation induction**, especially in pediatric patients and those with reactive airway diseases like asthma or COPD. **2. Why the Other Options are Incorrect:** * **Option B:** Halothane is actually **arrhythmogenic**. It sensitizes the myocardium to the effects of endogenous and exogenous catecholamines (epinephrine), which can lead to ventricular arrhythmias. * **Option C:** Halothane is associated with **"Halothane Hepatitis."** About 20% of the drug undergoes hepatic metabolism, producing trifluoroacetylated proteins that can trigger an immune-mediated hepatotoxicity. It is contraindicated in patients with pre-existing liver disease or a history of unexplained jaundice after previous exposure. * **Option D:** Halothane causes **uterine relaxation**, not contraction. This can lead to increased postpartum hemorrhage (PPH) if used in high concentrations during obstetric procedures. **High-Yield Clinical Pearls for NEET-PG:** * **Blood-Gas Partition Coefficient:** 2.4 (Slower induction/recovery compared to Sevoflurane). * **Halothane Shake:** Post-operative shivering is a common side effect. * **Malignant Hyperthermia:** Like all volatile anesthetics, Halothane is a known trigger. * **Preservation:** It is stored in amber-colored bottles with **Thymol (0.01%)** as a preservative to prevent spontaneous decomposition.

Question 407: Which of the following is a non-opioid intravenous anesthetic agent?

A. Tramadol
B. Pethidine
C. Fentanyl
D. Ketamine (Correct Answer)

Explanation: **Explanation:** The question asks to identify a **non-opioid** intravenous (IV) anesthetic agent. **Correct Answer: D. Ketamine** Ketamine is a phencyclidine derivative that acts primarily as an **NMDA receptor antagonist**. It is classified as a "dissociative anesthetic" because it induces a state where the patient appears awake (eyes open, intact cough reflex) but is dissociated from the environment and feels no pain. Unlike opioids, it does not act on the mu-opioid receptors for its primary anesthetic effect. It is unique among IV anesthetics for causing sympathetic stimulation (increased HR, BP, and CO) and bronchodilation. **Incorrect Options:** * **A. Tramadol:** A synthetic analogue of codeine. It is a weak opioid agonist and also inhibits the reuptake of serotonin and norepinephrine. It is used for analgesia, not for the induction of anesthesia. * **B. Pethidine (Meperidine):** A synthetic opioid agonist acting on mu and kappa receptors. It is known for its anticholinergic side effects and its metabolite, *normeperidine*, which can cause seizures. * **C. Fentanyl:** A potent synthetic phenylpiperidine derivative. It is a pure mu-opioid agonist used extensively in anesthesia for analgesia and blunting the intubation response, but it belongs to the opioid class. **High-Yield Clinical Pearls for NEET-PG:** * **Ketamine** is the drug of choice for induction in patients with **bronchial asthma** and **hypovolemic shock**. * It is **contraindicated** in patients with head injuries (increases ICP) and hypertensive heart disease. * **Emergence delirium** is a common side effect of Ketamine, which can be prevented by co-administering benzodiazepines (e.g., Midazolam).

Question 408: Which stage of anesthesia is known as the stage of analgesia?

A. Stage 1 (Correct Answer)
B. Stage 2
C. Stage 3
D. Stage 4

Explanation: **Explanation:** The stages of anesthesia were originally described by **Arthur Guedel** in 1920, based on the effects of inhaled diethyl ether. Understanding these stages is crucial for identifying the depth of anesthesia. **Correct Option: A. Stage 1 (Stage of Analgesia)** This stage begins with the induction of anesthesia and lasts until the loss of consciousness. It is characterized by the patient feeling drowsy and experiencing a significant reduction in pain perception (analgesia) while remaining conscious and able to follow commands. **Incorrect Options:** * **B. Stage 2 (Stage of Excitement/Delirium):** This stage starts from the loss of consciousness to the onset of automatic breathing. It is characterized by agitation, struggling, irregular respiration, and risk of laryngospasm or vomiting. * **C. Stage 3 (Stage of Surgical Anesthesia):** This is the goal for most surgeries. It is divided into four planes based on eye movements, pupil size, and respiratory patterns. It extends from the onset of regular breathing to respiratory paralysis. * **D. Stage 4 (Stage of Medullary Paralysis/Overdose):** This is a critical stage where severe depression of the vasomotor and respiratory centers in the medulla occurs. Without immediate support, it leads to circulatory collapse and death. **High-Yield Clinical Pearls for NEET-PG:** * **Guedel’s Classification** is most clearly seen with slow-acting agents like Ether; modern IV agents (Propofol) bypass Stages 1 and 2 almost instantaneously. * **Stage 2 Danger:** Always avoid stimulating a patient in Stage 2 due to the high risk of **laryngospasm**. * **Surgical Plane:** Plane 2 of Stage 3 is generally considered the ideal depth for most surgical procedures.

Question 409: Which of the following is FALSE regarding lumbar puncture in patients on anticoagulants or antiplatelets?

A. A patient on warfarin is contraindicated to lumbar puncture.
B. Low molecular weight heparin should be stopped 24 hours prior to lumbar puncture.
C. Intravenous heparin should be stopped 6 hours before lumbar puncture. (Correct Answer)
D. Aspirin is not an absolute contraindication to lumbar puncture.

Explanation: The primary concern when performing a lumbar puncture (LP) or neuraxial anesthesia in patients on anticoagulants is the risk of a **spinal-epidural hematoma**, which can lead to permanent neurological damage. ### **Explanation of Options** * **Option C (Correct - False Statement):** Intravenous (IV) heparin has a short half-life. According to ASRA (American Society of Regional Anesthesia) guidelines, IV heparin should be discontinued **4 to 6 hours** before the procedure, and the **aPTT must be checked** to ensure it has returned to the normal range. The statement is considered false in many exam contexts because the mere passage of 6 hours is insufficient without laboratory confirmation of normalized coagulation. * **Option A (True):** Warfarin is a Vitamin K antagonist. An LP is contraindicated if the patient is on warfarin unless the **INR is ≤ 1.4**. Warfarin must typically be stopped 4–5 days prior to the procedure. * **Option B (True):** For therapeutic doses of Low Molecular Weight Heparin (LMWH), a minimum of **24 hours** must elapse between the last dose and the needle placement to ensure adequate clearance. For prophylactic doses, 12 hours is usually sufficient. * **Option D (True):** NSAIDs and Aspirin, when used alone, do not significantly increase the risk of spinal hematoma. They are **not absolute contraindications** for neuraxial procedures, provided the patient has no other underlying coagulopathy. ### **High-Yield Clinical Pearls for NEET-PG** * **Clopidogrel (Plavix):** Must be stopped **5–7 days** before LP. * **Ticlopidine:** Must be stopped **10–14 days** before LP. * **Restarting Heparin:** IV heparin can be restarted **1 hour** after the procedure; LMWH should be restarted **4–24 hours** post-procedure depending on the dose. * **Gold Standard Monitoring:** Always check **INR for Warfarin** and **aPTT for Heparin** before proceeding with neuraxial blocks.

Question 410: Which muscle is most resistant to non-depolarizing neuromuscular blockade?

A. Intercostal muscles
B. Abdominal muscles
C. Diaphragm (Correct Answer)
D. Adductor muscles

Explanation: **Explanation:** The sensitivity of muscles to non-depolarizing neuromuscular blocking agents (NMBAs) varies significantly based on muscle type, blood flow, and acetylcholine receptor density. **Why the Diaphragm is the Correct Answer:** The **diaphragm** is the most resistant muscle to NMBAs. It requires approximately **1.5 to 2 times** the dose needed to paralyze peripheral muscles (like the adductor pollicis). This resistance is attributed to its high density of acetylcholine receptors, high mitochondrial content, and excellent regional blood flow, which allows for rapid delivery and washout of the drug. Consequently, the diaphragm is the **last to be paralyzed** and the **first to recover** during anesthesia. **Analysis of Incorrect Options:** * **Intercostal and Abdominal Muscles (A & B):** These are considered "intermediate" in sensitivity. While they are more resistant than peripheral limb muscles, they are more sensitive than the diaphragm. They typically paralyze after the peripheral muscles but before the diaphragm. * **Adductor Muscles (D):** Peripheral muscles, such as the adductor pollicis (used in thumb twitch monitoring), are highly sensitive to NMBAs. They are among the first to be paralyzed and the last to recover. **NEET-PG High-Yield Pearls:** * **Sequence of Paralysis:** Small, rapid muscles (eyes, fingers) → Limbs → Trunk (Abdominal) → Intercostals → Diaphragm. * **Sequence of Recovery:** Reverse order (Diaphragm recovers first). * **Clinical Monitoring:** The **Adductor pollicis** is the standard for monitoring *recovery* (onset is slow), while the **Orbicularis oculi** better reflects the *onset* of blockade at the diaphragm/larynx. * **Laryngeal Muscles:** These are also relatively resistant (similar to the diaphragm), which is why profound blockade is needed for endotracheal intubation.

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

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free