General Anesthesia — MCQs

General Anesthesia Indian Medical PG Practice Questions and MCQs

Question 551: Characteristic EEG pattern seen in surgical tolerance stage of anesthesia is?

A. Alpha
B. Beta
C. Delta (Correct Answer)
D. Theta

Explanation: ***Delta*** - The surgical tolerance stage of anesthesia is characterized by a **depressed central nervous system**, which manifests as **slow-wave activity** on EEG. - **Delta waves**, defined as 0.5-4 Hz, are indicative of deep sleep or profound CNS depression and are therefore characteristic of surgical anesthesia. *Alpha* - **Alpha waves** (8-13 Hz) are typically associated with a **relaxed, wakeful state** with closed eyes, not surgical anesthesia. - Their presence would indicate insufficient depth of anesthesia, risking intraoperative awareness. *Beta* - **Beta waves** (14-30 Hz) are characteristic of an **awake, alert, and active brain**, or light anesthesia. - Their predominance during surgery would suggest the patient is not adequately anesthetized. *Theta* - **Theta waves** (4-8 Hz) are typically associated with **light sleep**, drowsiness, or certain meditative states. - While slower than alpha waves, they do not signify the deep CNS depression required for surgical tolerance.

Question 552: Which muscle relaxant has the longest duration of action?

A. Doxacurium (Correct Answer)
B. Rocuronium
C. Vecuronium
D. Atracurium

Explanation: ***Doxacurium*** - **Doxacurium** is a long-acting, non-depolarizing neuromuscular blocker, meaning it typically has the longest duration of action among the options provided. - Its prolonged effect is due to its **slow metabolism** and **renal excretion**, leading to an estimated duration of action of 90-120 minutes. *Rocuronium* - **Rocuronium** is an intermediate-acting non-depolarizing neuromuscular blocker, with a typical duration of action of 30-40 minutes after an intubating dose. - It has a rapid onset, making it suitable for **rapid sequence intubation**, but its duration is significantly shorter than doxacurium. *Vecuronium* - **Vecuronium** is an intermediate-acting non-depolarizing neuromuscular blocker, similar to rocuronium, with a duration of action around 25-40 minutes. - It is often favored in patients with **renal insufficiency** as it undergoes significant hepatic metabolism and biliary excretion, but its duration is not as long as doxacurium. *Atracurium* - **Atracurium** is an intermediate-acting non-depolarizing neuromuscular blocker, known for its unique metabolism via **Hofmann elimination** and ester hydrolysis, independent of renal or hepatic function. - Its duration of action is typically 20-35 minutes, making it shorter-acting than doxacurium.

Question 553: IV administration of which anesthetic drug is most painful among the following?

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

Explanation: ***Propofol*** - **Propofol** is notoriously known for causing **significant pain on injection** due to its formulation with **soybean oil emulsion** and its direct irritation of venous free nerve endings. - This pain is often described as a **burning sensation** and can be severe enough to require pre-treatment with lidocaine or administering it in a larger vein. *Methohexital* - While **methohexital** can cause localized pain and sometimes **thrombophlebitis** during intravenous administration, it is generally considered less painful than propofol. - It is a **barbiturate** and its discomfort is typically related to its alkaline pH and potential for venous irritation. *Ketamine* - **Ketamine** typically causes **minimal pain on injection** when administered intravenously. - Its mechanism of action as an **NMDA receptor antagonist** does not generally involve direct irritation of venous endothelium in the same way as propofol. *Etomidate* - **Etomidate**, like methohexital, can cause some **pain and irritation on injection**, and poses a risk of **thrombophlebitis**. - However, the severity of pain is generally **less pronounced** compared to the distinct and often intense burning sensation associated with propofol.

Question 554: All of the following statements about neuromuscular blockage produced by succinylcholine are true, except for:

A. Sustained contraction during tetany
B. Train of four ratio < 0.4
C. Fade on tetanic stimulation (Correct Answer)
D. No fade on Train of four stimulation

Explanation: ***Fade on tetanic stimulation*** - Succinylcholine is a **depolarizing neuromuscular blocker** that initially causes fasciculations and then sustained depolarization. - In a typical depolarizing block (Phase I), there is **no fade** with tetanic or train-of-four (TOF) stimulation due to continuous activation of nicotinic receptors. *Sustained contraction during tetany* - **Sustained contraction during tetany** is characteristic of a depolarizing block (Phase I) where the muscle remains depolarized and unresponsive. - The muscle fibers are continuously stimulated, leading to a prolonged contractile state or paralysis without fade. *Train of four ratio < 0.4* - A **Train-of-Four (TOF) ratio < 0.4** indicates a **fade** in muscle response, which is a hallmark of a **non-depolarizing block (Phase II block)**. - In a typical depolarizing block (Phase I), the TOF ratio is close to 1 because there is no fade. *No fade on Train of four stimulation* - **No fade on Train-of-Four (TOF) stimulation** is a characteristic of a **depolarizing neuromuscular block (Phase I block)**. - This occurs because succinylcholine continuously activates the acetylcholine receptors, maintaining a persistent depolarization throughout the TOF stimuli.

Question 555: Which anesthetic agent is known for the fastest induction and recovery?

A. Halothane
B. Enflurane
C. Desflurane
D. N2O (Correct Answer)

Explanation: ***N2O*** - **Nitrous oxide** has a very **low blood-gas partition coefficient** (0.47), meaning it quickly saturates the blood and brain, leading to rapid induction and recovery. - Its **low solubility** allows for fast changes in anesthetic depth as it moves rapidly in and out of the bloodstream. *Desflurane* - While Desflurane also has a **low blood-gas partition coefficient** (0.42) and provides rapid induction and recovery, **N2O** is generally recognized as having the fastest kinetics. - Desflurane's volatility often requires a specialized heated vaporizer due to its **low boiling point**. *Halothane* - Halothane has a **higher blood-gas partition coefficient** (2.4) compared to N2O and desflurane, resulting in a slower induction and recovery time. - It is associated with potential **hepatotoxicity** (halothane hepatitis) and is no longer widely used. *Enflurane* - Enflurane has an intermediate **blood-gas partition coefficient** (1.9), making its induction and recovery slower than N2O, desflurane, and sevoflurane. - It can cause **seizures** at high concentrations and is also largely replaced by newer agents.

Question 556: Which inhalational agent has the least MAC?

A. Halothane (Correct Answer)
B. Xenon
C. Sevoflurane
D. Isoflurane

Explanation: ***Halothane*** - **Halothane** has a **MAC** of approximately **0.75%**, which is among the lowest for commonly used volatile anesthetics. - A lower **MAC** indicates a higher potency, meaning a lower concentration is needed to achieve anesthetic effect. *Xenon* - **Xenon** has a **MAC** of approximately **71%**, making it one of the least potent inhalational agents. - It is an inert gas with unique anesthetic properties, but its high **MAC** is a key characteristic. *Sevoflurane* - **Sevoflurane** has a **MAC** of approximately **2.0%**, which is higher than halothane. - It is known for its rapid onset and offset due to its low blood solubility. *Isoflurane* - **Isoflurane** has a **MAC** of approximately **1.15%**, which is higher than halothane. - It is often favored for its cardiovascular stability and relatively low metabolism.

Question 557: Which of the following anesthetics is known to increase intraocular pressure?

A. Thiopental
B. Alfentanil
C. Ketamine (Correct Answer)
D. Propofol

Explanation: ***Ketamine*** - **Ketamine** is known to increase **intraocular pressure (IOP)**, making it generally avoided in patients with **glaucoma** or those undergoing ocular surgery. - This effect is due to its influence on sympathetic nervous system activity and extraocular muscle tone. *Thiopental* - **Thiopental**, a barbiturate, typically causes a **reduction in intraocular pressure**, which can be beneficial in certain ocular procedures. - Its mechanism involves decreasing cerebral blood flow and metabolic rate, indirectly leading to a decrease in IOP. *Alfentanil* - **Alfentanil**, an opioid, generally has **minimal to no significant effect on intraocular pressure**. - Its primary actions are analgesia and sedation, without direct impact on oculomotor tone or fluid dynamics. *Propofol* - **Propofol** is known to **decrease intraocular pressure**, making it a favorable agent for ophthalmic surgery. - This effect is attributed to a reduction in cerebral blood flow and an inhibition of aqueous humor production.

Question 558: Dissociative anaesthesia is produced by?

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

Explanation: ***Ketamine*** - **Ketamine** is a unique anesthetic that produces a state of **dissociative anesthesia**, characterized by a trance-like state, analgesia, amnesia, and catalepsy. - This effect is primarily due to its antagonism of the **N-methyl-D-aspartate (NMDA) receptor**. *Etomidate* - **Etomidate** is an intravenous anesthetic characterized by its **cardiovascular stability**, making it suitable for patients with heart conditions. - It works primarily by modulating **GABA-A receptors** but does not produce dissociative anesthesia. *Propofol* - **Propofol** is a widely used intravenous anesthetic known for its **rapid onset and recovery**, and it is often used for induction and maintenance of general anesthesia. - Its primary mechanism of action involves enhancing the effects of **GABA-A receptors**, leading to central nervous system depression, but not dissociative anesthesia. *Thiopentone* - **Thiopentone** (Thiopental) is a barbiturate anesthetic that causes rapid loss of consciousness and has been historically used for inducing general anesthesia. - It acts as a **GABA-A receptor agonist**, depressing the central nervous system, but it does not produce the distinct dissociative state seen with ketamine.

Question 559: Who was the first to use ether as an anesthetic?

A. John Snow
B. William T.G. Morton (Correct Answer)
C. James Simpson
D. Joseph Lister

Explanation: ***William T.G. Morton*** - **William T.G. Morton** was a dentist who publicly demonstrated the use of **ether** as a surgical anesthetic in 1846 during a tooth extraction and later for a tumor removal at Massachusetts General Hospital. - His pioneering work popularized the use of ether, revolutionizing surgical practices by allowing pain-free procedures. *John Snow* - **John Snow** was an English physician known for his work in public health, particularly for tracing the source of a **cholera outbreak** in London. - He is remembered as one of the founders of **modern epidemiology**, not for anesthetic discoveries. *James Simpson* - **James Simpson** was a Scottish obstetrician who pioneered the use of **chloroform** as an anesthetic in obstetrics and surgery, not ether. - He advocated for its use to alleviate pain during childbirth, facing initial controversy. *Joseph Lister* - **Joseph Lister** was a British surgeon who introduced **antiseptic surgery**, significantly reducing post-operative infections. - He is known for promoting the use of **carbolic acid** to sterilize instruments and wounds, not for anesthetic development.

Question 560: Which of the following anesthetic agents causes the LEAST severe complications when accidentally injected intra-arterially?

A. Thiopentone
B. Propofol (Correct Answer)
C. Methohexitone
D. Midazolam

Explanation: **Propofol** * **Propofol** has a relatively low incidence and severity of complications if accidentally injected intra-arterially because of its **lipid emulsion formulation** and mild irritant properties compared to other agents. * While any intra-arterial injection can cause problems, the milder venoconstriction and less direct tissue damage make its intra-arterial complication profile less severe than alternative agents. *Thiopentone* * **Thiopentone** (Thiopental) is highly alkaline, and accidental intra-arterial injection can cause **intense pain**, **vasospasm**, and **gangrene** due to precipitation in the arterioles and widespread endothelial damage. * This severe complication arises from its extreme pH and crystal formation, leading to profound ischemia. *Midazolam* * Accidental intra-arterial injection of **Midazolam** can cause **pain**, **spasm**, and **local tissue damage** due to its relatively acidic pH and solvent properties, though generally less severe than thiopentone. * While not as catastrophic as thiopentone, it can still lead to significant discomfort and localized vascular issues. *Methohexitone* * **Methohexitone** is also an alkaline barbiturate derivative, similar in nature to thiopentone, and its intra-arterial injection carries a significant risk of **vasospasm**, **pain**, and potentially **tissue necrosis**. * Its strong irritant properties and ability to precipitate within the vasculature make it a dangerous agent for inadvertent intra-arterial administration.

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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