General Anesthesia — MCQs

General Anesthesia Indian Medical PG Practice Questions and MCQs

Question 501: Which of the following anaesthetic agent lacks analgesic effect? A) N2O B) Thiopentone C) Methohexitone D) Ketamine E) Fentanyl

A. N2O
B. Methohexitone
C. Ketamine
D. Fentanyl
E. Thiopentone (Correct Answer)

Explanation: ***Thiopentone*** - Thiopentone is a **barbiturate** anesthetic primarily used for inducing anesthesia. - It provides significant **hypnosis** and sedation but lacks intrinsic **analgesic properties**, meaning it does not relieve pain. *N2O* - **Nitrous oxide** (N2O) is an inhalation anesthetic that provides good **analgesia** at sub-anesthetic concentrations. - It is often used as an adjunct to other anesthetic agents to enhance pain relief during procedures. *Methohexitone* - Methohexitone is another **barbiturate** similar to thiopentone, used for induction of anesthesia. - While it provides rapid **hypnosis**, it also lacks significant **analgesic effects**. *Ketamine* - Ketamine is a **dissociative anesthetic** known for its potent **analgesic properties**. - It works by blocking **NMDA receptors**, providing pain relief even at sub-anesthetic doses. *Fentanyl* - Fentanyl is a powerful **opioid analgesic** that is commonly used in anesthesia for its strong pain-relieving effects. - It acts on **opioid receptors** in the central nervous system to reduce pain perception.

Question 502: The most appropriate treatment for hypothermia during anesthesia is

A. Treated with warm saline (Correct Answer)
B. Mechanism of heat loss is conduction
C. Occurs in all types of Anaesthesia
D. Is beneficial to patients

Explanation: ***Treated with warm saline*** - **Warm intravenous fluids**, particularly saline, are a primary and effective method for rewarming hypothermic patients during surgery. - This helps to directly transfer heat into the patient's core circulation and raise body temperature. *Mechanism of heat loss is conduction* - While **conduction** (heat loss to colder surfaces) is one mechanism of heat loss during anesthesia, **radiation** (heat loss to the environment) and **convection** (heat loss to moving air currents or blood) are often more significant. - Evaporation (from open surgical sites) also contributes substantially to heat loss. *Occurs in all types of Anaesthesia* - Hypothermia is a common complication of **general anesthesia** due to impaired thermoregulation, but it is less common or sometimes deliberately avoided in certain regional anesthesia techniques unless the patient is already cold. - The degree and likelihood of hypothermia vary depending on the type and duration of anesthesia, ambient temperature, and patient factors. *Is beneficial to patients* - **Hypothermia** is generally **detrimental** to most surgical patients, leading to complications like increased bleeding, impaired drug metabolism, prolonged recovery, and increased risk of wound infection. - Therapeutic hypothermia is only medically induced for specific conditions (e.g., post-cardiac arrest) and is not a general benefit during anesthesia.

Question 503: Risk of adverse effects of SCOLINE is greater in

A. Thoracic injury
B. Head injury
C. Spinal cord injury (Correct Answer)
D. Bone injury

Explanation: ***Spinal cord injury*** - Patients with **spinal cord injury** are at increased risk of developing **hyperkalemia** due to upregulation of extrajunctional acetylcholine receptors, which can be life-threatening after administration of **succinylcholine (Scoline)**. - This risk is highest in the period **7 days to several months post-injury**, making succinylcholine relatively contraindicated during this time. *Thoracic injury* - While thoracic injuries can be severe, they **do not directly lead to the widespread upregulation of extrajunctional acetylcholine receptors** that cause succinylcholine-induced hyperkalemia. - The primary concerns with succinylcholine in thoracic injury relate to its effects on **respiratory drive** or potential for **increased intrathoracic pressure**, but not extreme hyperkalemia. *Head injury* - Patients with head injuries may require rapid sequence intubation, and succinylcholine is often used, but it does **not inherently carry a higher risk of hyperkalemia** due to receptor upregulation. - The main concern with succinylcholine in head injury is a potential, albeit controversial, for a **transient increase in intracranial pressure**, which is different from hyperkalemia. *Bone injury* - **Isolated bone injuries**, even severe ones, do not cause the same profound muscle denervation or immobility that leads to the upregulation of extrajunctional acetylcholine receptors seen in spinal cord injury. - Therefore, the risk of **succinylcholine-induced hyperkalemia** is not significantly elevated in patients with only bone injuries.

Question 504: Competitive neuromuscular blockade is enhanced by all except

A. Acidosis
B. Aminoglycosides
C. Hypercalcemia (Correct Answer)
D. Hypermagnesemia

Explanation: ***Hypercalcemia*** - **Hypercalcemia** generally **antagonizes** the effects of neuromuscular blockers by increasing acetylcholine release at the presynaptic terminal and sensitizing the postsynaptic membrane to acetylcholine. - Therefore, it would **reduce**, rather than enhance, competitive neuromuscular blockade. *Acidosis* - **Acidosis** enhances competitive neuromuscular blockade by altering the sensitivity of the **nicotinic acetylcholine receptors** at the neuromuscular junction. - It also affects the pharmacokinetics and pharmacodynamics of neuromuscular blocking agents, leading to **prolonged blockade**. *Aminoglycosides* - **Aminoglycoside antibiotics** like gentamicin or amikacin can enhance neuromuscular blockade by **inhibiting presynaptic acetylcholine release** and blocking postsynaptic nicotinic receptors. - This effect is particularly pronounced when given concurrently with competitive neuromuscular blocking agents. *Hypermagnesemia* - **Hypermagnesemia** enhances neuromuscular blockade by **decreasing acetylcholine release** from the presynaptic nerve terminal. - It also directly **depresses muscle fiber excitability** and reduces the sensitivity of the postsynaptic membrane to acetylcholine.

Question 505: Which of the following intravenous anesthetic agents is contraindicated in epileptic patients posted for general anaesthesia

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

Explanation: ***Ketamine*** - Ketamine is known to have **proconvulsant effects**, particularly at higher doses, and can exacerbate seizures in epileptic patients. - It causes **dissociative anesthesia** and can increase intracranial pressure, which is generally undesirable in patients with seizure disorders. *Thiopentone* - Thiopentone is a **barbiturate** that acts as an anticonvulsant and is often used to treat seizures or status epilepticus, making it safe in epileptic patients. - It **decreases cerebral metabolic rate** and intracranial pressure, which are beneficial for patients with neurologic conditions. *Midazolam* - Midazolam is a **benzodiazepine** with strong anticonvulsant properties, frequently used to terminate seizures. - It enhances GABAergic inhibition, making it a **safe and effective sedative** for epileptic patients. *Propofol* - Propofol has **anticonvulsant properties** and is often used in the management of refractory status epilepticus. - It **decreases cerebral blood flow** and metabolic rate, making it a favorable choice in patients with epilepsy.

Question 506: Anesthetic agents causing bradycardia are all except:

A. Procaine
B. Ketamine (Correct Answer)
C. Prilocaine
D. Bupivacaine

Explanation: ***Ketamine*** - Ketamine characteristically causes **sympathetic stimulation**, leading to an increase in **heart rate** and blood pressure, rather than bradycardia. - Its effects can be beneficial in patients with **hemodynamic instability** or compromised cardiac function. *Procaine* - Procaine, like other local anesthetics, can cause **bradycardia** and other cardiac depressant effects, especially at higher doses or with systemic absorption. - This effect is due to its action on **cardiac ion channels**, impairing impulse generation and conduction. *Prilocaine* - Prilocaine can induce **bradycardia**, similar to other amide-type local anesthetics, due to its direct depressant effects on myocardial function and conduction. - High doses can also lead to **methemoglobinemia**, which, while not directly causing bradycardia, complicates cardiovascular status. *Bupivacaine* - Bupivacaine is particularly known for its **cardiotoxic potential**, including severe **bradycardia** and arrhythmias, especially with accidental intravascular injection. - Its prolonged binding to **cardiac sodium channels** makes it more difficult to resuscitate from bupivacaine-induced cardiac arrest.

Question 507: What causes sudden decreased end tidal CO2 in GA?

A. Cardiac arrest (Correct Answer)
B. Pulmonary embolism
C. Pulmonary hypertension
D. Malignant hyperthermia

Explanation: ***Cardiac arrest*** - In **cardiac arrest**, there is a sudden cessation of effective **cardiac output**, which leads to a dramatic reduction in pulmonary blood flow. - As a result, **CO2 is not transported to the lungs** for exhalation, causing an abrupt and severe drop in **end-tidal CO2**. *Pulmonary embolism* - A **pulmonary embolism** causes an acute obstruction of pulmonary arterial blood flow, leading to an **increase in alveolar dead space**. - While it can decrease **end-tidal CO2** due to reduced perfusion, the drop is often less sudden and complete than in cardiac arrest, and the primary mechanism is **ventilation-perfusion mismatch**. *Pulmonary hypertension* - **Pulmonary hypertension** involves chronically elevated pressures in the pulmonary arteries, which can lead to **right ventricular dysfunction** and reduced cardiac output over time. - It typically causes a more gradual and chronic reduction in **end-tidal CO2** due to impaired gas exchange, rather than a sudden, precipitous drop. *Malignant hyperthermia* - **Malignant hyperthermia** is characterized by a rapid and severe increase in **metabolic rate** and CO2 production. - This condition typically leads to a **sudden increase in end-tidal CO2** as the body produces more CO2 than can be eliminated, rather than a decrease.

Question 508: Train of four fade is a characteristic feature of:

A. Non depolarizing block (Correct Answer)
B. Depolarizing block
C. Both depolarizing and non-depolarizing block
D. Malignant hyperthermia

Explanation: ***Non depolarizing block*** - A **train-of-four (TOF) fade** is a hallmark of **non-depolarizing neuromuscular block**, due to the competitive antagonism of acetylcholine at the postsynaptic receptor. - The first twitch depletes a portion of readily releasable acetylcholine, and the subsequent twitches show progressive fade because less acetylcholine is released with each successive stimulus. *Depolarizing block* - In a **Phase I depolarizing block**, there is **no fade** with TOF stimulation because the acetylcholine receptor is continuously activated, leading to sustained depolarization. - During prolonged exposure to a depolarizing agent, a Phase II block may develop which *can* exhibit fade, but this is a secondary phenomenon, and the primary characteristic of a depolarizing block is lack of fade. *Both depolarizing and non-depolarizing block* - While a **Phase II depolarizing block** can show fade, it is not a *characteristic* feature of all depolarizing blocks, distinguishing it from the consistent fade seen in non-depolarizing blocks. - The primary action of depolarizing agents (Phase I block) does not involve fade, making this option incorrect as a universal characteristic. *Malignant hyperthermia* - **Malignant hyperthermia** is a hypermetabolic crisis triggered by certain anesthetic agents, primarily involving uncontrolled calcium release from the sarcoplasmic reticulum, not directly related to neuromuscular blockade monitoring patterns. - While muscle rigidity can be a symptom, it does not manifest as a **train-of-four fade**, which is specific to postsynaptic acetylcholine receptor interactions.

Question 509: Which of the following intravenous anaesthetic agent causes decrease in postoperative nausea and vomiting :

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

Explanation: ***Propofol*** - **Propofol** has antiemetic properties, which contributes to a reduced incidence of **postoperative nausea and vomiting (PONV)**. - Its mechanism of action in reducing PONV is thought to involve effects on **dopaminergic receptors** and **serotonin pathways** in the brain. *Etomidate* - **Etomidate** is not known to significantly reduce PONV and may even have a neutral effect or slightly increase it compared to propofol. - Its primary advantages include **cardiovascular stability**, which is unrelated to antiemetic effects. *Ketamine* - **Ketamine** is associated with a higher incidence of PONV, especially at higher doses, due to its **psychedelic side effects** and stimulation of the chemoreceptor trigger zone. - It is known for causing **emergence delirium** and does not possess antiemetic properties. *Thiopentone* - **Thiopentone** (Thiopental) does not have any significant antiemetic properties and is not typically used for its effect on PONV. - It was historically used as an induction agent but has largely been replaced by newer drugs like propofol.

Question 510: Hallucinations are seen after _______ anaesthesia:

A. Nitrous oxide
B. Fentanyl
C. Ketamine (Correct Answer)
D. Thiopentone

Explanation: ***Ketamine*** - Ketamine is known for its **dissociative anesthetic** properties, which can lead to vivid **hallucinations** and disturbing dreams during emergence from anesthesia, especially in adults. - This effect is due to its action as an **NMDA receptor antagonist**, disrupting normal sensory and cognitive processing. *Nitrous oxide* - While nitrous oxide can cause a sense of **euphoria** and altered perception, it is less commonly associated with vivid, distressing hallucinations typical of ketamine. - It is often used as an adjunct to other anesthetics to reduce their dose and enhance **analgesia**. *Fentanyl* - Fentanyl is a potent **opioid analgesic** primarily used for pain relief and sedation, and does not typically cause hallucinations. - Its main side effects include **respiratory depression**, nausea, and constipation. *Thiopentone* - Thiopentone is a **barbiturate** used for rapid induction of anesthesia, causing loss of consciousness quickly to facilitate intubation. - It primarily acts as a **GABA-A receptor agonist** and is not associated with hallucinogenic effects during emergence.

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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