General Anesthesia Practice Questions

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

Propofol. **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.

Q: Which anaesthetic drug contributes to green house effect?

Desflurane. **Desflurane** - **Desflurane** has the highest **global warming potential (GWP)** among commonly used volatile anesthetics, primarily due to its long atmospheric half-life and potent infrared absorption. - Its environmental impact is also amplified by its high **minimum alveolar concentration (MAC)** and low blood solubility, requiring higher delivered concentrations for anesthesia. *Enflurane* - **Enflurane** has a lower GWP compared to desflurane and is less commonly used in modern practice. - While it contributes to the greenhouse effect, its impact is significantly less than that of desflurane due to differences in chemical structure and atmospheric persistence. *Sevoflurane* - **Sevoflurane** has a relatively low GWP and a short atmospheric half-life compared to desflurane, making it a more environmentally friendly option among volatile anesthetics. - Although it still contributes to atmospheric warming, its overall environmental impact is considerably less than desflurane's. *Halothane* - **Halothane** is a potent greenhouse gas but is no longer used in many parts of the world due to concerns about hepatotoxicity and its significant ozone-depleting potential. - While it contributes to atmospheric warming, its current lack of clinical use limits its ongoing contribution to the greenhouse effect compared to currently utilized agents.

Q: Intraocular pressure is increased by which anaesthetic?

Ketamine. ***Ketamine*** - **Ketamine** is known to increase **intraocular pressure (IOP)**, making it generally avoided in patients with glaucoma or penetrating eye injuries. - This effect is thought to be due to its dissociative properties, causing **nystagmus**, and stimulating extraocular muscles. *Nitrous Oxide* - **Nitrous oxide** by itself has minimal or no direct effect on **intraocular pressure (IOP)**. - However, in cases of an air-filled globe (e.g., after retinal detachment surgery), it can increase IOP by expanding the gas bubble. *Isoflurane* - **Isoflurane**, like most volatile anesthetics, typically **decreases intraocular pressure (IOP)**. - This reduction is generally due to its effects on reducing aqueous humor production and increasing uveoscleral outflow. *Propofol* - **Propofol** is known for its ability to **decrease intraocular pressure (IOP)**. - This effect is mediated by a reduction in aqueous humor production and an increase in uveoscleral outflow, making it a favorable choice in ophthalmic surgery.

Q: Which anaesthetic is contraindicated in renal failure?

Methoxyflurane. ***Methoxyflurane*** - Methoxyflurane undergoes significant **metabolism** to produce inorganic **fluoride ions**, which are directly **nephrotoxic**. - This nephrotoxicity can cause **high-output renal failure** with reduced concentrating ability, making it contraindicated in patients with pre-existing renal impairment. *Isoflurane* - Isoflurane is minimally metabolized and produces very low levels of **fluoride ions**, making it generally **safe** for use in patients with renal failure. - Its elimination is primarily via the **lungs**, with very little hepatic metabolism or renal excretion of active compounds. *Desflurane* - Desflurane is also minimally metabolized, similar to isoflurane, and therefore produces negligible amounts of **fluoride ions**. - It is considered a **safe option** for patients with renal impairment due to its predominantly pulmonary elimination and lack of nephrotoxic metabolites. *Halothane* - While halothane can cause **hepatotoxicity**, it is generally **not directly nephrotoxic** in the way methoxyflurane is. - Its metabolism, though more extensive than isoflurane or desflurane, does not produce clinically significant levels of nephrotoxic fluoride ions to contraindicate its use in renal failure.

Q: Which of the following statements about Nitrous Oxide (N2O) is true?

Least potent inhalational anesthetic. **Least potent inhalational anesthetic** - Nitrous oxide has a **high Minimum Alveolar Concentration (MAC)** of approximately 104%, making it the least potent of the commonly used inhalational anesthetics. - Its high MAC means a very high concentration is required to achieve surgical anesthesia, which is why it is typically used as an adjunct to more potent agents. *Lighter than air* - The molecular weight of nitrous oxide (N2O) is 44, which is **heavier than air** (average molecular weight approximately 29 g/mol). - Its density is greater than air, meaning it would tend to sink rather than rise. *Effective muscle relaxant* - Nitrous oxide provides **minimal to no skeletal muscle relaxation** benefits. - If muscle relaxation is required, a neuromuscular blocking agent must be administered separately. *Does not cause diffusion hypoxia* - Nitrous oxide rapidly diffuses out of the blood into the alveoli during emergence, diluting the oxygen and carbon dioxide there. - This rapid diffusion can lead to **diffusion hypoxia** (also known as the "second gas effect"), necessitating the administration of 100% oxygen during recovery to prevent this complication.

Q: What is the primary clinical use of Sugammadex in anesthesia?

Reversal of NM blockers. ***Reversal of NM blockers*** - **Sugammadex** is a modified gamma-cyclodextrin that specifically encapsulates steroidal **neuromuscular blocking agents (NMBAs)** like **rocuronium** and **vecuronium**. - This encapsulation rapidly inactivates the NMBAs, leading to a dose-dependent and swift **reversal of neuromuscular blockade**. *Organophosphate poisoning* - Organophosphate poisoning is treated with **atropine** to block muscarinic effects and **pralidoxime** to reactivate inhibited acetylcholinesterase. - Sugammadex has no role in antagonizing the effects of **organophosphates** or regenerating acetylcholinesterase. *Treatment of local anaesthetic poisoning* - Local anesthetic systemic toxicity (LAST) is primarily managed with supportive care, including airway management, and the administration of **lipid emulsion therapy**. - Sugammadex does not bind to local anesthetics and therefore has no efficacy in treating local anesthetic poisoning. *Treatment of central anticholinergic syndrome* - Central anticholinergic syndrome is typically treated with **physostigmine**, an acetylcholinesterase inhibitor that can cross the blood-brain barrier. - Sugammadex is not an anticholinergic antagonist and does not affect the central nervous system to reverse anticholinergic effects.

Q: What is the drug of choice for reversing muscle relaxants after anesthesia?

Neostigmine. ***Neostigmine*** - **Neostigmine** is an **acetylcholinesterase inhibitor** that increases the amount of acetylcholine at the neuromuscular junction, thereby reversing the effects of non-depolarizing muscle relaxants. - It is often co-administered with an **anticholinergic agent** like atropine or glycopyrrolate to counteract its muscarinic side effects (e.g., bradycardia, increased secretions). *Pralidoxine* - **Pralidoxine (2-PAM)** is an **oxime cholinesterase reactivator** used primarily to treat organophosphate poisoning. - It works by regenerating acetylcholinesterase that has been inhibited by organophosphates, which is not the mechanism of action required for reversing typical muscle relaxants. *Atropine* - **Atropine** is an **anticholinergic drug** that blocks muscarinic acetylcholine receptors. - While it is often given with neostigmine to counteract muscarinic side effects like bradycardia, it does not directly reverse the neuromuscular blockade caused by muscle relaxants. *None of the options* - This option is incorrect because **neostigmine** is a well-established and commonly used drug for reversing non-depolarizing muscle relaxants.

Q: Phase II block is seen with:

SCh infusion. ***SCh infusion*** - A **prolonged infusion or high dose** of succinylcholine (SCh) can lead to a **Phase II block**, a desensitizing block resembling that of a non-depolarizing neuromuscular blocker. - This occurs due to the **persistent presence of SCh** at the neuromuscular junction, which initially depolarizes the endplate (Phase I) but eventually leads to **receptor desensitization** and repolarization, preventing further muscle contraction. *Single dose SCh* - A **single bolus dose of succinylcholine** typically produces a **Phase I block**, characterized by initial muscle fasciculations followed by flaccid paralysis due to persistent depolarization of the motor endplate. - It resolves relatively quickly as **succinylcholine is rapidly hydrolyzed** by pseudocholinesterase, usually not leading to a prolonged desensitization characteristic of Phase II. *Mivacurium* - **Mivacurium** is an intermediate-acting, **non-depolarizing neuromuscular blocker**. - Its mechanism of action involves **competitively binding to nicotinic acetylcholine receptors** at the neuromuscular junction, thereby preventing acetylcholine from binding and initiating muscle contraction, which is fundamentally different from a Phase II block caused by prolonged depolarization. *None of the options* - This option is incorrect because **SCh infusion** is a recognized cause of Phase II block. - The phenomenon of Phase II block is a well-established pharmacological response to **excessive and prolonged exposure** to depolarizing neuromuscular blockers like succinylcholine.

Q: Which anaesthetic agent has maximum MAC ?

Nitrous Oxide (N2O). ***Nitrous Oxide (N2O)*** - **Nitrous Oxide** has the highest **minimum alveolar concentration (MAC)** of all commonly used inhalational anesthetics, approximately 104%. - A high MAC indicates **low potency**, meaning that a large concentration is required to achieve anesthetic effects. *Ether* - **Ether** has a MAC of about 1.92%, which is significantly lower than that of Nitrous Oxide. - Its use has largely been replaced due to its flammability, slow induction, and recovery times. *Methoxyfluorane* - **Methoxyfluorane** is known for having a very low MAC, around 0.16%, making it the most potent inhalational anesthetic. - Due to its high potency and significant nephrotoxicity, its use is now very limited. *Halothane* - **Halothane** has a MAC of approximately 0.75%. - While it was a widely used inhalational anesthetic, it has largely been replaced due to concerns about **halothane hepatitis** and arrhythmogenicity.

Q: Stages of anesthesia were established by

Diethyl ether. ***Diethyl ether** - The classic stages of anesthesia (analgesia, excitement, surgical anesthesia, medullary depression) were originally described in relation to the administration of **diethyl ether**. - Its slow onset and prolonged half-life allowed for the clear observation and definition of these distinct stages. *Nitrous oxide* - This gaseous anesthetic has a rapid onset and offset, making it difficult to clearly delineate all four classical stages with its use. - It is often used as an adjunct to other anesthetics rather than as a sole agent for prolonged surgical anesthesia. *Halothane* - Halothane is a potent volatile anesthetic that became popular after ether, but its use also does not typically involve the clear, step-wise progression through all four anesthetic stages as seen with ether. - It was one of the first widely used inhaled anesthetics that largely replaced ether due to better patient control and fewer side effects. *Chloroform* - Chloroform was another early anesthetic but was associated with significant cardiac and hepatic toxicity, leading to its limited use and eventual discontinuation. - While it induced anesthesia, the clear staging of anesthetic depth was primarily established and standardized using diethyl ether.

Question 1

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

Accepted Answer

Propofol

Answer

Thiopentone

Answer

Methohexitone

Answer

Midazolam

Question 2

Which anaesthetic drug contributes to green house effect?

Accepted Answer

Desflurane

Answer

Enflurane

Answer

Sevoflurane

Answer

Halothane

Question 3

Intraocular pressure is increased by which anaesthetic?

Accepted Answer

Ketamine

Answer

Nitrous Oxide

Answer

Isoflurane

Answer

Propofol

Question 4

Which anaesthetic is contraindicated in renal failure?

Accepted Answer

Methoxyflurane

Answer

Isoflurane

Answer

Desflurane

Answer

Halothane

Question 5

Which of the following statements about Nitrous Oxide (N2O) is true?

Accepted Answer

Least potent inhalational anesthetic

Answer

Lighter than air

Answer

Effective muscle relaxant

Answer

Does not cause diffusion hypoxia

Question 6

What is the primary clinical use of Sugammadex in anesthesia?

Accepted Answer

Reversal of NM blockers

Answer

Organophosphate poisoning

Answer

Treatment of local anaesthetic poisoning

Answer

Treatment of central anticholinergic syndrome

Question 7

What is the drug of choice for reversing muscle relaxants after anesthesia?

Accepted Answer

Neostigmine

Answer

Pralidoxine

Answer

Atropine

Answer

None of the options

Question 8

Phase II block is seen with:

Accepted Answer

SCh infusion

Answer

Single dose SCh

Answer

Mivacurium

Answer

None of the options

Question 9

Which anaesthetic agent has maximum MAC ?

Accepted Answer

Nitrous Oxide (N2O)

Answer

Ether

Answer

Methoxyfluorane

Answer

Halothane

Question 10

Stages of anesthesia were established by

Accepted Answer

Diethyl ether

Answer

Nitrous oxide

Answer

Halothane

Answer

Chloroform

General Anesthesia — MCQs

General Anesthesia — MCQs

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