Anesthesiology
5 questionsCritical temperature of oxygen is?
Which anaesthetic belongs to the ester group?
Which inhalational agent has the least MAC?
Which anesthetic agent is known for the fastest induction and recovery?
Which of the following is not a sign of stellate ganglion block?
NEET-PG 2013 - Anesthesiology NEET-PG Practice Questions and MCQs
Question 1291: Critical temperature of oxygen is?
- A. -118°C (Correct Answer)
- B. 400°C
- C. 20°C
- D. 36.5°C
Explanation: ***-118°C*** - The **critical temperature** is the temperature above which a gas cannot be liquefied, no matter how much pressure is applied. - For oxygen, its critical temperature is approximately **-118°C**, meaning it can only exist as a gas above this temperature, regardless of pressure. *400°C* - This temperature is significantly **above** the critical temperature of oxygen, so oxygen would always be a gas at this temperature. - It does not represent any specific physical property of oxygen in relation to its phase changes. *20°C* - This temperature is also well **above** oxygen's critical temperature, so oxygen would remain in its gaseous state. - This is approximately room temperature, where oxygen is commonly found as a gas. *36.5°C* - This is close to typical human body temperature and is far **above** the critical temperature of oxygen. - At this temperature, oxygen exists only as a gas.
Question 1292: Which anaesthetic belongs to the ester group?
- A. Lignocaine
- B. Propofol
- C. Procaine (Correct Answer)
- D. Benzocaine
Explanation: ***Procaine*** - **Procaine** is a classical **ester-type** local anesthetic, characterized by an ester linkage between the aromatic and amine parts of its chemical structure. - Ester-type local anesthetics are metabolized by **plasma pseudocholinesterase**, leading to a shorter duration of action compared to amides. *Benzocaine* - **Benzocaine** is also an ester local anesthetic, but it is typically used topically due to its poor water solubility and absorption. - While an ester, the question implies a common injectable agent, making procaine a more representative answer for the "ester group" in general anesthetic use. *Lignocaine* - **Lignocaine** (also known as lidocaine) is an **amide-type** local anesthetic, which can be identified by an amide linkage in its chemical structure. - Amide local anesthetics are primarily metabolized in the **liver** and generally have a longer duration of action than esters. *Propofol* - **Propofol** is a **short-acting intravenous general anesthetic** and is not classified as a local anesthetic or belonging to the ester group. - It works by potentiation of **GABA-A receptors** and is used for induction and maintenance of general anesthesia.
Question 1293: 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 1294: 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 1295: Which of the following is not a sign of stellate ganglion block?
- A. Miosis
- B. Conjunctival redness
- C. Nasal congestion
- D. Exophthalmos (Correct Answer)
Explanation: ***Exophthalmos*** - A stellate ganglion block paralyses the **sympathetic nervous system** to the head and neck. - **Exophthalmos** (bulging of the eye) is a sign of sympathetic **hyperactivity**, not blockade. *Miosis* - **Miosis** (pupil constriction) is a classic sign of sympathetic blockade. - The **dilator pupillae muscle** is paralyzed, leading to unopposed parasympathetic action. *Nasal congestion* - **Nasal congestion** is a common sign due to the **vasodilation** of nasal blood vessels from sympathetic blockade. - Sympathetic nerves normally cause **vasoconstriction** in the nasal mucosa. *Conjunctival redness* - **Conjunctival redness** occurs due to **vasodilation** of conjunctival blood vessels, a direct effect of sympathetic blockade. - This is part of the **Horner's syndrome** presentation.
Biochemistry
1 questionsCritical temperature for liquid nitrogen is ?
NEET-PG 2013 - Biochemistry NEET-PG Practice Questions and MCQs
Question 1291: Critical temperature for liquid nitrogen is ?
- A. 36.5°C
- B. -20°C
- C. -147°C (Correct Answer)
- D. -242°C
Explanation: ***-147°C*** - The **critical temperature** is the temperature above which a gas cannot be liquefied, no matter how much pressure is applied. For **liquid nitrogen**, this value is approximately **-147°C**. - At temperatures above **-147°C**, nitrogen exists only in its gaseous phase. *36.5°C* - This temperature is close to **human body temperature** and is not relevant to the critical temperature of nitrogen. - Nitrogen would be in a gaseous state at this temperature and below its critical pressure. *-20°C* - While a low temperature, **-20°C** is still well above nitrogen's **critical temperature**. - At **-20°C**, nitrogen would be a gas unless subjected to very high pressures. *-242°C* - This temperature is below the **critical temperature** of nitrogen, but it is also below its **boiling point** of **-196°C**. - At **-242°C**, nitrogen would be a liquid, but this value is not its critical temperature.
Dental
1 questionsWhich of the following is not commonly used for local infiltration anesthesia?
NEET-PG 2013 - Dental NEET-PG Practice Questions and MCQs
Question 1291: Which of the following is not commonly used for local infiltration anesthesia?
- A. Lidocaine
- B. Ropivacaine
- C. Dibucaine (Correct Answer)
- D. Bupivacaine
Explanation: ***Dibucaine*** - **Dibucaine** is a local anesthetic with a long duration of action but is rarely used for local infiltration due to its **high toxicity**. - Its narrow therapeutic index makes it less safe for common use compared to other available local anesthetics. *Lidocaine* - **Lidocaine** is one of the most widely used local anesthetics for **local infiltration** due to its rapid onset and intermediate duration of action. - It is effective for a variety of minor surgical procedures and dental interventions. *Ropivacaine* - **Ropivacaine** is an amide-type local anesthetic commonly used for **local infiltration** and regional anesthesia due to its good safety profile and differential block. - It produces less motor block and has a lower potential for cardiotoxicity compared to bupivacaine. *Bupivacaine* - **Bupivacaine** is frequently used for **local infiltration** and regional anesthesia, especially when a longer duration of action is desired. - It is known for its prolonged sensory block but has a higher risk of **cardiac toxicity** compared to lidocaine.
Pharmacology
3 questionsIn ophthalmology, if a patient is allergic to aminoesters, which local anesthetic can be safely used?
In pseudocholinesterase deficiency, which drug should be used cautiously?
Which local anaesthetic is known to cause methemoglobinemia?
NEET-PG 2013 - Pharmacology NEET-PG Practice Questions and MCQs
Question 1291: In ophthalmology, if a patient is allergic to aminoesters, which local anesthetic can be safely used?
- A. Procaine
- B. Cocaine
- C. Prilocaine (Correct Answer)
- D. Tetracaine
Explanation: **Local anesthetics are classified into two chemical groups: esters (aminoesters) and amides. Allergies to esters typically do not cross-react with amides.** ***Prilocaine*** - **Prilocaine** is an **amide-type local anesthetic**, and allergies to **aminoesters** typically do not cross-react with **amides**. - It is a safe alternative in patients with a known allergy to **ester-type local anesthetics**. *Cocaine* - **Cocaine** is an **ester-type local anesthetic**, sharing a similar chemical structure with **aminoesters**. - Patients allergic to **aminoesters** are likely to experience a **cross-reaction** with **cocaine**. *Procaine* - **Procaine** is a classic **ester-type local anesthetic** (an aminoester). - An allergy to aminoesters directly implies an allergy to **procaine** due to its chemical classification. *Tetracaine* - **Tetracaine** is also an **ester-type local anesthetic** (an aminoester). - It is contraindicated in patients with an allergy to **aminoesters** due to the high risk of **allergic reaction**.
Question 1292: In pseudocholinesterase deficiency, which drug should be used cautiously?
- A. Succinylcholine (Correct Answer)
- B. Barbiturates
- C. Gallamine
- D. Halothane
Explanation: ***Succinylcholine*** - **Succinylcholine** is primarily metabolized by **pseudocholinesterase** (also known as butyrylcholinesterase). - In individuals with **pseudocholinesterase deficiency**, the metabolism of succinylcholine is significantly delayed, leading to **prolonged neuromuscular blockade** and extended paralysis. *Barbiturates* - **Barbiturates** are mainly metabolized by the **hepatic cytochrome P450 system** and do not depend on pseudocholinesterase for their breakdown. - Their metabolism would not be significantly affected by pseudocholinesterase deficiency. *Halothane (an inhalational anesthetic)* - **Halothane** is primarily metabolized by the **hepatic cytochrome P450 system** and excreted via the lungs. - Its metabolism is unrelated to **pseudocholinesterase activity**. *Gallamine (a neuromuscular blocker)* - **Gallamine** is a **nondepolarizing neuromuscular blocker** that is primarily eliminated by **renal excretion** as an unchanged drug. - Its metabolism and elimination are independent of **pseudocholinesterase**.
Question 1293: Which local anaesthetic is known to cause methemoglobinemia?
- A. Procaine
- B. Prilocaine (Correct Answer)
- C. Ropivacaine
- D. Etidocaine
Explanation: ***Prilocaine*** - **Prilocaine** is metabolized into **ortho-toluidine**, which can oxidize hemoglobin to **methemoglobin**, especially at higher doses or in susceptible individuals. - **Methemoglobinemia** symptoms include **cyanosis**, **dyspnea**, and in severe cases, central nervous system depression, due to reduced oxygen-carrying capacity of blood. *Procaine* - **Procaine** is an ester-type local anesthetic. It is metabolized to **para-aminobenzoic acid (PABA)**, which can cause allergic reactions, but it is not associated with methemoglobinemia. - It has a relatively **short duration of action** and is less commonly used now compared to amide-type local anesthetics. *Etidocaine* - **Etidocaine** is an amide-type local anesthetic that is known for its **long duration of action** and high potency. - While it can cause systemic toxicity with high doses due to its cardiac and neurological effects, **methemoglobinemia** is not a characteristic side effect. *Ropivacaine* - **Ropivacaine** is an amide-type local anesthetic similar to bupivacaine, known for its **motor-sparing effect** and use in regional anesthesia. - It is associated with a lower risk of **cardiotoxicity** compared to bupivacaine but does not cause methemoglobinemia.