General Anesthesia Practice Questions

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: The "MAC" of desflurane is:

6. ***6*** - The **Minimum Alveolar Concentration (MAC)** of desflurane is approximately **6%**. It is one of the highest MAC values among commonly used volatile anesthetics. - A higher MAC value indicates **lower potency** of the anesthetic agent. *1.15* - This value is close to the MAC of **isoflurane** (around 1.15%), which is significantly more potent than desflurane. - Using 1.15% desflurane would not provide adequate anesthesia for surgical stimulation. *2* - This MAC value is similar to that of **sevoflurane** (around 2%), another commonly used inhalational anesthetic. - Sevoflurane is less potent than isoflurane but more potent than desflurane. *4* - A MAC of 4% would indicate an anesthetic with potency between sevoflurane and desflurane, but it does not correspond to the MAC of any primary volatile anesthetic agent. - While desflurane's MAC is high, 4% is still too low for its actual value.

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.

Q: All of the following cause myocardial depression except:

Etomidate. ***Etomidate*** - **Etomidate** is known for its **hemodynamic stability** and minimal effect on myocardial contractility, making it a suitable induction agent for patients with cardiovascular compromise. - While it can cause some decrease in systemic vascular resistance, it maintains **cardiac output** much better than other agents listed. *Halothane* - **Halothane** is a potent volatile anesthetic that directly depresses **myocardial contractility** and reduces cardiac output. - It sensitizes the myocardium to **catecholamines**, increasing the risk of arrhythmias. *Thiopentone* - **Thiopentone** (thiopental) is a barbiturate that causes significant **dose-dependent myocardial depression** and systemic vasodilation. - This can lead to a substantial decrease in **blood pressure** and cardiac output, especially with rapid administration. *Ketamine* - Although ketamine often causes an increase in heart rate and blood pressure due to **sympathetic stimulation**, it can also have a direct **myocardial depressant effect** when the sympathetic nervous system is exhausted or blocked. - Its indirect stimulant effects *can mask* a direct negative inotropic effect on the myocardium.

Q: What does the Dibucaine number indicate in clinical practice?

Atypical acetylcholinesterase activity. ***Atypical acetylcholinesterase activity*** - The **Dibucaine number** quantifies the inhibition of **pseudocholinesterase (butyrylcholinesterase)** by the local anesthetic dibucaine. - A low Dibucaine number (e.g., < 20-30) indicates a genetically determined **atypical variant** of pseudocholinesterase, leading to prolonged duration of action of drugs like succinylcholine. *Potency of muscle relaxants* - The potency of muscle relaxants is typically assessed by the **ED95**, which is the dose required to produce 95% suppression of twitch response. - While Dibucaine is a local anesthetic that can cause muscle relaxation, the **Dibucaine number** specifically evaluates an enzyme's activity, not the strength of the relaxant itself. *Potency of general anesthetics* - The potency of general anesthetics is primarily measured by the **Minimum Alveolar Concentration (MAC)** required to prevent movement in 50% of patients in response to a noxious stimulus. - The Dibucaine number is unrelated to the mechanism or potency of general anesthetic agents. *None of the options* - This option is incorrect because **Atypical acetylcholinesterase activity** accurately describes what the Dibucaine number indicates. - The Dibucaine number is a specific laboratory test used to identify genetic variations in butyrylcholinesterase, which has significant clinical implications for drug metabolism.

Q: Which of the following statements about halothane is false?

Constricts bronchii. ***Constricts bronchii*** - Halothane is a **bronchodilator** that relaxes bronchial smooth muscle, making it useful in patients with asthma or COPD. - The statement that it constricts bronchi is **false**. *Volatile liquid with sweet odour* - **Halothane** is a **volatile liquid** and is known for its characteristic **sweet, non-pungent odour**. - This property makes it well-tolerated during induction of anesthesia, particularly in pediatric patients. *Sensitises heart to adrenaline* - Halothane **sensitizes the myocardium** to the effects of **catecholamines**, including adrenaline (epinephrine). - This can lead to the development of **cardiac arrhythmias**, especially ventricular arrhythmias, when adrenaline is administered or endogenous levels are high. *Causes malignant hyperthermia* - Halothane is a potent trigger for **malignant hyperthermia**, a rare but life-threatening pharmacogenetic disorder. - This condition is characterized by a rapid and severe increase in body temperature, muscle rigidity, and metabolic derangements due to uncontrolled release of calcium from the sarcoplasmic reticulum.

Q: Inducing agent of choice in hypovolemic shock?

Ketamine. ***Ketamine*** - **Ketamine** is preferred in **hypovolemic shock** due to its **sympathomimetic** properties, leading to an increase in **heart rate** and **blood pressure**, which helps maintain **hemodynamic stability**. - It also has a relatively **stable cardiovascular profile** compared to other inducing agents, making it safer in patients with compromised circulatory volume. *Isoflurane* - **Isoflurane** is an **inhalational anesthetic** that causes significant **vasodilation** and dose-dependent **myocardial depression**, which can worsen **hypotension** in a hypovolemic patient. - Its use during induction can lead to a further decrease in **blood pressure** and compromise **organ perfusion**. *Desflurane* - **Desflurane** is another **inhalational anesthetic** known for its tendency to cause **tachycardia** and a **pronounced decrease in systemic vascular resistance**, which can severely exacerbate **hypotension** in a patient with **hypovolemic shock**. - Its rapid onset and offset properties do not outweigh the **cardiovascular depressant effects** in this context. *Thiopentone* - **Thiopentone** (and other **barbiturates**) causes significant **myocardial depression** and **vasodilation**, leading to a sharp drop in **blood pressure**, which can be detrimental in patients with **hypovolemia**. - It rapidly redistributes and can cause severe **hemodynamic instability** which is poorly tolerated by a compromised cardiovascular system.

Q: Fast induction and recovery is seen in?

N2O. ***N2O*** - **Nitrous oxide (N2O)** has a very **low blood-gas partition coefficient**, meaning it rapidly equilibrates between the alveolar gas and blood. - This rapid equilibration leads to a **fast onset of anesthetic action** (induction) and quick elimination from the body (recovery). *methoxyflurane* - **Methoxyflurane** has a **high blood-gas partition coefficient**, which means it has high solubility in blood. - This high solubility leads to **slow induction and prolonged recovery** as more anesthetic needs to be dissolved and then eliminated from the blood. *ether* - **Diethyl ether** also has a relatively **high blood-gas partition coefficient**, resulting in slow induction and recovery. - Its high solubility in blood and tissues means it takes longer to achieve and then dissipate its anesthetic effect. *halothane* - **Halothane** has a **moderate blood-gas partition coefficient**, leading to a slower induction and recovery compared to N2O. - While faster than methoxyflurane or ether, its solubility is still significant enough to delay its onset and offset.

Q: Which anaesthetic agent is neither metabolised by liver nor by kidney?

Atracurium. ***Atracurium*** - **Atracurium** undergoes **Hofmann elimination**, a non-enzymatic chemical degradation in plasma, and also **ester hydrolysis** by non-specific plasma esterases [2]. - This unique metabolism makes its elimination largely independent of **liver** and **kidney function**, making it a good choice for patients with organ dysfunction [2]. *Vecuronium* - Primarily metabolized by the **liver** into active and inactive metabolites [1]. - Its elimination can be prolonged in patients with **hepatic impairment** [1]. *Pancuronium* - Undergoes significant **hepatic metabolism** and subsequent **renal excretion** of both parent drug and metabolites [1]. - Its duration of action is significantly affected by both **liver** and **kidney dysfunction** [1]. *Rocuronium* - Primarily eliminated unchanged via **biliary excretion** (liver) [1]. - Its duration of action is prolonged in patients with **hepatic impairment** [1].

Q: Who is known for demonstrating the levels of ether anesthesia?

Guedel. ***Guedel*** - Arthur Guedel developed and refined the **stages and planes of ether anesthesia** based on clinical observations of respiratory patterns, eye signs, and muscle tone. - His classification system, known as the **Guedel stages**, provided a systematic approach to monitoring anesthetic depth, especially useful before the advent of modern anesthetic agents and monitoring equipment. *Morton* - **William T.G. Morton** is credited with the first successful public demonstration of sulfuric ether as a surgical anesthetic in 1846 during a tooth extraction. - While he pioneered the use of ether for anesthesia, he did not develop the classic stages of anesthetic depth. *Thompson* - There is no widely recognized historical figure named Thompson who is primarily known for defining the **levels or stages of ether anesthesia**. - This name is not associated with the primary discovery or classification of anesthetic depth. *None of the options* - This option is incorrect because **Guedel** is specifically known for his work in defining the stages of ether anesthesia. - Guedel's contributions were significant in standardizing anesthetic practice for many years.

Question 1

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 2

The "MAC" of desflurane is:

Accepted Answer

6

Answer

1.15

Answer

4

Answer

2

Question 3

Stages of anesthesia were established by

Accepted Answer

Diethyl ether

Answer

Nitrous oxide

Answer

Halothane

Answer

Chloroform

Question 4

All of the following cause myocardial depression except:

Accepted Answer

Etomidate

Answer

Halothane

Answer

Thiopentone

Answer

Ketamine

Question 5

What does the Dibucaine number indicate in clinical practice?

Accepted Answer

Atypical acetylcholinesterase activity

Answer

Potency of muscle relaxants

Answer

Potency of general anesthetics

Answer

None of the options

Question 6

Which of the following statements about halothane is false?

Accepted Answer

Constricts bronchii

Answer

Volatile liquid with sweet odour

Answer

Causes malignant hyperthermia

Answer

Sensitises heart to adrenaline

Question 7

Inducing agent of choice in hypovolemic shock?

Accepted Answer

Ketamine

Answer

Isoflurane

Answer

Desflurane

Answer

Thiopentone

Question 8

Fast induction and recovery is seen in?

Accepted Answer

N2O

Answer

Methoxyflurane

Answer

Ether

Answer

Halothane

Question 9

Which anaesthetic agent is neither metabolised by liver nor by kidney?

Accepted Answer

Atracurium

Answer

Vecuronium

Answer

Pancuronium

Answer

Rocuronium

Question 10

Who is known for demonstrating the levels of ether anesthesia?

Accepted Answer

Guedel

Answer

Morton

Answer

Thompson

Answer

None of the options

General Anesthesia — MCQs

General Anesthesia — MCQs

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