Pharmacology of Intravenous Anesthetics — MCQs
Midazolam does not cause which of the following?
Which inducing agent is associated with the highest incidence of postoperative vomiting?
What is a significant disadvantage of ketamine?
How do benzodiazepines exert their sedative effects?
Which of the following anesthetic agent is not painful on intravenous administration?
Which one of the following increases intracranial tension
Intracranial pressure is increased by
Which IV anesthetic does not cause cardiac depression?
Which intravenous anaesthetic agent has analgesic effect also
Which is the intravenous anesthetic agent that contributes to good analgesia?
Pharmacology of Intravenous Anesthetics Indian Medical PG Practice Questions and MCQs
Question 1: Midazolam does not cause which of the following?
- A. Anterograde amnesia
- B. Decreased cardiovascular effects as compared to propofol
- C. Causes tachyphylaxis during high dose infusions
- D. Retrograde amnesia (Correct Answer)
Explanation: ***Retrograde amnesia*** - Midazolam, a benzodiazepine, primarily causes **anterograde amnesia** [2], meaning patients have difficulty forming new memories after drug administration. - It does not significantly affect memories formed **before drug administration** (retrograde amnesia). *Anterograde amnesia* - Midazolam is well-known for its ability to induce **anterograde amnesia**, which is often a desirable effect in procedural sedation [2]. - This effect helps patients forget unpleasant or painful procedures performed while under its influence. *Causes tachyphylaxis during high dose infusions* - Prolonged or high-dose infusions of midazolam can lead to **tachyphylaxis**, requiring increased doses to achieve the same effect [1]. - This phenomenon is due to the **down-regulation or desensitization of GABA-A receptors** with continuous stimulation. *Decreased cardiovascular effects as compared to propofol* - Midazolam generally causes **less pronounced cardiovascular depression** (e.g., hypotension) compared to propofol, especially in standard sedative doses [1]. - This makes midazolam a safer option for sedation in some patients with **fragile cardiovascular statuses**.
Question 2: Which inducing agent is associated with the highest incidence of postoperative vomiting?
- A. Thiopentone
- B. Propofol
- C. Etomidate
- D. Ketamine (Correct Answer)
Explanation: ***Ketamine*** - While **ketamine** is a valuable anesthetic, it is associated with a higher incidence of **postoperative nausea and vomiting (PONV)** due to its effects on the central nervous system. - This is particularly noted in adult patients undergoing procedures where ketamine is used as the primary inducing agent or for maintenance. *Etomidate* - **Etomidate** is known for its **hemodynamic stability**, making it a good choice for patients with cardiovascular disease. - It has a moderate incidence of **PONV**, generally considered lower than ketamine but higher than propofol. *Thiopentone* - **Thiopentone** (now less commonly used) was a traditional barbiturate inducing agent. - Its incidence of **PONV** is generally considered moderate and not the highest among common inducing agents. *Propofol* - **Propofol** is well-known for its **antiemetic properties**, which contribute to a significantly lower incidence of **PONV**. - It is often favored in patients at high risk for PONV precisely because of this beneficial side effect.
Question 3: What is a significant disadvantage of ketamine?
- A. Increased heart rate
- B. Increased ICT
- C. Delirium (Correct Answer)
- D. All of the options
Explanation: ***Delirium*** - Ketamine is known to cause **emergence phenomena**, which include **vivid dreams, hallucinations**, and **delirium**, particularly during recovery from anesthesia. - This psychotomimetic effect can be distressing for patients and may necessitate the co-administration of a **benzodiazepine** to mitigate these symptoms. *Increased heart rate* - While ketamine does cause an **increase in heart rate** and **blood pressure** due to sympathetic stimulation, this is often considered a disadvantage but not the *most significant* when compared to the unique cognitive side effects. - This effect can be beneficial in patients with **hemodynamic instability**, but can be problematic in those with **cardiovascular disease**. *Increased ICT* - It is often considered a contraindication in patients with **elevated intracranial pressure (ICP)** as it can potentially increase **cerebral blood flow** and thus ICP. - However, recent studies suggest that in adequately ventilated patients, the effect on ICP may be less pronounced than previously thought, making delirium a more consistent and prominent disadvantage for many patients. *All of the options* - While ketamine can cause an **increased heart rate** and potentially affect **intracranial pressure**, **delirium** and other emergence phenomena are often highlighted as a unique and significant disadvantage because they are highly distressing and difficult to manage. - The psychotomimetic effects are a hallmark side effect that often governs its cautious use without concurrent medication.
Question 4: How do benzodiazepines exert their sedative effects?
- A. They enhance GABAergic transmission. (Correct Answer)
- B. They increase norepinephrine levels and enhance GABA transmission.
- C. They block dopamine receptors and enhance GABA transmission.
- D. They inhibit acetylcholine release and enhance GABA transmission.
Explanation: ***They enhance GABAergic transmission.*** - Benzodiazepines bind to a specific site on the **GABA-A receptor**, increasing its affinity for the **neurotransmitter GABA**. - This binding leads to an increased frequency of **chloride channel opening**, hyperpolarizing the neuron and making it less excitable, which produces sedative effects. *They increase norepinephrine levels and enhance GABA transmission.* - While benzodiazepines enhance GABA transmission, they do **not primarily increase norepinephrine levels**. - Medications that increase norepinephrine levels, such as certain antidepressants, typically have stimulating rather than sedative effects. *They block dopamine receptors and enhance GABA transmission.* - While benzodiazepines enhance GABA transmission, they do **not block dopamine receptors**. - Blocking dopamine receptors is the primary mechanism of action for many **antipsychotic medications**, which have different pharmacological profiles and side effects compared to benzodiazepines. *They inhibit acetylcholine release and enhance GABA transmission.* - While benzodiazepines enhance GABA transmission, they generally do **not directly inhibit acetylcholine release**. - Muscarinic acetylcholine receptor antagonists (anticholinergics) inhibit acetylcholine and can cause sedation, but this is a distinct mechanism from benzodiazepines.
Question 5: Which of the following anesthetic agent is not painful on intravenous administration?
- A. Propofol
- B. Etomidate
- C. Ketamine (Correct Answer)
- D. Methohexital
Explanation: ***Ketamine*** - **Ketamine** is known for causing minimal pain on intravenous administration compared to other common induction agents. - Its mechanism of action as an **NMDA receptor antagonist** does not involve irritation of venous endothelium to the same extent as some other anesthetics. *Propofol* - **Propofol** is infamous for causing significant **injection pain** due to its formulation, which contains soybean oil, glycerol, and egg lecithin, acting as a direct irritant to the intima of veins. - The pain is often described as a **burning sensation** and can be severe enough to require pre-treatment with lidocaine. *Etomidate* - **Etomidate**, like propofol, can cause significant pain on injection, although generally less severe than propofol. - The pain is thought to be related to its **propylene glycol vehicle**, which can cause venous irritation. *Methohexital* - **Methohexital**, a barbiturate, is associated with a moderate incidence of **injection site pain and thrombophlebitis**. - Its alkaline pH and direct irritation of the **venous intima** are the primary reasons for patient discomfort during administration.
Question 6: Which one of the following increases intracranial tension
- A. Thiopentone
- B. Ketamine (Correct Answer)
- C. Propofol
- D. Halothane
Explanation: ***Ketamine*** - Ketamine causes a dose-dependent increase in **cerebral blood flow (CBF)** and **intracranial pressure (ICP)**, which is why it is generally avoided in patients with increased intracranial tension. - This effect is mediated by its mechanism of action as an **NMDA receptor antagonist**, which can indirectly lead to cerebral vasodilation. *Thiopentone* - Thiopentone, a **barbiturate**, decreases **cerebral metabolic rate of oxygen (CMRO2)**, leading to a reduction in **cerebral blood flow (CBF)** and consequently, a decrease in **intracranial pressure (ICP)**. - It is often used to treat elevated ICP, providing **neuroprotection** by reducing brain activity. *Propofol* - Propofol significantly reduces **cerebral blood flow (CBF)** and **cerebral metabolic rate of oxygen (CMRO2)**, leading to a decrease in **intracranial pressure (ICP)**. - Its rapid onset and offset, coupled with its ability to lower ICP, make it a favorable agent for sedation in neurosurgical patients. *Halothane* - While halothane can cause **cerebral vasodilation** and an increase in **cerebral blood flow (CBF)**, leading to increased ICP, its use has largely been replaced by newer inhalational agents like isoflurane and sevoflurane, which have less pronounced effects on ICP or even decrease it. - Its propensity for inducing dose-dependent **cerebral vasodilation** when used at higher concentrations makes it less ideal in situations where ICP is a concern.
Question 7: Intracranial pressure is increased by
- A. Ketamine (Correct Answer)
- B. Thiopentone
- C. Ether
- D. Halothane
Explanation: ***Ketamine*** - **Ketamine** is known to increase **cerebral blood flow** and thus intracranial pressure, making it generally avoided in patients with elevated ICP. - This effect is mediated by its influence on **cerebral metabolism** and **vasodilation**. *Thiopentone* - **Thiopentone** is a barbiturate that typically **reduces cerebral blood flow** and **metabolic rate**, thereby decreasing intracranial pressure. - It is often used for **neuroprotection** and to control elevated ICP due to its vasoconstrictive properties. *Ether* - **Ether** is an older inhalational anesthetic that generally causes **cerebral vasodilation**, which can lead to an increase in intracranial pressure. - While it does increase ICP, it is **no longer commonly used** in modern anesthesia practice due to its side effects and flammability. *Halothane* - **Halothane** is an inhalational anesthetic that causes dose-dependent **cerebral vasodilation**, leading to an increase in intracranial pressure. - Its use has largely been replaced by newer agents (**isoflurane, sevoflurane**) which have a more favorable ICP profile or are less likely to cause hepatic toxicity.
Question 8: Which IV anesthetic does not cause cardiac depression?
- A. Propofol
- B. Etomidate (Correct Answer)
- C. Thiopentone
- D. Methohexital
Explanation: **Etomidate** - **Etomidate** is known for its **minimal cardiovascular effects**, making it a preferred choice in patients with **pre-existing cardiac disease** or hemodynamic instability. - Unlike other IV anesthetics, it causes very little change in **heart rate**, **blood pressure**, or **cardiac output**. *Propofol* - **Propofol** frequently causes **dose-dependent myocardial depression** and **vasodilation**, leading to significant decreases in blood pressure. - Its cardiovascular effects can be problematic in patients with compromised cardiac function. *Thiopentone* - **Thiopentone**, a barbiturate, typically causes **dose-dependent cardiovascular depression**, including reduced **myocardial contractility** and **vasodilation**. - This can result in a decrease in **blood pressure** and **cardiac output**. *Methohexital* - **Methohexital**, another barbiturate, also causes **cardiovascular depression** similar to thiopentone. - It can lead to decreased **blood pressure** due to both **myocardial depression** and **peripheral vasodilation**.
Question 9: Which intravenous anaesthetic agent has analgesic effect also
- A. Thiopentone
- B. Ketamine (Correct Answer)
- C. Propofol
- D. Etomidate
Explanation: ***Ketamine*** - Ketamine acts as an **N-methyl-D-aspartate (NMDA) receptor antagonist**, providing significant **analgesia** in addition to its anaesthetic effects. - It induces a state of **dissociative anaesthesia**, where the patient appears awake but is unresponsive to pain, making it unique among intravenous anaesthetics. *Thiopentone* - Thiopentone is a **barbiturate** that acts as a potent hypnotic and anaesthetic but provides no significant analgesic properties. - It can even cause **anti-analgesia** (hyperalgesia) at sub-hypnotic doses, increasing sensitivity to pain. *Propofol* - Propofol is a potent intravenous anaesthetic that works primarily as a **GABA-A receptor agonist**, but it lacks intrinsic analgesic properties. - While it can cause some sedation and reduced pain perception due to CNS depression, it does not directly modulate pain pathways in the way an analgesic would. *Etomidate* - Etomidate is a hypnotic agent highly valued for its **cardiovascular stability**, making it suitable for patients with compromised cardiac function. - Like propofol and thiopentone, etomidate primarily acts on **GABA-A receptors** to induce unconsciousness and offers no significant analgesic effects.
Question 10: Which is the intravenous anesthetic agent that contributes to good analgesia?
- A. Ketamine (Correct Answer)
- B. Thiopentone
- C. Propofol
- D. Etomidate
Explanation: ***Ketamine*** - **Ketamine** is unique among intravenous anesthetics for its significant **analgesic properties**, primarily acting as an **NMDA receptor antagonist**. - It produces a state of **dissociative anesthesia**, where the patient appears "awake" but is unresponsive to pain. *Thiopentone* - **Thiopentone** is a barbiturate that induces rapid unconsciousness but offers no significant **analgesia**. - It works by potentiation of **GABA-A receptors** leading to central nervous system depression. *Propofol* - **Propofol** is a widely used intravenous anesthetic for induction and maintenance, providing rapid onset and recovery, but it lacks **analgesic effects**. - Its mechanism of action also involves potentiation of **GABA-A receptors**. *Etomidate* - **Etomidate** is an intravenous anesthetic known for its **cardiovascular stability**, making it suitable for patients with cardiac compromise, but it provides no analgesia. - It is another **GABA-A receptor agonist** that causes rapid induction of anesthesia.
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