Preventing PONV in Outpatients — MCQs
Which inducing agent is associated with the highest incidence of postoperative vomiting?
Which of the following intravenous anaesthetic agent causes decrease in postoperative nausea and vomiting :
Which of the following is the FIRST-LINE antiemetic drug most commonly used for post-operative nausea and vomiting (PONV) prophylaxis?
The following are used for treatment of postoperative nausea and vomiting following squint surgery in children except:-
Which of the following statements about Nitrous Oxide (N2O) is true?
All the following cause malignant hyperpyrexia except?
Which of the following anaesthetic agent causes bone marrow suppression?
A patient is admitted to a day care nursing home for a laparoscopic cholecystectomy. This patient is otherwise healthy. What is the anesthetic of choice in this patient?
A 20-year-old patient presents with early pregnancy for Medical Termination of Pregnancy (MTP) in a day care facility. What is the anesthetic induction agent of choice?
Which drug is commonly used in day care anesthesia?
Preventing PONV in Outpatients Indian Medical PG Practice Questions and MCQs
Question 1: 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 2: 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 3: Which of the following is the FIRST-LINE antiemetic drug most commonly used for post-operative nausea and vomiting (PONV) prophylaxis?
- A. Lorazepam
- B. Metoclopramide
- C. Promethazine
- D. Ondansetron (Correct Answer)
Explanation: ***Ondansetron*** - **Ondansetron** is a **5-HT3 receptor antagonist** and is considered a first-line agent due to its high efficacy and favorable side effect profile in preventing PONV. - It works by blocking serotonin receptors in the **chemoreceptor trigger zone** and the **gastrointestinal tract**, reducing the sensation of nausea and vomiting. *Lorazepam* - **Lorazepam** is a **benzodiazepine** primarily used for its **anxiolytic** and **sedative effects**, and sometimes as an adjunct for refractory nausea, but not as a first-line antiemetic for PONV prophylaxis. - While it can help indirectly by reducing anxiety, it does not directly target the key pathways involved in PONV as effectively as 5-HT3 antagonists. *Phenytoin* - **Phenytoin** is an **anticonvulsant** medication used to prevent seizures and has no role in the direct treatment or prophylaxis of PONV. - It primarily acts on voltage-gated sodium channels in neurons and does not possess antiemetic properties. *Metoclopramide* - **Metoclopramide** is a **dopamine D2 receptor antagonist** and a **prokinetic agent** that can be used for PONV, particularly when gastric stasis is a concern. - However, it is generally considered a second-line agent due to the risk of **extrapyramidal side effects**, especially with higher doses or prolonged use. *Promethazine* - **Promethazine** is a **first-generation antihistamine** with **antidopaminergic** and **anticholinergic properties** that can be effective for nausea and vomiting. - It is often used as a rescue antiemetic or in combination therapy, but its sedative effects and potential for extrapyramidal symptoms make it less preferable as a first-line prophylactic agent compared to ondansetron.
Question 4: The following are used for treatment of postoperative nausea and vomiting following squint surgery in children except:-
- A. Ondansetron
- B. Propofol
- C. Dexamethasone
- D. Ketamine (Correct Answer)
Explanation: ***Ketamine*** - **Ketamine** is an anesthetic and analgesic agent that is known to **increase the incidence of postoperative nausea and vomiting (PONV)**, particularly at higher doses, making it unsuitable for preventing PONV. - Its mechanism of action can stimulate the **chemoreceptor trigger zone** and **vestibular system**, contributing to emetogenic effects. *Ondansetron* - **Ondansetron** is a **serotonin 5-HT3 receptor antagonist** and is a first-line drug for the prevention and treatment of PONV in both adults and children. - It effectively blocks serotonin in the gastrointestinal tract and the **medulla oblongata**, reducing nausea and vomiting. *Propofol* - **Propofol** is an intravenous anesthetic that has **antiemetic properties**, making it useful for reducing PONV when used as part of the anesthetic regimen or as a sub-hypnotic bolus. - Its antiemetic effect is thought to be mediated through **dopamine receptor blockade** and action on the **GABAergic system**. *Dexamethasone* - **Dexamethasone** is a **corticosteroid** with significant antiemetic properties, commonly used as an adjunct for PONV prevention. - It is believed to act by inhibiting **prostaglandin synthesis** and reducing inflammation, thereby modulating pathways involved in nausea and vomiting.
Question 5: Which of the following statements about Nitrous Oxide (N2O) is true?
- A. Least potent inhalational anesthetic (Correct Answer)
- B. Lighter than air
- C. Effective muscle relaxant
- D. Does not cause diffusion hypoxia
Explanation: **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.
Question 6: All the following cause malignant hyperpyrexia except?
- A. Methoxyflurane
- B. N20 (Correct Answer)
- C. Isoflurane
- D. Halothane
Explanation: ***N2O*** - **Nitrous oxide (N2O)**, or laughing gas, is an inhaled anesthetic that does not trigger **malignant hyperthermia (MH)**. - It is often used as a carrier gas or adjunct during anesthesia, even in patients susceptible to MH, as it does not affect **ryanodine receptors**. *Methoxyflurane* - **Methoxyflurane** is a volatile inhaled anesthetic known to trigger **malignant hyperthermia (MH)** in susceptible individuals. - It causes an uncontrolled release of **calcium** from the sarcoplasmic reticulum in muscle cells, leading to severe hypermetabolism. *Isoflurane* - **Isoflurane** is a commonly used volatile inhaled anesthetic that can induce **malignant hyperthermia (MH)** in genetically predisposed individuals. - Like other volatile agents, it activates **ryanodine receptors** in skeletal muscle, leading to excessive muscle contraction and heat production. *Halothane* - **Halothane** is a potent volatile inhaled anesthetic historically associated with a high incidence of triggering **malignant hyperthermia (MH)**. - Its use has largely been replaced by newer agents due to concerns about MH and **hepatotoxicity**.
Question 7: Which of the following anaesthetic agent causes bone marrow suppression?
- A. Isoflurane
- B. Halothane
- C. Ketamine
- D. Nitrous Oxide (Correct Answer)
Explanation: ***Nitrous Oxide*** - **Nitrous oxide** can cause **bone marrow suppression** due to its ability to irreversibly oxidize the **cobalamin cofactor** of **methionine synthase**. - This inactivation leads to reduced DNA synthesis and impacts rapidly dividing cells like those in the bone marrow, potentially causing **megaloblastic anemia** with prolonged or repeated exposure. *Isoflurane* - **Isoflurane** is a volatile anesthetic known for its minimal effects on bone marrow function. - It primarily acts on the central nervous system to induce anesthesia and muscle relaxation with limited systemic toxicities. *Halothane* - **Halothane** is associated with **hepatotoxicity** (halothane hepatitis) in some susceptible individuals, but not bone marrow suppression. - Its use has largely been replaced by newer, safer volatile anesthetics due to this risk. *Ketamine* - **Ketamine** is a dissociative anesthetic that primarily affects the central nervous system, causing analgesia and amnesia. - It does not significantly impact bone marrow function or hematopoiesis.
Question 8: A patient is admitted to a day care nursing home for a laparoscopic cholecystectomy. This patient is otherwise healthy. What is the anesthetic of choice in this patient?
- A. Halothane
- B. Propofol (Correct Answer)
- C. Ketamine
- D. Ether
Explanation: **Explanation:** The primary goal of **Ambulatory (Day Care) Anesthesia** is to ensure a rapid, smooth recovery with minimal side effects, allowing the patient to be discharged safely on the same day. **Why Propofol is the Correct Answer:** Propofol is the **gold standard induction agent** for daycare surgery due to its unique pharmacokinetic profile: * **Rapid Onset and Recovery:** It has a short context-sensitive half-life, leading to quick emergence and clear-headedness ("clear-headed recovery"). * **Anti-emetic Properties:** Unlike inhalational agents, propofol possesses intrinsic anti-emetic effects, significantly reducing **Postoperative Nausea and Vomiting (PONV)**—the leading cause of delayed discharge in ambulatory settings. * **Smooth Induction:** It suppresses airway reflexes, making it ideal for Laryngeal Mask Airway (LMA) insertion. **Why Other Options are Incorrect:** * **Halothane:** It has a slow onset and recovery. More importantly, it is associated with "halothane hepatitis" and sensitizes the myocardium to catecholamines, making it unsuitable for modern daycare practice. * **Ketamine:** It causes a high incidence of **emergence delirium**, hallucinations, and prolonged recovery times, which are contraindicated in patients needing to go home shortly after surgery. * **Ether:** It is obsolete in modern anesthesia due to its high flammability, slow induction/recovery, and severe incidence of PONV. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice for TIVA** (Total Intravenous Anesthesia): Propofol. * **Ideal Inhalational Agent for Daycare:** **Desflurane** (fastest recovery due to lowest blood-gas solubility) or **Sevoflurane** (best for mask induction). * **Discharge Criteria:** The **Aldrete Score** or **PADSS** (Post-Anesthetic Discharge Scoring System) is used to determine if a patient is fit for discharge. A score of $\geq$ 9 is typically required.
Question 9: A 20-year-old patient presents with early pregnancy for Medical Termination of Pregnancy (MTP) in a day care facility. What is the anesthetic induction agent of choice?
- A. Thiopentone
- B. Ketamine
- C. Propofol (Correct Answer)
- D. Diazepam
Explanation: **Explanation:** The anesthetic agent of choice for day-care procedures like Medical Termination of Pregnancy (MTP) is **Propofol**. **Why Propofol is the Correct Choice:** The primary goal of ambulatory (day-care) anesthesia is a rapid onset of action, smooth maintenance, and, most importantly, **rapid and clear-headed recovery** to allow early discharge. Propofol is an ultra-short-acting intravenous anesthetic that undergoes rapid redistribution and hepatic clearance. It is preferred because: * It has a **superior recovery profile** with minimal "hangover" effect. * It possesses significant **anti-emetic properties**, reducing the incidence of Postoperative Nausea and Vomiting (PONV), which is a leading cause of delayed discharge in day-care surgery. **Why Other Options are Incorrect:** * **Thiopentone:** While it has a rapid onset, it undergoes slow metabolism and can lead to a "hangover" effect due to accumulation in adipose tissue, delaying discharge. * **Ketamine:** It is generally avoided in MTP because it can cause emergence delirium, hallucinations, and lacks the smooth recovery required for day-care settings. It also does not provide the necessary uterine relaxation if required. * **Diazepam:** This is a benzodiazepine used for sedation, not a primary induction agent. It has a long half-life and active metabolites, leading to prolonged sedation. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard:** Propofol is the "Gold Standard" for Total Intravenous Anesthesia (TIVA) and ambulatory anesthesia. * **MTP Specifics:** For MTP, Propofol provides excellent conditions but lacks analgesic properties; hence, it is often combined with a short-acting opioid like Fentanyl. * **Side Effect:** The most common side effect of Propofol induction is pain on injection and dose-dependent hypotension. * **Contraindication:** Use with caution in patients with egg or soy allergies (due to the lipid emulsion vehicle).
Question 10: Which drug is commonly used in day care anesthesia?
- A. Propofol (Correct Answer)
- B. Enflurane
- C. Xenon
- D. Thiopentone
Explanation: **Explanation:** **Propofol** is the gold standard induction agent for daycare (ambulatory) anesthesia. The primary goal of daycare anesthesia is a rapid, smooth recovery with minimal side effects to allow for early discharge. Propofol fits this profile perfectly due to its **rapid onset** and **ultra-short duration of action** (redistribution half-life of 2–4 minutes). Crucially, it possesses significant **anti-emetic properties**, which reduces the incidence of Postoperative Nausea and Vomiting (PONV)—the leading cause of delayed discharge and unplanned hospital admission. **Why the other options are incorrect:** * **Enflurane:** An older inhalational agent rarely used today. It has a higher blood-gas partition coefficient than modern agents (like Sevoflurane), leading to slower recovery. It is also associated with a risk of seizure-like activity (epileptiform EEG). * **Xenon:** While it has an excellent safety profile and rapid emergence, it is extremely expensive and requires specialized delivery systems, making it impractical for routine daycare settings. * **Thiopentone:** Although it has a rapid onset, it causes a "hangover effect" due to its slower metabolism and accumulation in fat stores. It also lacks anti-emetic properties, making it less ideal for early mobilization. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice for TIVA:** Propofol is the mainstay for Total Intravenous Anesthesia (TIVA). * **Ideal Inhalational Agent for Daycare:** Desflurane (fastest recovery) or Sevoflurane (smooth induction, especially in pediatrics). * **Discharge Criteria:** The **Aldrete Score** or **PADSS** (Post-Anesthetic Discharge Scoring System) is used to determine if a patient is fit for discharge. * **Propofol Side Effect:** Pain on injection (minimized by using larger veins or pretreatment with Lidocaine).
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