General Anesthesia — MCQs

General Anesthesia Indian Medical PG Practice Questions and MCQs

Question 241: Ketamine can be used in all of the following situations except:

A. Status asthmaticus
B. For analgesia and sedation (Correct Answer)
C. Obstetric hemorrhage
D. Ischemic heart disease and aortic aneurysm

Explanation: **Explanation:** Ketamine is a unique intravenous anesthetic agent that acts as an NMDA receptor antagonist, producing "dissociative anesthesia." **Why "For analgesia and sedation" is the correct answer (in the context of this question):** While Ketamine *does* provide potent analgesia and sedation, this option is technically incorrect as a "contraindication" or "exception" because it describes the primary pharmacological actions of the drug rather than a clinical scenario or disease state. In the context of NEET-PG MCQ patterns, when three options are specific clinical conditions and one is a physiological effect, the question is likely testing your knowledge of **absolute contraindications**. Ketamine is contraindicated in conditions where its sympathomimetic effects (increased heart rate and BP) are harmful. **Analysis of Incorrect Options (Contraindications/Indications):** * **Status Asthmaticus:** Ketamine is a **drug of choice** here because it causes bronchodilation via sympathomimetic action and inhibits catecholamine reuptake. * **Obstetric Hemorrhage:** Ketamine is preferred in hypovolemic shock/hemorrhage because it maintains blood pressure and cardiac output through sympathetic stimulation. * **Ischemic Heart Disease (IHD) and Aortic Aneurysm:** These are **absolute contraindications**. Ketamine increases myocardial oxygen demand (due to tachycardia and hypertension), which can worsen ischemia or cause a rupture in an aneurysm. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** NMDA receptor antagonist; acts on the Thalamo-neocortical system. * **Hallmark:** Dissociative anesthesia (eyes remain open with a slow nystagmic gaze). * **Reflexes:** Pharyngeal and laryngeal reflexes are usually maintained (though aspiration can still occur). * **Side Effects:** Emergence delirium (minimized by Benzodiazepines), increased Intraocular Pressure (IOP), and increased Intracranial Pressure (ICP). * **Secretions:** It is a potent sialagogue (increases salivation); pre-treatment with Glycopyrrolate is often required.

Question 242: Tachypnoea is associated with which of the following anesthetic agents?

A. Ether
B. Halothane
C. Trilene (Correct Answer)
D. Cyclopropane

Explanation: **Explanation:** The correct answer is **Trilene (Trichloroethylene)**. **Why Trilene causes Tachypnoea:** Trilene is a potent analgesic but a weak anesthetic agent. It is unique among volatile anesthetics because it significantly increases the respiratory rate (tachypnoea) while decreasing the tidal volume. This occurs due to the **sensitization of pulmonary stretch receptors** (Hering-Breuer reflex), which triggers rapid, shallow breathing. If the concentration of Trilene is increased too rapidly, it can lead to severe tachypnoea and cardiac arrhythmias. **Analysis of Incorrect Options:** * **Ether:** Diethyl ether is a respiratory irritant that stimulates secretions and initially increases minute ventilation, but it does not characteristically produce the rapid, shallow tachypnoea seen with Trilene. * **Halothane:** Halothane is a potent respiratory depressant. It typically decreases tidal volume and can increase respiratory rate slightly to compensate, but it is more famously associated with **bronchodilation** and sensitization of the myocardium to catecholamines. * **Cyclopropane:** This agent generally maintains or slightly depresses respiration. It is better known for causing "cyclopropane hypertension" and emergence delirium. **High-Yield Clinical Pearls for NEET-PG:** * **Trilene & Soda Lime:** Trilene must **never** be used in a closed circuit with soda lime. It reacts with soda lime to form **Dichloroacetylene** (neurotoxic, causing cranial nerve palsies, especially the Trigeminal nerve) and **Phosgene** (highly pulmonary toxic). * **Metabolism:** Trilene is metabolized to **Trichloroacetic acid**, which can be detected in urine. * **Analgesia:** It was historically favored for obstetric analgesia (self-administration via the **Minitt’s apparatus**) due to its potent analgesic properties.

Question 243: What is the choice of anesthesia for an infected tooth posted for extraction?

A. Local block with lignocaine
B. Local block with lignocaine and adrenaline
C. Isoflurane
D. Enflurane (Correct Answer)

Explanation: **Explanation:** The choice of anesthesia for an infected tooth extraction is dictated by the physiological changes in the infected tissue. **Why Enflurane is the Correct Answer:** In the presence of an **infection (abscess or cellulitis)**, the local tissue environment becomes **acidic (low pH)**. Local anesthetics (LAs) are weak bases. In an acidic medium, the LA molecules become ionized (charged), which prevents them from crossing the lipid nerve membrane to reach their site of action. Consequently, local blocks often fail in infected tissues. Therefore, **General Anesthesia (GA)** is preferred. Among the options provided, **Enflurane** (an inhalational GA agent) is the designated answer, as it ensures a pain-free procedure regardless of local tissue pH. **Analysis of Incorrect Options:** * **A & B (Local block with Lignocaine +/- Adrenaline):** These are likely to fail due to the acidic pH of the infected site. Furthermore, injecting into an infected area carries the risk of spreading the infection into deeper fascial spaces. * **C (Isoflurane):** While Isoflurane is a common GA agent, in older standardized textbooks and previous exam patterns (from which this question originates), Enflurane was frequently cited as a preferred agent for short dental procedures due to its stable cardiovascular profile, though in modern practice, Sevoflurane is more common. **High-Yield Clinical Pearls for NEET-PG:** * **The "pH Effect":** Local anesthetics work best at physiological pH (7.4). Infection drops pH to ~5.5-6.0, rendering LAs ineffective. * **Adrenaline in LA:** It is contraindicated in "end-artery" areas (fingers, toes, tip of nose, penis) but is used in dental blocks to prolong duration and provide vasoconstriction (hemostasis). * **Enflurane Fact:** It is known to lower the seizure threshold (epileptogenic), especially when combined with hypocapnia.

Question 244: Which of the following anesthetic agents is safe in heart failure?

A. Etomidate (Correct Answer)
B. Propofol
C. Thiopentone
D. Ketamine

Explanation: **Explanation:** The primary goal in managing anesthesia for a patient with heart failure is to maintain hemodynamic stability by avoiding drugs that cause myocardial depression or significant vasodilation. **Why Etomidate is Correct:** Etomidate is the induction agent of choice for patients with compromised cardiovascular status (heart failure, shock, or valvular disease). Its unique advantage is its **hemodynamic stability**; it causes minimal to no change in heart rate, systemic vascular resistance, or myocardial contractility. It achieves this by having negligible effects on the sympathetic nervous system and baroreceptor reflexes. **Why the other options are incorrect:** * **Propofol:** Causes significant peripheral vasodilation and direct myocardial depression, leading to a marked drop in blood pressure. This can be fatal in severe heart failure. * **Thiopentone:** A potent venodilator and myocardial depressant. It reduces preload and contractility, which can lead to cardiovascular collapse in patients with low cardiac reserve. * **Ketamine:** While it stimulates the sympathetic nervous system (increasing HR and BP), it is a **direct myocardial depressant**. In a failing heart that is already maximally sympathetically driven, the direct depressant effect can override the sympathetic surge, leading to a sudden drop in cardiac output. **High-Yield Clinical Pearls for NEET-PG:** * **Etomidate Side Effect:** The most characteristic side effect is **adrenocortical suppression** (inhibits 11-beta-hydroxylase), making it risky for long-term infusions in septic patients. * **Myoclonus:** Common with Etomidate; can be prevented by pre-treatment with opioids or benzodiazepines. * **Gold Standard:** For a "hemodynamically unstable" patient, Etomidate is the safest induction agent.

Question 245: Which of the following anesthetic agents is contraindicated in patients with hypertension?

A. Ketamine (Correct Answer)
B. Propofol
C. Etomidate
D. Diazepam

Explanation: **Explanation** **Ketamine** is the correct answer because it is a unique induction agent that acts as a **sympathomimetic**. Unlike most other anesthetics, it stimulates the sympathetic nervous system, leading to an increase in heart rate, cardiac output, and arterial blood pressure. This occurs due to the inhibition of neuronal catecholamine reuptake. Consequently, it is strictly **contraindicated** in patients with hypertension, ischemic heart disease, or a history of cerebrovascular accidents (stroke), as the sudden rise in blood pressure can trigger myocardial infarction or intracranial hemorrhage. **Why the other options are incorrect:** * **Propofol:** It is a potent vasodilator and myocardial depressant. It typically causes a **decrease** in blood pressure, making it a common choice for hypertensive patients but risky for those with hypotension. * **Etomidate:** Known for its **cardiovascular stability**, it causes minimal changes in heart rate and blood pressure. It is often the drug of choice for patients with cardiac compromise, though it is not contraindicated in hypertension. * **Diazepam:** As a benzodiazepine, it provides sedation and mild systemic vasodilation, generally leading to a slight decrease or no change in blood pressure. **High-Yield NEET-PG Pearls:** * **Drug of Choice:** Ketamine is the induction agent of choice for **hypovolemic shock** and **bronchial asthma** (due to its bronchodilatory properties). * **Dissociative Anesthesia:** Ketamine causes a state where the patient appears awake (eyes open) but is unconscious and amnesic. * **Other Contraindications:** Ketamine increases intracranial pressure (ICP) and intraocular pressure (IOP); therefore, it is avoided in head injuries and glaucoma.

Question 246: The drug combination which produces neuroleptanalgesia is?

A. Droperidol + Fentanyl (Correct Answer)
B. Droperidol + Ketamine
C. Droperidol + Ether
D. Droperidol + Thiopental sodium + Nitrous oxide

Explanation: **Explanation:** **1. Understanding the Concept:** Neuroleptanalgesia is a state of profound sedation and intense analgesia produced by the combined administration of a **neuroleptic (antipsychotic)** drug and a **narcotic analgesic**. In this state, the patient remains quiet, indifferent to surroundings, and pain-free, yet can often respond to simple commands. * **Droperidol** (a butyrophenone) acts as the neuroleptic, providing sedation and antiemetic effects. * **Fentanyl** (a potent opioid) provides intense analgesia. When a 65% mixture of **Nitrous Oxide (N₂O)** is added to this combination, it is termed **Neuroleptanesthesia**. **2. Analysis of Options:** * **Option A (Correct):** Droperidol + Fentanyl is the classic combination (often available in a fixed 50:1 ratio known as Innovar). * **Option B:** Ketamine produces "Dissociative Anesthesia," not neuroleptanalgesia. It is characterized by a functional dissociation between the thalamoneocortical and limbic systems. * **Option C:** Ether is an inhalational anesthetic used for general anesthesia; it does not fall under the neuroleptic category. * **Option D:** This combination describes a balanced anesthesia technique or neuroleptanesthesia (due to N₂O), but the specific term "neuroleptanalgesia" refers strictly to the neuroleptic + opioid duo. **3. High-Yield Clinical Pearls for NEET-PG:** * **Innovar:** Contains Droperidol (2.5 mg/mL) and Fentanyl (0.05 mg/mL). * **Key Features:** Patients exhibit a "waxy rigidity" (catalepsy), suppressed reflexes, and profound calmness. * **Contraindication:** Avoid Droperidol in patients with **Parkinson’s disease** because it is a dopamine antagonist and can worsen extrapyramidal symptoms. * **Side Effect:** Droperidol can cause **QT interval prolongation**; ECG monitoring is recommended.

Question 247: Muscle rigidity due to opioids is primarily attributed to their effect on which type of opioid receptor?

A. mu (Correct Answer)
B. kappa
C. sigma
D. delta

Explanation: **Explanation:** Opioid-induced muscle rigidity (specifically "Chest Wall Rigidity" or "Stiff Person Syndrome") is a well-known side effect of rapid, high-dose intravenous administration of potent synthetic opioids like **Fentanyl, Sufentanil, and Remifentanil**. **Why Mu (μ) is correct:** The primary mediator for this effect is the **Mu receptor**. While opioids are generally CNS depressants, they cause rigidity through a complex pathway involving the inhibition of GABAergic neurons and the subsequent activation of dopaminergic and cholinergic pathways in the **basal ganglia** (specifically the substantia nigra and corpus striatum). This leads to increased motor neuron output to skeletal muscles. **Why other options are incorrect:** * **Kappa (κ):** These receptors are primarily associated with spinal analgesia, sedation, and dysphoria. They do not play a significant role in skeletal muscle hypertonicity. * **Delta (δ):** These receptors contribute to supraspinal/spinal analgesia and modulating Mu receptor activity but are not implicated in the mechanism of rigidity. * **Sigma (σ):** Formerly classified as opioid receptors, they are now considered non-opioid binding sites associated with psychotomimetic effects (hallucinations) and dysphoria. **Clinical Pearls for NEET-PG:** 1. **"Wooden Chest" Phenomenon:** The rigidity of thoracic and abdominal muscles can make bag-mask ventilation nearly impossible during induction. 2. **Management:** The definitive treatment is the administration of a **neuromuscular blocking agent** (e.g., Succinylcholine) and endotracheal intubation. Opioid antagonists like Naloxone can reverse it but will also abolish analgesia. 3. **Prevention:** Rigidity can be minimized by slow injection speeds and pre-treatment with benzodiazepines or small doses of non-depolarizing muscle relaxants.

Question 248: Which patient position results in the least vital capacity under general anesthesia?

A. Trendelenburg (Correct Answer)
B. Lithotomy
C. Prone
D. Lateral

Explanation: **Explanation:** The **Trendelenburg position** results in the greatest reduction in vital capacity (VC) and functional residual capacity (FRC) under general anesthesia. This is primarily due to the **cephalad (headward) displacement of abdominal viscera** by gravity, which pushes against the diaphragm. This mechanical shift restricts diaphragmatic excursion and compresses the lung bases, leading to increased airway pressures, decreased pulmonary compliance, and significant atelectasis. **Analysis of Options:** * **Trendelenburg (Correct):** The steep head-down tilt causes the heaviest pressure on the diaphragm from abdominal organs, leading to the most profound decrease in VC (often a 20-30% reduction). * **Lithotomy:** While it also causes some cephalad displacement of viscera, the impact on VC is generally less severe than the steep Trendelenburg position. * **Prone:** If the patient is positioned correctly (using bolsters to allow the abdomen to hang free), the diaphragm can move relatively well. However, if the abdomen is compressed, VC decreases, but usually not to the extent of Trendelenburg. * **Lateral:** This position causes a ventilation-perfusion (V/Q) mismatch (the dependent lung is better perfused but less ventilated), but the overall reduction in total vital capacity is less than in Trendelenburg. **High-Yield Facts for NEET-PG:** * **FRC vs. Position:** FRC is highest in the standing position, decreases by ~10% when sitting, and by ~20% when supine. General anesthesia further reduces FRC by an additional 15-20%. * **Clinical Pearl:** In Trendelenburg, the risk of **endobronchial intubation** increases because the diaphragm and carina move cephalad, potentially causing the fixed ETT to enter the right mainstem bronchus. * **V/Q Mismatch:** In the lateral decubitus position under GA and paralysis, the "up" lung is preferentially ventilated (due to compliance), while the "down" lung is preferentially perfused (due to gravity), worsening the V/Q mismatch.

Question 249: Which anesthetic agent affects laryngeal and pharyngeal reflexes minimally?

A. Propanidid
B. Methohexital
C. Thiopental
D. Ketamine (Correct Answer)

Explanation: **Explanation:** **Ketamine** is a unique "dissociative" anesthetic agent that acts primarily as an NMDA receptor antagonist. Unlike most intravenous anesthetics that cause generalized central nervous system depression, ketamine creates a state of "dissociation" between the thalamocortical and limbic systems. One of its most significant clinical characteristics is the **preservation of protective airway reflexes** (laryngeal and pharyngeal reflexes). While the patient is unconscious, the cough and gag reflexes remain largely intact, and spontaneous respiration is usually maintained. This makes it a preferred agent in emergency situations where the patient has a "full stomach" or when performing procedures without endotracheal intubation. **Why the other options are incorrect:** * **Thiopental and Methohexital (Barbiturates):** These agents cause dose-dependent depression of the central nervous system, leading to the significant suppression of laryngeal and pharyngeal reflexes. Methohexital, in particular, is known to occasionally cause hiccups or laryngospasm during induction. * **Propanidid:** An older eugenol derivative (now largely obsolete) that causes rapid loss of consciousness and significant respiratory depression, leading to the loss of protective reflexes. **High-Yield Clinical Pearls for NEET-PG:** * **Airway:** Although reflexes are preserved, the risk of aspiration still exists; ketamine also increases **salivation** (sialagogue effect), which may require pretreatment with glycopyrrolate. * **Hemodynamics:** Ketamine is **sympathomimetic** (increases HR, BP, and CO), making it the induction agent of choice for patients in **hypovolemic shock**. * **Contraindications:** Avoid in patients with raised intracranial pressure (ICP) or intraocular pressure (IOP), and those with severe hypertension or ischemic heart disease. * **Emergence Delirium:** Can be minimized by co-administering benzodiazepines (e.g., Midazolam).

Question 250: What is neurolept analgesia?

A. It is used in patients with Parkinson's disease.
B. It precludes the use of succinylcholine.
C. It induces unconsciousness.
D. It is useful for minor surgical procedures. (Correct Answer)

Explanation: **Explanation:** **Neurolept analgesia** is a state of profound sedation and analgesia produced by the combination of a neuroleptic (typically **Droperidol**) and a potent opioid analgesic (typically **Fentanyl**). **Why Option D is Correct:** Neurolept analgesia induces a state of "quietude" where the patient is calm, indifferent to surroundings, and free from pain, but remains conscious and capable of following simple commands. This makes it ideal for **minor surgical procedures** or diagnostic interventions (e.g., endoscopies, burn dressings) where patient cooperation is beneficial but pain relief is essential. **Analysis of Incorrect Options:** * **Option A:** It is **contraindicated** in Parkinson’s disease. Droperidol is a dopamine (D2) receptor antagonist, which would exacerbate the motor symptoms of Parkinsonism. * **Option B:** It does **not** preclude the use of succinylcholine. If the combination is supplemented with Nitrous Oxide (N₂O), it becomes **Neurolept anesthesia**, which may require muscle relaxants like succinylcholine for intubation. * **Option C:** Neurolept analgesia specifically **does not induce unconsciousness**. The patient remains in a state of "dissociated" sedation. If consciousness is lost, the state has progressed to neurolept anesthesia. **High-Yield Clinical Pearls for NEET-PG:** * **Standard Combination:** Droperidol (50 parts) + Fentanyl (1 part). A common premixed preparation is **Innovar**. * **Clinical Features:** Characterized by "psychic indifference," intense analgesia, and decreased motor activity. * **Side Effects:** Droperidol can cause extrapyramidal symptoms (EPS) and QT prolongation. Fentanyl can cause chest wall rigidity (Wooden Chest Syndrome) if administered rapidly. * **Neurolept Anesthesia:** Neurolept analgesia + N₂O in Oxygen.

Practice by Chapter

History of Anesthesia

Practice Questions

Preoperative Evaluation

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Pharmacology of Inhalational Anesthetics

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Pharmacology of Intravenous Anesthetics

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Neuromuscular Blocking Agents

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Airway Management

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Endotracheal Intubation

Practice Questions

Difficult Airway Algorithms

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Intraoperative Monitoring

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Depth of Anesthesia Monitoring

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Emergence from Anesthesia

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Postoperative Care

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