General Anesthesia — MCQs

General Anesthesia Indian Medical PG Practice Questions and MCQs

Question 261: Use of nitrous oxide is contraindicated in all of the following surgeries except?

A. Cochlear implant
B. Microlaryngeal surgery
C. Vitrioretinal surgery
D. Exentration operation (Correct Answer)

Explanation: **Explanation:** The core concept behind this question is the **Blood-Gas Partition Coefficient** of Nitrous Oxide ($N_2O$). $N_2O$ is 34 times more soluble in blood than Nitrogen ($N_2$). Consequently, $N_2O$ leaves the blood and enters air-filled closed spaces faster than $N_2$ can leave them, leading to an increase in **volume** (in compliant spaces) or **pressure** (in non-compliant spaces). **Why Exenteration is the Correct Answer:** Exenteration (orbital or pelvic) involves the radical removal of contents from an open body cavity. Since there is no enclosed, air-filled space, $N_2O$ cannot cause pressure buildup or expansion. Therefore, it is safe to use. **Why the Other Options are Contraindicated:** * **Cochlear Implant/Tympanoplasty:** The middle ear is a non-compliant space. $N_2O$ increases middle ear pressure, which can displace a tympanic membrane graft or interfere with delicate implant placement. * **Microlaryngeal Surgery:** These procedures often involve the use of lasers. $N_2O$ supports combustion and increases the risk of an **airway fire**, making it hazardous. * **Vitreoretinal Surgery:** If an intraocular gas bubble (e.g., $SF_6$ or $C_3F_8$) is used to flatten the retina, $N_2O$ will rapidly diffuse into the bubble, increasing intraocular pressure (IOP) and potentially causing retinal artery occlusion and blindness. **High-Yield Clinical Pearls for NEET-PG:** * **Diffusion Hypoxia:** Occurs at the end of surgery when $N_2O$ floods the alveoli; prevent by giving 100% $O_2$ for 5–10 minutes. * **Second Gas Effect:** $N_2O$ speeds up the uptake of a companion volatile anesthetic. * **Absolute Contraindications:** Pneumothorax (doubles in size in 10 mins), air embolism, bowel obstruction, and recent vitreoretinal surgery (avoid $N_2O$ for 7–10 days after $SF_6$ use).

Question 262: All the following are true about Regional anesthesia EXCEPT?

A. Increases blood loss (Correct Answer)
B. Less complications after vascular surgery
C. Decreases shivering after induction of anaesthesia
D. Less complications after colon surgery

Explanation: **Explanation:** The correct answer is **A (Increases blood loss)** because Regional Anesthesia (RA), specifically neuraxial blocks like spinal and epidural anesthesia, actually **decreases** intraoperative blood loss. This occurs due to two primary mechanisms: 1. **Sympathetic Blockade:** Leads to vasodilation and a controlled reduction in mean arterial pressure (hypotension). 2. **Reduced Venous Pressure:** Lowering peripheral venous pressure reduces oozing from the surgical site. **Analysis of other options:** * **Option B & D:** RA is associated with fewer complications in major surgeries. In **vascular surgery**, it reduces the risk of graft thrombosis (due to improved blood flow and attenuated hypercoagulability). In **colon surgery**, it facilitates earlier return of bowel function (reduced ileus) and provides superior analgesia compared to opioids, which can slow motility. * **Option C:** While RA can cause shivering due to core-to-peripheral heat redistribution, it is often used to **decrease the metabolic stress response** and oxygen consumption associated with the intense shivering seen during emergence from General Anesthesia (GA). **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard for Post-op Pain:** Epidural analgesia is superior to systemic opioids for major abdominal and thoracic surgeries. * **DVT/PE Prophylaxis:** RA significantly reduces the incidence of Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE) by improving lower limb blood flow and preventing the pro-thrombotic state triggered by surgical stress. * **Cardiac Benefits:** RA reduces the incidence of postoperative myocardial infarction by decreasing the surge in catecholamines.

Question 263: Which of the following anesthetic drugs is contraindicated in hepatic failure?

A. Desflurane
B. Remifentanil
C. Halothane (Correct Answer)
D. Isoflurane

Explanation: **Explanation:** **Halothane** is the correct answer because of its significant potential for hepatotoxicity, historically categorized into two types: a mild, transient elevation of transaminases and a rare, life-threatening condition known as **Halothane Hepatitis**. The underlying mechanism involves the metabolism of halothane by the cytochrome P450 system into **trifluoroacetylated (TFA) proteins**. In susceptible individuals, these act as haptens, triggering an immune-mediated response that leads to massive hepatic necrosis. Because halothane undergoes significant hepatic metabolism (up to 20%), it is strictly contraindicated in patients with pre-existing hepatic failure or a history of unexplained jaundice after previous exposure. **Analysis of Incorrect Options:** * **Desflurane & Isoflurane:** These are modern volatile anesthetics with much lower metabolism rates (0.02% and 0.2%, respectively). They produce minimal TFA proteins and are considered safe alternatives in patients with liver disease. * **Remifentanil:** This is an ultra-short-acting opioid metabolized by **non-specific plasma and tissue esterases**, not the liver. Its clearance is entirely independent of hepatic function, making it an ideal choice for patients with liver failure. **High-Yield Clinical Pearls for NEET-PG:** * **Metabolism Rule:** Halothane (20%) > Sevoflurane (2%) > Isoflurane (0.2%) > Desflurane (0.02%). * **Drug of Choice:** **Isoflurane** is often preferred in liver surgery because it best preserves hepatic blood flow (the "Hepatic Artery Buffer Response"). * **Atracurium/Cisatracurium:** These are the muscle relaxants of choice in hepatic failure due to **Hofmann elimination**.

Question 264: What is the definitive sign of stage I of anesthesia?

A. Fixation of the eyeball (Correct Answer)
B. Pupillary dilatation
C. Blurring of vision
D. Intercostal paralysis

Explanation: **Explanation:** The stages of anesthesia are traditionally described using **Guedel’s Classification**, which was originally based on the effects of diethyl ether. **Why "Fixation of the eyeball" is correct:** Stage I (Stage of Analgesia) begins from the induction of anesthesia and lasts until the loss of consciousness. As the patient transitions from Stage I to Stage II (Stage of Excitement), the eyes, which were previously moving or wandering, become **fixed** in a central position. Therefore, the fixation of the eyeball is considered the definitive clinical sign marking the end of Stage I and the onset of the deeper planes of anesthesia. **Analysis of Incorrect Options:** * **B. Pupillary dilatation:** This is characteristic of **Stage II** (due to sympathetic stimulation) or **Stage IV** (due to medullary depression/toxic overdose). It is not a definitive sign of Stage I. * **C. Blurring of vision:** While this occurs during Stage I as the patient loses sensory perception, it is a subjective symptom rather than a definitive clinical sign used by the anesthetist to stage anesthesia. * **D. Intercostal paralysis:** This is a hallmark of **Stage III, Plane 3** (Surgical Anesthesia). It indicates deep anesthesia where breathing becomes purely diaphragmatic. **High-Yield Clinical Pearls for NEET-PG:** * **Stage I:** Analgesia and amnesia occur. The patient is conscious but drowsy. * **Stage II (Excitement):** Risk of laryngospasm, vomiting, and irregular respiration. The goal is to pass through this stage as quickly as possible. * **Stage III (Surgical Anesthesia):** Divided into 4 planes. **Plane 2** is the ideal plane for most surgeries (loss of corneal and laryngeal reflexes). * **Stage IV (Medullary Paralysis):** Respiratory and vasomotor center failure; this is an overdose stage and must be avoided.

Question 265: Pentothal sodium should preferably be injected into which of the following veins?

A. Femoral vein
B. Antecubital vein
C. Neck vein
D. Veins on the outer aspect of the forearm (Correct Answer)

Explanation: **Explanation:** The preferred site for injecting **Pentothal Sodium (Thiopentone)** is the veins on the **outer aspect of the forearm** or the **dorsum of the hand**. The primary medical reason for this preference is **safety and the prevention of accidental intra-arterial injection**. Thiopentone is highly alkaline (pH 10.5). If accidentally injected into an artery, it reacts with blood to form crystals, leading to intense vasospasm, chemical endarteritis, and subsequent gangrene of the limb. By choosing the outer aspect of the forearm, the clinician stays away from major arteries that are more superficial in other regions. **Analysis of Options:** * **Antecubital vein (Incorrect):** While commonly used for blood draws, it is avoided for Thiopentone because the **brachial artery** lies in close proximity (separated only by the bicipital aponeurosis). An aberrant ulnar artery may also be present superficially in this area, increasing the risk of catastrophic intra-arterial injection. * **Femoral vein (Incorrect):** This is a deep central vein. It is reserved for emergency access or CVC placement and is not a routine site for induction agents due to the risk of DVT and proximity to the femoral artery. * **Neck vein (Incorrect):** External or internal jugular veins are used for central access, not routine peripheral induction. **Clinical Pearls for NEET-PG:** * **Management of Accidental Intra-arterial Injection:** If it occurs, **do not remove the needle**. Inject a vasodilator (e.g., **Papaverine** or **Lidocaine**) through the same needle to counteract vasospasm and perform a **Stellate Ganglion Block** or Brachial Plexus block to induce sympathetic washout. * **Concentration:** Thiopentone is typically used as a **2.5% solution**. Higher concentrations (5%) significantly increase the risk of tissue necrosis if extravasation occurs. * **Contraindication:** It is strictly contraindicated in **Porphyria** (induces ALA synthetase).

Question 266: Which of the following statements regarding halothane is true?

A. Reduces arterial pressure (Correct Answer)
B. Increases heart rate
C. Decreases cardiac output
D. Increases sympathoadrenal activity

Explanation: **Explanation:** Halothane is a potent volatile anesthetic agent that primarily causes a dose-dependent reduction in arterial blood pressure. **1. Why Option A is Correct:** Halothane reduces arterial pressure through two main mechanisms: **direct myocardial depression** (negative inotropy) and a reduction in cardiac output. Unlike other volatile agents (like isoflurane), it causes minimal peripheral vasodilation, meaning the drop in blood pressure is almost entirely due to its effect on the heart muscle itself. **2. Why the other options are incorrect:** * **Option B (Increases heart rate):** Halothane actually tends to cause **bradycardia** or maintain a normal heart rate. It blunts the baroreceptor reflex, meaning the body does not mount a compensatory tachycardia in response to the falling blood pressure. * **Option C (Decreases cardiac output):** While halothane *does* decrease cardiac output, the question asks for the most definitive clinical effect. In many standardized exams, "reduction in arterial pressure" is considered the hallmark hemodynamic effect of halothane. (Note: In some contexts, C is also physiologically true, but A is the primary clinical manifestation). * **Option D (Increases sympathoadrenal activity):** Halothane **depresses** the sympathetic nervous system. It does not cause the "sympathetic surge" seen with agents like desflurane. **High-Yield NEET-PG Pearls for Halothane:** * **Catecholamine Sensitization:** Halothane sensitizes the myocardium to epinephrine, increasing the risk of **ventricular arrhythmias** if exogenous adrenaline is used. * **Hepatotoxicity:** Associated with "Halothane Hepatitis" (Type II is immune-mediated and severe). * **Uterine Relaxation:** It is a potent uterine relaxant, making it useful for version but risky for postpartum hemorrhage. * **Sweet Odor:** It is non-pungent, making it the classic agent for **smooth inhalation induction** in pediatric patients.

Question 267: The plane of surgical anesthesia during ether anesthesia is defined as?

A. Loss of consciousness
B. Loss of consciousness to the onset of spontaneous respiration
C. From onset of regular respiration to cessation of spontaneous breathing (Correct Answer)
D. Absence of reflexes

Explanation: This question refers to **Guedel’s Classification of Ether Anesthesia**, a classic pharmacological framework used to describe the stages of general anesthesia. ### **Explanation of the Correct Answer** The correct answer is **Option C**. Guedel divided anesthesia into four stages. **Stage III (Surgical Anesthesia)** begins with the **onset of regular automatic respiration** and ends with the **cessation of spontaneous breathing** (paralysis of the diaphragm). This stage is further divided into four planes (Plane 1 to Plane 4) based on the progressive loss of ocular movements, pupillary reflexes, and finally, respiratory muscle function. Most surgical procedures are performed during Plane 2 or 3 of Stage III. ### **Analysis of Incorrect Options** * **Option A:** Loss of consciousness marks the end of **Stage I (Analgesia)** and the beginning of **Stage II (Delirium/Excitement)**. It does not define the surgical plane. * **Option B:** This is a distractor. Spontaneous respiration is present throughout Stage II and most of Stage III; it only ceases at the end of Stage III. * **Option D:** While reflexes (like the eyelash or swallowing reflex) are lost during Stage III, "absence of reflexes" is too vague. For example, the corneal reflex is lost in Plane 2, while the pupillary light reflex is lost in Plane 3. ### **High-Yield Clinical Pearls for NEET-PG** * **Stage II (Excitement):** Characterized by struggling, breath-holding, and vomiting. It is the most dangerous stage; modern IV induction agents (like Propofol) are used to bypass this stage rapidly. * **Stage IV (Medullary Paralysis):** Begins from the cessation of breathing to circulatory collapse/death. * **Modern Context:** Guedel’s stages were specifically designed for **Ether** (a slow-acting agent). They are difficult to observe with modern rapid-acting IV agents and neuromuscular blockers, but the classification remains a fundamental concept in anesthetic depth. * **First reflex to be lost:** Eyelash reflex (marks the transition from Stage I to II).

Question 268: All of the following are features of Verrill's sign except?

A. Partial ptosis
B. Tingling sensation (Correct Answer)
C. Blurring vision
D. Slurring speech

Explanation: **Verrill’s sign** is a clinical endpoint used primarily in intravenous sedation (conscious sedation), most commonly associated with the administration of benzodiazepines like **Diazepam** or **Midazolam**. It serves as a reliable indicator that the patient has reached an adequate level of sedation for dental or minor surgical procedures without progressing into deep anesthesia or respiratory depression. ### **Explanation of Options:** * **Correct Answer: B (Tingling sensation):** Tingling (paresthesia) is not a component of Verrill’s sign. While some patients may experience subjective sensations during drug induction, it is not a clinical marker of the sedation endpoint. * **Option A (Partial ptosis):** This is the **hallmark** of Verrill’s sign. It is defined as the drooping of the upper eyelid such that it covers approximately **half of the pupil**. * **Option C & D (Blurring vision & Slurring speech):** These are associated signs of central nervous system depression. As the patient approaches the Verrill’s sign endpoint, they typically experience diplopia (double vision), blurred vision, and a noticeable slowing or slurring of speech. ### **Clinical Pearls for NEET-PG:** 1. **The "50% Rule":** Verrill’s sign is specifically the **50% ptosis** of the eyelid. If ptosis exceeds this or the patient loses the lash reflex, they are entering a deeper stage of anesthesia than intended for conscious sedation. 2. **Guedel’s Chart vs. Verrill’s:** While Guedel’s stages describe ether anesthesia, Verrill’s sign is the specific gold standard for **IV Diazepam sedation**. 3. **Safety Margin:** Reaching Verrill’s sign indicates that the patient is relaxed and amnesic but can still maintain a patent airway and respond to verbal commands. 4. **O'Beirne's Sign:** Do not confuse Verrill's with O'Beirne's sign (related to the rectum/defecation) or Guedel's signs (stages of GA).

Question 269: What is the inducing agent of choice in DIC?

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

Explanation: **Explanation:** The correct answer is **Ketamine**. In patients with **Disseminated Intravascular Coagulation (DIC)**, the primary clinical concern during induction is hemodynamic instability and severe hypotension, often resulting from underlying sepsis, trauma, or obstetric emergencies. **Why Ketamine is the choice:** Ketamine is a phencyclidine derivative that acts as a potent sympathomimetic. It stimulates the release of endogenous catecholamines, leading to an increase in heart rate, blood pressure, and cardiac output. This "pressor effect" makes it the induction agent of choice in hemodynamically unstable patients (shock) or those with active bleeding, which are common precursors to DIC. **Analysis of Incorrect Options:** * **Thiopentone:** A barbiturate that causes significant peripheral vasodilation and direct myocardial depression. In a patient with DIC/shock, this can lead to a catastrophic drop in blood pressure. * **Propofol:** Similar to Thiopentone, Propofol causes marked vasodilation and decreases systemic vascular resistance (SVR). It is contraindicated in patients who are hemodynamically compromised. * **Methohexitone:** Another barbiturate that, like Thiopentone, causes cardiovascular depression and is generally avoided in unstable patients. **High-Yield Clinical Pearls for NEET-PG:** * **Agent of choice for Shock/Hypovolemia:** Ketamine. * **Agent of choice for Bronchial Asthma:** Ketamine (due to bronchodilatory properties). * **Agent of choice for Day-care Surgery:** Propofol (due to rapid recovery and anti-emetic properties). * **Agent of choice for Neurosurgery/Increased ICT:** Thiopentone (decreases Cerebral Metabolic Rate and ICP). * **Contraindication for Ketamine:** Patients with Hypertension, IHD, or increased Intraocular/Intracranial pressure.

Question 270: What is the definition of conscious sedation?

A. Central nervous system depression with unconsciousness
B. Sedation with inability to respond to verbal commands
C. Sedation with ability to respond to verbal commands (Correct Answer)
D. Any of the above

Explanation: **Explanation:** **Conscious Sedation** (also known as Procedural Sedation) is a drug-induced depression of consciousness during which patients respond purposefully to verbal commands, either alone or accompanied by light tactile stimulation. 1. **Why Option C is correct:** The hallmark of conscious sedation is the maintenance of the patient’s **airway reflexes** and the **ability to follow commands**. While the patient’s coordination and cognitive function may be impaired, they remain conscious and do not require mechanical ventilation or airway adjuncts. 2. **Why other options are incorrect:** * **Option A:** CNS depression with unconsciousness describes **General Anesthesia**, where the patient is unarousable even by painful stimuli and often requires airway support. * **Option B:** Inability to respond to verbal commands indicates **Deep Sedation**. In this state, patients can only be aroused by repeated or painful stimulation, and their spontaneous ventilation may be inadequate. **High-Yield Clinical Pearls for NEET-PG:** * **Continuum of Sedation:** Sedation is a spectrum: Minimal (Anxiolysis) → Moderate (Conscious) → Deep → General Anesthesia. * **Airway:** In conscious sedation, spontaneous ventilation is adequate, and cardiovascular function is usually maintained. * **Common Drugs:** Midazolam (Benzodiazepine) and Fentanyl (Opioid) are frequently used. Propofol can be used but carries a higher risk of transitioning the patient into deep sedation or general anesthesia. * **Monitoring:** Pulse oximetry and clinical monitoring of respiratory rate and heart rate are mandatory.

Practice by Chapter

History of Anesthesia

Practice Questions

Preoperative Evaluation

Practice Questions

Pharmacology of Inhalational Anesthetics

Practice Questions

Pharmacology of Intravenous Anesthetics

Practice Questions

Neuromuscular Blocking Agents

Practice Questions

Airway Management

Practice Questions

Endotracheal Intubation

Practice Questions

Difficult Airway Algorithms

Practice Questions

Intraoperative Monitoring

Practice Questions

Depth of Anesthesia Monitoring

Practice Questions

Emergence from Anesthesia

Practice Questions

Postoperative Care

Practice Questions

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