General Anesthesia Practice Questions

Q: Which of the following intravenous agents is commonly used for outpatient procedures?

Propofol. ***Propofol*** - It is the **drug of choice** for outpatient anesthesia due to its **rapid onset** and short duration of action, allowing for a **rapid recovery** profile. - It possesses **anti-emetic properties** and provides clear-headed recovery, making it ideal for **day-case surgery**. *Ketamine* - It is a **dissociative anesthetic** associated with **post-operative emergence delirium** and hallucinations in adults. - While useful in emergency or pediatric settings, it causes **increased salivation** and **increased intracranial/intraocular pressure**, limiting its routine outpatient use. *Thiopental* - An ultrashort-acting **barbiturate** that was historically used for induction but has a long redistribution phase, leading to a **prolonged hang-over effect**. - Its use is largely obsolete in outpatient settings due to **cardiovascular depression** and a slower recovery compared to newer agents. *Etomidate* - Known for cardiovascular stability, but it causes **adrenocortical suppression** with prolonged infusion, making it less suitable for anything beyond single-dose induction. - Frequently associated with **post-operative nausea and vomiting (PONV)** and **myoclonus**, which can interfere with the immediate post-operative experience in a day-care setting.

Q: A 40-year-old female is scheduled for parotid surgery and is administered general Anaesthesia. Approximately 10 minutes into the procedure, the following findings are noted: - Rise in end-tidal CO2 (EtCO2) - Temperature: 104°F (40°C) - Heart rate: 150 bpm - Blood pressure: 180/110 mmHg What is the most likely diagnosis?

Malignant hyperthermia. ***Malignant hyperthermia*** - This is a pharmacogenetic disorder triggered by volatile inhalational anesthetics or succinylcholine, characterized by a hypermetabolic state. - The rapid rise in **end-tidal CO2 (EtCO2)** is often the earliest sign, followed by **tachycardia**, severe **hyperthermia**, and **hypertension** due to muscle rigidity. *Heat stroke* - Typically caused by environmental exposure or extreme physical exertion, not triggered by anesthetic agents. - Patients often present with altered mental status and dry skin, occurring much later and not immediately following induction. *Heat cramps* - This is a mild form of heat illness characterized by painful muscle spasms caused by salt and water depletion. - It does not present with the systemic hypermetabolic crisis seen here, such as the rapid rise in **EtCO2** or life-threatening tachycardia. *Heat pyrexia* - Also known as heat exhaustion, this condition involves systemic symptoms like dizziness and fatigue due to heat stress. - It lacks the acute, life-threatening hypermetabolic surge associated with anesthesia administration.

Q: A 34-year-old asthmatic male undergoes elective laparoscopic cholecystectomy under general anesthesia with endotracheal intubation. Fifteen minutes after induction, the ventilator alarm sounds for high peak airway pressure. The anesthesiologist notes the waveform shown on the capnograph monitor (Image 1). What is the most likely cause of this capnographic pattern?

A. Severe bronchospasm causing expiratory flow obstruction. ***A. Severe bronchospasm causing expiratory flow obstruction*** - The classic **"shark-fin"** appearance on capnography (sloping Phase II and upward-slanting Phase III) indicates **expiratory flow obstruction** where alveoli empty asynchronously. - In an **asthmatic** patient, this pattern combined with **increased peak airway pressures** is highly diagnostic of acute bronchospasm during general anesthesia. *B. Esophageal intubation with absent alveolar gas exchange* - **Esophageal intubation** typically results in a complete **absence of CO2** or a few rapidly decreasing small waves as stomach gas is depleted. - It does not produce the sustained, characteristic waveform morphology associated with **obstructive lung disease**. *C. Pulmonary embolism causing increased alveolar dead space* - **Pulmonary embolism** increases **alveolar dead space**, which typically causes a sharp **decrease in End-Tidal CO2 (EtCO2)** levels. - The waveform morphology remains relatively normal, rather than showing the **obstructive upswing** seen in bronchospasm. *D. Malignant hyperthermia causing increased CO2 production* - **Malignant hyperthermia** presents with a rapid, massive **increase in EtCO2** due to hypermetabolism. - While total CO2 levels rise significantly, the **plateau phase (Phase III)** of the capnogram usually remains flat unless secondary airway issues occur.

Q: Diffusion hypoxia is seen with which drug?

Nitrous oxide. **Explanation:** **Nitrous Oxide (N₂O)** is the correct answer because of its unique pharmacokinetic property: high solubility in blood compared to nitrogen, but low overall solubility compared to other anesthetics. **The Mechanism (Fink Effect):** Diffusion hypoxia occurs during the **recovery phase** of anesthesia. When N₂O administration is stopped, it rushes out of the blood and into the alveoli down its concentration gradient. Because N₂O is 30 times more soluble than nitrogen, it floods the alveoli in massive volumes. This "dilutes" the alveolar oxygen and carbon dioxide. The resulting drop in alveolar oxygen tension ($PAO_2$) leads to arterial hypoxemia. To prevent this, clinicians administer **100% oxygen for 5–10 minutes** after discontinuing N₂O. **Analysis of Incorrect Options:** * **Ketamine:** An intravenous NMDA receptor antagonist. It does not involve alveolar gas exchange mechanisms and is known for maintaining airway reflexes and respiratory drive. * **Theophylline:** A methylxanthine used as a bronchodilator in asthma/COPD. It is not an anesthetic gas and does not cause diffusion hypoxia. * **Halothane:** A volatile inhalational anesthetic. While it can cause respiratory depression, it does not diffuse in large enough volumes to dilute alveolar oxygen significantly. **High-Yield NEET-PG Pearls:** * **Second Gas Effect:** N₂O speeds up the induction of a companion volatile anesthetic (e.g., Halothane) by creating a "vacuum" in the alveoli as it is rapidly absorbed. * **Concentration Effect:** The higher the concentration of N₂O inhaled, the more rapidly the arterial concentration rises. * **Contraindication:** N₂O should be avoided in closed-space pathologies (e.g., pneumothorax, intestinal obstruction, middle ear surgery) because it expands air-filled cavities.

Q: All of the following are modes to decrease pain on injection caused by propofol except?

Use vein on the dorsum of hand. **Explanation:** Propofol is a highly lipophilic drug, but its aqueous phase contains free propofol molecules that irritate the venous intima and activate the **kallikrein-kinin system**, leading to significant pain on injection. **Why Option C is the Correct Answer (The "Except"):** Using a vein on the **dorsum of the hand** actually **increases** the incidence and severity of pain compared to larger, more proximal veins. For NEET-PG, remember that the gold standard for reducing propofol-induced pain is using a **large-bore cannula in a large vein** (e.g., the antecubital fossa), which allows for faster dilution of the drug and less contact with the vessel wall. **Analysis of Other Options:** * **A. Mix Lignocaine with Propofol:** This is the most common clinical practice. Lignocaine (10–40 mg) acts as a local anesthetic on the vein wall and stabilizes the kinin cascade. * **B. Give Fentanyl prior to Propofol:** Pre-treatment with opioids like Fentanyl or Alfentanil increases the pain threshold and provides central analgesia, effectively reducing the injection pain. * **D. Cooling of the Drug:** Cooling propofol to 4°C reduces the concentration of free propofol in the aqueous phase and slows down the activation of pain mediators. **High-Yield Clinical Pearls for NEET-PG:** * **Propofol Formulation:** It is an emulsion (1% propofol, 10% soybean oil, 2.25% glycerol, and 1.2% egg phosphatide). * **Other methods to reduce pain:** Using Long-Chain Triglyceride/Medium-Chain Triglyceride (LCT/MCT) emulsions or the **Bier’s Block technique** (applying a tourniquet before injecting lignocaine). * **Contraindication:** Avoid propofol in patients with a documented severe allergy to **egg yolk** (though most egg allergies are to the albumin in the white).

Question 1

Which of the following intravenous agents is commonly used for outpatient procedures?

Accepted Answer

Propofol

Answer

Ketamine

Answer

Thiopental

Answer

Etomidate

Question 2

A 40-year-old female is scheduled for parotid surgery and is administered general Anaesthesia.
Approximately 10 minutes into the procedure, the following findings are noted:
- Rise in end-tidal CO2 (EtCO2)
- Temperature: 104°F (40°C)
- Heart rate: 150 bpm
- Blood pressure: 180/110 mmHg
What is the most likely diagnosis?

Accepted Answer

Malignant hyperthermia

Answer

Heat stroke

Answer

Heat cramps

Answer

Heat pyrexia

Question 3

A 34-year-old asthmatic male undergoes elective laparoscopic cholecystectomy under general anesthesia with endotracheal intubation. Fifteen minutes after induction, the ventilator alarm sounds for high peak airway pressure. The anesthesiologist notes the waveform shown on the capnograph monitor (Image 1). What is the most likely cause of this capnographic pattern?

Accepted Answer

A. Severe bronchospasm causing expiratory flow obstruction

Answer

B. Esophageal intubation with absent alveolar gas exchange

Answer

C. Pulmonary embolism causing increased alveolar dead space

Answer

D. Malignant hyperthermia causing increased CO2 production

Question 4

Diffusion hypoxia is seen with which drug?

Accepted Answer

Nitrous oxide

Answer

Ketamine

Answer

Theophylline

Answer

Halothane

Question 5

All of the following are modes to decrease pain on injection caused by propofol except?

Accepted Answer

Use vein on the dorsum of hand

Answer

Mix lignocaine with propofol

Answer

Give fentanyl prior to propofol

Answer

Cooling of the drug

General Anesthesia — MCQs

General Anesthesia — MCQs

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