INI-CET 2025 — Anesthesiology
3 Previous Year Questions with Answers & Explanations
A 65-year-old patient is on mechanical ventilation for acute respiratory distress syndrome (ARDS). Suddenly, the patient becomes hypotensive, tachycardic, and shows absent breath sounds on the left side with tracheal deviation to the right. What is the most common cause of this in patients receiving mechanical ventilation?
A 50-year-old male patient underwent lower abdominal surgery under general anaesthesia. Vecuronium was administered as a muscle relaxant during the procedure. At the end of the surgery, which of the following is the most appropriate agent to reverse the effects of vecuronium?
According to the Muir-Barclay formula, which of the following is considered the best colloid for volume replacement?
INI-CET 2025 - Anesthesiology INI-CET Practice Questions and MCQs
Question 1: A 65-year-old patient is on mechanical ventilation for acute respiratory distress syndrome (ARDS). Suddenly, the patient becomes hypotensive, tachycardic, and shows absent breath sounds on the left side with tracheal deviation to the right. What is the most common cause of this in patients receiving mechanical ventilation?
- A. Barotrauma due to high airway pressure (Correct Answer)
- B. Endotracheal tube malposition
- C. Oxygen toxicity
- D. High tidal volume
Explanation: ### **Explanation** The clinical presentation of sudden **hypotension, tachycardia, absent breath sounds**, and **tracheal deviation** in a ventilated patient is a classic description of a **Tension Pneumothorax**. **1. Why Option A is Correct:** In patients with **ARDS**, the lungs are "stiff" (low compliance), necessitating higher airway pressures to maintain ventilation. **Barotrauma** refers to alveolar rupture caused by high **Peak Inspiratory Pressure (PIP)** or high **Plateau Pressure (>30 cm H₂O)**. This allows air to escape into the pleural space. Under positive pressure ventilation, this air accumulates rapidly, causing a "one-way valve" effect that shifts the mediastinum, compresses the great veins, and leads to obstructive shock (hypotension). **2. Analysis of Incorrect Options:** * **B. Endotracheal tube malposition:** While common (usually right mainstem intubation), it typically causes absent breath sounds on the left but **does not** cause tracheal deviation or sudden hemodynamic collapse unless associated with a secondary pneumothorax. * **C. Oxygen toxicity:** This is a chronic complication of high FiO₂ (>0.6) leading to free radical damage and absorption atelectasis; it does not present with acute surgical emphysema or tension physiology. * **D. High tidal volume:** While high tidal volumes lead to **Volutrauma**, the immediate mechanical cause of a pneumothorax is the resultant high pressure (**Barotrauma**). Barotrauma is the specific term for the complication described. --- ### **High-Yield Clinical Pearls for INI-CET** * **Management:** Tension pneumothorax is a **clinical diagnosis**. Do not wait for a X-ray. Immediate treatment is **Needle Decompression** (traditionally 2nd intercostal space, now preferred in the **5th intercostal space** anterior to the mid-axillary line) followed by an Intercostal Drainage (ICD) tube. * **ARDS Strategy:** To prevent barotrauma, use **Lung Protective Ventilation**: Low tidal volumes (6 mL/kg PBW) and keeping Plateau Pressure **<30 cm H₂O**. * **Early Sign:** A sudden increase in **Peak Airway Pressure** on the ventilator monitor is often the first sign of impending barotrauma.
Question 2: A 50-year-old male patient underwent lower abdominal surgery under general anaesthesia. Vecuronium was administered as a muscle relaxant during the procedure. At the end of the surgery, which of the following is the most appropriate agent to reverse the effects of vecuronium?
- A. Baclofen
- B. Neostigmine (Correct Answer)
- C. Atropine
- D. Drotaverine
Explanation: ### **Explanation** The correct answer is **B. Neostigmine**. #### **Mechanism of Action** **Vecuronium** is a **non-depolarizing neuromuscular blocking agent (NDMR)** that works by competitively inhibiting nicotinic acetylcholine receptors at the neuromuscular junction. To reverse its effects, we must increase the concentration of acetylcholine (ACh) at the synapse. **Neostigmine** is an **acetylcholinesterase inhibitor**. By inhibiting the enzyme that breaks down ACh, it increases the availability of ACh, which then outcompetes the vecuronium molecules for the receptor sites, thereby restoring muscle power. #### **Analysis of Incorrect Options** * **A. Baclofen:** This is a **GABA-B agonist** used as a centrally acting muscle relaxant for chronic spasticity (e.g., multiple sclerosis). it has no role in reversing surgical neuromuscular blockade. * **C. Atropine:** This is an **anticholinergic (muscarinic antagonist)**. While it is almost always given *alongside* neostigmine to prevent bradycardia and secretions caused by increased ACh at muscarinic sites, it does not reverse the muscle relaxant effect itself. * **D. Drotaverine:** This is an **antispasmodic** (phosphodiesterase-4 inhibitor) used primarily for smooth muscle relaxation in cases of biliary or renal colic. #### **High-Yield Clinical Pearls for INI-CET** * **The "Gold Standard" Pair:** Neostigmine is co-administered with **Glycopyrrolate** (preferred over Atropine) to counteract the parasympathetic side effects (bradycardia, salivation, bronchospasm). * **Sugammadex:** A newer, high-yield reversal agent specifically for **Rocuronium** and **Vecuronium**. It works by **encapsulation** (chelating the drug) rather than enzyme inhibition. * **Monitoring:** Reversal should ideally be guided by **Train-of-Four (TOF)** monitoring; a TOF ratio of **>0.9** indicates adequate recovery from blockade.
Question 3: According to the Muir-Barclay formula, which of the following is considered the best colloid for volume replacement?
- A. Fresh Frozen Plasma (FFP)
- B. Packed Red Blood Cells (PRBC)
- C. Dextran 40
- D. Albumin (Correct Answer)
Explanation: ### **Explanation: Muir-Barclay Formula and Colloid Replacement** The **Muir-Barclay formula** is a classic calculation used primarily in the management of fluid resuscitation for **burn patients**. It is based on the principle of replacing plasma volume lost due to increased capillary permeability following thermal injury. #### **Why Albumin is the Correct Answer** The formula specifically calculates the volume of **plasma (or a plasma substitute)** required to maintain oncotic pressure and intravascular volume. * **Albumin** is considered the "gold standard" colloid in this context because it is the primary protein responsible for **plasma oncotic pressure**. * The formula divides the post-burn period into six 4-hour or 6-hour intervals, providing a specific volume of colloid (usually **5% Albumin** or reconstituted dried plasma) for each period based on the formula: > **(Total Area of Burn % × Weight in kg) / 2 = Volume (ml) per aliquot.** #### **Analysis of Incorrect Options** * **Fresh Frozen Plasma (FFP):** While FFP contains albumin and clotting factors, it carries risks of transfusion-related acute lung injury (TRALI) and infections. It is reserved for coagulopathies, not routine volume expansion in burns. * **Packed Red Blood Cells (PRBC):** These are used to improve oxygen-carrying capacity in cases of anemia or hemorrhage, not for plasma volume replacement in the acute phase of burn resuscitation. * **Dextran 40:** This is a synthetic colloid. While it expands volume, it can interfere with platelet function and cross-matching, and it lacks the physiological oncotic properties of albumin required by the Muir-Barclay protocol. #### **High-Yield Clinical Pearls for INI-CET** * **Parkland Formula vs. Muir-Barclay:** While Muir-Barclay focuses on **colloids**, the more commonly tested **Parkland Formula** uses **Crystalloids (Ringer’s Lactate)**: $4 \text{ ml} \times \text{Body Weight (kg)} \times \text{TBSA \%}$. * **Rule of Nines:** Always use Wallace’s Rule of Nines to calculate the Total Body Surface Area (TBSA) before applying these formulas. * **End-point of Resuscitation:** Regardless of the formula used, the most reliable indicator of adequate fluid resuscitation is **Urine Output** (Target: $0.5\text{--}1.0 \text{ ml/kg/hr}$ in adults).