The waveform shown in the image represents which of the following physiological parameters?
A patient is scheduled for laparoscopic surgery under general anesthesia in a day care setting. Which of the following factors makes him unsuitable for day care surgery?
During general anesthesia, which nerve is commonly monitored using a nerve stimulator to assess neuromuscular blockade?
A patient under anesthesia is found to be in a “cannot intubate, cannot ventilate” (CICV) scenario. What is the next best step in management?
A patient undergoing surgery develops sudden deranged vitals following a failed attempt at subclavian vein catheterization. On examination, the trachea is shifted to one side and breath sounds are absent on the opposite side. What is the most likely diagnosis?
In malignant hyperthermia, a genetic mutation in the ryanodine receptor (RYR1) leads to a life-threatening reaction to certain anesthetic agents. What is the primary ionic abnormality caused by this receptor defect?
FMGE 2025 - Anesthesiology FMGE Practice Questions and MCQs
Question 11: The waveform shown in the image represents which of the following physiological parameters?
- A. Tidal volume
- B. Arterial oxygen saturation
- C. Functional residual capacity
- D. End-tidal carbon dioxide (Correct Answer)
Explanation: ***End-tidal carbon dioxide*** - The image displays a **capnogram**, which is a graphical representation of the concentration or partial pressure of **carbon dioxide (CO2)** in respiratory gases over time. The y-axis is clearly labeled **CO2 (mmHg)**. - The characteristic rectangular waveform represents the respiratory cycle: the plateau indicates the exhalation of **alveolar gas**, and the peak at the end of the plateau is the **end-tidal CO2 (ETCO2)**, which normally ranges from 35-45 mmHg. *Arterial oxygen saturation* - Arterial oxygen saturation (SpO2) is measured by **pulse oximetry** and is reported as a **percentage**, not in mmHg. - The waveform associated with pulse oximetry is a **plethysmograph**, which reflects changes in blood volume in the tissue with each heartbeat, not respiratory gas exchange. *Functional residual capacity* - **Functional residual capacity (FRC)** is a static lung **volume** (measured in liters or milliliters), representing the amount of air remaining in the lungs after a normal exhalation. - It is not a dynamically changing parameter measured with each breath and cannot be represented by this type of real-time waveform. *Tidal volume* - **Tidal volume** is the **volume** of air inhaled or exhaled during a single breath, measured in milliliters or liters. - A graph of tidal volume over time (spirometry) would show a sinusoidal wave representing the volume change, which looks distinctly different from the capnogram shown.
Question 12: A patient is scheduled for laparoscopic surgery under general anesthesia in a day care setting. Which of the following factors makes him unsuitable for day care surgery?
- A. The patient has had general anesthesia in the past without complications
- B. The surgical procedure is expected to last slightly over 1 hour
- C. No attendant is available at home to care for the patient postoperatively (Correct Answer)
- D. Home is 45 minutes away from the hospital
Explanation: ***No attendant is available at home to care for the patient postoperatively***- Discharge following **general anesthesia** (GA) in a day care setting requires a responsible adult to escort the patient home and remain with them for the subsequent **24 hours** to monitor for complications.- Lack of a competent adult caregiver is a **strict contraindication** for ambulatory surgery requiring GA, as the patient's judgment and motor skills remain significantly impaired.*Home is 45 minutes away from the hospital*- The proximity criterion for day care surgery typically specifies that the patient should live within a **reasonable travel time** (often 60–90 minutes) of the hospital for accessible emergency readmission.- A 45-minute travel time falls well within acceptable limits and therefore does not make the patient unsuitable.*The surgical procedure is expected to last slightly over 1 hour*- For most day care protocols, surgical procedures should usually last less than **2 hours** to minimize recovery time and risks associated with prolonged anesthesia.- A procedure lasting slightly over 1 hour is considered standard and fully compatible with **ambulatory surgery** guidelines.*The patient has had general anesthesia in the past without complications*- Prior uncomplicated exposure to **general anesthesia** is viewed as a favorable predictive factor, suggesting a reduced risk of rare but severe anesthetic reactions like **Malignant Hyperthermia**.- This historical data actually increases the patient's suitability for a day care setting, rather than ruling it out.
Question 13: During general anesthesia, which nerve is commonly monitored using a nerve stimulator to assess neuromuscular blockade?
- A. Ulnar nerve (Correct Answer)
- B. Tibial nerve
- C. Median nerve
- D. Radial nerve
Explanation: ***Ulnar nerve*** - The **ulnar nerve** is the most common site for monitoring neuromuscular blockade because it is superficially located at the wrist, making it easily accessible for stimulation with surface electrodes. - Stimulation of the ulnar nerve causes contraction of the **adductor pollicis** muscle, leading to thumb adduction, which is a reliable and easily observable response to assess the degree of muscle relaxation. *Radial nerve* - The **radial nerve** is located deeper at the wrist compared to the ulnar nerve, making it more difficult to stimulate effectively with surface electrodes. - While it can be stimulated to produce wrist and finger extension, the response is generally less consistent and harder to quantify than the thumb adduction seen with ulnar nerve stimulation. *Median nerve* - Stimulation of the **median nerve** causes contraction of the thenar muscles, resulting in thumb opposition, which can be a more complex and sometimes painful response. - The median nerve lies between the tendons of the flexor carpi radialis and palmaris longus, making precise electrode placement more challenging and potentially leading to direct muscle stimulation. *Tibial nerve* - The **tibial nerve** can be stimulated behind the medial malleolus to elicit plantar flexion of the great toe (via the **flexor hallucis brevis** muscle). - However, the foot is often less accessible than the hand during surgery due to patient positioning and surgical draping, making the ulnar nerve a more practical choice.
Question 14: A patient under anesthesia is found to be in a “cannot intubate, cannot ventilate” (CICV) scenario. What is the next best step in management?
- A. Insert a laryngeal mask airway
- B. Insert nasopharyngeal airway
- C. Perform a tracheostomy
- D. Perform a cricothyroidotomy (Correct Answer)
Explanation: ***Perform a cricothyroidotomy*** - In a “cannot intubate, cannot ventilate” (**CICV**) scenario, immediate establishment of a surgical airway is life-saving to prevent **hypoxic brain injury** and death. - A **cricothyroidotomy** is the fastest and most definitive emergency procedure to secure the airway by making an incision through the **cricothyroid membrane** into the trachea, bypassing any upper airway obstruction. *Insert nasopharyngeal airway* - A nasopharyngeal airway is a basic airway adjunct designed to relieve soft tissue obstruction at the level of the pharynx. It does not provide a definitive airway for ventilation. - In a **CICV** situation, basic maneuvers and adjuncts like this have already been attempted and failed; it is an inadequate intervention for this life-threatening emergency. *Insert a laryngeal mask airway* - A laryngeal mask airway (**LMA**) is a supraglottic airway device. A **CICV** scenario is declared only after attempts to secure the airway with both an endotracheal tube and a supraglottic device have failed. - Wasting further time attempting to insert an LMA is inappropriate when ventilation is not possible and a surgical airway is urgently needed. *Perform a tracheostomy* - A **tracheostomy** is a formal, time-consuming surgical procedure that is more complex and has a higher complication rate in an emergency setting compared to a cricothyroidotomy. - While it is a definitive airway, it is not the procedure of choice for a time-critical airway emergency. A cricothyroidotomy is the standard emergent surgical airway.
Question 15: A patient undergoing surgery develops sudden deranged vitals following a failed attempt at subclavian vein catheterization. On examination, the trachea is shifted to one side and breath sounds are absent on the opposite side. What is the most likely diagnosis?
- A. Tension pneumothorax (Correct Answer)
- B. Aspiration pneumonitis
- C. Pulmonary embolism
- D. Bronchospasm
Explanation: ***Correct: Tension pneumothorax*** - **Classic complication of subclavian vein catheterization** - inadvertent puncture of the pleura causes air accumulation in the pleural space - **Pathognomonic clinical features** present in this case: - **Tracheal deviation away from the affected side** (toward the opposite side where breath sounds are absent) - **Absent breath sounds on the affected side** due to complete lung collapse - **Hemodynamic instability** ("deranged vitals") from mediastinal shift compressing the great vessels and heart - **Medical emergency** requiring immediate needle decompression followed by chest tube insertion - The **tension** component occurs when air enters pleural space during inspiration but cannot escape during expiration (one-way valve effect), causing progressive pressure buildup *Incorrect: Aspiration pneumonitis* - Would present with bilateral crackles, hypoxia, and potential bronchospasm - Does **not cause tracheal deviation** or unilateral absent breath sounds - Typically occurs during induction or emergence from anesthesia, not during vascular access procedures *Incorrect: Pulmonary embolism* - Presents with sudden dyspnea, hypoxia, tachycardia, and possible hypotension - Does **not cause tracheal deviation** or unilateral absent breath sounds - Breath sounds remain present bilaterally (though may have localized crackles) - Not directly related to subclavian catheterization attempts *Incorrect: Bronchospasm* - Presents with **bilateral wheezing** and increased airway pressures - Does **not cause tracheal deviation** or unilateral findings - Breath sounds present bilaterally (though may be diminished with severe bronchospasm) - Would not explain the immediate temporal relationship with failed subclavian line attempt
Question 16: In malignant hyperthermia, a genetic mutation in the ryanodine receptor (RYR1) leads to a life-threatening reaction to certain anesthetic agents. What is the primary ionic abnormality caused by this receptor defect?
- A. Increased sodium influx into the muscle cell
- B. Increased potassium uptake into the sarcoplasmic reticulum
- C. Increased calcium release from the sarcoplasmic reticulum (Correct Answer)
- D. Increased chloride efflux from the muscle cell
Explanation: ***Increased calcium release from the sarcoplasmic reticulum*** - The **ryanodine receptor 1 (RYR1)** mutation found in malignant hyperthermia causes the receptor channel on the sarcoplasmic reticulum (SR) to become hypersensitive and spontaneously release large, uncontrolled amounts of **calcium** into the myoplasm upon exposure to triggering agents (e.g., volatile anesthetics like halothane, succinylcholine). - This massive, sustained elevation of intracellular **calcium** drives continuous muscle contraction, leading to muscle rigidity, hypermetabolism, heat production, rhabdomyolysis, and the characteristic life-threatening features of malignant hyperthermia. - Treatment with **dantrolene** works by inhibiting calcium release from the SR, confirming calcium dysregulation as the primary mechanism. *Increased sodium influx into the muscle cell* - Sodium influx is crucial for initiating the muscle action potential via **voltage-gated sodium channels**, but it is not the primary pathological trigger or defining ionic abnormality in malignant hyperthermia. - The sustained muscle contraction in MH is driven by excessive **calcium** in the myoplasm, not sodium influx which is only involved in initial depolarization. *Increased potassium uptake into the sarcoplasmic reticulum* - The sarcoplasmic reticulum's main function is the storage and release of **calcium**, not potassium regulation. - In severe MH, rhabdomyolysis causes **hyperkalemia** due to potassium *efflux* from damaged muscle cells into the bloodstream, not uptake into the SR. *Increased chloride efflux from the muscle cell* - Chloride channels maintain resting membrane potential and regulate cell volume, but their dysregulation is not the central mechanism of malignant hyperthermia. - The life-threatening symptoms of MH (hyperthermia, rigidity, hypermetabolism, acidosis) are a direct consequence of massive, uncontrolled **calcium release** from the SR, not chloride movement.