FMGE 2023 — Anesthesiology

Q: Which of the following is most suitable for intravenous regional anesthesia?

Lidocaine. ***Lidocaine***- It is the most commonly used agent for **intravenous regional anesthesia (IVRA)**, also known as a **Bier block**, due to its rapid onset and favorable safety profile upon systemic absorption.- Lidocaine is an intermediate-acting amide local anesthetic often supplied without epinephrine for IVRA to minimize the risks of **systemic vasoconstriction** should the tourniquet be released early.*Bupivacaine*- Bupivacaine is highly **cardiotoxic**; if the tourniquet fails or is released prematurely, high systemic concentrations can cause severe and potentially **lethal cardiac arrhythmias**.- This long-acting anesthetic is generally **contraindicated** for IVRA precisely due to its significant risk of systemic toxicity.*Mepivacaine*- While an intermediate-acting amide suitable for infiltration, mepivacaine is less commonly chosen than lidocaine for IVRA due to its similarity in properties but greater cost or lack of a clear safety advantage.- Some reports suggest mepivacaine may have slightly **higher neurotoxicity** compared to lidocaine, making lidocaine the preferred standard.*Procaine*- Procaine is an **ester-type** local anesthetic with a very short duration of action, making it unsuitable for procedures requiring sustained anesthesia (typically 45-60 minutes in IVRA).- Ester-type anesthetics are metabolized to **p-aminobenzoic acid (PABA)**, which increases the likelihood of **allergic reactions** compared to amide anesthetics. [Practice more Anesthesiology PYQs on OnCourse]

Q: Which of the following airway devices helps maintain Fio2 of 0.25-0.60, irrespective of the patient's breathing effort?

Venturi mask. ***Venturi mask***- This device utilizes the **Bernoulli principle** to mix a specific flow of 100% oxygen with a fixed volume of **room air** via interchangeable jet adapters, achieving a precise FIO2 (0.24-0.60).- Because the total gas flow delivered to the patient (O2 + entrained air) greatly exceeds the patient's peak inspiratory flow, the delivered FIO2 is **independent of the patient's breathing effort** (rate and depth).*Nasal cannula*- The actual FIO2 delivered is highly **variable** and dependent on the patient's **inspiratory flow rate** and pattern, as the device primarily provides supplemental oxygen flow into the pharynx.- It typically provides a maximum FIO2 of about 0.44 at flow rates up to 6 L/min, which is insufficient for predictable FIO2 control in the moderate range.*Simple face mask*- The FIO2 delivered is variable (typically 0.35–0.50) because a significant amount of **room air is entrained** through the ports and the seal around the mask, highly dependent on the patient’s ventilation pattern.- It requires a flow rate of at least 5 L/min to flush out the volume in the mask and prevent the risk of **carbon dioxide ($ ext{CO}_2$) rebreathing** from the mask's dead space.*Non-rebreathing mask*- Offers the **highest FIO2 available** non-invasively (up to 0.90–0.95); however, its primary purpose is maximizing oxygen delivery, not maintaining a precise, lower concentration (0.25-0.60).- While a valve prevents exhaled air from entering the reservoir bag, the exact FIO2 delivered still requires a tight seal and is generally used when high concentrations are needed, making it unsuitable for precise intermediate FIO2. [Practice more Anesthesiology PYQs on OnCourse]

Q: A patient in the ICU with an endotracheal tube now needs a tracheostomy tube. Which type of tube will you use?

Cuffed tracheostomy tube. ***Cuffed tracheostomy tube*** - A **cuffed tracheostomy tube** is mandatory in the ICU setting, especially when transitioning from an endotracheal tube, because it provides a seal necessary for **positive pressure ventilation** (PPCV). - The cuff also provides crucial protection against the aspiration of **oral secretions** and **gastric contents**, which is a high risk in critically ill, often sedated, ICU patients. *Uncuffed tracheostomy tube* - *Uncuffed tubes* are inadequate for patients requiring mechanical ventilation as they cannot create the necessary sealed circuit to deliver **tidal volume**. - These tubes are generally reserved for stable patients who require a chronic airway, are not on ventilation, and have a low risk of **aspiration**. *Metallic tracheostomy tube.* - **Metallic tracheostomy tubes** (like those used historically or specific specialized tubes) are typically uncuffed and are not suitable for patients requiring mandatory **mechanical ventilation** or aspiration protection in the acute ICU setting. - They are primarily used for *long-term placement* in ambulatory patients who require a stable, durable airway and often need their tube removed and cleaned frequently. *Endotracheal tube* - An **endotracheal tube (ETT)** is the device currently in use and is being *replaced* by a tracheostomy, making this option incorrect. - While the ETT provides airway management, a tracheostomy tube offers advantages for **long-term airway maintenance** (e.g., improved comfort, easier weaning, better oral hygiene). [Practice more Anesthesiology PYQs on OnCourse]

Q: Which of the following is a dimension of the medical device shown?

Diameter. ***Diameter*** - Endotracheal tubes (ETTs) are primarily sized by their **internal diameter (ID)**, measured in millimeters (mm). This measurement is crucial for selecting the appropriate tube size to ensure adequate ventilation and minimize airway trauma. - The ID directly affects **airway resistance** and the work of breathing; a larger ID results in lower resistance. The size is clearly marked on the tube, for example, 'ID 7.5'. *Curvature* - While ETTs have a pre-formed curve (often called a **Magill curve**) to facilitate passage through the airway anatomy, this is a design feature, not a sizing dimension. - The curvature can be temporarily modified with a **stylet** to aid in difficult intubations, but it is not a standardized measurement used for selecting a tube. *Circumference* - Circumference is mathematically related to the diameter (Circumference = π × Diameter), but it is not the standard clinical measurement used for sizing ETTs. - The universal convention in anesthesiology and critical care is to refer to the tube's **internal diameter**, not its circumference, for selection and documentation. *Length* - The length of the ETT is important for determining the correct **depth of insertion** into the trachea, which is guided by the centimeter markings along the tube. - However, length is a secondary parameter related to placement, whereas the **internal diameter** is the primary dimension used to select the correct *size* of the tube for the patient. [Practice more Anesthesiology PYQs on OnCourse]

Q: Resistance of the tube shown below is primarily because of

Diameter. ***Diameter*** - According to **Poiseuille's law**, resistance to laminar flow is inversely proportional to the radius raised to the fourth power (r⁴). Therefore, even a small change in the tube's **diameter** has a profound effect on airflow resistance. - The image shows an endotracheal tube, where the internal diameter is the most critical factor determining the work of breathing for a patient, as it dictates the primary resistance to gas flow. *Curvature* - The curvature of the tube can induce **turbulent flow**, especially at high flow rates, which does increase resistance. - However, its contribution to total resistance is significantly less than that of the tube's internal **diameter**. *Circumference* - Circumference is directly proportional to the diameter (Circumference = π × Diameter), so it is related to resistance. - However, the physical principle governing flow resistance, **Poiseuille's law**, specifically uses the **radius (or diameter)** to the fourth power, making it the primary determinant, not circumference. *Length* - Resistance is directly proportional to the **length** of the tube. A longer tube will have more resistance than a shorter one of the same diameter. - While length is a factor, its effect is linear, whereas the effect of the **diameter** is exponential (to the fourth power), making diameter a much more significant variable. [Practice more Anesthesiology PYQs on OnCourse]

5 Previous Year Questions with Answers & Explanations

Questions

Which of the following is most suitable for intravenous regional anesthesia?

Which of the following airway devices helps maintain Fio2 of 0.25-0.60, irrespective of the patient's breathing effort?

A patient in the ICU with an endotracheal tube now needs a tracheostomy tube. Which type of tube will you use?

Which of the following is a dimension of the medical device shown?

Resistance of the tube shown below is primarily because of

FMGE 2023 - Anesthesiology FMGE Practice Questions and MCQs

Question 1: Which of the following is most suitable for intravenous regional anesthesia?

A. Lidocaine (Correct Answer)
B. Bupivacaine
C. Mepivacaine
D. Procaine

Explanation: ***Lidocaine***- It is the most commonly used agent for **intravenous regional anesthesia (IVRA)**, also known as a **Bier block**, due to its rapid onset and favorable safety profile upon systemic absorption.- Lidocaine is an intermediate-acting amide local anesthetic often supplied without epinephrine for IVRA to minimize the risks of **systemic vasoconstriction** should the tourniquet be released early.*Bupivacaine*- Bupivacaine is highly **cardiotoxic**; if the tourniquet fails or is released prematurely, high systemic concentrations can cause severe and potentially **lethal cardiac arrhythmias**.- This long-acting anesthetic is generally **contraindicated** for IVRA precisely due to its significant risk of systemic toxicity.*Mepivacaine*- While an intermediate-acting amide suitable for infiltration, mepivacaine is less commonly chosen than lidocaine for IVRA due to its similarity in properties but greater cost or lack of a clear safety advantage.- Some reports suggest mepivacaine may have slightly **higher neurotoxicity** compared to lidocaine, making lidocaine the preferred standard.*Procaine*- Procaine is an **ester-type** local anesthetic with a very short duration of action, making it unsuitable for procedures requiring sustained anesthesia (typically 45-60 minutes in IVRA).- Ester-type anesthetics are metabolized to **p-aminobenzoic acid (PABA)**, which increases the likelihood of **allergic reactions** compared to amide anesthetics.

Question 2: Which of the following airway devices helps maintain Fio2 of 0.25-0.60, irrespective of the patient's breathing effort?

A. Simple face mask
B. Venturi mask (Correct Answer)
C. Non-rebreathing mask
D. Nasal cannula

Explanation: ***Venturi mask***- This device utilizes the **Bernoulli principle** to mix a specific flow of 100% oxygen with a fixed volume of **room air** via interchangeable jet adapters, achieving a precise FIO2 (0.24-0.60).- Because the total gas flow delivered to the patient (O2 + entrained air) greatly exceeds the patient's peak inspiratory flow, the delivered FIO2 is **independent of the patient's breathing effort** (rate and depth).*Nasal cannula*- The actual FIO2 delivered is highly **variable** and dependent on the patient's **inspiratory flow rate** and pattern, as the device primarily provides supplemental oxygen flow into the pharynx.- It typically provides a maximum FIO2 of about 0.44 at flow rates up to 6 L/min, which is insufficient for predictable FIO2 control in the moderate range.*Simple face mask*- The FIO2 delivered is variable (typically 0.35–0.50) because a significant amount of **room air is entrained** through the ports and the seal around the mask, highly dependent on the patient’s ventilation pattern.- It requires a flow rate of at least 5 L/min to flush out the volume in the mask and prevent the risk of **carbon dioxide ($ ext{CO}_2$) rebreathing** from the mask's dead space.*Non-rebreathing mask*- Offers the **highest FIO2 available** non-invasively (up to 0.90–0.95); however, its primary purpose is maximizing oxygen delivery, not maintaining a precise, lower concentration (0.25-0.60).- While a valve prevents exhaled air from entering the reservoir bag, the exact FIO2 delivered still requires a tight seal and is generally used when high concentrations are needed, making it unsuitable for precise intermediate FIO2.

Question 3: A patient in the ICU with an endotracheal tube now needs a tracheostomy tube. Which type of tube will you use?

A. Cuffed tracheostomy tube (Correct Answer)
B. Metallic tracheostomy tube
C. Endotracheal tube
D. Uncuffed tracheostomy tube

Explanation: ***Cuffed tracheostomy tube*** - A **cuffed tracheostomy tube** is mandatory in the ICU setting, especially when transitioning from an endotracheal tube, because it provides a seal necessary for **positive pressure ventilation** (PPCV). - The cuff also provides crucial protection against the aspiration of **oral secretions** and **gastric contents**, which is a high risk in critically ill, often sedated, ICU patients. *Uncuffed tracheostomy tube* - *Uncuffed tubes* are inadequate for patients requiring mechanical ventilation as they cannot create the necessary sealed circuit to deliver **tidal volume**. - These tubes are generally reserved for stable patients who require a chronic airway, are not on ventilation, and have a low risk of **aspiration**. *Metallic tracheostomy tube.* - **Metallic tracheostomy tubes** (like those used historically or specific specialized tubes) are typically uncuffed and are not suitable for patients requiring mandatory **mechanical ventilation** or aspiration protection in the acute ICU setting. - They are primarily used for *long-term placement* in ambulatory patients who require a stable, durable airway and often need their tube removed and cleaned frequently. *Endotracheal tube* - An **endotracheal tube (ETT)** is the device currently in use and is being *replaced* by a tracheostomy, making this option incorrect. - While the ETT provides airway management, a tracheostomy tube offers advantages for **long-term airway maintenance** (e.g., improved comfort, easier weaning, better oral hygiene).

Question 4: Which of the following is a dimension of the medical device shown?

A. Curvature
B. Diameter (Correct Answer)
C. Circumference
D. Length

Explanation: ***Diameter*** - Endotracheal tubes (ETTs) are primarily sized by their **internal diameter (ID)**, measured in millimeters (mm). This measurement is crucial for selecting the appropriate tube size to ensure adequate ventilation and minimize airway trauma. - The ID directly affects **airway resistance** and the work of breathing; a larger ID results in lower resistance. The size is clearly marked on the tube, for example, 'ID 7.5'. *Curvature* - While ETTs have a pre-formed curve (often called a **Magill curve**) to facilitate passage through the airway anatomy, this is a design feature, not a sizing dimension. - The curvature can be temporarily modified with a **stylet** to aid in difficult intubations, but it is not a standardized measurement used for selecting a tube. *Circumference* - Circumference is mathematically related to the diameter (Circumference = π × Diameter), but it is not the standard clinical measurement used for sizing ETTs. - The universal convention in anesthesiology and critical care is to refer to the tube's **internal diameter**, not its circumference, for selection and documentation. *Length* - The length of the ETT is important for determining the correct **depth of insertion** into the trachea, which is guided by the centimeter markings along the tube. - However, length is a secondary parameter related to placement, whereas the **internal diameter** is the primary dimension used to select the correct *size* of the tube for the patient.

Question 5: Resistance of the tube shown below is primarily because of

A. Diameter (Correct Answer)
B. Curvature
C. Length
D. Circumference

Explanation: ***Diameter*** - According to **Poiseuille's law**, resistance to laminar flow is inversely proportional to the radius raised to the fourth power (r⁴). Therefore, even a small change in the tube's **diameter** has a profound effect on airflow resistance. - The image shows an endotracheal tube, where the internal diameter is the most critical factor determining the work of breathing for a patient, as it dictates the primary resistance to gas flow. *Curvature* - The curvature of the tube can induce **turbulent flow**, especially at high flow rates, which does increase resistance. - However, its contribution to total resistance is significantly less than that of the tube's internal **diameter**. *Circumference* - Circumference is directly proportional to the diameter (Circumference = π × Diameter), so it is related to resistance. - However, the physical principle governing flow resistance, **Poiseuille's law**, specifically uses the **radius (or diameter)** to the fourth power, making it the primary determinant, not circumference. *Length* - Resistance is directly proportional to the **length** of the tube. A longer tube will have more resistance than a shorter one of the same diameter. - While length is a factor, its effect is linear, whereas the effect of the **diameter** is exponential (to the fourth power), making diameter a much more significant variable.