Perioperative Ultrasound

Perioperative Ultrasound Indian Medical PG Question 1: FAST USG focuses on all of the following areas except-

• A. Splenic
• B. Pleura (Correct Answer)
• C. Hepatic
• D. Pelvic

Perioperative Ultrasound Explanation: ***Pleura*** - While pleural assessment is included in **extended FAST (E-FAST)** for detecting pneumothorax and hemothorax, the **traditional FAST protocol** focuses specifically on detecting **free fluid** in the **peritoneal** and **pericardial** spaces in trauma patients. - The pleura is not one of the standard **four views** of traditional FAST USG, though it is assessed in the expanded E-FAST protocol. *Splenic* - The **splenorenal recess** (left upper quadrant space between the spleen and left kidney) is one of the four key regions in FAST USG to detect **free fluid**. - Fluid accumulation in this area can indicate injury to the spleen or other abdominal organs. *Hepatic* - The **hepatorenal recess (Morison's pouch)** between the liver and right kidney is a critical view in FAST USG for identifying **free fluid**. - This is often the first place fluid collects in the peritoneum in supine patients and is the most sensitive area for detecting intraperitoneal fluid. *Pelvic* - The **pouch of Douglas** (rectovesical in males or rectouterine in females) is a standard view in FAST USG to detect **free fluid** in the pelvis. - Fluid here can indicate significant abdominal or pelvic injury.

Perioperative Ultrasound Indian Medical PG Question 2: What is the best way to diagnose gallbladder stones?

• A. USG (Correct Answer)
• B. Oral cholecystography
• C. Percutaneous transhepatic cholangiography
• D. Intravenous cholangiogram

Perioperative Ultrasound Explanation: ***USG*** - **Ultrasound (USG)** is the preferred and most **sensitive imaging modality** for detecting gallbladder stones due to its non-invasive nature and high diagnostic accuracy. - It can effectively visualize stones as **echogenic foci** with **posterior acoustic shadowing** within the gallbladder lumen. *Oral cholecystography* - This method involves ingesting a contrast agent, which is then absorbed and excreted by the liver into the bile, outlining the gallbladder. - It has largely been replaced by ultrasound due to its **lower sensitivity** for small stones, **patient inconvenience**, and potential for **adverse reactions** to the contrast. *Percutaneous transhepatic cholangiography* - **PTC** is an **invasive procedure** where a needle is inserted through the skin and liver into the bile ducts to inject contrast. - It is typically reserved for cases where **other imaging modalities are inconclusive** or for **therapeutic interventions** in patients with biliary obstruction, not routine stone detection. *Intravenous cholangiogram* - This involves intravenous administration of a contrast agent that is concentrated in the bile and allows visualization of the bile ducts and gallbladder. - It has also been **largely replaced by USG and ERCP** due to the risk of **allergic reactions** to contrast, **poor visualization** in cases of liver dysfunction, and lower sensitivity than ultrasound.

Perioperative Ultrasound Indian Medical PG Question 3: To obtain adequate diagnostic imaging in a morbidly obese patient, what modification to X-ray technique is most important?

• A. Increase MAS
• B. Decrease KVP
• C. Increase KVP (Correct Answer)
• D. Decrease MAS

Perioperative Ultrasound Explanation: ***Increase KVP*** - Increasing the **kilovoltage peak (KVP)** is essential for imaging morbidly obese patients because it increases the **penetrating power** of the X-ray beam, allowing adequate transmission through thick body tissues. - Higher KVP (typically 90-120 kVp range) ensures the X-ray beam can penetrate increased soft tissue thickness and reach the image receptor with sufficient intensity. - While higher KVP produces **longer scale (lower) contrast**, it is necessary for adequate **penetration** in obese patients - without sufficient KVP, the image would be underexposed and non-diagnostic. - In practice, both KVP and MAS are increased for obese patients, but **KVP increase is more critical** for penetration. *Increase MAS* - Increasing **milliampere-seconds (MAS)** increases the quantity of X-ray photons and image density (brightness), which is also helpful for obese patients. - However, MAS alone without adequate KVP cannot solve the penetration problem - the photons would still be too low energy to penetrate thick tissues effectively. - MAS increase without KVP increase would result in high patient dose with poor image quality. *Decrease KVP* - Decreasing KVP reduces **beam penetration**, which would be catastrophic for imaging an obese patient. - The X-ray beam would be absorbed by superficial tissues, resulting in a severely **underexposed** and non-diagnostic image. - While lower KVP produces higher contrast in theory, it is completely inappropriate for thick body parts. *Decrease MAS* - Decreasing MAS reduces the number of X-ray photons, resulting in an **underexposed, lighter** image. - This would make it even more difficult to obtain adequate imaging through increased body mass, resulting in a non-diagnostic radiograph with excessive quantum mottle.

Perioperative Ultrasound Indian Medical PG Question 4: The ultrasonic sound waves employed by ultrasound machines for medical sonography have the frequency of:

• A. 20 – 20,000 Hz
• B. 2 – 20 MHz (Correct Answer)
• C. Less than 1 MHz
• D. Greater than 100 MHz

Perioperative Ultrasound Explanation: ***2 – 20 MHz*** - Medical ultrasound utilizes **high-frequency sound waves**, typically in the **megahertz (MHz)** range, to penetrate tissues and create images. - This frequency range provides a good balance between **penetration depth** and **image resolution** for diagnostic purposes. *20 – 20,000 Hz* - This range represents the spectrum of **human audible sound**. - These frequencies are too low to provide the necessary spatial resolution for medical imaging. *Less than 1 MHz* - Frequencies below 1 MHz would have **poor spatial resolution** for detailed anatomical imaging. - While they would penetrate deeper, the images produced would be of **insufficient quality** for most diagnostic applications. *Greater than 100 MHz* - Frequencies above 100 MHz offer **extremely high resolution** but have very **limited penetration depth**. - They are primarily used for very superficial imaging, such as in **ophthalmology** or dermatological applications, not for general abdominal or cardiac sonography.

Perioperative Ultrasound Indian Medical PG Question 5: In an emphysematous patient with bullous lesions, which is the best investigation to measure lung volumes?

• A. Body plethysmography (Correct Answer)
• B. Helium dilution
• C. Trans diaphragmatic pressure
• D. DLCO

Perioperative Ultrasound Explanation: ***Body plethysmography*** - This method measures **total lung capacity (TLC)** by applying **Boyle's Law** and is not significantly affected by **trapped air** in bullae. - It directly measures changes in volume and pressure within a sealed chamber, providing accurate lung volumes even in the presence of **non-communicating air spaces**. *Helium dilution* - The **helium dilution technique** underestimates lung volumes in conditions with **trapped air** or poorly communicating air spaces, such as **bullae**, because helium cannot diffuse into these areas. - This method relies on the equilibration of a known amount of helium throughout the lungs, which is unreliable when significant parts of the lung are not ventilated. *Trans diaphragmatic pressure* - **Transdiaphragmatic pressure (Pdi)** is primarily used to assess **diaphragmatic strength and function**, not for measuring static lung volumes. - It involves measuring the pressure difference between the gastric and esophageal balloons and is unrelated to **total lung capacity** or **residual volume**. *DLCO* - **Diffusing capacity of the lung for carbon monoxide (DLCO)** measures the efficiency of gas transfer from the alveoli to the red blood cells, not lung volumes. - While it is a valuable test in emphysema (typically reduced), it does not provide information about the **absolute volumes of the lung**.

Perioperative Ultrasound Indian Medical PG Question 6: In correct positioning the tip of the instrument shown in the image should lie at:

• A. Thyroid cartilage
• B. Above esophagus
• C. Vocal cords
• D. Epiglottis (Correct Answer)

Perioperative Ultrasound Explanation: ***Epiglottis*** - The image shows a **Laryngeal Mask Airway (LMA)**, which is designed to sit in the hypopharynx, with its tip resting at the **epiglottis**. - This positioning allows the LMA to create a seal around the laryngeal inlet, facilitating effective ventilation without entering the trachea. *Vocal cords* - The LMA is designed to provide a seal *above* the vocal cords, ensuring ventilation of the trachea without direct intubation of the vocal cords themselves. - Positioning the tip *at* the vocal cords would hinder proper airway sealing and could cause trauma. *Thyroid cartilage* - The thyroid cartilage is an anterior neck structure and is not the anatomical landmark for the tip of a properly placed LMA. - The LMA sits deeper in the pharynx, above the glottic opening, making the epiglottis the relevant landmark. *Above esophagus* - While the LMA sits **above the esophageal inlet**, diverting air primarily into the trachea, its *tip* specifically rests at the epiglottis, covering the laryngeal opening. - Stating "above the esophagus" is too general; the precise anatomical placement for the tip is at the epiglottis.

Perioperative Ultrasound Indian Medical PG Question 7: During ultrasound-guided internal jugular vein cannulation, you observe the vein collapsing with minimal probe pressure while the artery remains patent. The vein appears enlarged and the artery-to-vein ratio is 1:3. A spontaneously breathing patient shows respiratory variation. Evaluate the most appropriate interpretation and management strategy.

• A. This indicates hypovolemia; fluid resuscitation should be considered before central line insertion (Correct Answer)
• B. This is normal anatomy; proceed with cannulation using standard technique
• C. This suggests venous thrombosis; consider alternative site
• D. This indicates increased central venous pressure; use ultrasound compression technique

Perioperative Ultrasound Explanation: ***This indicates hypovolemia; fluid resuscitation should be considered before central line insertion*** - Significant **respiratory variation** and ease of **venous collapse** with minimal probe pressure are classic ultrasound indicators of a **low intravascular volume state**. - Managing the **hypovolemia** first improves the safety of the procedure by increasing the target vessel size, thereby reducing the risk of **accidental arterial puncture**. *This is normal anatomy; proceed with cannulation using standard technique* - While the **internal jugular vein** is normally larger than the artery, excessive **compressibility** and collapse indicate an abnormal physiological state that complicates cannulation. - Proceeding without addressing the **underfilled vein** increases the technical difficulty and the likelihood of a **transfixion injury** where the needle passes through both walls. *This suggests venous thrombosis; consider alternative site* - **Venous thrombosis** would manifest as a **non-compressible** vein, often containing visible **distal echoes** or intraluminal clots. - In this scenario, the vein is noted to be **highly compressible**, which is the physiological opposite of what is seen in **deep vein thrombosis (DVT)**. *This indicates increased central venous pressure; use ultrasound compression technique* - High **central venous pressure (CVP)** would result in a **distended, non-collapsible** vein that does not vary significantly with the respiratory cycle. - An **artery-to-vein ratio** where the vein is excessively small or collapses easily specifically contradicts the diagnosis of **fluid overload** or **right heart failure**.

Perioperative Ultrasound Indian Medical PG Question 8: A 55-year-old patient with previous lumbar spine surgery requires epidural catheter placement for postoperative analgesia. Pre-procedure ultrasound shows loss of normal posterior complex and irregular acoustic shadowing at L3-L4 and L4-L5 levels. The L2-L3 level shows preserved anatomy with a depth of 6 cm to the epidural space. Which technical modification would provide the best success rate?

• A. Use paramedian approach at L3-L4 with fluoroscopy guidance
• B. Attempt midline approach at L2-L3 with ultrasound pre-scanning for trajectory (Correct Answer)
• C. Perform caudal epidural with threading of catheter to lumbar level
• D. Use loss of resistance to saline at L4-L5 with multiple attempts

Perioperative Ultrasound Explanation: ***Attempt midline approach at L2-L3 with ultrasound pre-scanning for trajectory*** - Identifying a level with **preserved anatomy** (L2-L3) via ultrasound is the most reliable predictor of success in patients with prior **spinal surgery**. - **Pre-scanning** allows for precise measurement of **epidural depth** and determination of the optimal needle trajectory, bypassing levels with surgical scarring. *Use paramedian approach at L3-L4 with fluoroscopy guidance* - The L3-L4 level shows **irregular acoustic shadowing** and loss of normal complexes, indicating surgical distortion that makes access difficult despite a paramedian approach. - While **fluoroscopy** provides real-time imaging, it involves **radiation exposure** and is less desirable than utilizing a healthy adjacent level (L2-L3). *Perform caudal epidural with threading of catheter to lumbar level* - Threading a **caudal catheter** to the mid-lumbar levels is technically challenging and frequently results in **malpositioning** or inadequate analgesia. - This approach is generally reserved for patients where all **lumbar access** points are completely obliterated by extensive fusion or hardware. *Use loss of resistance to saline at L4-L5 with multiple attempts* - Multiple attempts at L4-L5, which shows **anatomical distortion**, significantly increase the risk of **dural puncture** and technical failure. - Relying solely on **loss of resistance** without respecting ultrasound signs of **posterior complex loss** is poor clinical practice in

Perioperative Ultrasound Indian Medical PG Question 9: A 28-year-old ASA I patient undergoes ultrasound-guided axillary block. Despite clear visualization of local anesthetic spread around all three major nerves, the patient develops incomplete block in the distribution of musculocutaneous nerve. What is the most likely anatomical explanation?

• A. The musculocutaneous nerve has already entered the coracobrachialis muscle at the level of injection (Correct Answer)
• B. The nerve has anatomical variation with dual innervation
• C. Inadequate volume of local anesthetic was used
• D. The needle was placed too proximal in the axilla

Perioperative Ultrasound Explanation: ***The musculocutaneous nerve has already entered the coracobrachialis muscle at the level of injection*** - The **musculocutaneous nerve** frequently exits the **neurovascular sheath** high in the axilla to enter the **coracobrachialis muscle**, often by the level of the pectoralis minor. - Because it travels separately from the **median, ulnar, and radial nerves**, it is often missed during a standard **axillary block** unless specifically identified and blocked within the muscle body. *The nerve has anatomical variation with dual innervation* - While **anatomical variations** exist, dual innervation from the **median nerve** is less common than simple proximal separation of the nerve. - This would not explain the failure of a block where local anesthetic spread was clearly visualized around the main nerves in the sheath. *Inadequate volume of local anesthetic was used* - The prompt states there was **clear visualization** of local anesthetic spread around the three major nerves, suggesting the volume was sufficient for the sheath compartments. - Increasing volume within the **axillary sheath** will not typically reach a nerve that has already anatomically deviated into a separate muscular plane. *The needle was placed too proximal in the axilla* - Placing the needle **proximal** would actually increase the likelihood of capturing the musculocutaneous nerve before it branches off. - Blocks performed more **distally** in the axilla are the ones most likely to miss the nerve as it moves laterally and deep into the **coracobrachialis**.

Perioperative Ultrasound Indian Medical PG Question 10: During ultrasound-guided supraclavicular block, you observe the brachial plexus as a 'bunch of grapes' appearance. The subclavian artery appears pulsatile underneath. You notice a hyperechoic line moving with respiration above the artery. What does this structure represent and what is its clinical significance?

• A. First rib - landmark for needle placement
• B. Pleura - indicates risk of pneumothorax (Correct Answer)
• C. Prevertebral fascia - anatomical landmark
• D. Subclavian vein - vascular complication risk

Perioperative Ultrasound Explanation: ***Pleura - indicates risk of pneumothorax*** - The **pleura** appears as a **hyperechoic**, shimmering line that exhibits **respiratory sliding**, located deep and lateral to the **subclavian artery**. - Identifying this structure is critical to avoid accidental needle puncture, which can lead to a **pneumothorax**, a classic complication of the supraclavicular approach. *First rib - landmark for needle placement* - The **first rib** is also **hyperechoic** but presents as a static, shadowing structure that does not move with respiration. - It serves as a safety barrier; keeping the needle tip above the **first rib** prevents it from entering the underlying lung tissue. *Prevertebral fascia - anatomical landmark* - The **prevertebral fascia** envelops the **brachial plexus** trunks but does not demonstrate the characteristic **sliding motion** seen with the pleura during breathing. - While it is a key landmark for identifying the **plexus sheath**, it does not correlate with the dynamic respiratory movement described in the prompt. *Subclavian vein - vascular complication risk* - The **subclavian vein** is typically located medial to the **subclavian artery** and appears as an **anechoic** (black), compressible oval. - It is not a hyperechoic line and does not possess the distinct **shimmering** appearance associated with the visceral and parietal pleural interface.

Perioperative Ultrasound Flashcard 1 of 4

Question: Percentage of glottic opening (POGO score) and Cormack Lehane (CL) classification is broadly used to describe _____ view during direct laryngoscopy

Answer: laryngeal

Perioperative Ultrasound Flashcard 2 of 4

Question: 2020 AHA guidelines recommendations:Parameters such as _____ may be used to monitor and optimize CPR quality

Answer: ETCO2

Perioperative Ultrasound Flashcard 3 of 4

Question: _____ is the most sensitive depth of anesthesia monitor.

Answer: Middle latency auditory evoked potential

Perioperative Ultrasound Flashcard 4 of 4

Question: In case of endotracheal intubation or tracheostomy, the _____ component of the score is denoted as NT.

Answer: verbal