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 - It has largely been replaced by ultrasound due to its **lower sensitivity** for small stones, **patient inconvenience**, and potential for **adverse reactions** to the contrast.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: 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 5: 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 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