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.
Q2
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?
Q3
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?
Q4
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?
Q5
A patient is scheduled for femoral nerve block. On ultrasound, you identify a pulsatile structure lateral to the femoral vein. How should you proceed?
Perioperative Ultrasound Indian Medical PG Practice Questions and MCQs
Question 1: 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
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**.
Question 2: 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
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
Question 3: 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
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**.
Question 4: 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
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.
Question 5: A patient is scheduled for femoral nerve block. On ultrasound, you identify a pulsatile structure lateral to the femoral vein. How should you proceed?
A. Inject local anesthetic medial to this structure
B. Inject local anesthetic lateral to this structure (Correct Answer)
C. This is the femoral artery; inject between artery and vein
D. This represents the nerve; inject at this location
Explanation: ***Inject local anesthetic lateral to this structure***
- The pulsatile structure lateral to the femoral vein is the **femoral artery**; based on the **NAVEL** mnemonic (Nerve, Artery, Vein, Empty space, Lymphatics) from lateral to medial, the nerve is located most laterally.
- For a successful femoral nerve block, local anesthetic must be deposited **lateral to the artery**, specifically deep to the **fascia iliaca** to surround the hyperechoic nerve bundle.
*Inject local anesthetic medial to this structure*
- Injecting medial to the femoral artery results in deposition near the **femoral vein** or the **femoral canal**, which contains lymphatics but no major nerves.
- This approach carries a high risk of **accidental intravascular injection** into the femoral vein and will not achieve a nerve block.
*This is the femoral artery; inject between artery and vein*
- The space between the femoral artery and vein contains connective tissue but does not house the **femoral nerve**.
- Injecting in this plane increases the risk of **vascular injury** and systemic toxicity without providing any clinical analgesia for the femoral territory.
*This represents the nerve; inject at this location*
- A **pulsatile structure** on ultrasound is characteristic of an artery (the femoral artery), whereas the femoral nerve appears as a non-pulsatile, **hyperechoic**, triangular or oval structure.
- Injecting directly into a pulsatile structure would result in an **intra-arterial injection**, potentially leading to **Local Anesthetic Systemic Toxicity (LAST)** or distal ischemia.
