VABC Ultrasound Guidance 4 — Questions and Answers
Question 1: Which finding on venous ultrasound assessment is most consistent with deep vein thrombosis at a previous access site?
- Vessel augmentation with distal compression
- Non-compressibility of the vessel with probe pressure (Correct answer)
- Phasic flow with respiration on Doppler
- Hyperechoic vessel wall with normal lumen
Correct answer: Non-compressibility of the vessel with probe pressure
Non-compressibility of the vein when direct probe pressure is applied is the most reliable ultrasound sign of DVT.
Question 2: During real-time ultrasound-guided cannulation, the needle tip is most easily lost when using which approach?
- Long-axis (in-plane) approach
- Short-axis (out-of-plane) approach (Correct answer)
- Oblique approach at 45 degrees
- Combined long- and short-axis approach
Correct answer: Short-axis (out-of-plane) approach
In the short-axis approach, the needle is seen as a dot and can be confused with the needle shaft, making true tip tracking difficult.
Question 3: What is the primary advantage of the 'dynamic needle tip positioning' (DNTP) technique in ultrasound-guided access?
- It eliminates the need for sterile technique
- It keeps the needle tip continuously in the ultrasound plane during advancement (Correct answer)
- It increases insertion speed by using a pre-set angle guide
- It replaces the need for guidewire confirmation
Correct answer: It keeps the needle tip continuously in the ultrasound plane during advancement
DNTP involves moving the probe to follow the needle tip, maintaining continuous real-time tip visualization throughout the insertion path.
Question 4: When scanning for a suitable peripheral vein using ultrasound, which minimum vessel diameter is generally recommended for successful catheterization?
- 1 mm
- 3 mm (Correct answer)
- 5 mm
- 7 mm
Correct answer: 3 mm
A vessel diameter of at least 3 mm is generally considered the minimum for reliable peripheral IV catheter placement under ultrasound guidance.
Question 5: The 'tenting' sign seen on ultrasound during needle advancement refers to:
- The vessel wall moving away as the needle approaches without penetration (Correct answer)
- Acoustic enhancement posterior to the vessel
- Reverberation artifact from the catheter hub
- Compression of the vessel wall by the transducer
Correct answer: The vessel wall moving away as the needle approaches without penetration
Tenting occurs when the needle pushes the near vessel wall inward without penetrating it, indicating the needle has not yet entered the lumen.
Question 6: When using ultrasound to guide a midline catheter insertion in the upper arm, the target vein should ideally be located at a depth no greater than:
- 0.5 cm
- 1.0 cm
- 1.5 cm (Correct answer)
- 2.5 cm
Correct answer: 1.5 cm
For midline and peripheral IV placement, a vessel depth of up to 1.5 cm is generally considered accessible with standard-length catheters under ultrasound guidance.
Question 7: Which aseptic technique component is essential and specific to ultrasound-guided central venous catheter insertion to prevent infection?
- Wearing sterile gloves only
- Using a sterile transducer cover and sterile ultrasound gel (Correct answer)
- Placing the probe on an alcohol wipe before use
- Limiting probe contact to the drape edges only
Correct answer: Using a sterile transducer cover and sterile ultrasound gel
A sterile transducer sheath/cover and sterile gel are required to maintain sterile field integrity when the probe operates within the procedural site.
VABC Ultrasound Guidance 4
Which finding on venous ultrasound assessment is most consistent with deep vein thrombosis at a previous access site?