Just because this material has never shown up in the past papers does not mean it can safely be neglected. Many questions approach this indirectly. When asked about the disadvantages to the use of any intravascular indwelling device, the CVC complications can be brought up. Never previously seen in the exams, the existence of this chapter was vindicated when Question 15 from the second paper of 2015 had asked about the potential complications of CVC insertion, as well as the various ways one can tell the difference between neck vessels on ultrasound.
There are only a few strong reasons for the insertion of a central venous access device:
Extended indications also include:
This was asked about specifically in Question 15 from the second paper of 2015. The college only felt this issue merits 30% of the total question marks (the rest went into the question about using ultrasound to distinguish the carotid artery from the IJ vein)
Question 15 from the second paper of 2015 asked for these features. For most of us, the two vessels are fairly easy to tell apart, but... if one were asked to articulate exactly how they differ, one might come to trouble. "Squishy" and "roundly pulsatey" are probably inappropriately loose terms to use in this context. Instead, please find the table below:
|Features||Internal Jugular Vein||Carotid Artery|
|Pulsatility||Occasionally, might pulsate (eg. in severe TR)||Always (should be ) pulsatile|
|Response to Valsalva||Increases in diameter||Remains unchanged with Valsalva|
|Colour Dopper||May demonstrate pulsatile blood flow||Should demonstrate pulsatile blood flow|
|Flow direction||Flow should be laminar and present during both systole and diastole||Flow should be laminar and present only during systole|
|Nyquist scale||Low scale required (i.e. low velocity flow)||High scale required (or, aliasing occurs)|
This table comes in part from the college answer, and in part from Vascular ultrasound of the neck: an interpretive atlas.
Williams, William M. Vascular ultrasound of the neck: an interpretive atlas. Lippincott Williams & Wilkins, 2001.