Hi Chrissie,
In my clinical setting I have not encountered viabahn stents so immediately post op,
The only ones I scan are at least weeks and usually months after placement and in this setting I have not had a problem.
I agree gas in the surgical field can be a problem, although this should be fairly obvious on the scan,
I would be looking at the distal end of the graft where it re-enters the native vessels and assess the waveform at this location.
I would expect a biphasic waveform with good input pressure if the graft is patent.
If scans are performed in this immediate post op phase here in Adelaide they would be done by the vascular sonographer working directly for the surgeon rather than by a sono like me working in a radiology setting,
Steve.