Extract:
“This case highlights the difficulty of interpreting blood gas samples taken from a CVC in a patient with an AV fistula. The presence of a high pO2 cannot be interpreted accurately because of abnormal flow of arterial blood from the fistula. However, results compatible with venous samples were taken from the proximal lumens of the CVC which complicated the interpretation of results. Although rare, cases of patients with AV fistulae in whom CVC location is unclear due to unexpected blood gas analysis data have been previously reported. It is well established that the central veins demonstrate laminar flow and that laminae vary in their oxygenation, indicating that mixing of content between the laminae does not necessarily occur. It seems most likely in our case that the distal CVC lumen was situated sufficiently close to the fistula to allow aspiration from an arterial, well-oxygenated stream of blood.”
Reference:
Evans CR, Hall TM. Challenges in confirming the position of a central venous catheter in the presence of an arterio-venous haemodialysis fistula. Anaesth Rep. 2023 Nov 28;11(2):e12264. doi: 10.1002/anr3.12264. PMID: 38031632; PMCID: PMC10682965.