Residual flow of the radial artery in the presence of an arterial catheter: A single-centre retrospective observational study.

Background: Arterial catheterisation is a common procedure used to manage critically ill patients. The radial artery, both for its favourable anatomical position and the presence of ulnar collateral circulation, is the most used. While there is a consensus for a catheter/vein ratio of ⩽33% for venous catheterisation, there are no strong indications for arterial catheterisation.