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. Some authors have hypothesised that a catheter/artery ratio of less than 45% is advisable. This study aimed to explore the relationship between residual flow in the Radial Artery, the catheter/artery ratio, and ulnar compensation. Methods: This retrospective observational study included patients with radial artery catheters in general wards and intensive care units of a tertiary hospital in Italy. Residual flow in the radial artery was calculated by measuring the Peak Systolic Velocity and diameter of the artery at the midpoint of the arm. The reverse Barbeau test was used to assess the residual perfusion. The sample was stratified and analysed to the catheter/artery ratio being greater or less than 33% and 45% and to the score obtained during the reverse Barbeau test. Results: The data obtained showed a significant statistical correlation between residual flow, catheter/artery ratio, and the reverse Barbeau test (p < 0.0001 and p = 0.0074 respectively). Almost 80% of the sample had a catheter with an exit site less than 4 cm from the wrist crease. Conclusion: Adhering to the current guidelines, especially using ultrasound to ensure a catheter/artery ratio of at least 45%, can help maintain preserved perfusion through the cannulated radial artery. Ulnar compensation appears to be crucial for maintaining good tissue perfusion and should always be evaluated before catheterisation. Therefore, further studies are warranted.