Use of Doppler ultrasound flow volume to assess the impact of peripheral arterial catheters on proximal arterial flow

Peripheral arterial catheters are frequently used in critical care for continuous hemodynamic monitoring and arterial blood gas sampling. Prior work suggests that a lower catheter-to-vessel ratio (CVR) <40% may help preserve distal cannulated-artery perfusion. However, in pediatrics many arterial line injuries occur proximal to the cannulation site, which may be related to obstructed flow. To assess this obstruction, Doppler peak systolic velocity (PSV) alone may not reflect volumetric flow, particularly when the catheter occupies a large percentage of the lumen. We present a hypothesis-generating case series of five pediatric intensive care patients with indwelling radial arterial catheters and a CVR 50%-70%. Doppler PSV and flow volume (FV) were measured in the cannulated radial artery proximal to the catheter tip and compared to the ipsilateral ulnar artery. Radial-to-ulnar PSV ratios were higher in all patients (0.49-0.91) compared with radial-to-ulnar FV ratios (0.03-0.37). Differences between PSV and FV ratios within individual patients ranged from 0.12 to 0.80, suggesting that FV may provide complementary information about proximal arterial flow in high-CVR situations. Larger studies incorporating pre-cannulation assessments and patient outcomes are needed to determine the clinical significance of these Doppler findings.