critical care medicine
How To Do Femoral Artery Cannulation, Ultrasound Guided
Additional Considerations
The short-axis (cross-sectional, transverse) ultrasound view is easy to obtain and is the better view for identifying veins and arteries and their orientation to each other. Identifying a needle tip in cross section requires some skill because the needle appears as an echogenic (ie, white) dot and the tip can be distinguished only by the dot's disappearance and reappearance as the needle tip traverses back and forth across the imaging plane.The short-axis view typically is used to determine a suitable vascular impalement site and to guide steeply angled (eg, ≥ 45°) needle insertions. The long-axis (longitudinal, in-plane) ultrasound view is technically more difficult to obtain (must keep probe, artery, and needle in one plane), but it shows the needle longitudinally, so the entire needle—including the tip—can be imaged continuously as it approaches and enters the vessel; this helps avoid aberrant placement.The long-axis view is helpful when the angle of needle insertion is shallow (eg, in axillary/subclavian cannulations) and to affirm proper longitudinal needle alignment during short-axis insertions. If a new attempt at cannulation is necessary, use new equipment (ie, do not re-use needles, catheters, or other equipment because they may have become blocked with tissue or blood). During cardiopulmonary arrest, or even low blood pressure and hypoxia, arterial blood may be dark and not pulsatile and may be mistaken for venous blood. 