We appreciate the comments regarding our recently published practice guidelines for ultrasound-guided vascular access. Dr. LeDonne describes the availability of commercial needle guides for the long-axis approach to ultrasound-guided vascular cannulation. The main advantage of the long-axis over the short-axis approach is visualization of the needle as it is advanced under the skin and control of needle depth. Misalignment is readily apparent when the needle is not in plane during long-axis imaging, because the needle is not visible on the image display. During short-axis imaging, only a slice of the needle is visible as a small cross-section on the image plane where the needle intersects the ultrasound plane, providing no information as to the needle position distal to the imaging plane. The main purpose of the needle guide is to direct the needle into the imaging plane of the transducer and control the depth of initial intersection of the needle and that image plane. This is of greatest benefit for less experienced operators, offsetting the loss of freedom afforded experienced operators who use an unrestrained freehand technique. It is worth noting that not all manufacturers offer short-axis or long-axis needle guides with all transducers, and their costs vary from several dollars to more than $100. Clinicians should be aware of these issues and be familiar with various needle guides and transducers and their availability regardless of short-axis or long-axis approach.
The subclavian vein arises from the axillary vein at the lateral border of the first rib and extends to the medial border of the anterior scalene muscle, where it joins the internal jugular vein to form the innominate vein. It is impossible to state unequivocally which vein is being displayed on the basis of a static image alone without an appreciation of the transducer position and first rib location relative to the vein. The figure provided by Dr. LeDonne is obviously different from Figure 13 in our report. The cephalic vein is clearly visualized in Dr. LeDonne’s image, indicating that this image was obtained from a more lateral scanning plane. We therefore agree that Dr. LeDonne’s image is of the axillary vein. The cephalic vein is not readily apparent in our Figure 13, so the venous structure cannot be definitively identified as the axillary, leaving the identification up to the operator holding the probe relative to the first rib. The subclavian vein can be imaged in the infraclavicular fossa but requires a transducer with a smaller width. Last, the “subclavian approach” is a term used in practice to describe the general approach to placing a catheter into the central venous circulation via the subclavian vein; either the axillary vein or subclavian vein itself may be cannulated depending on the exact location of needle entry.
The video provided by Dr. LeDonne demonstrates a more lateral approach into the axillary vein. This video complements the ultrasound-guided cannulation approach to the internal jugular vein provided with the online version of our report. It is important that clinicians recognize these subtle differences. We appreciate Dr. LeDonne’s contribution to video education.