Reply

Abstract

We read the above letter with interest, and we recognize the many contributions made by Tordoir et al to improve the planning of arteriovenous access procedures. First, regarding the lack of data on reproducibility of the “congestion methods,” the method-reproducibility of inflating a standard-size cuff to a standardized pressure is likely to be high compared with that of a manually adjusted tourniquet. The variation they found in measured vein diameters on different days is not necessarily a reflection of variability of the congestion method, but is more likely the result of fluctuations in baseline venous-wall muscle tone. This is affected by such things as temperature, activity, time of day, hydration, and mental stress, among others. Second, regarding the influence of arm length and valve distribution, we did not gather data on either so we cannot comment on this. We look forward to seeing the author’s data on this. Third, regarding the clinical relevance of “maximum” venous diameter, the method we recommend (measurement sitting, after immersion in warm water) does not require any tourniquet application at all and, therefore, the intravenous pressure will be in the physiologic venous range. Aside from intraluminal pressure, an important mechanism for dilation of the vein, both after arterialization and after warm water immersion, is the increase in flow-related shear stress at the endothelial surface, resulting in nitric oxide release and vein-wall smooth muscle relaxation. Fourth, regarding the elliptical cross section of superficial veins, we agree that superficial arm veins often do not have a circular cross-sectional area. A comprehensive description would indeed require reporting of both the longest and shortest axis of the ellipse. This would be better than using the largest axis only, as has been practiced in the past. We submit that averaging of the longest and shortest axis results in a single number, which can be practical, because the difference between the two after dilation is not more than 15%. Finally, we re-emphasize that although size matters for arm veins, it forms only a small piece of the puzzle with regard to predicting arteriovenous fistula function compared with other vein characteristics such as wall fibrosis, calcification, superficial phlebitis, and central stenosis. Regarding “Improvement in the visualization of superficial arm veins being evaluated for access and bypass”Journal of Vascular SurgeryVol. 43Issue 3PreviewIn their recent report, van Bemmelen et al (J Vasc Surg 2005;42:957-62) address the lack of standardized evaluation of upper-extremity superficial veins before dialysis access arteriovenous fistula (AVF) creation. The authors compared six different methods to determine maximum venous diameter and conclude that forearm superficial veins distend maximally in a sitting position without the use of a tourniquet with the arm dangling down after the use of warm water immersion. Full-Text PDF Open Archive