To the Editor:—
We read with interest the article by Kitagawa et al. 1regarding the proper shoulder position for subclavian vein (SCV) puncture. They are to be congratulated for performing an important study about the anatomical backgrounds of SCV catheterization. The major finding of their article was that, when compared with neutral and elevated positions, the lowered shoulder position is the best for the SCV approach. However, we would like to make a few comments regarding the article.
First, the longest overlap length between the lower border of the clavicle and the SCV in the inner third of the clavicle was one of the main reasons for quoting the lowered shoulder position. However, a needle path aiming at the suprasternal notch may cross the lower border of the clavicle somewhere between the midclavicular line and the inner third of the clavicle. In addition, the shaded overlap area in figure 1 of the article1extends out of the SCV, even to the innominate vein.
Second, one of the most important factors for successful catheterization is probability of contact between the puncture needle and the SCV. Because the cross-sectional area rather than the diameter on a plane is more important for the probability of contact, the cross-sectional area of the SCV beneath the inner third of the clavicle should be regarded as a major factor. If the cross-sectional area is not available, there may be another way of analyzing the probability of contact. Overlap length of the SCV on an imaginary line drawn between the needle entry point and the midportion of the clavicular head seems to be more relevant than that on the lower border of the clavicle. In figure 1 of the article,1we can realize that the neutral and lowered positions are comparable, but the elevated position has the shortest overlap length on the imaginary line.
Third, with regard to the small clinical trial, why were the neutral and lowered positions not compared? Where was the catheter tip located? Were there any catheters directed to the internal jugular vein (IJV)? As explained in figure 4 of the article,1the angle formed between the SCV and the innominate vein becomes narrower with the shoulder lowered. Considering the fact that, in children, a right SCV catheter is frequently positioned in the IJV because the angle formed between the SCV and the innominate vein is more acute,2there seems to be a risk of directing the SCV catheter into the IJV when the shoulder is lowered.
Last, changing the shoulder position after successful venipuncture, as suggested in the article,1carries the risk of withdrawing the puncture needle out of the vein. Even changing the shoulder position after advancing the guide wire may not be helpful, because a guide wire may already be directed to the IJV because of the short distance between the SCV puncture point and the confluence of the IJV and the SCV. If SCV catheterization is attempted with the shoulder lowered, tilting the head toward the catheterization side without movement of the shoulder may be more helpful in reducing the incidence of catheter malposition into the IJV.3
All the above-mentioned concerns should be clarified before deciding whether we should adopt the lowered shoulder position during SCV catheterization.
* Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea. firstname.lastname@example.org