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Department of Anesthesiology and Clinical Research Institute, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea
To the Editor:
I read with interest the article by Andropoulos et al. (1) regarding the guidelines for correct initial length of insertion of central venous catheters (CVC) in children, where they had the goal of avoiding placement of the catheter in the right atrium (RA). I would like to raise two points concerning the article. First, where is the optimal place for CVC in children? Second, what is the scientific basis for combining the results of the internal jugular and subclavian vein catheters? There has been considerable debate in the literature about the optimal place. However, it is clear that as the axes of the catheter and vein are aligned parallel, there would be less perforation. Upper superior vena cava (SVC) is suitable only for tips of catheters placed via the right internal jugular route, and low SVC and upper RA is a suitable tip site from any access point in the upper body (2). The optimal position can be different depending on the route of entry.
In children, subclavian catheter frequently positions in the internal jugular vein (3,4) because the angle formed between the subclavian and innominate veins is more acute than in adults (3). Gross anatomic dissections and coronal magnetic resonance imaging demonstrated that the subclavian and internal jugular veins joined at an angle of 90° or greater in the neutral anatomic position (5). Although the subclavian catheter is directed to the SVC, if it is not pushed sufficiently deep after a sharp bend at the junction from the subclavian vein into the brachiocephalic vein, it may not be aligned parallel to the vessel wall. Thus CVC placement in the upper RA should not be abandoned but may be approved at least for the subclavian catheter. This is also supported by the fact that the relative location of CVC compared with the RA-SVC junction tends to appear deeper than the actual location on the portable anteroposterior radiograph (6).
References
Division of Pediatric Cardiovascular Anesthesiology, Texas Children’s Hospital, Baylor College of Medicine, Houston, TX
In Response:
We appreciate Dr. Bahk’s comments about optimal location for central venous catheter (CVC) placement in children. We agree that CVCs parallel to the superior vena cava (SVC) wall, whether high, mid, or low SVC, are much less likely to perforate the vessel (1). We also agree that right subclavian catheters have a higher incidence of being positioned across the midline, and may migrate after placement if left too high (2). Lower positioning in the low SVC with right subclavian CVC may be preferable because a longer length of catheter is parallel to the vein wall and less likely to migrate. We also agree that a CVC tip high in the right atrium (RA) that stays fixed in position, well away from the free wall, poses little risk of perforation.
However, we believe that positioning the CVC tip above the RA confers a greater margin of safety, particularly during "blind" insertion methods where the CVC will not be imaged for several hours. Thus our arguments that CVC tips should not be intentionally positioned in the RA are as follows.
One may consider placing the CVC tip high in the SVC to be preferable because perforation at this level is above the pericardial reflection and less likely to cause tamponade. Perforation in the RA may, of course, lead to catastrophe (7,8). During several hundred transesophageal echocardiographically guided CVC placements (2), we have observed the distance from the SVC/RA junction to the RA free wall to be only 2–3 cm or less in patients weighing less than 10 kg. Therefore, a seemingly small migration of the tip may place the CVC much deeper in the RA and at increased perforation risk.
We combined right subclavian and right internal jugular data because, after separate evaluation, the proposed guidelines for the depth of insertion were the same for both groups. Combining the data meant that one set of clinically useful guidelines could be made for both insertion sites, with a high degree of success in predicted proper placement, i.e., 97% for all CVC versus 99% and 93% for right internal jugular and right subclavian alone, respectively, when using the height based formulae, and similar success predicted when using the weight-based formulae.
In our opinion, given the individual variation in each patient, the best method to ensure proper placement is to image the CVC tip as soon as possible. Transesophageal echocardiography, if available, is useful because the tip position can be easily adjusted before final securing (2). If this is not possible, chest radiography should be performed as soon as possible to confirm tip position. In certain difficult or questionable cases, immediate radiography in the operating room before the start of a long surgical procedure may be indicated.
References
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