Bedside prediction of central venous catheter insertion depth
Dublin, Ireland
E-mail: muhammadfarooqch{at}yahoo.com
Editor—I read this article1 with keen interest, as it may change the practice of routine chest X-ray (CXR) after central line insertion in ICU patients. This practice can lead to a decrease in cost of patient care and radiation exposure. However, this technique of checking line tip position is not suitable for those patients who have no CXR before central line insertion. If a patient requires a CXR to establish the position of the carina and to measure length from the clavicle notch to the carina, then why not do this after central line insertion, when we can see the tip of the line and serious complications such as pneumothorax. Another point is that the length between the insertion site, clavicular notch, and carina is a subjective measure which may lead to bias and erroneous results.
Seoul, Korea
* E-mail: bahkjh{at}snu.ac.kr
Editor—We would like to thank Dr Farooq for his interest on our article.1 However, there seems to be some misunderstanding. The practical purpose of our study was not to prove that a CXR may be omitted after central venous catheterization, but to minimize post-procedural adjustments of central venous catheter insertion depth. We agree that our technique is not so helpful for patients without prior CXR. Patients likely to require central venous catheterization may well have a CXR taken before operation or before being admitted to ICU. Although it was not studied, it is probable that optimal central venous catheter insertion depth should depend on the distance from the insertion point to the clavicular notch. Besides, it is possible that very tall patients would have the clavicular notch appear more peripherally on the CXR, augmenting the clavicular notch to carina distance as the parallax effect would be greater peripherally. However, because routine posterior–anterior CXR is taken at a fixed distance between the X-ray tube and film (72 in), we think that such bias is negligible in most cases. If we measure the insertion point to clavicular notch distance after insertion of a guidewire or catheter, there is no reason to introduce any serious error during simple distance measurements.
References
1 Ryu H-G, Bahk J-H, Kim J-T, Lee J-H. Bedside prediction of the central venous catheter insertion depth. Br J Anaesth (2007) 98:225–7.
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