Letters

Author's reply

Used with the imaging guided technique, coaxial systems that use 21-22 gauge needles to introduce catheters provide a greater margin of safety than the larger, traditional needles: this is important, because coagulopathies are not always fully correctable.

The comments by Duncan Young and colleagues suggest unfamiliarity with the use of imaging modalities and misinterpretation of the literature: ultrasound scanning helps to avoid arterial puncture but cannot ensure correct placement of the catheter in the superior vena cava. Mansfield et al did not use real time ultrasound scanning; they simply marked the position of the vein using a preliminary scan, which is a much inferior method, and they themselves acknowledge that this may explain the problems they encountered.¹ Fluoroscopic guidance after the initial puncture ensures correct placement in virtually all cases. Fluoroscopy at the end of the procedure is better than nothing but is no substitute for guidance during placement, which eliminates misplacement and ensures that the catheter is the right length.

When discussing the imaging guided technique I did not recommend that the tip of the catheter should be in the right atrium, as Malcolm Hilton and colleagues mistakenly state. Their comment is based on unfamiliarity with the technique used: a long sheath is placed into the atrium, or even the inferior vena cava, but the catheter is cut to the correct length before placement, the necessary length having been measured during fluoroscopy. The catheter's tip is left at the junction of the superior vena cava and right atrium, and the sheath is then peeled away.

I agree with Jacqueline Filshie and colleagues that there are advantages to a centralised venous access service. Imaging guidance and modern methods that enable catheters to be inserted on an outpatient basis make it possible to rationalise the insertion of central venous catheters, improve training, and minimise trauma and inconvenience to patients.

Expert surgical teams can undoubtedly achieve satisfactory results with an inferior method, but this is no reason to deny progress; imaging guidance and modern catheters can do better.

Professor of interventional radiology Department of Radiology, Guy's Hospital, London SE1 9RT

A Adam 

1. Mansfield PF, Hohn DC, Fornage BD, Georgurich MA, Ota DM. Complications and failures of subclavian-vein catheterization. N Engl J Med 1994;331:1735-8. [Abstract/Free Full Text]