The carina as a radiological landmark for central venous catheter tip position.

BACKGROUND Many publications, including the instructions accompanying central venous catheters, state that it is negligent to site the catheter tip in the right atrium. If the catheter tip is above the carina on a post-procedure radiograph then it is generally accepted that the catheter lies outside the right atrium. It is also recommended that the catheter tip should lie in the long axis of the superior vena cava without acute abutment to the vein wall. We performed a retrospective audit of the position of central venous catheter tips on routine post-procedure chest radiographs in intensive care unit patients, to see if these potentially conflicting requirements had been met. METHODS We identified 213 central venous catheters suitable for analysis, within a study population of 200 consecutive cases. We measured the distance of the central venous catheter tip above or below the carina and the angle of the central venous catheter tip to the vertical (a surrogate marker for the angle of abutment of the tip to the approximately vertical superior vena cava wall). RESULTS For right-sided catheters there was a high (74/163) number placed with their tips below the carina, but a very low number (4/163) with their tips at a steep (>40 degrees ) angle to the vertical. For left-sided catheters very few (7/50) were placed with their tips below the carina, but for those 43 sited above the carina most could be considered to be in suboptimal positions. This was because they were either too high and had not even crossed the midline (9), or had an acute angle (>40 degrees ) between the tip and the vertical (27). CONCLUSIONS We suggest that for left-sided catheters placement of the tip below the carina is more likely to result in a satisfactory placement.