So my resident and I removed a central line today and he asked me to cut a piece to send for culture. Once it was completely removed, I went to snip a piece of the area when the line entered the skin. Then the resident told me that was the wrong location and that I could cut the tip. Since line infections usually originate from the insertion site (skin flora, etc), what exactly is the reason behind culturing the tip?
bb
Great question, and not just for the technical aspects of which part of the catheter to culture, but also helps to shed some light on the whole issue of what constitutes a line infection.
First, your resident is right - you want to clip the distal tip (i.e. where the fluid would come out if you injected). The lab will take the tip, filet it open and unravel it, and scrape it across the dish, etc. (or whatever they use to culture it).
Here is a little background:
Historically, there has been heterogeneity in the literature with regard to how we characterize line infection. While a positive culture from the skin around the insertion site of a line is a RISK FACTOR for an infected line (and, by extension, a risk factor for line SEPSIS), it is not, per se, synonymous with line sepsis. Some have argued that a bacteria culture here should demand removal/replacement of the line. I say if you did that, you'd be changing every line every 12 hours. This line of reasoning is why we are now spending thousands of dollars on sterile bundles for the insertion of art lines - because a recent paper showed that the rate of cultures at the insertion site of A lines was pretty high. Not so surprising, I say - but I don't think it matters.
Instead, when fever arises in a patient and you're looking for a source, a more prudent course in my opinion is culture of the line TIP + blood culture drawn from another site. If they're both positive, then the inference is that the bacteria in the catheter seeded the blood and you've cinched the diagnosis of line sepsis (though it seems possible that the bacteria could have latched onto the tip in transit, too, but either way, the line needs to be removed).
In truth, I almost never send line/tip cultures though. If the patient is acting septic with that fever, than I remove/replace all lines then draw cultures anyway. In this instance, culturing tip wouldn't really change my management (although it might confirm that it was line sepsis as opposed to another source, but I don't care about this so much).
