bbpiano1

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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
 

bulgethetwine

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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).
 

bigdan

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Bulge -

Nice post.

In my medical experiences, there was never a question about tip cultures in the ICU - if you presumed line infection, you sent the tip for culture. Now, here in my intern year ICU experience, we've got one attending that NEVER sends tips. She believes that you'll only drag the tip thru skin flora upon line removal, and so that it's not worth sending. When she's on, we draw one culture set from the line before it's removed, but the tip goes into the trash.

Anyone else share this view about not culturing tips?

dc
 

proman

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The following is the criteria for catheter-related bloodstream infections (National Nosocomial Infections Surveillance System):

A) Presence of a recognized pathogen cultured from 1 or more blood cultures
AND organism cultured from blood not related to infection at another site

OR

B) Presence of at least 1: Fever (T >38), Chills, Hypotension
AND Signs and symptoms and positive results not related to infection at another site
AND Presence of at least 1: Common skin contaminant cultured from 2 or more blood samples drawn on separate occasions, common skin contaminant cultured from at least 1 blood culture in a sample from a patient with an intravascular catheter, positive antigen test on blood.

Note that culture of the catheter itself is not required for diagnosis of CRBSI. This criteria was used for the Michigan Keystone ICU project, which demonstrated a lasting reduction in CRBSI (NEJM 12/28/2006).
 

HomerSD

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We never send central line tips for cultures. Either you already have positive or pending blood cultures, or have a high clinical suspicion of an infected line that you're pulling the line. The tip culture adds nothing in my opinion, as the line is now already out and you've dragged it through who knows what.