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In point of fact, blood cultures obtained through indwelling lines are twice as likely to result in "contamination" than blood cultures obtained through a venipuncture. This is because the coagulase negative staphylococci that grow in the blood culture are found in biofilms on the plastic catheter (inside the port or on the hub) and simple wiping with disinfectant does not easily remove them or kill them. So lines should ideally be prepared more vigorously and more diligently than skin before blood cultures are obtained. Here is our protocol:
1. Wash hands or disinfect with alcohol gel. Put on gloves.
2 Clamp catheter.
3. Prep hub thoroughly with alcohol.
4. Remove the stopcock or needleless connector and use clean alcohol wipe to vigorously clean luer lock threads “as though juicing an orange”. Attach a new stopcock or needleless connector.
5. Attach 20 ml syringe and draw 20 ml blood.
6. Flush line according to protocol.
A key component is the removal of the old connector (safe-site valve at our hospital) and placement of a new one before drawing blood.
There are lots of references and each of them is different. Some advocate a discard volume of blood, some advocate push-pull of blood through the line before drawing blood cultures, etc. I think you can find one for each method advocated. You need to work with your Infectious Disease doctors, your Infection Control team, and your Nursing Educators to arrive at a realistic policy that can be taught and enforced. Good luck.
E.J. Baron, Ph.D., D(ABMM)
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